#include "EXTERN.h" #include "perl.h" #include "XSUB.h" /* Jenkins Hash http://burtleburtle.net/bob/hash/doobs.html */ const int DEBUG = 0; #define MIX(a,b,c) \ { \ a -= b; a -= c; a ^= (c>>13); \ b -= c; b -= a; b ^= (a<<8); \ c -= a; c -= b; c ^= (b>>13); \ a -= b; a -= c; a ^= (c>>12); \ b -= c; b -= a; b ^= (a<<16); \ c -= a; c -= b; c ^= (b>>5); \ a -= b; a -= c; a ^= (c>>3); \ b -= c; b -= a; b ^= (a<<10); \ c -= a; c -= b; c ^= (b>>15); \ } unsigned long jhash( SV* str ) { STRLEN rawlen; char* p; unsigned long a, b, c, len, length; /* extract the string data and string length from the perl scalar */ p = (char*)SvPV(str, rawlen); length = len = (unsigned long)rawlen; /* Test for undef or null string case and return 0 */ if ( length == 0 ) { DEBUG && printf( "Recieved a null or undef string!\n" ); return 0; } DEBUG && printf( "Received string '%.*s'.\n", (int)len, p ); a = b = 0x9e3779b9; /* golden ratio suggested by Jenkins */ c = 0; while (len >= 12) { a += (p[0] + (((unsigned long)p[1])<<8) + (((unsigned long)p[2])<<16) + (((unsigned long)p[3])<<24)); b += (p[4] + (((unsigned long)p[5])<<8) + (((unsigned long)p[6])<<16) + (((unsigned long)p[7])<<24)); c += (p[8] + (((unsigned long)p[9])<<8) + (((unsigned long)p[10])<<16) + (((unsigned long)p[11])<<24)); MIX(a, b, c); p += 12; len -= 12; } c += length; switch(len) { case 11: c+=((unsigned int)p[10]<<24); case 10: c+=((unsigned int)p[9]<<16); case 9: c+=((unsigned int)p[8]<<8); case 8: b+=((unsigned int)p[7]<<24); case 7: b+=((unsigned int)p[6]<<16); case 6: b+=((unsigned int)p[5]<<8); case 5: b+=((unsigned int)p[4]); case 4: a+=((unsigned int)p[3]<<24); case 3: a+=((unsigned int)p[2]<<16); case 2: a+=((unsigned int)p[1]<<8); case 1: a+=((unsigned int)p[0]); } MIX(a, b, c); DEBUG && printf( "Hash value is %d.\n", (int)(c) ); return(c); } MODULE = Digest::JHash PACKAGE = Digest::JHash unsigned long jhash(str) SV* str # Digest::JHash.pm package Digest::JHash; use strict; require Exporter; require DynaLoader; our @ISA = qw(Exporter DynaLoader); our @EXPORT_OK = qw( jhash ); our $VERSION = '0.02'; bootstrap Digest::JHash $VERSION; 1; =head1 NAME Digest::JHash - Perl extension for JHash Hashing Algoritm =head1 SYNOPSIS use Digest::JHash qw(jhash); $digest = jhash($data); # note that calling jhash() directly like this is the fastest way: $digest = Digest::JHash::jhash($data); =head1 DESCRIPTION The C module allows you to use the fast JHash hashing algorithm developed by Bob Jenkins from within Perl programs. The algorithm takes as input a message of arbitrary length and produces as output a 32-bit "message digest" of the input in the form of an unsigned long integer. Call it a low calorie version of MD5 if you like. See http://burtleburtle.net/bob/hash/doobs.html for more information. =head1 FUNCTIONS =over 4 =item jhash($data) This function will calculate the JHash digest of the "message" in $data and return a 32 bit integer result (an unsigned long in the C) =back =head1 EXPORTS None by default but you can have the jhash() function if you ask nicely. See below for reasons not to use Exporter (it is slower than a direct call) =head1 SPEED NOTE If speed is a major issue it is roughly twice as fast to do call the jhash() function like Digest::JHash::jhash('message') than it is to import the jhash() method using Exporter so you can call it as simply jhash('message'). There is a short script that demonstrates the speed of differecnt calling methods (direct, OO and Imported) in misc/oo_vs_func.pl =head1 AUTHORS The JHash implementation was written by Bob Jenkins (C). This perl extension was written by Andrew Towers (C). A few mods were added by James Freeman (C). =head1 SEE ALSO http://burtleburtle.net/bob/hash/doobs.html =cut