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 GPERF(1)                      GNU gperf 3.0.4                      GPERF(1)
 FSF                                                                     FSF

                                February 2009



 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



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 GPERF(1)                      GNU gperf 3.0.4                      GPERF(1)
 FSF                                                                     FSF

                                February 2009



           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



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 GPERF(1)                      GNU gperf 3.0.4                      GPERF(1)
 FSF                                                                     FSF

                                February 2009



           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.




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 GPERF(1)                      GNU gperf 3.0.4                      GPERF(1)
 FSF                                                                     FSF

                                February 2009



      -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, 2009 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



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 GPERF(1)                      GNU gperf 3.0.4                      GPERF(1)
 FSF                                                                     FSF

                                February 2009



      should give you access to the complete manual.



















































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