hash.h

   1 /*
   2  * Copyright (C) 2007-2008 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file hash.h Inline functions for hash values. */
   8
   9 #include "portable_io.h"
  10
  11 /** hash arrays are always unsigned char. */
  12 #define HASH_TYPE unsigned char
  13
  14 #include "sha1.h"
  15 /** We use openssl's sha1 implementation. */
  16 #define hash_function sha1_hash
  17
  18 /**
  19  * Compare two hashes.
  20  *
  21  * \param h1 Pointer to the first hash value.
  22  * \param h2 Pointer to the second hash value.
  23  *
  24  * \return 1, -1, or zero, depending on whether \a h1 is greater than,
  25  * less than or equal to h2, respectively.
  26  */
  27 _static_inline_ int hash_compare(HASH_TYPE *h1, HASH_TYPE *h2)
  28 {
  29         int i;
  30
  31         for (i = 0; i < HASH_SIZE; i++) {
  32                 if (h1[i] < h2[i])
  33                         return -1;
  34                 if (h1[i] > h2[i])
  35                         return 1;
  36         }
  37         return 0;
  38 }
  39
  40 /**
  41  * Convert a hash value to ascii format.
  42  *
  43  * \param hash the hash value.
  44  * \param asc Result pointer.
  45  *
  46  * \a asc must point to an area of at least 2 * \p HASH_SIZE + 1 bytes which
  47  * will be filled by the function with the ascii representation of the hash
  48  * value given by \a hash, and a terminating \p NULL byte.
  49  */
  50 _static_inline_ void hash_to_asc(HASH_TYPE *hash, char *asc)
  51 {
  52         int i;
  53         const char hexchar[] = "0123456789abcdef";
  54
  55         for (i = 0; i < HASH_SIZE; i++) {
  56                 asc[2 * i] = hexchar[hash[i] >> 4];
  57                 asc[2 * i + 1] = hexchar[hash[i] & 0xf];
  58         }
  59         asc[2 * HASH_SIZE] = '\0';
  60 }