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<TITLE>User's Guide to gperf - 1 Introduction</TITLE>
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<H1><A NAME="SEC6" HREF="gperf_toc.html#TOC6">1 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 >= n</VAR>. If
<VAR>k = n</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.
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<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 Pascal, GNU
Modula 3, and GNU indent. Complete C++ source code for <CODE>gperf</CODE> is
available via anonymous ftp from <CODE>ics.uci.edu</CODE> and
<CODE>ftp.santafe.edu</CODE>. <CODE>gperf</CODE> was also distributed along with
the GNU libg++ library for several years. A highly portable,
functionally equivalent K&R C version of <CODE>gperf</CODE> is archived in
comp.sources.unix, volume 20. Finally, a paper describing
<CODE>gperf</CODE>'s design and implementation in greater detail is available
in the Second USENIX C++ Conference proceedings.
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