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GPERF(1)                              FSF                             GPERF(1)

NAME
       gperf - generate a perfect hash function from a key set

SYNOPSIS
       gperf [OPTION]... [INPUT-FILE]

DESCRIPTION
       GNU 'gperf' generates perfect hash functions.

       If a long option shows an argument as mandatory, then it is mandatory
       for the equivalent short option also.

   Output file location:
       --output-file=FILE Write output to specified file.

       The results are written to standard output if no output file is
       specified or if it is -.

   Input file interpretation:
       -e, --delimiters=DELIMITER-LIST
              Allow user to provide a string containing delimiters used to
              separate keywords from their attributes.  Default is ",".

       -t, --struct-type
              Allows the user to include a structured type declaration for
              generated code. Any text before %% is considered part of the
              type declaration. Key words and additional fields may follow
              this, one group of fields per line.

       --ignore-case
              Consider upper and lower case ASCII characters as equivalent.
              Note that locale dependent case mappings are ignored.

   Language for the output code:
       -L, --language=LANGUAGE-NAME
              Generates code in the specified language. Languages handled are
              currently C++, ANSI-C, C, and KR-C. The default is C.

   Details in the output code:
       -K, --slot-name=NAME
              Select name of the keyword component in the keyword structure.

       -F, --initializer-suffix=INITIALIZERS
              Initializers for additional components in the keyword structure.

       -H, --hash-function-name=NAME
              Specify name of generated hash function. Default is 'hash'.

       -N, --lookup-function-name=NAME
              Specify name of generated lookup function. Default name is
              'in_word_set'.

       -Z, --class-name=NAME
              Specify name of generated C++ class. Default name is
              'Perfect_Hash'.

       -7, --seven-bit
              Assume 7-bit characters.

       -l, --compare-lengths
              Compare key lengths before trying a string comparison. This is
              necessary if the keywords contain NUL bytes. It also helps cut
              down on the number of string comparisons made during the lookup.

       -c, --compare-strncmp
              Generate comparison code using strncmp rather than strcmp.

       -C, --readonly-tables
              Make the contents of generated lookup tables constant, i.e.,
              readonly.

       -E, --enum
              Define constant values using an enum local to the lookup
              function rather than with defines.

       -I, --includes
              Include the necessary system include file <string.h> at the
              beginning of the code.

       -G, --global-table
              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).

       -P, --pic
              Optimize the generated table for inclusion in shared libraries.
              This reduces the startup time of programs using a shared library
              containing the generated code.

       -Q, --string-pool-name=NAME
              Specify name of string pool generated by option --pic.  Default
              name is 'stringpool'.

       --null-strings
              Use NULL strings instead of empty strings for empty keyword
              table entries.

       -W, --word-array-name=NAME
              Specify name of word list array. Default name is 'wordlist'.

       --length-table-name=NAME
              Specify name of length table array. Default name is
              'lengthtable'.

       -S, --switch=COUNT
              Causes the generated C code to use a switch statement scheme,
              rather than an array lookup table.  This can lead to a reduction
              in both time and space requirements for some keyfiles. The COUNT
              argument determines how many switch statements are generated.  A
              value of 1 generates 1 switch containing all the elements, a
              value of 2 generates 2 tables with 1/2 the elements in each
              table, etc. If COUNT is very large, say 1000000, the generated C
              code does a binary search.

       -T, --omit-struct-type
              Prevents the transfer of the type declaration to the output
              file. Use this option if the type is already defined elsewhere.

   Algorithm employed by gperf:
       -k, --key-positions=KEYS
              Select the key positions used in the hash function.  The
              allowable choices range between 1-255, inclusive.  The positions
              are separated by commas, ranges may be used, and key positions
              may occur in any order.  Also, the meta-character '*' causes the
              generated hash function to consider ALL key positions, and $
              indicates the "final character" of a key, e.g., $,1,2,4,6-10.

       -D, --duplicates
              Handle keywords that hash to duplicate values. This is useful
              for certain highly redundant keyword sets.

       -m, --multiple-iterations=ITERATIONS
              Perform multiple choices of the -i and -j values, and choose the
              best results. This increases the running time by a factor of
              ITERATIONS but does a good job minimizing the generated table
              size.

       -i, --initial-asso=N
              Provide an initial value for the associate values array. Default
              is 0. Setting this value larger helps inflate the size of the
              final table.

       -j, --jump=JUMP-VALUE
              Affects the "jump value", i.e., how far to advance the
              associated character value upon collisions. Must be an odd
              number, default is 5.

       -n, --no-strlen
              Do not include the length of the keyword when computing the hash
              function.

       -r, --random
              Utilizes randomness to initialize the associated values table.

       -s, --size-multiple=N
              Affects the size of the generated hash table. The numeric
              argument N indicates "how many times larger or smaller" the
              associated value range should be, in relationship to the number
              of keys, e.g. a value of 3 means "allow the maximum associated
              value to be about 3 times larger than the number of input keys".
              Conversely, a value of 1/3 means "make the maximum associated
              value about 3 times smaller than the number of input keys". A
              larger table should decrease the time required for an
              unsuccessful search, at the expense of extra table space.
              Default value is 1.

   Informative output:
       -h, --help
              Print this message.

       -v, --version
              Print the gperf version number.

       -d, --debug
              Enables the debugging option (produces verbose output to the
              standard error).

AUTHOR
       Written by Douglas C. Schmidt and Bruno Haible.

REPORTING BUGS
       Report bugs to <bug-gnu-gperf@gnu.org>.

COPYRIGHT
       Copyright (C) 1989-1998, 2000-2004, 2006-2007 Free Software Foundation,
       Inc.
       This is free software; see the source for copying conditions.  There is
       NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
       PURPOSE.

SEE ALSO
       The full documentation for gperf is maintained as a Texinfo manual.  If
       the info and gperf programs are properly installed at your site, the
       command

              info gperf

       should give you access to the complete manual.

GNU gperf 3.0.3                    May 2007                           GPERF(1)

NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO

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