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gperf (1)
  • gperf (1) ( FreeBSD man: Команды и прикладные программы пользовательского уровня )
  • >> gperf (1) ( Linux man: Команды и прикладные программы пользовательского уровня )
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    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.  

    Input file interpretation:

    -e, --delimiters=DELIMITER-LIST
    Allow user to provide a string containing delimiters used to separate keywords from their attributes. Default is ",\n".
    -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.
     

    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-fn-name=NAME
    Specify name of generated hash function. Default is `hash'.
    -N, --lookup-fn-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.
    -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
    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).
    -W, --word-array-name=NAME
    Specify name of word list array. Default name is `wordlist'.
    -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 1-126, 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.
    -l, --compare-strlen
    Compare key lengths before trying a string comparison. This helps cut down on the number of string comparisons made during the lookup.
    -D, --duplicates
    Handle keywords that hash to duplicate values. This is useful for certain highly redundant keyword sets.
    -f, --fast=ITERATIONS
    Generate the gen-perf.hash function ``fast''. This decreases gperf's running time at the cost of minimizing generated table size. The numeric argument represents the number of times to iterate when resolving a collision. `0' means ``iterate by the number of keywords''.
    -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.
    -o, --occurrence-sort
    Reorders input keys by frequency of occurrence of the key sets. This should decrease the search time dramatically.
    -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 -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).
     

    REPORTING BUGS

    Report bugs to <bug-gnu-utils@gnu.org>.  

    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.


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    Input file interpretation:
    Language for the output code:
    Details in the output code:
    Algorithm employed by gperf:
    Informative output:
    REPORTING BUGS
    SEE ALSO


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