120 lines
6.7 KiB
Plaintext
120 lines
6.7 KiB
Plaintext
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GNU `gperf' generates perfect hash functions.
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Usage: ../src/gperf [OPTION]... [INPUT-FILE]
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If a long option shows an argument as mandatory, then it is mandatory
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for the equivalent short option also.
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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 delimiters
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used to separate keywords from their attributes.
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Default is ",\n".
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-t, --struct-type Allows the user to include a structured type
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declaration 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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Language for the output code:
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-L, --language=LANGUAGE-NAME
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Generates code in the specified language. Languages
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handled are currently C++, ANSI-C, C, and KR-C. The
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default is C.
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Details in the output code:
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-K, --slot-name=NAME Select name of the keyword component in the keyword
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structure.
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-H, --hash-fn-name=NAME
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Specify name of generated hash function. Default is
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`hash'.
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-N, --lookup-fn-name=NAME
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Specify name of generated lookup function. Default
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name is `in_word_set'.
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-Z, --class-name=NAME Specify name of generated C++ class. Default name is
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`Perfect_Hash'.
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-7, --seven-bit Assume 7-bit characters.
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-c, --compare-strncmp Generate comparison code using strncmp rather than
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strcmp.
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-C, --readonly-tables Make the contents of generated lookup tables
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constant, i.e., readonly.
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-E, --enum 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 Include the necessary system include file <string.h>
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at the beginning of the code.
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-G, --global Generate the static table of keywords as a static
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global variable, rather than hiding it inside of the
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lookup function (which is the default behavior).
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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 Causes the generated C code to use a switch
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statement scheme, rather than an array lookup table.
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This can lead to a reduction in both time and space
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requirements for some keyfiles. The COUNT argument
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determines how many switch statements are generated.
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A value of 1 generates 1 switch containing all the
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elements, a value of 2 generates 2 tables with 1/2
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the elements in each table, etc. If COUNT is very
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large, say 1000000, the generated C code does a
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binary search.
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-T, --omit-struct-type
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Prevents the transfer of the type declaration to the
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output file. Use this option if the type is already
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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 function.
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The allowable choices range between 1-126, inclusive.
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The positions are separated by commas, ranges may be
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used, and key positions may occur in any order.
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Also, the meta-character '*' causes the generated
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hash function to consider ALL key positions, and $
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indicates the ``final character'' of a key, e.g.,
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$,1,2,4,6-10.
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-l, --compare-strlen Compare key lengths before trying a string
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comparison. This helps cut down on the number of
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string comparisons made during the lookup.
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-D, --duplicates Handle keywords that hash to duplicate values. This
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is useful for certain highly redundant keyword sets.
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-f, --fast=ITERATIONS Generate the gen-perf.hash function ``fast''. This
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decreases gperf's running time at the cost of
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minimizing generated table size. The numeric
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argument represents the number of times to iterate
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when resolving a collision. `0' means ``iterate by
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the number of keywords''.
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-i, --initial-asso=N Provide an initial value for the associate values
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array. Default is 0. Setting this value larger helps
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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
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the associated character value upon collisions. Must
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be an odd number, default is 5.
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-n, --no-strlen Do not include the length of the keyword when
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computing the hash function.
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-o, --occurrence-sort Reorders input keys by frequency of occurrence of
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the key sets. This should decrease the search time
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dramatically.
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-r, --random Utilizes randomness to initialize the associated
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values table.
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-s, --size-multiple=N Affects the size of the generated hash table. The
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numeric argument N indicates ``how many times larger
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or smaller'' the associated value range should be,
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in relationship to the number of keys, e.g. a value
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of 3 means ``allow the maximum associated value to
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be about 3 times larger than the number of input
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keys.'' Conversely, a value of -3 means ``make the
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maximum associated value about 3 times smaller than
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the number of input keys. A larger table should
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decrease the time required for an unsuccessful
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search, at the expense of extra table space. Default
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value is 1.
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Informative output:
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-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
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output to the standard error).
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Report bugs to <bug-gnu-utils@gnu.org>.
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