Provided by: gperf_3.0.3-1ubuntu1_amd64
gperf - generate a perfect hash function from a key set
gperf [OPTION]... [INPUT-FILE]
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).
Written by Douglas C. Schmidt and Bruno Haible.
Report bugs to <firstname.lastname@example.org>.
Copyright © 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.
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.