mirror of
https://git.savannah.gnu.org/git/gperf.git
synced 2025-12-02 13:09:22 +00:00
2483 lines
99 KiB
HTML
2483 lines
99 KiB
HTML
<HTML>
|
|
<HEAD>
|
|
<!-- This HTML file has been created by texi2html 1.52b
|
|
from gperf.texi on 1 February 2009 -->
|
|
|
|
<META HTTP-EQUIV="content-type" CONTENT="text/html; charset=UTF-8">
|
|
<TITLE>Perfect Hash Function Generator</TITLE>
|
|
</HEAD>
|
|
<BODY>
|
|
<H1>User's Guide to <CODE>gperf</CODE> 3.0.4</H1>
|
|
<H2>The GNU Perfect Hash Function Generator</H2>
|
|
<H2>Edition 3.0.4, 1 February 2009</H2>
|
|
<ADDRESS>Douglas C. Schmidt</ADDRESS>
|
|
<ADDRESS>Bruno Haible</ADDRESS>
|
|
<P>
|
|
<P><HR><P>
|
|
<H1>Table of Contents</H1>
|
|
<UL>
|
|
<LI><A NAME="TOC1" HREF="gperf.html#SEC1">GNU GENERAL PUBLIC LICENSE</A>
|
|
<LI><A NAME="TOC2" HREF="gperf.html#SEC2">Contributors to GNU <CODE>gperf</CODE> Utility</A>
|
|
<LI><A NAME="TOC3" HREF="gperf.html#SEC3">2 Introduction</A>
|
|
<LI><A NAME="TOC4" HREF="gperf.html#SEC4">3 Static search structures and GNU <CODE>gperf</CODE></A>
|
|
<LI><A NAME="TOC5" HREF="gperf.html#SEC5">4 High-Level Description of GNU <CODE>gperf</CODE></A>
|
|
<UL>
|
|
<LI><A NAME="TOC6" HREF="gperf.html#SEC6">4.1 Input Format to <CODE>gperf</CODE></A>
|
|
<UL>
|
|
<LI><A NAME="TOC7" HREF="gperf.html#SEC7">4.1.1 Declarations</A>
|
|
<UL>
|
|
<LI><A NAME="TOC8" HREF="gperf.html#SEC8">4.1.1.1 User-supplied <CODE>struct</CODE></A>
|
|
<LI><A NAME="TOC9" HREF="gperf.html#SEC9">4.1.1.2 Gperf Declarations</A>
|
|
<LI><A NAME="TOC10" HREF="gperf.html#SEC10">4.1.1.3 C Code Inclusion</A>
|
|
</UL>
|
|
<LI><A NAME="TOC11" HREF="gperf.html#SEC11">4.1.2 Format for Keyword Entries</A>
|
|
<LI><A NAME="TOC12" HREF="gperf.html#SEC12">4.1.3 Including Additional C Functions</A>
|
|
<LI><A NAME="TOC13" HREF="gperf.html#SEC13">4.1.4 Where to place directives for GNU <CODE>indent</CODE>.</A>
|
|
</UL>
|
|
<LI><A NAME="TOC14" HREF="gperf.html#SEC14">4.2 Output Format for Generated C Code with <CODE>gperf</CODE></A>
|
|
<LI><A NAME="TOC15" HREF="gperf.html#SEC15">4.3 Use of NUL bytes</A>
|
|
<LI><A NAME="TOC16" HREF="gperf.html#SEC16">4.4 The Copyright of the Output</A>
|
|
</UL>
|
|
<LI><A NAME="TOC17" HREF="gperf.html#SEC17">5 Invoking <CODE>gperf</CODE></A>
|
|
<UL>
|
|
<LI><A NAME="TOC18" HREF="gperf.html#SEC18">5.1 Specifying the Location of the Output File</A>
|
|
<LI><A NAME="TOC19" HREF="gperf.html#SEC19">5.2 Options that affect Interpretation of the Input File</A>
|
|
<LI><A NAME="TOC20" HREF="gperf.html#SEC20">5.3 Options to specify the Language for the Output Code</A>
|
|
<LI><A NAME="TOC21" HREF="gperf.html#SEC21">5.4 Options for fine tuning Details in the Output Code</A>
|
|
<LI><A NAME="TOC22" HREF="gperf.html#SEC22">5.5 Options for changing the Algorithms employed by <CODE>gperf</CODE></A>
|
|
<LI><A NAME="TOC23" HREF="gperf.html#SEC23">5.6 Informative Output</A>
|
|
</UL>
|
|
<LI><A NAME="TOC24" HREF="gperf.html#SEC24">6 Known Bugs and Limitations with <CODE>gperf</CODE></A>
|
|
<LI><A NAME="TOC25" HREF="gperf.html#SEC25">7 Things Still Left to Do</A>
|
|
<LI><A NAME="TOC26" HREF="gperf.html#SEC26">8 Bibliography</A>
|
|
<LI><A NAME="TOC27" HREF="gperf.html#SEC27">Concept Index</A>
|
|
</UL>
|
|
<P><HR><P>
|
|
|
|
<P>
|
|
Copyright (C) 1989-2009 Free Software Foundation, Inc.
|
|
|
|
</P>
|
|
|
|
<P>
|
|
Permission is granted to make and distribute verbatim copies of
|
|
this manual provided the copyright notice and this permission notice
|
|
are preserved on all copies.
|
|
|
|
</P>
|
|
<P>
|
|
Permission is granted to copy and distribute modified versions of this
|
|
manual under the conditions for verbatim copying, provided also that the
|
|
section entitled “GNU General Public License” is included
|
|
exactly as in the original, and provided that the entire resulting
|
|
derived work is distributed under the terms of a permission notice
|
|
identical to this one.
|
|
|
|
</P>
|
|
<P>
|
|
Permission is granted to copy and distribute translations of this manual
|
|
into another language, under the above conditions for modified versions,
|
|
except that the section entitled “GNU General Public License” may be
|
|
included in a translation approved by the author instead of in the
|
|
original English.
|
|
|
|
</P>
|
|
|
|
|
|
|
|
<H1><A NAME="SEC1" HREF="gperf.html#TOC1">GNU GENERAL PUBLIC LICENSE</A></H1>
|
|
<P>
|
|
Version 3, 29 June 2007
|
|
|
|
</P>
|
|
|
|
|
|
<PRE>
|
|
Copyright (C) 2007 Free Software Foundation, Inc. <A HREF="http://fsf.org/">http://fsf.org/</A>
|
|
|
|
Everyone is permitted to copy and distribute verbatim copies of this
|
|
license document, but changing it is not allowed.
|
|
</PRE>
|
|
|
|
|
|
<H2>1.0 Preamble</H2>
|
|
|
|
<P>
|
|
The GNU General Public License is a free, copyleft license for
|
|
software and other kinds of works.
|
|
|
|
</P>
|
|
<P>
|
|
The licenses for most software and other practical works are designed
|
|
to take away your freedom to share and change the works. By contrast,
|
|
the GNU General Public License is intended to guarantee your freedom
|
|
to share and change all versions of a program--to make sure it remains
|
|
free software for all its users. We, the Free Software Foundation,
|
|
use the GNU General Public License for most of our software; it
|
|
applies also to any other work released this way by its authors. You
|
|
can apply it to your programs, too.
|
|
|
|
</P>
|
|
<P>
|
|
When we speak of free software, we are referring to freedom, not
|
|
price. Our General Public Licenses are designed to make sure that you
|
|
have the freedom to distribute copies of free software (and charge for
|
|
them if you wish), that you receive source code or can get it if you
|
|
want it, that you can change the software or use pieces of it in new
|
|
free programs, and that you know you can do these things.
|
|
|
|
</P>
|
|
<P>
|
|
To protect your rights, we need to prevent others from denying you
|
|
these rights or asking you to surrender the rights. Therefore, you
|
|
have certain responsibilities if you distribute copies of the
|
|
software, or if you modify it: responsibilities to respect the freedom
|
|
of others.
|
|
|
|
</P>
|
|
<P>
|
|
For example, if you distribute copies of such a program, whether
|
|
gratis or for a fee, you must pass on to the recipients the same
|
|
freedoms that you received. You must make sure that they, too,
|
|
receive or can get the source code. And you must show them these
|
|
terms so they know their rights.
|
|
|
|
</P>
|
|
<P>
|
|
Developers that use the GNU GPL protect your rights with two steps:
|
|
(1) assert copyright on the software, and (2) offer you this License
|
|
giving you legal permission to copy, distribute and/or modify it.
|
|
|
|
</P>
|
|
<P>
|
|
For the developers' and authors' protection, the GPL clearly explains
|
|
that there is no warranty for this free software. For both users' and
|
|
authors' sake, the GPL requires that modified versions be marked as
|
|
changed, so that their problems will not be attributed erroneously to
|
|
authors of previous versions.
|
|
|
|
</P>
|
|
<P>
|
|
Some devices are designed to deny users access to install or run
|
|
modified versions of the software inside them, although the
|
|
manufacturer can do so. This is fundamentally incompatible with the
|
|
aim of protecting users' freedom to change the software. The
|
|
systematic pattern of such abuse occurs in the area of products for
|
|
individuals to use, which is precisely where it is most unacceptable.
|
|
Therefore, we have designed this version of the GPL to prohibit the
|
|
practice for those products. If such problems arise substantially in
|
|
other domains, we stand ready to extend this provision to those
|
|
domains in future versions of the GPL, as needed to protect the
|
|
freedom of users.
|
|
|
|
</P>
|
|
<P>
|
|
Finally, every program is threatened constantly by software patents.
|
|
States should not allow patents to restrict development and use of
|
|
software on general-purpose computers, but in those that do, we wish
|
|
to avoid the special danger that patents applied to a free program
|
|
could make it effectively proprietary. To prevent this, the GPL
|
|
assures that patents cannot be used to render the program non-free.
|
|
|
|
</P>
|
|
<P>
|
|
The precise terms and conditions for copying, distribution and
|
|
modification follow.
|
|
|
|
</P>
|
|
|
|
<H2>1.1 TERMS AND CONDITIONS</H2>
|
|
|
|
|
|
<OL>
|
|
<LI>Definitions.
|
|
|
|
“This License” refers to version 3 of the GNU General Public License.
|
|
|
|
“Copyright” also means copyright-like laws that apply to other kinds
|
|
of works, such as semiconductor masks.
|
|
|
|
“The Program” refers to any copyrightable work licensed under this
|
|
License. Each licensee is addressed as “you”. “Licensees” and
|
|
“recipients” may be individuals or organizations.
|
|
|
|
To “modify” a work means to copy from or adapt all or part of the work
|
|
in a fashion requiring copyright permission, other than the making of
|
|
an exact copy. The resulting work is called a “modified version” of
|
|
the earlier work or a work “based on” the earlier work.
|
|
|
|
A “covered work” means either the unmodified Program or a work based
|
|
on the Program.
|
|
|
|
To “propagate” a work means to do anything with it that, without
|
|
permission, would make you directly or secondarily liable for
|
|
infringement under applicable copyright law, except executing it on a
|
|
computer or modifying a private copy. Propagation includes copying,
|
|
distribution (with or without modification), making available to the
|
|
public, and in some countries other activities as well.
|
|
|
|
To “convey” a work means any kind of propagation that enables other
|
|
parties to make or receive copies. Mere interaction with a user
|
|
through a computer network, with no transfer of a copy, is not
|
|
conveying.
|
|
|
|
An interactive user interface displays “Appropriate Legal Notices” to
|
|
the extent that it includes a convenient and prominently visible
|
|
feature that (1) displays an appropriate copyright notice, and (2)
|
|
tells the user that there is no warranty for the work (except to the
|
|
extent that warranties are provided), that licensees may convey the
|
|
work under this License, and how to view a copy of this License. If
|
|
the interface presents a list of user commands or options, such as a
|
|
menu, a prominent item in the list meets this criterion.
|
|
|
|
<LI>Source Code.
|
|
|
|
The “source code” for a work means the preferred form of the work for
|
|
making modifications to it. “Object code” means any non-source form
|
|
of a work.
|
|
|
|
A “Standard Interface” means an interface that either is an official
|
|
standard defined by a recognized standards body, or, in the case of
|
|
interfaces specified for a particular programming language, one that
|
|
is widely used among developers working in that language.
|
|
|
|
The “System Libraries” of an executable work include anything, other
|
|
than the work as a whole, that (a) is included in the normal form of
|
|
packaging a Major Component, but which is not part of that Major
|
|
Component, and (b) serves only to enable use of the work with that
|
|
Major Component, or to implement a Standard Interface for which an
|
|
implementation is available to the public in source code form. A
|
|
“Major Component”, in this context, means a major essential component
|
|
(kernel, window system, and so on) of the specific operating system
|
|
(if any) on which the executable work runs, or a compiler used to
|
|
produce the work, or an object code interpreter used to run it.
|
|
|
|
The “Corresponding Source” for a work in object code form means all
|
|
the source code needed to generate, install, and (for an executable
|
|
work) run the object code and to modify the work, including scripts to
|
|
control those activities. However, it does not include the work's
|
|
System Libraries, or general-purpose tools or generally available free
|
|
programs which are used unmodified in performing those activities but
|
|
which are not part of the work. For example, Corresponding Source
|
|
includes interface definition files associated with source files for
|
|
the work, and the source code for shared libraries and dynamically
|
|
linked subprograms that the work is specifically designed to require,
|
|
such as by intimate data communication or control flow between those
|
|
subprograms and other parts of the work.
|
|
|
|
The Corresponding Source need not include anything that users can
|
|
regenerate automatically from other parts of the Corresponding Source.
|
|
|
|
The Corresponding Source for a work in source code form is that same
|
|
work.
|
|
|
|
<LI>Basic Permissions.
|
|
|
|
All rights granted under this License are granted for the term of
|
|
copyright on the Program, and are irrevocable provided the stated
|
|
conditions are met. This License explicitly affirms your unlimited
|
|
permission to run the unmodified Program. The output from running a
|
|
covered work is covered by this License only if the output, given its
|
|
content, constitutes a covered work. This License acknowledges your
|
|
rights of fair use or other equivalent, as provided by copyright law.
