scripts/basic/hash.c

   1 /*
   2  * Copyright (C) 2008 Red Hat, Inc., Jason Baron <jbaron@redhat.com>
   3  *
   4  */
   5
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <string.h>
   9
  10 #define DYNAMIC_DEBUG_HASH_BITS 6
  11
  12 static const char *program;
  13
  14 static void usage(void)
  15 {
  16         printf("Usage: %s <djb2|r5> <modname>\n", program);
  17         exit(1);
  18 }
  19
  20 /* djb2 hashing algorithm by Dan Bernstein. From:
  21  * http://www.cse.yorku.ca/~oz/hash.html
  22  */
  23
  24 static unsigned int djb2_hash(char *str)
  25 {
  26         unsigned long hash = 5381;
  27         int c;
  28
  29         c = *str;
  30         while (c) {
  31                 hash = ((hash << 5) + hash) + c;
  32                 c = *++str;
  33         }
  34         return (unsigned int)(hash & ((1 << DYNAMIC_DEBUG_HASH_BITS) - 1));
  35 }
  36
  37 static unsigned int r5_hash(char *str)
  38 {
  39         unsigned long hash = 0;
  40         int c;
  41
  42         c = *str;
  43         while (c) {
  44                 hash = (hash + (c << 4) + (c >> 4)) * 11;
  45                 c = *++str;
  46         }
  47         return (unsigned int)(hash & ((1 << DYNAMIC_DEBUG_HASH_BITS) - 1));
  48 }
  49
  50 int main(int argc, char *argv[])
  51 {
  52         program = argv[0];
  53
  54         if (argc != 3)
  55                 usage();
  56         if (!strcmp(argv[1], "djb2"))
  57                 printf("%d\n", djb2_hash(argv[2]));
  58         else if (!strcmp(argv[1], "r5"))
  59                 printf("%d\n", r5_hash(argv[2]));
  60         else
  61                 usage();
  62         exit(0);
  63 }
  64