GSP
Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Support
Contact Us
Online Help
Handbooks
Domain Status
Man Pages

FAQ
Virtual Servers
Pricing
Billing
Technical

Network
Facilities
Connectivity
Topology Map

Miscellaneous
Server Agreement
Year 2038
Credits
 

USA Flag

 

 

Man Pages


Manual Reference Pages  -  GPERF (1)

NAME

gperf - generate a perfect hash function from a key set

CONTENTS

Synopsis
Description
Author
Copyright

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.

    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 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.
-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).

AUTHOR

Written by Douglas C. Schmidt and Bruno Haible.

REPORTING BUGS

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

COPYRIGHT

Copyright © 1989-1998, 2000-2004, 2006-2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

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.
Search for    or go to Top of page |  Section 1 |  Main Index


GNU gperf 3.0.3 GPERF (1) May 2007

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.