|
|
|
|
You may make, run and propagate covered works that you do not convey,
|
|
without conditions so long as your license otherwise remains in force.
|
|
You may convey covered works to others for the sole purpose of having
|
|
them make modifications exclusively for you, or provide you with
|
|
facilities for running those works, provided that you comply with the
|
|
terms of this License in conveying all material for which you do not
|
|
control copyright. Those thus making or running the covered works for
|
|
you must do so exclusively on your behalf, under your direction and
|
|
control, on terms that prohibit them from making any copies of your
|
|
copyrighted material outside their relationship with you.
|
|
|
|
Conveying under any other circumstances is permitted solely under the
|
|
conditions stated below. Sublicensing is not allowed; section 10
|
|
makes it unnecessary.
|
|
|
|
<LI>Protecting Users' Legal Rights From Anti-Circumvention Law.
|
|
|
|
No covered work shall be deemed part of an effective technological
|
|
measure under any applicable law fulfilling obligations under article
|
|
11 of the WIPO copyright treaty adopted on 20 December 1996, or
|
|
similar laws prohibiting or restricting circumvention of such
|
|
measures.
|
|
|
|
When you convey a covered work, you waive any legal power to forbid
|
|
circumvention of technological measures to the extent such
|
|
circumvention is effected by exercising rights under this License with
|
|
respect to the covered work, and you disclaim any intention to limit
|
|
operation or modification of the work as a means of enforcing, against
|
|
the work's users, your or third parties' legal rights to forbid
|
|
circumvention of technological measures.
|
|
|
|
<LI>Conveying Verbatim Copies.
|
|
|
|
You may convey verbatim copies of the Program's source code as you
|
|
receive it, in any medium, provided that you conspicuously and
|
|
appropriately publish on each copy an appropriate copyright notice;
|
|
keep intact all notices stating that this License and any
|
|
non-permissive terms added in accord with section 7 apply to the code;
|
|
keep intact all notices of the absence of any warranty; and give all
|
|
recipients a copy of this License along with the Program.
|
|
|
|
You may charge any price or no price for each copy that you convey,
|
|
and you may offer support or warranty protection for a fee.
|
|
|
|
<LI>Conveying Modified Source Versions.
|
|
|
|
You may convey a work based on the Program, or the modifications to
|
|
produce it from the Program, in the form of source code under the
|
|
terms of section 4, provided that you also meet all of these
|
|
conditions:
|
|
|
|
|
|
<OL>
|
|
<LI>
|
|
|
|
The work must carry prominent notices stating that you modified it,
|
|
and giving a relevant date.
|
|
|
|
<LI>
|
|
|
|
The work must carry prominent notices stating that it is released
|
|
under this License and any conditions added under section 7. This
|
|
requirement modifies the requirement in section 4 to “keep intact all
|
|
notices”.
|
|
|
|
<LI>
|
|
|
|
You must license the entire work, as a whole, under this License to
|
|
anyone who comes into possession of a copy. This License will
|
|
therefore apply, along with any applicable section 7 additional terms,
|
|
to the whole of the work, and all its parts, regardless of how they
|
|
are packaged. This License gives no permission to license the work in
|
|
any other way, but it does not invalidate such permission if you have
|
|
separately received it.
|
|
|
|
<LI>
|
|
|
|
If the work has interactive user interfaces, each must display
|
|
Appropriate Legal Notices; however, if the Program has interactive
|
|
interfaces that do not display Appropriate Legal Notices, your work
|
|
need not make them do so.
|
|
</OL>
|
|
|
|
A compilation of a covered work with other separate and independent
|
|
works, which are not by their nature extensions of the covered work,
|
|
and which are not combined with it such as to form a larger program,
|
|
in or on a volume of a storage or distribution medium, is called an
|
|
“aggregate” if the compilation and its resulting copyright are not
|
|
used to limit the access or legal rights of the compilation's users
|
|
beyond what the individual works permit. Inclusion of a covered work
|
|
in an aggregate does not cause this License to apply to the other
|
|
parts of the aggregate.
|
|
|
|
<LI>Conveying Non-Source Forms.
|
|
|
|
You may convey a covered work in object code form under the terms of
|
|
sections 4 and 5, provided that you also convey the machine-readable
|
|
Corresponding Source under the terms of this License, in one of these
|
|
ways:
|
|
|
|
|
|
<OL>
|
|
<LI>
|
|
|
|
Convey the object code in, or embodied in, a physical product
|
|
(including a physical distribution medium), accompanied by the
|
|
Corresponding Source fixed on a durable physical medium customarily
|
|
used for software interchange.
|
|
|
|
<LI>
|
|
|
|
Convey the object code in, or embodied in, a physical product
|
|
(including a physical distribution medium), accompanied by a written
|
|
offer, valid for at least three years and valid for as long as you
|
|
offer spare parts or customer support for that product model, to give
|
|
anyone who possesses the object code either (1) a copy of the
|
|
Corresponding Source for all the software in the product that is
|
|
covered by this License, on a durable physical medium customarily used
|
|
for software interchange, for a price no more than your reasonable
|
|
cost of physically performing this conveying of source, or (2) access
|
|
to copy the Corresponding Source from a network server at no charge.
|
|
|
|
<LI>
|
|
|
|
Convey individual copies of the object code with a copy of the written
|
|
offer to provide the Corresponding Source. This alternative is
|
|
allowed only occasionally and noncommercially, and only if you
|
|
received the object code with such an offer, in accord with subsection
|
|
6b.
|
|
|
|
<LI>
|
|
|
|
Convey the object code by offering access from a designated place
|
|
(gratis or for a charge), and offer equivalent access to the
|
|
Corresponding Source in the same way through the same place at no
|
|
further charge. You need not require recipients to copy the
|
|
Corresponding Source along with the object code. If the place to copy
|
|
the object code is a network server, the Corresponding Source may be
|
|
on a different server (operated by you or a third party) that supports
|
|
equivalent copying facilities, provided you maintain clear directions
|
|
next to the object code saying where to find the Corresponding Source.
|
|
Regardless of what server hosts the Corresponding Source, you remain
|
|
obligated to ensure that it is available for as long as needed to
|
|
satisfy these requirements.
|
|
|
|
<LI>
|
|
|
|
Convey the object code using peer-to-peer transmission, provided you
|
|
inform other peers where the object code and Corresponding Source of
|
|
the work are being offered to the general public at no charge under
|
|
subsection 6d.
|
|
|
|
</OL>
|
|
|
|
A separable portion of the object code, whose source code is excluded
|
|
from the Corresponding Source as a System Library, need not be
|
|
included in conveying the object code work.
|
|
|
|
A “User Product” is either (1) a “consumer product”, which means any
|
|
tangible personal property which is normally used for personal,
|
|
family, or household purposes, or (2) anything designed or sold for
|
|
incorporation into a dwelling. In determining whether a product is a
|
|
consumer product, doubtful cases shall be resolved in favor of
|
|
coverage. For a particular product received by a particular user,
|
|
“normally used” refers to a typical or common use of that class of
|
|
product, regardless of the status of the particular user or of the way
|
|
in which the particular user actually uses, or expects or is expected
|
|
to use, the product. A product is a consumer product regardless of
|
|
whether the product has substantial commercial, industrial or
|
|
non-consumer uses, unless such uses represent the only significant
|
|
mode of use of the product.
|
|
|
|
“Installation Information” for a User Product means any methods,
|
|
procedures, authorization keys, or other information required to
|
|
install and execute modified versions of a covered work in that User
|
|
Product from a modified version of its Corresponding Source. The
|
|
information must suffice to ensure that the continued functioning of
|
|
the modified object code is in no case prevented or interfered with
|
|
solely because modification has been made.
|
|
|
|
If you convey an object code work under this section in, or with, or
|
|
specifically for use in, a User Product, and the conveying occurs as
|
|
part of a transaction in which the right of possession and use of the
|
|
User Product is transferred to the recipient in perpetuity or for a
|
|
fixed term (regardless of how the transaction is characterized), the
|
|
Corresponding Source conveyed under this section must be accompanied
|
|
by the Installation Information. But this requirement does not apply
|
|
if neither you nor any third party retains the ability to install
|
|
modified object code on the User Product (for example, the work has
|
|
been installed in ROM).
|
|
|
|
The requirement to provide Installation Information does not include a
|
|
requirement to continue to provide support service, warranty, or
|
|
updates for a work that has been modified or installed by the
|
|
recipient, or for the User Product in which it has been modified or
|
|
installed. Access to a network may be denied when the modification
|
|
itself materially and adversely affects the operation of the network
|
|
or violates the rules and protocols for communication across the
|
|
network.
|
|
|
|
Corresponding Source conveyed, and Installation Information provided,
|
|
in accord with this section must be in a format that is publicly
|
|
documented (and with an implementation available to the public in
|
|
source code form), and must require no special password or key for
|
|
unpacking, reading or copying.
|
|
|
|
<LI>Additional Terms.
|
|
|
|
“Additional permissions” are terms that supplement the terms of this
|
|
License by making exceptions from one or more of its conditions.
|
|
Additional permissions that are applicable to the entire Program shall
|
|
be treated as though they were included in this License, to the extent
|
|
that they are valid under applicable law. If additional permissions
|
|
apply only to part of the Program, that part may be used separately
|
|
under those permissions, but the entire Program remains governed by
|
|
this License without regard to the additional permissions.
|
|
|
|
When you convey a copy of a covered work, you may at your option
|
|
remove any additional permissions from that copy, or from any part of
|
|
it. (Additional permissions may be written to require their own
|
|
removal in certain cases when you modify the work.) You may place
|
|
additional permissions on material, added by you to a covered work,
|
|
for which you have or can give appropriate copyright permission.
|
|
|
|
Notwithstanding any other provision of this License, for material you
|
|
add to a covered work, you may (if authorized by the copyright holders
|
|
of that material) supplement the terms of this License with terms:
|
|
|
|
|
|
<OL>
|
|
<LI>
|
|
|
|
Disclaiming warranty or limiting liability differently from the terms
|
|
of sections 15 and 16 of this License; or
|
|
|
|
<LI>
|
|
|
|
Requiring preservation of specified reasonable legal notices or author
|
|
attributions in that material or in the Appropriate Legal Notices
|
|
displayed by works containing it; or
|
|
|
|
<LI>
|
|
|
|
Prohibiting misrepresentation of the origin of that material, or
|
|
requiring that modified versions of such material be marked in
|
|
reasonable ways as different from the original version; or
|
|
|
|
<LI>
|
|
|
|
Limiting the use for publicity purposes of names of licensors or
|
|
authors of the material; or
|
|
|
|
<LI>
|
|
|
|
Declining to grant rights under trademark law for use of some trade
|
|
names, trademarks, or service marks; or
|
|
|
|
<LI>
|
|
|
|
Requiring indemnification of licensors and authors of that material by
|
|
anyone who conveys the material (or modified versions of it) with
|
|
contractual assumptions of liability to the recipient, for any
|
|
liability that these contractual assumptions directly impose on those
|
|
licensors and authors.
|
|
</OL>
|
|
|
|
All other non-permissive additional terms are considered “further
|
|
restrictions” within the meaning of section 10. If the Program as you
|
|
received it, or any part of it, contains a notice stating that it is
|
|
governed by this License along with a term that is a further
|
|
restriction, you may remove that term. If a license document contains
|
|
a further restriction but permits relicensing or conveying under this
|
|
License, you may add to a covered work material governed by the terms
|
|
of that license document, provided that the further restriction does
|
|
not survive such relicensing or conveying.
|
|
|
|
If you add terms to a covered work in accord with this section, you
|
|
must place, in the relevant source files, a statement of the
|
|
additional terms that apply to those files, or a notice indicating
|
|
where to find the applicable terms.
|
|
|
|
Additional terms, permissive or non-permissive, may be stated in the
|
|
form of a separately written license, or stated as exceptions; the
|
|
above requirements apply either way.
|
|
|
|
<LI>Termination.
|
|
|
|
You may not propagate or modify a covered work except as expressly
|
|
provided under this License. Any attempt otherwise to propagate or
|
|
modify it is void, and will automatically terminate your rights under
|
|
this License (including any patent licenses granted under the third
|
|
paragraph of section 11).
|
|
|
|
However, if you cease all violation of this License, then your license
|
|
from a particular copyright holder is reinstated (a) provisionally,
|
|
unless and until the copyright holder explicitly and finally
|
|
terminates your license, and (b) permanently, if the copyright holder
|
|
fails to notify you of the violation by some reasonable means prior to
|
|
60 days after the cessation.
|
|
|
|
Moreover, your license from a particular copyright holder is
|
|
reinstated permanently if the copyright holder notifies you of the
|
|
violation by some reasonable means, this is the first time you have
|
|
received notice of violation of this License (for any work) from that
|
|
copyright holder, and you cure the violation prior to 30 days after
|
|
your receipt of the notice.
|
|
|
|
Termination of your rights under this section does not terminate the
|
|
licenses of parties who have received copies or rights from you under
|
|
this License. If your rights have been terminated and not permanently
|
|
reinstated, you do not qualify to receive new licenses for the same
|
|
material under section 10.
|
|
|
|
<LI>Acceptance Not Required for Having Copies.
|
|
|
|
You are not required to accept this License in order to receive or run
|
|
a copy of the Program. Ancillary propagation of a covered work
|
|
occurring solely as a consequence of using peer-to-peer transmission
|
|
to receive a copy likewise does not require acceptance. However,
|
|
nothing other than this License grants you permission to propagate or
|
|
modify any covered work. These actions infringe copyright if you do
|
|
not accept this License. Therefore, by modifying or propagating a
|
|
covered work, you indicate your acceptance of this License to do so.
|
|
|
|
<LI>Automatic Licensing of Downstream Recipients.
