sbin/hammer/test_dupkey.c

   1 /*
   2  * This is a really simple stupid standalone program which will find two
   3  * filenames with the same CRC, used to test the directory iterator.
   4  *
   5  * cc -I /usr/src/sys test_dupkey.c /usr/src/sys/libkern/crc32.c -o test_dupkey
   6  *
   7  * $DragonFly: src/sbin/hammer/test_dupkey.c,v 1.1 2008/06/26 04:07:57 dillon Exp $
   8  */
   9
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <unistd.h>
  13 #include "hammer_util.h"
  14
  15 static u_int32_t namekey(const char *name);
  16 static void randomname(char *name);
  17
  18 u_int32_t bitmap[0x80000000U / 32];
  19
  20 int
  21 main(int ac, char **av)
  22 {
  23         char name[32];
  24         u_int32_t key;
  25         u_int32_t *ptr;
  26         u_int32_t mask;
  27         u_int32_t count;
  28         u_int32_t saved;
  29
  30         srandom(0);     /* reproducable random sequence number */
  31         count = 0;
  32         for (;;) {
  33                 randomname(name);
  34                 key = namekey(name);
  35                 ptr = &bitmap[key / 32];
  36                 mask = 1 << (key & 31);
  37                 if (*ptr & mask) {
  38                         break;
  39                 }
  40                 *ptr |= mask;
  41                 ++count;
  42         }
  43         printf("duplicate found at count %d key %08x\n", count, key);
  44         printf("'%s' and", name);
  45         saved = key;
  46
  47         srandom(0);
  48         count = 0;
  49         for (;;) {
  50                 randomname(name);
  51                 key = namekey(name);
  52                 if (saved == key)
  53                         break;
  54                 ++count;
  55         }
  56         printf(" '%s'\n", name);
  57 }
  58
  59 static
  60 u_int32_t
  61 namekey(const char *name)
  62 {
  63         u_int32_t key;
  64
  65         key = crc32(name, strlen(name)) & 0x7FFFFFFF;
  66         if (key == 0)
  67                 key = 1;
  68         return(key);
  69 }
  70
  71 static
  72 void
  73 randomname(char *name)
  74 {
  75         int len = random() % 16 + 8;
  76         int i;
  77
  78         for (i = 0; i < len; ++i)
  79                 name[i] = random() % 26 + 'a';
  80         name[i] = 0;
  81 }
  82
  83