227 lines
8.2 KiB
Plaintext
227 lines
8.2 KiB
Plaintext
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GPERF(1) FSF GPERF(1)
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NAME
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gperf - generate a perfect hash function from a key set
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SYNOPSIS
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gperf [OPTION]... [INPUT-FILE]
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DESCRIPTION
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GNU 'gperf' generates perfect hash functions.
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If a long option shows an argument as mandatory, then it
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is mandatory for the equivalent short option also.
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Output file location:
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--output-file=FILE Write output to specified file.
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The results are written to standard output if no output
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file is specified or if it is -.
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Input file interpretation:
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-e, --delimiters=DELIMITER-LIST
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Allow user to provide a string containing delim-
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iters used to separate keywords from their
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attributes. Default is ",".
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-t, --struct-type
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Allows the user to include a structured type dec-
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laration for generated code. Any text before %%
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is considered part of the type declaration. Key
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words and additional fields may follow this, one
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group of fields per line.
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--ignore-case
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Consider upper and lower case ASCII characters as
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equivalent. Note that locale dependent case map-
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pings are ignored.
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Language for the output code:
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-L, --language=LANGUAGE-NAME
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Generates code in the specified language. Lan-
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guages handled are currently C++, ANSI-C, C, and
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KR-C. The default is C.
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Details in the output code:
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-K, --slot-name=NAME
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Select name of the keyword component in the key-
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word structure.
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-F, --initializer-suffix=INITIALIZERS
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Initializers for additional components in the
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keyword structure.
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-H, --hash-function-name=NAME
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Specify name of generated hash function. Default
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is 'hash'.
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-N, --lookup-function-name=NAME
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Specify name of generated lookup function.
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Default name is 'in_word_set'.
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-Z, --class-name=NAME
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Specify name of generated C++ class. Default name
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is 'Perfect_Hash'.
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-7, --seven-bit
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Assume 7-bit characters.
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-l, --compare-lengths
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Compare key lengths before trying a string com-
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parison. This is necessary if the keywords con-
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tain NUL bytes. It also helps cut down on the
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number of string comparisons made during the
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lookup.
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-c, --compare-strncmp
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Generate comparison code using strncmp rather
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than strcmp.
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-C, --readonly-tables
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Make the contents of generated lookup tables con-
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stant, i.e., readonly.
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-E, --enum
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Define constant values using an enum local to the
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lookup function rather than with defines.
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-I, --includes
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Include the necessary system include file
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<string.h> at the beginning of the code.
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-G, --global-table
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Generate the static table of keywords as a static
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global variable, rather than hiding it inside of
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the lookup function (which is the default behav-
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ior).
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-P, --pic
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Optimize the generated table for inclusion in
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shared libraries. This reduces the startup time
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of programs using a shared library containing the
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generated code.
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-Q, --string-pool-name=NAME
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Specify name of string pool generated by option
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--pic. Default name is 'stringpool'.
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--null-strings
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Use NULL strings instead of empty strings for
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empty keyword table entries.
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-W, --word-array-name=NAME
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Specify name of word list array. Default name is
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'wordlist'.
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-S, --switch=COUNT
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Causes the generated C code to use a switch
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statement scheme, rather than an array lookup ta-
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ble. This can lead to a reduction in both time
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and space requirements for some keyfiles. The
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COUNT argument determines how many switch state-
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ments are generated. A value of 1 generates 1
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switch containing all the elements, a value of 2
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generates 2 tables with 1/2 the elements in each
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table, etc. If COUNT is very large, say 1000000,
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the generated C code does a binary search.
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-T, --omit-struct-type
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Prevents the transfer of the type declaration to
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the output file. Use this option if the type is
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already defined elsewhere.
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Algorithm employed by gperf:
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-k, --key-positions=KEYS
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Select the key positions used in the hash func-
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tion. The allowable choices range between 1-255,
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inclusive. The positions are separated by com-
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mas, ranges may be used, and key positions may
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occur in any order. Also, the meta-character '*'
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causes the generated hash function to consider
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ALL key positions, and $ indicates the "final
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character" of a key, e.g., $,1,2,4,6-10.
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-D, --duplicates
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Handle keywords that hash to duplicate values.
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This is useful for certain highly redundant key-
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word sets.
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-m, --multiple-iterations=ITERATIONS
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Perform multiple choices of the -i and -j values,
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and choose the best results. This increases the
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running time by a factor of ITERATIONS but does a
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good job minimizing the generated table size.
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-i, --initial-asso=N
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Provide an initial value for the associate values
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array. Default is 0. Setting this value larger
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helps inflate the size of the final table.
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-j, --jump=JUMP-VALUE
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Affects the "jump value", i.e., how far to
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advance the associated character value upon col-
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lisions. Must be an odd number, default is 5.
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-n, --no-strlen
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Do not include the length of the keyword when
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computing the hash function.
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-r, --random
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Utilizes randomness to initialize the associated
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values table.
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-s, --size-multiple=N
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Affects the size of the generated hash table. The
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numeric argument N indicates "how many times
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larger or smaller" the associated value range
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should be, in relationship to the number of keys,
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e.g. a value of 3 means "allow the maximum asso-
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ciated value to be about 3 times larger than the
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number of input keys". Conversely, a value of 1/3
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means "make the maximum associated value about 3
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times smaller than the number of input keys". A
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larger table should decrease the time required
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for an unsuccessful search, at the expense of
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extra table space. Default value is 1.
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Informative output:
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-h, --help
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Print this message.
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-v, --version
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Print the gperf version number.
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-d, --debug
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Enables the debugging option (produces verbose
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output to the standard error).
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AUTHOR
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Written by Douglas C. Schmidt and Bruno Haible.
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REPORTING BUGS
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Report bugs to <bug-gnu-gperf@gnu.org>.
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COPYRIGHT
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Copyright (C) 1989-1998, 2000-2003 Free Software Founda-
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tion, Inc.
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This is free software; see the source for copying condi-
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tions. There is NO warranty; not even for MERCHANTABIL-
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ITY or FITNESS FOR A PARTICULAR PURPOSE.
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SEE ALSO
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The full documentation for gperf is maintained as a Tex-
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info manual. If the info and gperf programs are prop-
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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)
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