|
|
|
|
Each time you convey a covered work, the recipient automatically
|
|
receives a license from the original licensors, to run, modify and
|
|
propagate that work, subject to this License. You are not responsible
|
|
for enforcing compliance by third parties with this License.
|
|
|
|
An “entity transaction” is a transaction transferring control of an
|
|
organization, or substantially all assets of one, or subdividing an
|
|
organization, or merging organizations. If propagation of a covered
|
|
work results from an entity transaction, each party to that
|
|
transaction who receives a copy of the work also receives whatever
|
|
licenses to the work the party's predecessor in interest had or could
|
|
give under the previous paragraph, plus a right to possession of the
|
|
Corresponding Source of the work from the predecessor in interest, if
|
|
the predecessor has it or can get it with reasonable efforts.
|
|
|
|
You may not impose any further restrictions on the exercise of the
|
|
rights granted or affirmed under this License. For example, you may
|
|
not impose a license fee, royalty, or other charge for exercise of
|
|
rights granted under this License, and you may not initiate litigation
|
|
(including a cross-claim or counterclaim in a lawsuit) alleging that
|
|
any patent claim is infringed by making, using, selling, offering for
|
|
sale, or importing the Program or any portion of it.
|
|
|
|
<LI>Patents.
|
|
|
|
A “contributor” is a copyright holder who authorizes use under this
|
|
License of the Program or a work on which the Program is based. The
|
|
work thus licensed is called the contributor's “contributor version”.
|
|
|
|
A contributor's “essential patent claims” are all patent claims owned
|
|
or controlled by the contributor, whether already acquired or
|
|
hereafter acquired, that would be infringed by some manner, permitted
|
|
by this License, of making, using, or selling its contributor version,
|
|
but do not include claims that would be infringed only as a
|
|
consequence of further modification of the contributor version. For
|
|
purposes of this definition, “control” includes the right to grant
|
|
patent sublicenses in a manner consistent with the requirements of
|
|
this License.
|
|
|
|
Each contributor grants you a non-exclusive, worldwide, royalty-free
|
|
patent license under the contributor's essential patent claims, to
|
|
make, use, sell, offer for sale, import and otherwise run, modify and
|
|
propagate the contents of its contributor version.
|
|
|
|
In the following three paragraphs, a “patent license” is any express
|
|
agreement or commitment, however denominated, not to enforce a patent
|
|
(such as an express permission to practice a patent or covenant not to
|
|
sue for patent infringement). To “grant” such a patent license to a
|
|
party means to make such an agreement or commitment not to enforce a
|
|
patent against the party.
|
|
|
|
If you convey a covered work, knowingly relying on a patent license,
|
|
and the Corresponding Source of the work is not available for anyone
|
|
to copy, free of charge and under the terms of this License, through a
|
|
publicly available network server or other readily accessible means,
|
|
then you must either (1) cause the Corresponding Source to be so
|
|
available, or (2) arrange to deprive yourself of the benefit of the
|
|
patent license for this particular work, or (3) arrange, in a manner
|
|
consistent with the requirements of this License, to extend the patent
|
|
license to downstream recipients. “Knowingly relying” means you have
|
|
actual knowledge that, but for the patent license, your conveying the
|
|
covered work in a country, or your recipient's use of the covered work
|
|
in a country, would infringe one or more identifiable patents in that
|
|
country that you have reason to believe are valid.
|
|
|
|
If, pursuant to or in connection with a single transaction or
|
|
arrangement, you convey, or propagate by procuring conveyance of, a
|
|
covered work, and grant a patent license to some of the parties
|
|
receiving the covered work authorizing them to use, propagate, modify
|
|
or convey a specific copy of the covered work, then the patent license
|
|
you grant is automatically extended to all recipients of the covered
|
|
work and works based on it.
|
|
|
|
A patent license is “discriminatory” if it does not include within the
|
|
scope of its coverage, prohibits the exercise of, or is conditioned on
|
|
the non-exercise of one or more of the rights that are specifically
|
|
granted under this License. You may not convey a covered work if you
|
|
are a party to an arrangement with a third party that is in the
|
|
business of distributing software, under which you make payment to the
|
|
third party based on the extent of your activity of conveying the
|
|
work, and under which the third party grants, to any of the parties
|
|
who would receive the covered work from you, a discriminatory patent
|
|
license (a) in connection with copies of the covered work conveyed by
|
|
you (or copies made from those copies), or (b) primarily for and in
|
|
connection with specific products or compilations that contain the
|
|
covered work, unless you entered into that arrangement, or that patent
|
|
license was granted, prior to 28 March 2007.
|
|
|
|
Nothing in this License shall be construed as excluding or limiting
|
|
any implied license or other defenses to infringement that may
|
|
otherwise be available to you under applicable patent law.
|
|
|
|
<LI>No Surrender of Others' Freedom.
|
|
|
|
If conditions are imposed on you (whether by court order, agreement or
|
|
otherwise) that contradict the conditions of this License, they do not
|
|
excuse you from the conditions of this License. If you cannot convey
|
|
a covered work so as to satisfy simultaneously your obligations under
|
|
this License and any other pertinent obligations, then as a
|
|
consequence you may not convey it at all. For example, if you agree
|
|
to terms that obligate you to collect a royalty for further conveying
|
|
from those to whom you convey the Program, the only way you could
|
|
satisfy both those terms and this License would be to refrain entirely
|
|
from conveying the Program.
|
|
|
|
<LI>Use with the GNU Affero General Public License.
|
|
|
|
Notwithstanding any other provision of this License, you have
|
|
permission to link or combine any covered work with a work licensed
|
|
under version 3 of the GNU Affero General Public License into a single
|
|
combined work, and to convey the resulting work. The terms of this
|
|
License will continue to apply to the part which is the covered work,
|
|
but the special requirements of the GNU Affero General Public License,
|
|
section 13, concerning interaction through a network will apply to the
|
|
combination as such.
|
|
|
|
<LI>Revised Versions of this License.
|
|
|
|
The Free Software Foundation may publish revised and/or new versions
|
|
of the GNU General Public License from time to time. Such new
|
|
versions will be similar in spirit to the present version, but may
|
|
differ in detail to address new problems or concerns.
|
|
|
|
Each version is given a distinguishing version number. If the Program
|
|
specifies that a certain numbered version of the GNU General Public
|
|
License “or any later version” applies to it, you have the option of
|
|
following the terms and conditions either of that numbered version or
|
|
of any later version published by the Free Software Foundation. If
|
|
the Program does not specify a version number of the GNU General
|
|
Public License, you may choose any version ever published by the Free
|
|
Software Foundation.
|
|
|
|
If the Program specifies that a proxy can decide which future versions
|
|
of the GNU General Public License can be used, that proxy's public
|
|
statement of acceptance of a version permanently authorizes you to
|
|
choose that version for the Program.
|
|
|
|
Later license versions may give you additional or different
|
|
permissions. However, no additional obligations are imposed on any
|
|
author or copyright holder as a result of your choosing to follow a
|
|
later version.
|
|
|
|
<LI>Disclaimer of Warranty.
|
|
|
|
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
|
|
APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
|
|
HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT
|
|
WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT
|
|
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
|
A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND
|
|
PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE
|
|
DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR
|
|
CORRECTION.
|
|
|
|
<LI>Limitation of Liability.
|
|
|
|
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
|
|
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR
|
|
CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
|
|
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES
|
|
ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT
|
|
NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR
|
|
LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM
|
|
TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER
|
|
PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
|
|
|
|
<LI>Interpretation of Sections 15 and 16.
|
|
|
|
If the disclaimer of warranty and limitation of liability provided
|
|
above cannot be given local legal effect according to their terms,
|
|
reviewing courts shall apply local law that most closely approximates
|
|
an absolute waiver of all civil liability in connection with the
|
|
Program, unless a warranty or assumption of liability accompanies a
|
|
copy of the Program in return for a fee.
|
|
|
|
</OL>
|
|
|
|
|
|
<H2>1.2 END OF TERMS AND CONDITIONS</H2>
|
|
|
|
|
|
<H2>1.3 How to Apply These Terms to Your New Programs</H2>
|
|
|
|
<P>
|
|
If you develop a new program, and you want it to be of the greatest
|
|
possible use to the public, the best way to achieve this is to make it
|
|
free software which everyone can redistribute and change under these
|
|
terms.
|
|
|
|
</P>
|
|
<P>
|
|
To do so, attach the following notices to the program. It is safest
|
|
to attach them to the start of each source file to most effectively
|
|
state the exclusion of warranty; and each file should have at least
|
|
the “copyright” line and a pointer to where the full notice is found.
|
|
|
|
</P>
|
|
|
|
<PRE>
|
|
<VAR>one line to give the program's name and a brief idea of what it does.</VAR>
|
|
Copyright (C) <VAR>year</VAR> <VAR>name of author</VAR>
|
|
|
|
This program is free software: you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation, either version 3 of the License, or (at
|
|
your option) any later version.
|
|
|
|
This program is distributed in the hope that it will be useful, but
|
|
WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program. If not, see <A HREF="http://www.gnu.org/licenses/">http://www.gnu.org/licenses/</A>.
|
|
</PRE>
|
|
|
|
<P>
|
|
Also add information on how to contact you by electronic and paper mail.
|
|
|
|
</P>
|
|
<P>
|
|
If the program does terminal interaction, make it output a short
|
|
notice like this when it starts in an interactive mode:
|
|
|
|
</P>
|
|
|
|
<PRE>
|
|
<VAR>program</VAR> Copyright (C) <VAR>year</VAR> <VAR>name of author</VAR>
|
|
This program comes with ABSOLUTELY NO WARRANTY; for details type <SAMP>‘show w’</SAMP>.
|
|
This is free software, and you are welcome to redistribute it
|
|
under certain conditions; type <SAMP>‘show c’</SAMP> for details.
|
|
</PRE>
|
|
|
|
<P>
|
|
The hypothetical commands <SAMP>‘show w’</SAMP> and <SAMP>‘show c’</SAMP> should show
|
|
the appropriate parts of the General Public License. Of course, your
|
|
program's commands might be different; for a GUI interface, you would
|
|
use an “about box”.
|
|
|
|
</P>
|
|
<P>
|
|
You should also get your employer (if you work as a programmer) or school,
|
|
if any, to sign a “copyright disclaimer” for the program, if necessary.
|
|
For more information on this, and how to apply and follow the GNU GPL, see
|
|
<A HREF="http://www.gnu.org/licenses/">http://www.gnu.org/licenses/</A>.
|
|
|
|
</P>
|
|
<P>
|
|
The GNU General Public License does not permit incorporating your
|
|
program into proprietary programs. If your program is a subroutine
|
|
library, you may consider it more useful to permit linking proprietary
|
|
applications with the library. If this is what you want to do, use
|
|
the GNU Lesser General Public License instead of this License. But
|
|
first, please read <A HREF="http://www.gnu.org/philosophy/why-not-lgpl.html">http://www.gnu.org/philosophy/why-not-lgpl.html</A>.
|
|
|
|
</P>
|
|
|
|
|
|
<H1><A NAME="SEC2" HREF="gperf.html#TOC2">Contributors to GNU <CODE>gperf</CODE> Utility</A></H1>
|
|
|
|
|
|
<UL>
|
|
<LI>
|
|
|
|
<A NAME="IDX1"></A>
|
|
The GNU <CODE>gperf</CODE> perfect hash function generator utility was
|
|
written in GNU C++ by Douglas C. Schmidt. The general
|
|
idea for the perfect hash function generator was inspired by Keith
|
|
Bostic's algorithm written in C, and distributed to net.sources around
|
|
1984. The current program is a heavily modified, enhanced, and extended
|
|
implementation of Keith's basic idea, created at the University of
|
|
California, Irvine. Bugs, patches, and suggestions should be reported
|
|
to <CODE><bug-gnu-gperf@gnu.org></CODE>.
|
|
|
|
<LI>
|
|
|
|
Special thanks is extended to Michael Tiemann and Doug Lea, for
|
|
providing a useful compiler, and for giving me a forum to exhibit my
|
|
creation.
|
|
|
|
In addition, Adam de Boor and Nels Olson provided many tips and insights
|
|
that greatly helped improve the quality and functionality of <CODE>gperf</CODE>.
|
|
|
|
<LI>
|
|
|
|
Bruno Haible enhanced and optimized the search algorithm. He also rewrote
|
|
the input routines and the output routines for better reliability, and
|
|
added a testsuite.
|
|
</UL>
|
|
|
|
|
|
|
|
<H1><A NAME="SEC3" HREF="gperf.html#TOC3">2 Introduction</A></H1>
|
|
|
|
<P>
|
|
<CODE>gperf</CODE> is a perfect hash function generator written in C++. It
|
|
transforms an <VAR>n</VAR> element user-specified keyword set <VAR>W</VAR> into a
|
|
perfect hash function <VAR>F</VAR>. <VAR>F</VAR> uniquely maps keywords in
|
|
<VAR>W</VAR> onto the range 0..<VAR>k</VAR>, where <VAR>k</VAR> >= <VAR>n-1</VAR>. If <VAR>k</VAR>
|
|
= <VAR>n-1</VAR> then <VAR>F</VAR> is a <EM>minimal</EM> perfect hash function.
|
|
<CODE>gperf</CODE> generates a 0..<VAR>k</VAR> element static lookup table and a
|
|
pair of C functions. These functions determine whether a given
|
|
character string <VAR>s</VAR> occurs in <VAR>W</VAR>, using at most one probe into
|
|
the lookup table.
|
|
|
|
</P>
|
|
<P>
|
|
<CODE>gperf</CODE> currently generates the reserved keyword recognizer for
|
|
lexical analyzers in several production and research compilers and
|
|
language processing tools, including GNU C, GNU C++, GNU Java, GNU Pascal,
|
|
GNU Modula 3, and GNU indent. Complete C++ source code for <CODE>gperf</CODE> is
|
|
available from <CODE>http://ftp.gnu.org/pub/gnu/gperf/</CODE>.
