| GPERF(1) FSF GPERF(1) |
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| NAME |
| gperf - generate a perfect hash function from a key set |
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| SYNOPSIS |
| gperf [OPTION]... [INPUT-FILE] |
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| DESCRIPTION |
| GNU 'gperf' generates perfect hash functions. |
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| If a long option shows an argument as mandatory, then it |
| is mandatory for the equivalent short option also. |
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| Output file location: |
| --output-file=FILE Write output to specified file. |
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| The results are written to standard output if no output |
| file is specified or if it is -. |
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| Input file interpretation: |
| -e, --delimiters=DELIMITER-LIST |
| Allow user to provide a string containing delim- |
| iters used to separate keywords from their |
| attributes. Default is ",". |
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| -t, --struct-type |
| Allows the user to include a structured type dec- |
| laration 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. |
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| --ignore-case |
| Consider upper and lower case ASCII characters as |
| equivalent. Note that locale dependent case map- |
| pings are ignored. |
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| Language for the output code: |
| -L, --language=LANGUAGE-NAME |
| Generates code in the specified language. Lan- |
| guages handled are currently C++, ANSI-C, C, and |
| KR-C. The default is C. |
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| Details in the output code: |
| -K, --slot-name=NAME |
| Select name of the keyword component in the key- |
| word structure. |
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| -F, --initializer-suffix=INITIALIZERS |
| Initializers for additional components in the |
| keyword structure. |
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| -H, --hash-function-name=NAME |
| Specify name of generated hash function. Default |
| is 'hash'. |
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| -N, --lookup-function-name=NAME |
| Specify name of generated lookup function. |
| Default name is 'in_word_set'. |
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| -Z, --class-name=NAME |
| Specify name of generated C++ class. Default name |
| is 'Perfect_Hash'. |
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| -7, --seven-bit |
| Assume 7-bit characters. |
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| -l, --compare-lengths |
| Compare key lengths before trying a string com- |
| parison. This is necessary if the keywords con- |
| tain NUL bytes. It also helps cut down on the |
| number of string comparisons made during the |
| lookup. |
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| -c, --compare-strncmp |
| Generate comparison code using strncmp rather |
| than strcmp. |
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| -C, --readonly-tables |
| Make the contents of generated lookup tables con- |
| stant, i.e., readonly. |
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| -E, --enum |
| Define constant values using an enum local to the |
| lookup function rather than with defines. |
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| -I, --includes |
| Include the necessary system include file |
| <string.h> at the beginning of the code. |
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| -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 behav- |
| ior). |
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| -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. |
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| -Q, --string-pool-name=NAME |
| Specify name of string pool generated by option |
| --pic. Default name is 'stringpool'. |
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| --null-strings |
| Use NULL strings instead of empty strings for |
| empty keyword table entries. |
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| -W, --word-array-name=NAME |
| Specify name of word list array. Default name is |
| 'wordlist'. |
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| -S, --switch=COUNT |
| Causes the generated C code to use a switch |
| statement scheme, rather than an array lookup ta- |
| ble. This can lead to a reduction in both time |
| and space requirements for some keyfiles. The |
| COUNT argument determines how many switch state- |
| ments 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. |
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| -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. |
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| Algorithm employed by gperf: |
| -k, --key-positions=KEYS |
| Select the key positions used in the hash func- |
| tion. The allowable choices range between 1-255, |
| inclusive. The positions are separated by com- |
| mas, 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. |
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| -D, --duplicates |
| Handle keywords that hash to duplicate values. |
| This is useful for certain highly redundant key- |
| word sets. |
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| -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. |
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| -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. |
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| -j, --jump=JUMP-VALUE |
| Affects the "jump value", i.e., how far to |
| advance the associated character value upon col- |
| lisions. Must be an odd number, default is 5. |
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| -n, --no-strlen |
| Do not include the length of the keyword when |
| computing the hash function. |
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| -r, --random |
| Utilizes randomness to initialize the associated |
| values table. |
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| -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 asso- |
| ciated 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. |
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| Informative output: |
| -h, --help |
| Print this message. |
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| -v, --version |
| Print the gperf version number. |
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| -d, --debug |
| Enables the debugging option (produces verbose |
| output to the standard error). |
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| AUTHOR |
| Written by Douglas C. Schmidt and Bruno Haible. |
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| REPORTING BUGS |
| Report bugs to <bug-gnu-gperf@gnu.org>. |
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| COPYRIGHT |
| Copyright (C) 1989-1998, 2000-2003 Free Software Founda- |
| tion, Inc. |
| This is free software; see the source for copying condi- |
| tions. There is NO warranty; not even for MERCHANTABIL- |
| ITY or FITNESS FOR A PARTICULAR PURPOSE. |
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| SEE ALSO |
| The full documentation for gperf is maintained as a Tex- |
| info manual. If the info and gperf programs are prop- |
| erly installed at your site, the command |
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| info gperf |
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| should give you access to the complete manual. |
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| GNU gperf 3.0.1 June 2003 GPERF(1) |
