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GNU 'gperf' generates perfect hash functions.
Usage: ../src/gperf [OPTION]... [INPUT-FILE]
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 ANSI-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.
--constants-prefix=PREFIX
Specify prefix for the constants like TOTAL_KEYWORDS.
-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).
Report bugs to <bug-gperf@gnu.org>.
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