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42 lines
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42 lines
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<!-- This HTML file has been created by texi2html 1.52
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from gperf.texi on 13 January 2006 -->
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<TITLE>Perfect Hash Function Generator - 1 Introduction</TITLE>
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</HEAD>
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<BODY>
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Go to the <A HREF="gperf_1.html">first</A>, <A HREF="gperf_2.html">previous</A>, <A HREF="gperf_4.html">next</A>, <A HREF="gperf_10.html">last</A> section, <A HREF="gperf_toc.html">table of contents</A>.
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<P><HR><P>
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<H1><A NAME="SEC5" HREF="gperf_toc.html#TOC5">1 Introduction</A></H1>
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<P>
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<CODE>gperf</CODE> is a perfect hash function generator written in C++. It
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transforms an <VAR>n</VAR> element user-specified keyword set <VAR>W</VAR> into a
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perfect hash function <VAR>F</VAR>. <VAR>F</VAR> uniquely maps keywords in
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<VAR>W</VAR> onto the range 0..<VAR>k</VAR>, where <VAR>k</VAR> >= <VAR>n-1</VAR>. If <VAR>k</VAR>
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= <VAR>n-1</VAR> then <VAR>F</VAR> is a <EM>minimal</EM> perfect hash function.
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<CODE>gperf</CODE> generates a 0..<VAR>k</VAR> element static lookup table and a
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pair of C functions. These functions determine whether a given
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character string <VAR>s</VAR> occurs in <VAR>W</VAR>, using at most one probe into
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the lookup table.
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</P>
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<P>
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<CODE>gperf</CODE> currently generates the reserved keyword recognizer for
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lexical analyzers in several production and research compilers and
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language processing tools, including GNU C, GNU C++, GNU Java, GNU Pascal,
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GNU Modula 3, and GNU indent. Complete C++ source code for <CODE>gperf</CODE> is
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available from <CODE>http://ftp.gnu.org/pub/gnu/gperf/</CODE>.
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A paper describing <CODE>gperf</CODE>'s design and implementation in greater
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detail is available in the Second USENIX C++ Conference proceedings
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or from <CODE>http://www.cs.wustl.edu/~schmidt/resume.html</CODE>.
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</P>
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<P><HR><P>
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Go to the <A HREF="gperf_1.html">first</A>, <A HREF="gperf_2.html">previous</A>, <A HREF="gperf_4.html">next</A>, <A HREF="gperf_10.html">last</A> section, <A HREF="gperf_toc.html">table of contents</A>.
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</BODY>
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</HTML>
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