|
|
A paper describing <CODE>gperf</CODE>'s design and implementation in greater
|
|
detail is available in the Second USENIX C++ Conference proceedings
|
|
or from <CODE>http://www.cs.wustl.edu/~schmidt/resume.html</CODE>.
|
|
|
|
</P>
|
|
|
|
|
|
<H1><A NAME="SEC4" HREF="gperf.html#TOC4">3 Static search structures and GNU <CODE>gperf</CODE></A></H1>
|
|
<P>
|
|
<A NAME="IDX2"></A>
|
|
|
|
</P>
|
|
<P>
|
|
A <EM>static search structure</EM> is an Abstract Data Type with certain
|
|
fundamental operations, e.g., <EM>initialize</EM>, <EM>insert</EM>,
|
|
and <EM>retrieve</EM>. Conceptually, all insertions occur before any
|
|
retrievals. In practice, <CODE>gperf</CODE> generates a <EM>static</EM> array
|
|
containing search set keywords and any associated attributes specified
|
|
by the user. Thus, there is essentially no execution-time cost for the
|
|
insertions. It is a useful data structure for representing <EM>static
|
|
search sets</EM>. Static search sets occur frequently in software system
|
|
applications. Typical static search sets include compiler reserved
|
|
words, assembler instruction opcodes, and built-in shell interpreter
|
|
commands. Search set members, called <EM>keywords</EM>, are inserted into
|
|
the structure only once, usually during program initialization, and are
|
|
not generally modified at run-time.
|
|
|
|
</P>
|
|
<P>
|
|
Numerous static search structure implementations exist, e.g.,
|
|
arrays, linked lists, binary search trees, digital search tries, and
|
|
hash tables. Different approaches offer trade-offs between space
|
|
utilization and search time efficiency. For example, an <VAR>n</VAR> element
|
|
sorted array is space efficient, though the average-case time
|
|
complexity for retrieval operations using binary search is
|
|
proportional to log <VAR>n</VAR>. Conversely, hash table implementations
|
|
often locate a table entry in constant time, but typically impose
|
|
additional memory overhead and exhibit poor worst case performance.
|
|
|
|
</P>
|
|
<P>
|
|
<A NAME="IDX3"></A>
|
|
<EM>Minimal perfect hash functions</EM> provide an optimal solution for a
|
|
particular class of static search sets. A minimal perfect hash
|
|
function is defined by two properties:
|
|
|
|
</P>
|
|
|
|
<UL>
|
|
<LI>
|
|
|
|
It allows keyword recognition in a static search set using at most
|
|
<EM>one</EM> probe into the hash table. This represents the “perfect”
|
|
property.
|
|
<LI>
|
|
|
|
The actual memory allocated to store the keywords is precisely large
|
|
enough for the keyword set, and <EM>no larger</EM>. This is the
|
|
“minimal” property.
|
|
</UL>
|
|
|
|
<P>
|
|
For most applications it is far easier to generate <EM>perfect</EM> hash
|
|
functions than <EM>minimal perfect</EM> hash functions. Moreover,
|
|
non-minimal perfect hash functions frequently execute faster than
|
|
minimal ones in practice. This phenomena occurs since searching a
|
|
sparse keyword table increases the probability of locating a “null”
|
|
entry, thereby reducing string comparisons. <CODE>gperf</CODE>'s default
|
|
behavior generates <EM>near-minimal</EM> perfect hash functions for
|
|
keyword sets. However, <CODE>gperf</CODE> provides many options that permit
|
|
user control over the degree of minimality and perfection.
|
|
|
|
</P>
|
|
<P>
|
|
Static search sets often exhibit relative stability over time. For
|
|
example, Ada's 63 reserved words have remained constant for nearly a
|
|
decade. It is therefore frequently worthwhile to expend concerted
|
|
effort building an optimal search structure <EM>once</EM>, if it
|
|
subsequently receives heavy use multiple times. <CODE>gperf</CODE> removes
|
|
the drudgery associated with constructing time- and space-efficient
|
|
search structures by hand. It has proven a useful and practical tool
|
|
for serious programming projects. Output from <CODE>gperf</CODE> is currently
|
|
used in several production and research compilers, including GNU C, GNU
|
|
C++, GNU Java, GNU Pascal, and GNU Modula 3. The latter two compilers are
|
|
not yet part of the official GNU distribution. Each compiler utilizes
|
|
<CODE>gperf</CODE> to automatically generate static search structures that
|
|
efficiently identify their respective reserved keywords.
|
|
|
|
</P>
|
|
|
|
|
|
<H1><A NAME="SEC5" HREF="gperf.html#TOC5">4 High-Level Description of GNU <CODE>gperf</CODE></A></H1>
|
|
|
|
<P>
|
|
The perfect hash function generator <CODE>gperf</CODE> reads a set of
|
|
“keywords” from an input file (or from the standard input by
|
|
default). It attempts to derive a perfect hashing function that
|
|
recognizes a member of the <EM>static keyword set</EM> with at most a
|
|
single probe into the lookup table. If <CODE>gperf</CODE> succeeds in
|
|
generating such a function it produces a pair of C source code routines
|
|
that perform hashing and table lookup recognition. All generated C code
|
|
is directed to the standard output. Command-line options described
|
|
below allow you to modify the input and output format to <CODE>gperf</CODE>.
|
|
|
|
</P>
|
|
<P>
|
|
By default, <CODE>gperf</CODE> attempts to produce time-efficient code, with
|
|
less emphasis on efficient space utilization. However, several options
|
|
exist that permit trading-off execution time for storage space and vice
|
|
versa. In particular, expanding the generated table size produces a
|
|
sparse search structure, generally yielding faster searches.
|
|
Conversely, you can direct <CODE>gperf</CODE> to utilize a C <CODE>switch</CODE>
|
|
statement scheme that minimizes data space storage size. Furthermore,
|
|
using a C <CODE>switch</CODE> may actually speed up the keyword retrieval time
|
|
somewhat. Actual results depend on your C compiler, of course.
|
|
|
|
</P>
|
|
<P>
|
|
In general, <CODE>gperf</CODE> assigns values to the bytes it is using
|
|
for hashing until some set of values gives each keyword a unique value.
|
|
A helpful heuristic is that the larger the hash value range, the easier
|
|
it is for <CODE>gperf</CODE> to find and generate a perfect hash function.
|
|
Experimentation is the key to getting the most from <CODE>gperf</CODE>.
|
|
|
|
</P>
|
|
|
|
|
|
<H2><A NAME="SEC6" HREF="gperf.html#TOC6">4.1 Input Format to <CODE>gperf</CODE></A></H2>
|
|
<P>
|
|
<A NAME="IDX4"></A>
|
|
<A NAME="IDX5"></A>
|
|
<A NAME="IDX6"></A>
|
|
<A NAME="IDX7"></A>
|
|
You can control the input file format by varying certain command-line
|
|
arguments, in particular the <SAMP>‘-t’</SAMP> option. The input's appearance
|
|
is similar to GNU utilities <CODE>flex</CODE> and <CODE>bison</CODE> (or UNIX
|
|
utilities <CODE>lex</CODE> and <CODE>yacc</CODE>). Here's an outline of the general
|
|
format:
|
|
|
|
</P>
|
|
|
|
<PRE>
|
|
declarations
|
|
%%
|
|
keywords
|
|
%%
|
|
functions
|
|
</PRE>
|
|
|
|
<P>
|
|
<EM>Unlike</EM> <CODE>flex</CODE> or <CODE>bison</CODE>, the declarations section and
|
|
the functions section are optional. The following sections describe the
|
|
input format for each section.
|
|
|
|
</P>
|
|
|
|
<P>
|
|
It is possible to omit the declaration section entirely, if the <SAMP>‘-t’</SAMP>
|
|
option is not given. In this case the input file begins directly with the
|
|
first keyword line, e.g.:
|
|
|
|
</P>
|
|
|
|
<PRE>
|
|
january
|
|
february
|
|
march
|
|
april
|
|
...
|
|
</PRE>
|
|
|
|
|
|
|
|
<H3><A NAME="SEC7" HREF="gperf.html#TOC7">4.1.1 Declarations</A></H3>
|
|
|
|
<P>
|
|
The keyword input file optionally contains a section for including
|
|
arbitrary C declarations and definitions, <CODE>gperf</CODE> declarations that
|
|
act like command-line options, as well as for providing a user-supplied
|
|
<CODE>struct</CODE>.
|
|
|
|
</P>
|
|
|
|
|
|
|
|
<H4><A NAME="SEC8" HREF="gperf.html#TOC8">4.1.1.1 User-supplied <CODE>struct</CODE></A></H4>
|
|
|
|
<P>
|
|
If the <SAMP>‘-t’</SAMP> option (or, equivalently, the <SAMP>‘%struct-type’</SAMP> declaration)
|
|
<EM>is</EM> enabled, you <EM>must</EM> provide a C <CODE>struct</CODE> as the last
|
|
component in the declaration section from the input file. The first
|
|
field in this struct must be of type <CODE>char *</CODE> or <CODE>const char *</CODE>
|
|
if the <SAMP>‘-P’</SAMP> option is not given, or of type <CODE>int</CODE> if the option
|
|
<SAMP>‘-P’</SAMP> (or, equivalently, the <SAMP>‘%pic’</SAMP> declaration) is enabled.
|
|
This first field must be called <SAMP>‘name’</SAMP>, although it is possible to modify
|
|
its name with the <SAMP>‘-K’</SAMP> option (or, equivalently, the
|
|
<SAMP>‘%define slot-name’</SAMP> declaration) described below.
|
|
|
|
</P>
|
|
<P>
|
|
Here is a simple example, using months of the year and their attributes as
|
|
input:
|
|
|
|
</P>
|
|
|
|
<PRE>
|
|
struct month { char *name; int number; int days; int leap_days; };
|
|
%%
|
|
january, 1, 31, 31
|
|
february, 2, 28, 29
|
|
march, 3, 31, 31
|
|
april, 4, 30, 30
|
|
may, 5, 31, 31
|
|
june, 6, 30, 30
|
|
july, 7, 31, 31
|
|
august, 8, 31, 31
|
|
september, 9, 30, 30
|
|
october, 10, 31, 31
|
|
november, 11, 30, 30
|
|
december, 12, 31, 31
|
|
</PRE>
|
|
|
|
<P>
|
|
<A NAME="IDX8"></A>
|
|
Separating the <CODE>struct</CODE> declaration from the list of keywords and
|
|
other fields are a pair of consecutive percent signs, <SAMP>‘%%’</SAMP>,
|
|
appearing left justified in the first column, as in the UNIX utility
|
|
<CODE>lex</CODE>.
|
|
|
|
</P>
|
|
<P>
|
|
If the <CODE>struct</CODE> has already been declared in an include file, it can
|
|
be mentioned in an abbreviated form, like this:
|
|
|
|
</P>
|
|
|
|
<PRE>
|
|
struct month;
|
|
%%
|
|
january, 1, 31, 31
|
|
...
|
|
</PRE>
|
|
|
|
|
|
|
|
<H4><A NAME="SEC9" HREF="gperf.html#TOC9">4.1.1.2 Gperf Declarations</A></H4>
|
|
|
|
<P>
|
|
The declaration section can contain <CODE>gperf</CODE> declarations. They
|
|
influence the way <CODE>gperf</CODE> works, like command line options do.
|
|
In fact, every such declaration is equivalent to a command line option.
|
|
There are three forms of declarations:
|
|
|
|
</P>
|
|
|
|
<OL>
|
|
<LI>
|
|
|
|
Declarations without argument, like <SAMP>‘%compare-lengths’</SAMP>.
|
|
|
|
<LI>
|
|
|
|
Declarations with an argument, like <SAMP>‘%switch=<VAR>count</VAR>’</SAMP>.
|
|
|
|
<LI>
|
|
|
|
Declarations of names of entities in the output file, like
|
|
<SAMP>‘%define lookup-function-name <VAR>name</VAR>’</SAMP>.
|
|
</OL>
|
|
|
|
<P>
|
|
When a declaration is given both in the input file and as a command line
|
|
option, the command-line option's value prevails.
|
|
|
|
</P>
|
|
<P>
|
|
The following <CODE>gperf</CODE> declarations are available.
|
|
|
|
</P>
|
|
<DL COMPACT>
|
|
|
|
<DT><SAMP>‘%delimiters=<VAR>delimiter-list</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX9"></A>
|
|
Allows you to provide a string containing delimiters used to
|
|
separate keywords from their attributes. The default is ",". This
|
|
option is essential if you want to use keywords that have embedded
|
|
commas or newlines.
|
|
|
|
<DT><SAMP>‘%struct-type’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX10"></A>
|
|
Allows you to include a <CODE>struct</CODE> type declaration for generated
|
|
code; see above for an example.
|
|
|
|
<DT><SAMP>‘%ignore-case’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX11"></A>
|
|
Consider upper and lower case ASCII characters as equivalent. The string
|
|
comparison will use a case insignificant character comparison. Note that
|
|
locale dependent case mappings are ignored.
|
|
|
|
<DT><SAMP>‘%language=<VAR>language-name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX12"></A>
|
|
Instructs <CODE>gperf</CODE> to generate code in the language specified by the
|
|
option's argument. Languages handled are currently:
|
|
|
|
<DL COMPACT>
|
|
|
|
<DT><SAMP>‘KR-C’</SAMP>
|
|
<DD>
|
|
Old-style K&R C. This language is understood by old-style C compilers and
|
|
ANSI C compilers, but ANSI C compilers may flag warnings (or even errors)
|
|
because of lacking <SAMP>‘const’</SAMP>.
|
|
|
|
<DT><SAMP>‘C’</SAMP>
|
|
<DD>
|
|
Common C. This language is understood by ANSI C compilers, and also by
|
|
old-style C compilers, provided that you <CODE>#define const</CODE> to empty
|
|
for compilers which don't know about this keyword.
