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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 con-tain contain
              tain 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 ta-ble. table.
              ble.  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  posi-tions positions
              tions 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 colli-sions. collisions.
              sions. 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)