|
|
|
|
<DT><SAMP>‘ANSI-C’</SAMP>
|
|
<DD>
|
|
ANSI C. This language is understood by ANSI C (C89, ISO C90) compilers,
|
|
ISO C99 compilers, and C++ compilers.
|
|
|
|
<DT><SAMP>‘C++’</SAMP>
|
|
<DD>
|
|
C++. This language is understood by C++ compilers.
|
|
</DL>
|
|
|
|
The default is C.
|
|
|
|
<DT><SAMP>‘%define slot-name <VAR>name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX13"></A>
|
|
This declaration is only useful when option <SAMP>‘-t’</SAMP> (or, equivalently, the
|
|
<SAMP>‘%struct-type’</SAMP> declaration) has been given.
|
|
By default, the program assumes the structure component identifier for
|
|
the keyword is <SAMP>‘name’</SAMP>. This option allows an arbitrary choice of
|
|
identifier for this component, although it still must occur as the first
|
|
field in your supplied <CODE>struct</CODE>.
|
|
|
|
<DT><SAMP>‘%define initializer-suffix <VAR>initializers</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX14"></A>
|
|
This declaration is only useful when option <SAMP>‘-t’</SAMP> (or, equivalently, the
|
|
<SAMP>‘%struct-type’</SAMP> declaration) has been given.
|
|
It permits to specify initializers for the structure members following
|
|
<VAR>slot-name</VAR> in empty hash table entries. The list of initializers
|
|
should start with a comma. By default, the emitted code will
|
|
zero-initialize structure members following <VAR>slot-name</VAR>.
|
|
|
|
<DT><SAMP>‘%define hash-function-name <VAR>name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX15"></A>
|
|
Allows you to specify the name for the generated hash function. Default
|
|
name is <SAMP>‘hash’</SAMP>. This option permits the use of two hash tables in
|
|
the same file.
|
|
|
|
<DT><SAMP>‘%define lookup-function-name <VAR>name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX16"></A>
|
|
Allows you to specify the name for the generated lookup function.
|
|
Default name is <SAMP>‘in_word_set’</SAMP>. This option permits multiple
|
|
generated hash functions to be used in the same application.
|
|
|
|
<DT><SAMP>‘%define class-name <VAR>name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX17"></A>
|
|
This option is only useful when option <SAMP>‘-L C++’</SAMP> (or, equivalently,
|
|
the <SAMP>‘%language=C++’</SAMP> declaration) has been given. It
|
|
allows you to specify the name of generated C++ class. Default name is
|
|
<CODE>Perfect_Hash</CODE>.
|
|
|
|
<DT><SAMP>‘%7bit’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX18"></A>
|
|
This option specifies that all strings that will be passed as arguments
|
|
to the generated hash function and the generated lookup function will
|
|
solely consist of 7-bit ASCII characters (bytes in the range 0..127).
|
|
(Note that the ANSI C functions <CODE>isalnum</CODE> and <CODE>isgraph</CODE> do
|
|
<EM>not</EM> guarantee that a byte is in this range. Only an explicit
|
|
test like <SAMP>‘c >= 'A' && c <= 'Z'’</SAMP> guarantees this.)
|
|
|
|
<DT><SAMP>‘%compare-lengths’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX19"></A>
|
|
Compare keyword lengths before trying a string comparison. This option
|
|
is mandatory for binary comparisons (see section <A HREF="gperf.html#SEC15">4.3 Use of NUL bytes</A>). It also might
|
|
cut down on the number of string comparisons made during the lookup, since
|
|
keywords with different lengths are never compared via <CODE>strcmp</CODE>.
|
|
However, using <SAMP>‘%compare-lengths’</SAMP> might greatly increase the size of the
|
|
generated C code if the lookup table range is large (which implies that
|
|
the switch option <SAMP>‘-S’</SAMP> or <SAMP>‘%switch’</SAMP> is not enabled), since the length
|
|
table contains as many elements as there are entries in the lookup table.
|
|
|
|
<DT><SAMP>‘%compare-strncmp’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX20"></A>
|
|
Generates C code that uses the <CODE>strncmp</CODE> function to perform
|
|
string comparisons. The default action is to use <CODE>strcmp</CODE>.
|
|
|
|
<DT><SAMP>‘%readonly-tables’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX21"></A>
|
|
Makes the contents of all generated lookup tables constant, i.e.,
|
|
“readonly”. Many compilers can generate more efficient code for this
|
|
by putting the tables in readonly memory.
|
|
|
|
<DT><SAMP>‘%enum’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX22"></A>
|
|
Define constant values using an enum local to the lookup function rather
|
|
than with #defines. This also means that different lookup functions can
|
|
reside in the same file. Thanks to James Clark <CODE><jjc@ai.mit.edu></CODE>.
|
|
|
|
<DT><SAMP>‘%includes’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX23"></A>
|
|
Include the necessary system include file, <CODE><string.h></CODE>, at the
|
|
beginning of the code. By default, this is not done; the user must
|
|
include this header file himself to allow compilation of the code.
|
|
|
|
<DT><SAMP>‘%global-table’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX24"></A>
|
|
Generate the static table of keywords as a static global variable,
|
|
rather than hiding it inside of the lookup function (which is the
|
|
default behavior).
|
|
|
|
<DT><SAMP>‘%pic’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX25"></A>
|
|
Optimize the generated table for inclusion in shared libraries. This
|
|
reduces the startup time of programs using a shared library containing
|
|
the generated code. If the <SAMP>‘%struct-type’</SAMP> declaration (or,
|
|
equivalently, the option <SAMP>‘-t’</SAMP>) is also given, the first field of the
|
|
user-defined struct must be of type <SAMP>‘int’</SAMP>, not <SAMP>‘char *’</SAMP>, because
|
|
it will contain offsets into the string pool instead of actual strings.
|
|
To convert such an offset to a string, you can use the expression
|
|
<SAMP>‘stringpool + <VAR>o</VAR>’</SAMP>, where <VAR>o</VAR> is the offset. The string pool
|
|
name can be changed through the <SAMP>‘%define string-pool-name’</SAMP> declaration.
|
|
|
|
<DT><SAMP>‘%define string-pool-name <VAR>name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX26"></A>
|
|
Allows you to specify the name of the generated string pool created by
|
|
the declaration <SAMP>‘%pic’</SAMP> (or, equivalently, the option <SAMP>‘-P’</SAMP>).
|
|
The default name is <SAMP>‘stringpool’</SAMP>. This declaration permits the use of
|
|
two hash tables in the same file, with <SAMP>‘%pic’</SAMP> and even when the
|
|
<SAMP>‘%global-table’</SAMP> declaration (or, equivalently, the option <SAMP>‘-G’</SAMP>)
|
|
is given.
|
|
|
|
<DT><SAMP>‘%null-strings’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX27"></A>
|
|
Use NULL strings instead of empty strings for empty keyword table entries.
|
|
This reduces the startup time of programs using a shared library containing
|
|
the generated code (but not as much as the declaration <SAMP>‘%pic’</SAMP>), at the
|
|
expense of one more test-and-branch instruction at run time.
|
|
|
|
<DT><SAMP>‘%define word-array-name <VAR>name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX28"></A>
|
|
Allows you to specify the name for the generated array containing the
|
|
hash table. Default name is <SAMP>‘wordlist’</SAMP>. This option permits the
|
|
use of two hash tables in the same file, even when the option <SAMP>‘-G’</SAMP>
|
|
(or, equivalently, the <SAMP>‘%global-table’</SAMP> declaration) is given.
|
|
|
|
<DT><SAMP>‘%define length-table-name <VAR>name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX29"></A>
|
|
Allows you to specify the name for the generated array containing the
|
|
length table. Default name is <SAMP>‘lengthtable’</SAMP>. This option permits the
|
|
use of two length tables in the same file, even when the option <SAMP>‘-G’</SAMP>
|
|
(or, equivalently, the <SAMP>‘%global-table’</SAMP> declaration) is given.
|
|
|
|
<DT><SAMP>‘%switch=<VAR>count</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX30"></A>
|
|
Causes the generated C code to use a <CODE>switch</CODE> statement scheme,
|
|
rather than an array lookup table. This can lead to a reduction in both
|
|
time and space requirements for some input files. The argument to this
|
|
option determines how many <CODE>switch</CODE> statements are generated. A
|
|
value of 1 generates 1 <CODE>switch</CODE> containing all the elements, a
|
|
value of 2 generates 2 tables with 1/2 the elements in each
|
|
<CODE>switch</CODE>, etc. This is useful since many C compilers cannot
|
|
correctly generate code for large <CODE>switch</CODE> statements. This option
|
|
was inspired in part by Keith Bostic's original C program.
|
|
|
|
<DT><SAMP>‘%omit-struct-type’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX31"></A>
|
|
Prevents the transfer of the type declaration to the output file. Use
|
|
this option if the type is already defined elsewhere.
|
|
</DL>
|
|
|
|
|
|
|
|
<H4><A NAME="SEC10" HREF="gperf.html#TOC10">4.1.1.3 C Code Inclusion</A></H4>
|
|
|
|
<P>
|
|
<A NAME="IDX32"></A>
|
|
<A NAME="IDX33"></A>
|
|
Using a syntax similar to GNU utilities <CODE>flex</CODE> and <CODE>bison</CODE>, it
|
|
is possible to directly include C source text and comments verbatim into
|
|
the generated output file. This is accomplished by enclosing the region
|
|
inside left-justified surrounding <SAMP>‘%{’</SAMP>, <SAMP>‘%}’</SAMP> pairs. Here is
|
|
an input fragment based on the previous example that illustrates this
|
|
feature:
|
|
|
|
</P>
|
|
|
|
<PRE>
|
|
%{
|
|
#include <assert.h>
|
|
/* This section of code is inserted directly into the output. */
|
|
int return_month_days (struct month *months, int is_leap_year);
|
|
%}
|
|
struct month { char *name; int number; int days; int leap_days; };
|
|
%%
|
|
january, 1, 31, 31
|
|
february, 2, 28, 29
|
|
march, 3, 31, 31
|
|
...
|
|
</PRE>
|
|
|
|
|
|
|
|
<H3><A NAME="SEC11" HREF="gperf.html#TOC11">4.1.2 Format for Keyword Entries</A></H3>
|
|
|
|
<P>
|
|
The second input file format section contains lines of keywords and any
|
|
associated attributes you might supply. A line beginning with <SAMP>‘#’</SAMP>
|
|
in the first column is considered a comment. Everything following the
|
|
<SAMP>‘#’</SAMP> is ignored, up to and including the following newline. A line
|
|
beginning with <SAMP>‘%’</SAMP> in the first column is an option declaration and
|
|
must not occur within the keywords section.
|
|
|
|
</P>
|
|
<P>
|
|
The first field of each non-comment line is always the keyword itself. It
|
|
can be given in two ways: as a simple name, i.e., without surrounding
|
|
string quotation marks, or as a string enclosed in double-quotes, in
|
|
C syntax, possibly with backslash escapes like <CODE>\"</CODE> or <CODE>\234</CODE>
|
|
or <CODE>\xa8</CODE>. In either case, it must start right at the beginning
|
|
of the line, without leading whitespace.
|
|
In this context, a “field” is considered to extend up to, but
|
|
not include, the first blank, comma, or newline. Here is a simple
|
|
example taken from a partial list of C reserved words:
|
|
|
|
</P>
|
|
|
|
<PRE>
|
|
# These are a few C reserved words, see the c.gperf file
|
|
# for a complete list of ANSI C reserved words.
|
|
unsigned
|
|
sizeof
|
|
switch
|
|
signed
|
|
if
|
|
default
|
|
for
|
|
while
|
|
return
|
|
</PRE>
|
|
|
|
<P>
|
|
Note that unlike <CODE>flex</CODE> or <CODE>bison</CODE> the first <SAMP>‘%%’</SAMP> marker
|
|
may be elided if the declaration section is empty.
|
|
|
|
</P>
|
|
<P>
|
|
Additional fields may optionally follow the leading keyword. Fields
|
|
should be separated by commas, and terminate at the end of line. What
|
|
these fields mean is entirely up to you; they are used to initialize the
|
|
elements of the user-defined <CODE>struct</CODE> provided by you in the
|
|
declaration section. If the <SAMP>‘-t’</SAMP> option (or, equivalently, the
|
|
<SAMP>‘%struct-type’</SAMP> declaration) is <EM>not</EM> enabled
|
|
these fields are simply ignored. All previous examples except the last
|
|
one contain keyword attributes.
|
|
|
|
</P>
|
|
|
|
|
|
<H3><A NAME="SEC12" HREF="gperf.html#TOC12">4.1.3 Including Additional C Functions</A></H3>
|
|
|
|
<P>
|
|
The optional third section also corresponds closely with conventions
|
|
found in <CODE>flex</CODE> and <CODE>bison</CODE>. All text in this section,
|
|
starting at the final <SAMP>‘%%’</SAMP> and extending to the end of the input
|
|
file, is included verbatim into the generated output file. Naturally,
|
|
it is your responsibility to ensure that the code contained in this
|
|
section is valid C.
|
|
|
|
</P>
|
|
|
|
|
|
<H3><A NAME="SEC13" HREF="gperf.html#TOC13">4.1.4 Where to place directives for GNU <CODE>indent</CODE>.</A></H3>
|
|
|
|
<P>
|
|
If you want to invoke GNU <CODE>indent</CODE> on a <CODE>gperf</CODE> input file,
|
|
you will see that GNU <CODE>indent</CODE> doesn't understand the <SAMP>‘%%’</SAMP>,
|
|
<SAMP>‘%{’</SAMP> and <SAMP>‘%}’</SAMP> directives that control <CODE>gperf</CODE>'s
|
|
interpretation of the input file. Therefore you have to insert some
|
|
directives for GNU <CODE>indent</CODE>. More precisely, assuming the most
|
|
general input file structure
|
|
|
|
</P>
|
|
|
|
<PRE>
|
|
declarations part 1
|
|
%{
|
|
verbatim code
|
|
%}
|
|
declarations part 2
|
|
%%
|
|
keywords
|
|
%%
|
|
functions
|
|
</PRE>
|
|
|
|
<P>
|
|
you would insert <SAMP>‘*INDENT-OFF*’</SAMP> and <SAMP>‘*INDENT-ON*’</SAMP> comments
|
|
as follows:
|
|
|
|
</P>
|
|
|
|
<PRE>
|
|
/* *INDENT-OFF* */
|
|
declarations part 1
|
|
%{
|
|
/* *INDENT-ON* */
|
|
verbatim code
|
|
/* *INDENT-OFF* */
|
|
%}
|
|
declarations part 2
|
|
%%
|
|
keywords
|
|
%%
|
|
/* *INDENT-ON* */
|
|
functions
|
|
</PRE>
|
|
|
|
|
|
|
|
<H2><A NAME="SEC14" HREF="gperf.html#TOC14">4.2 Output Format for Generated C Code with <CODE>gperf</CODE></A></H2>
|
|
<P>
|
|
<A NAME="IDX34"></A>
|
|
|
|
</P>
|
|
<P>
|
|
Several options control how the generated C code appears on the standard
|
|
output. Two C functions are generated. They are called <CODE>hash</CODE> and
|
|
<CODE>in_word_set</CODE>, although you may modify their names with a command-line
|
|
option. Both functions require two arguments, a string, <CODE>char *</CODE>
|
|
<VAR>str</VAR>, and a length parameter, <CODE>int</CODE> <VAR>len</VAR>. Their default
|
|
function prototypes are as follows:
|
|
|
|
</P>
|
|
<P>
|
|
<DL>
|
|
<DT><U>Function:</U> unsigned int <B>hash</B> <I>(const char * <VAR>str</VAR>, unsigned int <VAR>len</VAR>)</I>
|
|
<DD><A NAME="IDX35"></A>
|
|
By default, the generated <CODE>hash</CODE> function returns an integer value
|
|
created by adding <VAR>len</VAR> to several user-specified <VAR>str</VAR> byte
|
|
positions indexed into an <EM>associated values</EM> table stored in a
|
|
local static array. The associated values table is constructed
|
|
internally by <CODE>gperf</CODE> and later output as a static local C array
|
|
called <SAMP>‘hash_table’</SAMP>. The relevant selected positions (i.e. indices
|
|
into <VAR>str</VAR>) are specified via the <SAMP>‘-k’</SAMP> option when running
|
|
<CODE>gperf</CODE>, as detailed in the <EM>Options</EM> section below (see section <A HREF="gperf.html#SEC17">5 Invoking <CODE>gperf</CODE></A>).
|
|
</DL>
|
|
|
|
</P>
|
|
<P>
|
|
<DL>
|
|
<DT><U>Function:</U> <B>in_word_set</B> <I>(const char * <VAR>str</VAR>, unsigned int <VAR>len</VAR>)</I>
|
|
<DD><A NAME="IDX36"></A>
|
|
If <VAR>str</VAR> is in the keyword set, returns a pointer to that
|
|
keyword. More exactly, if the option <SAMP>‘-t’</SAMP> (or, equivalently, the
|
|
<SAMP>‘%struct-type’</SAMP> declaration) was given, it returns
|
|
a pointer to the matching keyword's structure. Otherwise it returns
|
|
<CODE>NULL</CODE>.
|
|
</DL>
|
|
|
|
</P>
|
|
<P>
|
|
If the option <SAMP>‘-c’</SAMP> (or, equivalently, the <SAMP>‘%compare-strncmp’</SAMP>
|
|
declaration) is not used, <VAR>str</VAR> must be a NUL terminated
|
|
string of exactly length <VAR>len</VAR>. If <SAMP>‘-c’</SAMP> (or, equivalently, the
|
|
<SAMP>‘%compare-strncmp’</SAMP> declaration) is used, <VAR>str</VAR> must
|
|
simply be an array of <VAR>len</VAR> bytes and does not need to be NUL
|
|
terminated.
|
|
|
|
</P>
|
|
<P>
|
|
The code generated for these two functions is affected by the following
|
|
options:
|
|
|
|
</P>
|
|
<DL COMPACT>
|
|
|
|
<DT><SAMP>‘-t’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--struct-type’</SAMP>
|
|
<DD>
|
|
Make use of the user-defined <CODE>struct</CODE>.
|
|
|
|
<DT><SAMP>‘-S <VAR>total-switch-statements</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--switch=<VAR>total-switch-statements</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX37"></A>
|
|
Generate 1 or more C <CODE>switch</CODE> statement rather than use a large,
|
|
(and potentially sparse) static array. Although the exact time and
|
|
space savings of this approach vary according to your C compiler's
|
|
degree of optimization, this method often results in smaller and faster
|
|
code.
|
|
</DL>
|
|
|
|
<P>
|
|
If the <SAMP>‘-t’</SAMP> and <SAMP>‘-S’</SAMP> options (or, equivalently, the
|
|
<SAMP>‘%struct-type’</SAMP> and <SAMP>‘%switch’</SAMP> declarations) are omitted, the default
|
|
action
|
|
is to generate a <CODE>char *</CODE> array containing the keywords, together with
|
|
additional empty strings used for padding the array. By experimenting
|
|
with the various input and output options, and timing the resulting C
|
|
code, you can determine the best option choices for different keyword
|
|
set characteristics.
|
|
|
|
</P>
|
|
|
|
|
|
<H2><A NAME="SEC15" HREF="gperf.html#TOC15">4.3 Use of NUL bytes</A></H2>
|
|
<P>
|
|
<A NAME="IDX38"></A>
|
|
|
|
</P>
|
|
<P>
|
|
By default, the code generated by <CODE>gperf</CODE> operates on zero
|
|
terminated strings, the usual representation of strings in C. This means
|
|
that the keywords in the input file must not contain NUL bytes,
|
|
and the <VAR>str</VAR> argument passed to <CODE>hash</CODE> or <CODE>in_word_set</CODE>
|
|
must be NUL terminated and have exactly length <VAR>len</VAR>.
|
|
|
|
</P>
|
|
<P>
|
|
If option <SAMP>‘-c’</SAMP> (or, equivalently, the <SAMP>‘%compare-strncmp’</SAMP>
|
|
declaration) is used, then the <VAR>str</VAR> argument does not need
|
|
to be NUL terminated. The code generated by <CODE>gperf</CODE> will only
|
|
access the first <VAR>len</VAR>, not <VAR>len+1</VAR>, bytes starting at <VAR>str</VAR>.
|
|
However, the keywords in the input file still must not contain NUL
|
|
bytes.
|
|
|
|
</P>
|
|
<P>
|
|
If option <SAMP>‘-l’</SAMP> (or, equivalently, the <SAMP>‘%compare-lengths’</SAMP>
|
|
declaration) is used, then the hash table performs binary
|
|
comparison. The keywords in the input file may contain NUL bytes,
|
|
written in string syntax as <CODE>\000</CODE> or <CODE>\x00</CODE>, and the code
|
|
generated by <CODE>gperf</CODE> will treat NUL like any other byte.
|
|
Also, in this case the <SAMP>‘-c’</SAMP> option (or, equivalently, the
|
|
<SAMP>‘%compare-strncmp’</SAMP> declaration) is ignored.
|
|
|
|
</P>
|
|
|
|
|
|
<H2><A NAME="SEC16" HREF="gperf.html#TOC16">4.4 The Copyright of the Output</A></H2>
|
|
<P>
|
|
<A NAME="IDX39"></A>
|
|
|
|
</P>
|
|
<P>
|
|
<CODE>gperf</CODE> is under GPL, but that does not cause the output produced
|
|
by <CODE>gperf</CODE> to be under GPL. The reason is that the output contains
|
|
only small pieces of text that come directly from <CODE>gperf</CODE>'s source
|
|
code -- only about 7 lines long, too small for being significant --, and
|
|
therefore the output is not a “work based on <CODE>gperf</CODE>” (in the
|
|
sense of the GPL version 3).
|
|
|
|
</P>
|
|
<P>
|
|
On the other hand, the output produced by <CODE>gperf</CODE> contains
|
|
essentially all of the input file. Therefore the output is a
|
|
“derivative work” of the input (in the sense of U.S. copyright law);
|
|
and its copyright status depends on the copyright of the input. For most
|
|
software licenses, the result is that the the output is under the same
|
|
license, with the same copyright holder, as the input that was passed to
|
|
<CODE>gperf</CODE>.
|
|
|
|
</P>
|
|
|
|
|
|
<H1><A NAME="SEC17" HREF="gperf.html#TOC17">5 Invoking <CODE>gperf</CODE></A></H1>
|
|
|
|
<P>
|
|
There are <EM>many</EM> options to <CODE>gperf</CODE>. They were added to make
|
|
the program more convenient for use with real applications. “On-line”
|
|
help is readily available via the <SAMP>‘--help’</SAMP> option. Here is the
|
|
complete list of options.
|
|
|
|
</P>
|
|
|
|
|
|
|
|
<H2><A NAME="SEC18" HREF="gperf.html#TOC18">5.1 Specifying the Location of the Output File</A></H2>
|
|
|
|
<DL COMPACT>
|
|
|
|
<DT><SAMP>‘--output-file=<VAR>file</VAR>’</SAMP>
|
|
<DD>
|
|
Allows you to specify the name of the file to which the output is written to.
|
|
</DL>
|
|
|
|
<P>
|
|
The results are written to standard output if no output file is specified
|
|
or if it is <SAMP>‘-’</SAMP>.
|
|
|
|
</P>
|
|
|
|
|
|
<H2><A NAME="SEC19" HREF="gperf.html#TOC19">5.2 Options that affect Interpretation of the Input File</A></H2>
|
|
|
|
<P>
|
|
These options are also available as declarations in the input file
|
|
(see section <A HREF="gperf.html#SEC9">4.1.1.2 Gperf Declarations</A>).
|
|
|
|
</P>
|
|
<DL COMPACT>
|
|
|
|
<DT><SAMP>‘-e <VAR>keyword-delimiter-list</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--delimiters=<VAR>keyword-delimiter-list</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX40"></A>
|
|
Allows you to provide a string containing delimiters used to
|
|
separate keywords from their attributes. The default is ",". This
|
|
option is essential if you want to use keywords that have embedded
|
|
commas or newlines. One useful trick is to use -e'TAB', where TAB is
|
|
the literal tab character.
|
|
|
|
<DT><SAMP>‘-t’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--struct-type’</SAMP>
|
|
<DD>
|
|
Allows you to include a <CODE>struct</CODE> type declaration for generated
|
|
code. Any text before a pair of consecutive <SAMP>‘%%’</SAMP> is considered
|
|
part of the type declaration. Keywords and additional fields may follow
|
|
this, one group of fields per line. A set of examples for generating
|
|
perfect hash tables and functions for Ada, C, C++, Pascal, Modula 2,
|
|
Modula 3 and JavaScript reserved words are distributed with this release.
|
|
|
|
<DT><SAMP>‘--ignore-case’</SAMP>
|
|
<DD>
|
|
Consider upper and lower case ASCII characters as equivalent. The string
|
|
comparison will use a case insignificant character comparison. Note that
|
|
locale dependent case mappings are ignored. This option is therefore not
|
|
suitable if a properly internationalized or locale aware case mapping
|
|
should be used. (For example, in a Turkish locale, the upper case equivalent
|
|
of the lowercase ASCII letter <SAMP>‘i’</SAMP> is the non-ASCII character
|
|
<SAMP>‘capital i with dot above’</SAMP>.) For this case, it is better to apply
|
|
an uppercase or lowercase conversion on the string before passing it to
|
|
the <CODE>gperf</CODE> generated function.
|
|
</DL>
|
|
|
|
|
|
|
|
<H2><A NAME="SEC20" HREF="gperf.html#TOC20">5.3 Options to specify the Language for the Output Code</A></H2>
|
|
|
|
<P>
|
|
These options are also available as declarations in the input file
|
|
(see section <A HREF="gperf.html#SEC9">4.1.1.2 Gperf Declarations</A>).
|
|
|
|
</P>
|
|
<DL COMPACT>
|
|
|
|
<DT><SAMP>‘-L <VAR>generated-language-name</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--language=<VAR>generated-language-name</VAR>’</SAMP>
|
|
<DD>
|
|
Instructs <CODE>gperf</CODE> to generate code in the language specified by the
|
|
option's argument. Languages handled are currently:
|
|
|
|
<DL COMPACT>
|
|
|
|
<DT><SAMP>‘KR-C’</SAMP>
|
|
<DD>
|
|
Old-style K&R C. This language is understood by old-style C compilers and
|
|
ANSI C compilers, but ANSI C compilers may flag warnings (or even errors)
|
|
because of lacking <SAMP>‘const’</SAMP>.
|
|
|
|
<DT><SAMP>‘C’</SAMP>
|
|
<DD>
|
|
Common C. This language is understood by ANSI C compilers, and also by
|
|
old-style C compilers, provided that you <CODE>#define const</CODE> to empty
|
|
for compilers which don't know about this keyword.
|
|
|
|
<DT><SAMP>‘ANSI-C’</SAMP>
|
|
<DD>
|
|
ANSI C. This language is understood by ANSI C compilers and C++ compilers.
|
|
|
|
<DT><SAMP>‘C++’</SAMP>
|
|
<DD>
|
|
C++. This language is understood by C++ compilers.
|
|
</DL>
|
|
|
|
The default is C.
|
|
|
|
<DT><SAMP>‘-a’</SAMP>
|
|
<DD>
|
|
This option is supported for compatibility with previous releases of
|
|
<CODE>gperf</CODE>. It does not do anything.
|
|
|
|
<DT><SAMP>‘-g’</SAMP>
|
|
<DD>
|
|
This option is supported for compatibility with previous releases of
|
|
<CODE>gperf</CODE>. It does not do anything.
|
|
</DL>
|
|
|
|
|
|
|
|
<H2><A NAME="SEC21" HREF="gperf.html#TOC21">5.4 Options for fine tuning Details in the Output Code</A></H2>
|
|
|
|
<P>
|
|
Most of these options are also available as declarations in the input file
|
|
(see section <A HREF="gperf.html#SEC9">4.1.1.2 Gperf Declarations</A>).
|
|
|
|
</P>
|
|
<DL COMPACT>
|
|
|
|
<DT><SAMP>‘-K <VAR>slot-name</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--slot-name=<VAR>slot-name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX41"></A>
|
|
This option is only useful when option <SAMP>‘-t’</SAMP> (or, equivalently, the
|
|
<SAMP>‘%struct-type’</SAMP> declaration) has been given.
|
|
By default, the program assumes the structure component identifier for
|
|
the keyword is <SAMP>‘name’</SAMP>. This option allows an arbitrary choice of
|
|
identifier for this component, although it still must occur as the first
|
|
field in your supplied <CODE>struct</CODE>.
|
|
|
|
<DT><SAMP>‘-F <VAR>initializers</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--initializer-suffix=<VAR>initializers</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX42"></A>
|
|
This option is only useful when option <SAMP>‘-t’</SAMP> (or, equivalently, the
|
|
<SAMP>‘%struct-type’</SAMP> declaration) has been given.
|
|
It permits to specify initializers for the structure members following
|
|
<VAR>slot-name</VAR> in empty hash table entries. The list of initializers
|
|
should start with a comma. By default, the emitted code will
|
|
zero-initialize structure members following <VAR>slot-name</VAR>.
|
|
|
|
<DT><SAMP>‘-H <VAR>hash-function-name</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--hash-function-name=<VAR>hash-function-name</VAR>’</SAMP>
|
|
<DD>
|
|
Allows you to specify the name for the generated hash function. Default
|
|
name is <SAMP>‘hash’</SAMP>. This option permits the use of two hash tables in
|
|
the same file.
|
|
|
|
<DT><SAMP>‘-N <VAR>lookup-function-name</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--lookup-function-name=<VAR>lookup-function-name</VAR>’</SAMP>
|
|
<DD>
|
|
Allows you to specify the name for the generated lookup function.
|
|
Default name is <SAMP>‘in_word_set’</SAMP>. This option permits multiple
|
|
generated hash functions to be used in the same application.
|
|
|
|
<DT><SAMP>‘-Z <VAR>class-name</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--class-name=<VAR>class-name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX43"></A>
|
|
This option is only useful when option <SAMP>‘-L C++’</SAMP> (or, equivalently,
|
|
the <SAMP>‘%language=C++’</SAMP> declaration) has been given. It
|
|
allows you to specify the name of generated C++ class. Default name is
|
|
<CODE>Perfect_Hash</CODE>.
|
|
|
|
<DT><SAMP>‘-7’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--seven-bit’</SAMP>
|
|
<DD>
|
|
This option specifies that all strings that will be passed as arguments
|
|
to the generated hash function and the generated lookup function will
|
|
solely consist of 7-bit ASCII characters (bytes in the range 0..127).
|
|
(Note that the ANSI C functions <CODE>isalnum</CODE> and <CODE>isgraph</CODE> do
|
|
<EM>not</EM> guarantee that a byte is in this range. Only an explicit
|
|
test like <SAMP>‘c >= 'A' && c <= 'Z'’</SAMP> guarantees this.) This was the
|
|
default in versions of <CODE>gperf</CODE> earlier than 2.7; now the default is
|
|
to support 8-bit and multibyte characters.
|
|
|
|
<DT><SAMP>‘-l’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--compare-lengths’</SAMP>
|
|
<DD>
|
|
Compare keyword lengths before trying a string comparison. This option
|
|
is mandatory for binary comparisons (see section <A HREF="gperf.html#SEC15">4.3 Use of NUL bytes</A>). It also might
|
|
cut down on the number of string comparisons made during the lookup, since
|
|
keywords with different lengths are never compared via <CODE>strcmp</CODE>.
|
|
However, using <SAMP>‘-l’</SAMP> might greatly increase the size of the
|
|
generated C code if the lookup table range is large (which implies that
|
|
the switch option <SAMP>‘-S’</SAMP> or <SAMP>‘%switch’</SAMP> is not enabled), since the length
|
|
table contains as many elements as there are entries in the lookup table.
|
|
|
|
<DT><SAMP>‘-c’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--compare-strncmp’</SAMP>
|
|
<DD>
|
|
Generates C code that uses the <CODE>strncmp</CODE> function to perform
|
|
string comparisons. The default action is to use <CODE>strcmp</CODE>.
|
|
|
|
<DT><SAMP>‘-C’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--readonly-tables’</SAMP>
|
|
<DD>
|
|
Makes the contents of all generated lookup tables constant, i.e.,
|
|
“readonly”. Many compilers can generate more efficient code for this
|
|
by putting the tables in readonly memory.
|
|
|
|
<DT><SAMP>‘-E’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--enum’</SAMP>
|
|
<DD>
|
|
Define constant values using an enum local to the lookup function rather
|
|
than with #defines. This also means that different lookup functions can
|
|
reside in the same file. Thanks to James Clark <CODE><jjc@ai.mit.edu></CODE>.
|
|
|
|
<DT><SAMP>‘-I’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--includes’</SAMP>
|
|
<DD>
|
|
Include the necessary system include file, <CODE><string.h></CODE>, at the
|
|
beginning of the code. By default, this is not done; the user must
|
|
include this header file himself to allow compilation of the code.
|
|
|
|
<DT><SAMP>‘-G’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--global-table’</SAMP>
|
|
<DD>
|
|
Generate the static table of keywords as a static global variable,
|
|
rather than hiding it inside of the lookup function (which is the
|
|
default behavior).
|
|
|
|
<DT><SAMP>‘-P’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--pic’</SAMP>
|
|
<DD>
|
|
Optimize the generated table for inclusion in shared libraries. This
|
|
reduces the startup time of programs using a shared library containing
|
|
the generated code. If the option <SAMP>‘-t’</SAMP> (or, equivalently, the
|
|
<SAMP>‘%struct-type’</SAMP> declaration) is also given, the first field of the
|
|
user-defined struct must be of type <SAMP>‘int’</SAMP>, not <SAMP>‘char *’</SAMP>, because
|
|
it will contain offsets into the string pool instead of actual strings.
|
|
To convert such an offset to a string, you can use the expression
|
|
<SAMP>‘stringpool + <VAR>o</VAR>’</SAMP>, where <VAR>o</VAR> is the offset. The string pool
|
|
name can be changed through the option <SAMP>‘--string-pool-name’</SAMP>.
|
|
|
|
<DT><SAMP>‘-Q <VAR>string-pool-name</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--string-pool-name=<VAR>string-pool-name</VAR>’</SAMP>
|
|
<DD>
|
|
Allows you to specify the name of the generated string pool created by
|
|
option <SAMP>‘-P’</SAMP>. The default name is <SAMP>‘stringpool’</SAMP>. This option
|
|
permits the use of two hash tables in the same file, with <SAMP>‘-P’</SAMP> and
|
|
even when the option <SAMP>‘-G’</SAMP> (or, equivalently, the <SAMP>‘%global-table’</SAMP>
|
|
declaration) is given.
|
|
|
|
<DT><SAMP>‘--null-strings’</SAMP>
|
|
<DD>
|
|
Use NULL strings instead of empty strings for empty keyword table entries.
|
|
This reduces the startup time of programs using a shared library containing
|
|
the generated code (but not as much as option <SAMP>‘-P’</SAMP>), at the expense
|
|
of one more test-and-branch instruction at run time.
|
|
|
|
<DT><SAMP>‘-W <VAR>hash-table-array-name</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--word-array-name=<VAR>hash-table-array-name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX44"></A>
|
|
Allows you to specify the name for the generated array containing the
|
|
hash table. Default name is <SAMP>‘wordlist’</SAMP>. This option permits the
|
|
use of two hash tables in the same file, even when the option <SAMP>‘-G’</SAMP>
|
|
(or, equivalently, the <SAMP>‘%global-table’</SAMP> declaration) is given.
|
|
|
|
<DT><SAMP>‘--length-table-name=<VAR>length-table-array-name</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX45"></A>
|
|
Allows you to specify the name for the generated array containing the
|
|
length table. Default name is <SAMP>‘lengthtable’</SAMP>. This option permits the
|
|
use of two length tables in the same file, even when the option <SAMP>‘-G’</SAMP>
|
|
(or, equivalently, the <SAMP>‘%global-table’</SAMP> declaration) is given.
|
|
|
|
<DT><SAMP>‘-S <VAR>total-switch-statements</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--switch=<VAR>total-switch-statements</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX46"></A>
|
|
Causes the generated C code to use a <CODE>switch</CODE> statement scheme,
|
|
rather than an array lookup table. This can lead to a reduction in both
|
|
time and space requirements for some input files. The argument to this
|
|
option determines how many <CODE>switch</CODE> statements are generated. A
|
|
value of 1 generates 1 <CODE>switch</CODE> containing all the elements, a
|
|
value of 2 generates 2 tables with 1/2 the elements in each
|
|
<CODE>switch</CODE>, etc. This is useful since many C compilers cannot
|
|
correctly generate code for large <CODE>switch</CODE> statements. This option
|
|
was inspired in part by Keith Bostic's original C program.
|
|
|
|
<DT><SAMP>‘-T’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--omit-struct-type’</SAMP>
|
|
<DD>
|
|
Prevents the transfer of the type declaration to the output file. Use
|
|
this option if the type is already defined elsewhere.
|
|
|
|
<DT><SAMP>‘-p’</SAMP>
|
|
<DD>
|
|
This option is supported for compatibility with previous releases of
|
|
<CODE>gperf</CODE>. It does not do anything.
|
|
</DL>
|
|
|
|
|
|
|
|
<H2><A NAME="SEC22" HREF="gperf.html#TOC22">5.5 Options for changing the Algorithms employed by <CODE>gperf</CODE></A></H2>
|
|
|
|
<DL COMPACT>
|
|
|
|
<DT><SAMP>‘-k <VAR>selected-byte-positions</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--key-positions=<VAR>selected-byte-positions</VAR>’</SAMP>
|
|
<DD>
|
|
Allows selection of the byte positions used in the keywords'
|
|
hash function. The allowable choices range between 1-255, inclusive.
|
|
The positions are separated by commas, e.g., <SAMP>‘-k 9,4,13,14’</SAMP>;
|
|
ranges may be used, e.g., <SAMP>‘-k 2-7’</SAMP>; and positions may occur
|
|
in any order. Furthermore, the wildcard '*' causes the generated
|
|
hash function to consider <STRONG>all</STRONG> byte positions in each keyword,
|
|
whereas '$' instructs the hash function to use the “final byte”
|
|
of a keyword (this is the only way to use a byte position greater than
|
|
255, incidentally).
|
|
|
|
For instance, the option <SAMP>‘-k 1,2,4,6-10,'$'’</SAMP> generates a hash
|
|
function that considers positions 1,2,4,6,7,8,9,10, plus the last
|
|
byte in each keyword (which may be at a different position for each
|
|
keyword, obviously). Keywords
|
|
with length less than the indicated byte positions work properly, since
|
|
selected byte positions exceeding the keyword length are simply not
|
|
referenced in the hash function.
|
|
|
|
This option is not normally needed since version 2.8 of <CODE>gperf</CODE>;
|
|
the default byte positions are computed depending on the keyword set,
|
|
through a search that minimizes the number of byte positions.
|
|
|
|
<DT><SAMP>‘-D’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--duplicates’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX47"></A>
|
|
Handle keywords whose selected byte sets hash to duplicate values.
|
|
Duplicate hash values can occur if a set of keywords has the same names, but
|
|
possesses different attributes, or if the selected byte positions are not well
|
|
chosen. With the -D option <CODE>gperf</CODE> treats all these keywords as
|
|
part of an equivalence class and generates a perfect hash function with
|
|
multiple comparisons for duplicate keywords. It is up to you to completely
|
|
disambiguate the keywords by modifying the generated C code. However,
|
|
<CODE>gperf</CODE> helps you out by organizing the output.
|
|
|
|
Using this option usually means that the generated hash function is no
|
|
longer perfect. On the other hand, it permits <CODE>gperf</CODE> to work on
|
|
keyword sets that it otherwise could not handle.
|
|
|
|
<DT><SAMP>‘-m <VAR>iterations</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--multiple-iterations=<VAR>iterations</VAR>’</SAMP>
|
|
<DD>
|
|
Perform multiple choices of the <SAMP>‘-i’</SAMP> and <SAMP>‘-j’</SAMP> values, and
|
|
choose the best results. This increases the running time by a factor of
|
|
<VAR>iterations</VAR> but does a good job minimizing the generated table size.
|
|
|
|
<DT><SAMP>‘-i <VAR>initial-value</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--initial-asso=<VAR>initial-value</VAR>’</SAMP>
|
|
<DD>
|
|
Provides an initial <VAR>value</VAR> for the associate values array. Default
|
|
is 0. Increasing the initial value helps inflate the final table size,
|
|
possibly leading to more time efficient keyword lookups. Note that this
|
|
option is not particularly useful when <SAMP>‘-S’</SAMP> (or, equivalently,
|
|
<SAMP>‘%switch’</SAMP>) is used. Also,
|
|
<SAMP>‘-i’</SAMP> is overridden when the <SAMP>‘-r’</SAMP> option is used.
|
|
|
|
<DT><SAMP>‘-j <VAR>jump-value</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--jump=<VAR>jump-value</VAR>’</SAMP>
|
|
<DD>
|
|
<A NAME="IDX48"></A>
|
|
Affects the “jump value”, i.e., how far to advance the associated
|
|
byte value upon collisions. <VAR>Jump-value</VAR> is rounded up to an
|
|
odd number, the default is 5. If the <VAR>jump-value</VAR> is 0 <CODE>gperf</CODE>
|
|
jumps by random amounts.
|
|
|
|
<DT><SAMP>‘-n’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--no-strlen’</SAMP>
|
|
<DD>
|
|
Instructs the generator not to include the length of a keyword when
|
|
computing its hash value. This may save a few assembly instructions in
|
|
the generated lookup table.
|
|
|
|
<DT><SAMP>‘-r’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--random’</SAMP>
|
|
<DD>
|
|
Utilizes randomness to initialize the associated values table. This
|
|
frequently generates solutions faster than using deterministic
|
|
initialization (which starts all associated values at 0). Furthermore,
|
|
using the randomization option generally increases the size of the
|
|
table.
|
|
|
|
<DT><SAMP>‘-s <VAR>size-multiple</VAR>’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--size-multiple=<VAR>size-multiple</VAR>’</SAMP>
|
|
<DD>
|
|
Affects the size of the generated hash table. The numeric argument for
|
|
this option indicates “how many times larger or smaller” the maximum
|
|
associated value range should be, in relationship to the number of keywords.
|
|
It can be written as an integer, a floating-point number or a fraction.
|
|
For example, a value of 3 means “allow the maximum associated value to be
|
|
about 3 times larger than the number of input keywords”.
|
|
Conversely, a value of 1/3 means “allow the maximum associated value to
|
|
be about 3 times smaller than the number of input keywords”. Values
|
|
smaller than 1 are useful for limiting the overall size of the generated hash
|
|
table, though the option <SAMP>‘-m’</SAMP> is better at this purpose.
|
|
|
|
If `generate switch' option <SAMP>‘-S’</SAMP> (or, equivalently, <SAMP>‘%switch’</SAMP>) is
|
|
<EM>not</EM> enabled, the maximum
|
|
associated value influences the static array table size, and a larger
|
|
table should decrease the time required for an unsuccessful search, at
|
|
the expense of extra table space.
|
|
|
|
The default value is 1, thus the default maximum associated value about
|
|
the same size as the number of keywords (for efficiency, the maximum
|
|
associated value is always rounded up to a power of 2). The actual
|
|
table size may vary somewhat, since this technique is essentially a
|
|
heuristic.
|
|
</DL>
|
|
|
|
|
|
|
|
<H2><A NAME="SEC23" HREF="gperf.html#TOC23">5.6 Informative Output</A></H2>
|
|
|
|
<DL COMPACT>
|
|
|
|
<DT><SAMP>‘-h’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--help’</SAMP>
|
|
<DD>
|
|
Prints a short summary on the meaning of each program option. Aborts
|
|
further program execution.
|
|
|
|
<DT><SAMP>‘-v’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--version’</SAMP>
|
|
<DD>
|
|
Prints out the current version number.
|
|
|
|
<DT><SAMP>‘-d’</SAMP>
|
|
<DD>
|
|
<DT><SAMP>‘--debug’</SAMP>
|
|
<DD>
|
|
Enables the debugging option. This produces verbose diagnostics to
|
|
“standard error” when <CODE>gperf</CODE> is executing. It is useful both for
|
|
maintaining the program and for determining whether a given set of
|
|
options is actually speeding up the search for a solution. Some useful
|
|
information is dumped at the end of the program when the <SAMP>‘-d’</SAMP>
|
|
option is enabled.
|
|
</DL>
|
|
|
|
|
|
|
|
<H1><A NAME="SEC24" HREF="gperf.html#TOC24">6 Known Bugs and Limitations with <CODE>gperf</CODE></A></H1>
|
|
|
|
<P>
|
|
The following are some limitations with the current release of
|
|
<CODE>gperf</CODE>:
|
|
|
|
</P>
|
|
|
|
<UL>
|
|
<LI>
|
|
|
|
The <CODE>gperf</CODE> utility is tuned to execute quickly, and works quickly
|
|
for small to medium size data sets (around 1000 keywords). It is
|
|
extremely useful for maintaining perfect hash functions for compiler
|
|
keyword sets. Several recent enhancements now enable <CODE>gperf</CODE> to
|
|
work efficiently on much larger keyword sets (over 15,000 keywords).
|
|
When processing large keyword sets it helps greatly to have over 8 megs
|
|
of RAM.
|
|
|
|
<LI>
|
|
|
|
The size of the generate static keyword array can get <EM>extremely</EM>
|
|
large if the input keyword file is large or if the keywords are quite
|
|
similar. This tends to slow down the compilation of the generated C
|
|
code, and <EM>greatly</EM> inflates the object code size. If this
|
|
situation occurs, consider using the <SAMP>‘-S’</SAMP> option to reduce data
|
|
size, potentially increasing keyword recognition time a negligible
|
|
amount. Since many C compilers cannot correctly generate code for
|
|
large switch statements it is important to qualify the <VAR>-S</VAR> option
|
|
with an appropriate numerical argument that controls the number of
|
|
switch statements generated.
|
|
|
|
<LI>
|
|
|
|
The maximum number of selected byte positions has an
|
|
arbitrary limit of 255. This restriction should be removed, and if
|
|
anyone considers this a problem write me and let me know so I can remove
|
|
the constraint.
|
|
</UL>
|
|
|
|
|
|
|
|
<H1><A NAME="SEC25" HREF="gperf.html#TOC25">7 Things Still Left to Do</A></H1>
|
|
|
|
<P>
|
|
It should be “relatively” easy to replace the current perfect hash
|
|
function algorithm with a more exhaustive approach; the perfect hash
|
|
module is essential independent from other program modules. Additional
|
|
worthwhile improvements include:
|
|
|
|
</P>
|
|
|
|
<UL>
|
|
<LI>
|
|
|
|
Another useful extension involves modifying the program to generate
|
|
“minimal” perfect hash functions (under certain circumstances, the
|
|
current version can be rather extravagant in the generated table size).
|
|
This is mostly of theoretical interest, since a sparse table
|
|
often produces faster lookups, and use of the <SAMP>‘-S’</SAMP> <CODE>switch</CODE>
|
|
option can minimize the data size, at the expense of slightly longer
|
|
lookups (note that the gcc compiler generally produces good code for
|
|
<CODE>switch</CODE> statements, reducing the need for more complex schemes).
|
|
|
|
<LI>
|
|
|
|
In addition to improving the algorithm, it would also be useful to
|
|
generate an Ada package as the code output, in addition to the current
|
|
C and C++ routines.
|
|
</UL>
|
|
|
|
|
|
|
|
<H1><A NAME="SEC26" HREF="gperf.html#TOC26">8 Bibliography</A></H1>
|
|
|
|
<P>
|
|
[1] Chang, C.C.: <I>A Scheme for Constructing Ordered Minimal Perfect
|
|
Hashing Functions</I> Information Sciences 39(1986), 187-195.
|
|
|
|
</P>
|
|
<P>
|
|
[2] Cichelli, Richard J. <I>Author's Response to “On Cichelli's Minimal Perfect Hash
|
|
Functions Method”</I> Communications of the ACM, 23, 12(December 1980), 729.
|
|
|
|
</P>
|
|
<P>
|
|
[3] Cichelli, Richard J. <I>Minimal Perfect Hash Functions Made Simple</I>
|
|
Communications of the ACM, 23, 1(January 1980), 17-19.
|
|
|
|
</P>
|
|
<P>
|
|
[4] Cook, C. R. and Oldehoeft, R.R. <I>A Letter Oriented Minimal
|
|
Perfect Hashing Function</I> SIGPLAN Notices, 17, 9(September 1982), 18-27.
|
|
|
|
</P>
|
|
<P>
|
|
[5] Cormack, G. V. and Horspool, R. N. S. and Kaiserwerth, M.
|
|
<I>Practical Perfect Hashing</I> Computer Journal, 28, 1(January 1985), 54-58.
|
|
|
|
</P>
|
|
<P>
|
|
[6] Jaeschke, G. <I>Reciprocal Hashing: A Method for Generating Minimal
|
|
Perfect Hashing Functions</I> Communications of the ACM, 24, 12(December
|
|
1981), 829-833.
|
|
|
|
</P>
|
|
<P>
|
|
[7] Jaeschke, G. and Osterburg, G. <I>On Cichelli's Minimal Perfect
|
|
Hash Functions Method</I> Communications of the ACM, 23, 12(December 1980),
|
|
728-729.
|
|
|
|
</P>
|
|
<P>
|
|
[8] Sager, Thomas J. <I>A Polynomial Time Generator for Minimal Perfect
|
|
Hash Functions</I> Communications of the ACM, 28, 5(December 1985), 523-532
|
|
|
|
</P>
|
|
<P>
|
|
[9] Schmidt, Douglas C. <I>GPERF: A Perfect Hash Function Generator</I>
|
|
Second USENIX C++ Conference Proceedings, April 1990.
|
|
|
|
</P>
|
|
<P>
|
|
[10] Schmidt, Douglas C. <I>GPERF: A Perfect Hash Function Generator</I>
|
|
C++ Report, SIGS 10 10 (November/December 1998).
|
|
|
|
</P>
|
|
<P>
|
|
[11] Sebesta, R.W. and Taylor, M.A. <I>Minimal Perfect Hash Functions
|
|
for Reserved Word Lists</I> SIGPLAN Notices, 20, 12(September 1985), 47-53.
|
|
|
|
</P>
|
|
<P>
|
|
[12] Sprugnoli, R. <I>Perfect Hashing Functions: A Single Probe
|
|
Retrieving Method for Static Sets</I> Communications of the ACM, 20
|
|
11(November 1977), 841-850.
|
|
|
|
</P>
|
|
<P>
|
|
[13] Stallman, Richard M. <I>Using and Porting GNU CC</I> Free Software Foundation,
|
|
1988.
|
|
|
|
</P>
|
|
<P>
|
|
[14] Stroustrup, Bjarne <I>The C++ Programming Language.</I> Addison-Wesley, 1986.
|
|
|
|
</P>
|
|
<P>
|
|
[15] Tiemann, Michael D. <I>User's Guide to GNU C++</I> Free Software
|
|
Foundation, 1989.
|
|
|
|
</P>
|
|
|
|
|
|
<H1><A NAME="SEC27" HREF="gperf.html#TOC27">Concept Index</A></H1>
|
|
|
|
<P>
|
|
Jump to:
|
|
<A HREF="#cindex_&">&</A>
|
|
-
|
|
<A HREF="#cindex_a">a</A>
|
|
-
|
|
<A HREF="#cindex_b">b</A>
|
|
-
|
|
<A HREF="#cindex_c">c</A>
|
|
-
|
|
<A HREF="#cindex_d">d</A>
|
|
-
|
|
<A HREF="#cindex_f">f</A>
|
|
-
|
|
<A HREF="#cindex_h">h</A>
|
|
-
|
|
<A HREF="#cindex_i">i</A>
|
|
-
|
|
<A HREF="#cindex_j">j</A>
|
|
-
|
|
<A HREF="#cindex_k">k</A>
|
|
-
|
|
<A HREF="#cindex_m">m</A>
|
|
-
|
|
<A HREF="#cindex_n">n</A>
|
|
-
|
|
<A HREF="#cindex_s">s</A>
|
|
<P>
|
|
<H2><A NAME="cindex_&">&</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX8"><SAMP>‘%%’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX18"><SAMP>‘%7bit’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX19"><SAMP>‘%compare-lengths’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX20"><SAMP>‘%compare-strncmp’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX17"><SAMP>‘%define class-name’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX15"><SAMP>‘%define hash-function-name’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX14"><SAMP>‘%define initializer-suffix’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX29"><SAMP>‘%define length-table-name’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX16"><SAMP>‘%define lookup-function-name’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX13"><SAMP>‘%define slot-name’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX26"><SAMP>‘%define string-pool-name’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX28"><SAMP>‘%define word-array-name’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX9"><SAMP>‘%delimiters’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX22"><SAMP>‘%enum’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX24"><SAMP>‘%global-table’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX11"><SAMP>‘%ignore-case’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX23"><SAMP>‘%includes’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX12"><SAMP>‘%language’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX27"><SAMP>‘%null-strings’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX31"><SAMP>‘%omit-struct-type’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX25"><SAMP>‘%pic’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX21"><SAMP>‘%readonly-tables’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX10"><SAMP>‘%struct-type’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX30"><SAMP>‘%switch’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX32"><SAMP>‘%{’</SAMP></A>
|
|
<LI><A HREF="gperf.html#IDX33"><SAMP>‘%}’</SAMP></A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_a">a</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX44">Array name</A>, <A HREF="gperf.html#IDX45">Array name</A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_b">b</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX1">Bugs</A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_c">c</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX43">Class name</A>
|
|
<LI><A HREF="gperf.html#IDX39">Copyright</A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_d">d</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX5">Declaration section</A>
|
|
<LI><A HREF="gperf.html#IDX40">Delimiters</A>
|
|
<LI><A HREF="gperf.html#IDX47">Duplicates</A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_f">f</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX4">Format</A>
|
|
<LI><A HREF="gperf.html#IDX7">Functions section</A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_h">h</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX35">hash</A>
|
|
<LI><A HREF="gperf.html#IDX34">hash table</A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_i">i</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX36">in_word_set</A>
|
|
<LI><A HREF="gperf.html#IDX42">Initializers</A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_j">j</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX48">Jump value</A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_k">k</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX6">Keywords section</A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_m">m</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX3">Minimal perfect hash functions</A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_n">n</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX38">NUL</A>
|
|
</DIR>
|
|
<H2><A NAME="cindex_s">s</A></H2>
|
|
<DIR>
|
|
<LI><A HREF="gperf.html#IDX41">Slot name</A>
|
|
<LI><A HREF="gperf.html#IDX2">Static search structure</A>
|
|
<LI><A HREF="gperf.html#IDX37"><CODE>switch</CODE></A>, <A HREF="gperf.html#IDX46"><CODE>switch</CODE></A>
|
|
</DIR>
|
|
|
|
</P>
|
|
|
|
<P><HR><P>
|
|
This document was generated on 1 February 2009 using the
|
|
<A HREF="http://wwwinfo.cern.ch/dis/texi2html/">texi2html</A>
|
|
translator version 1.52b.</P>
|
|
</BODY>
|
|
</HTML>
|