+
+/** Size of the hash value in bytes. */
+#define HASH_SIZE 20
+
+void hash_function(const char *data, unsigned long len, unsigned char *hash);
+
+/**
+ * Compare two hashes.
+ *
+ * \param h1 Pointer to the first hash value.
+ * \param h2 Pointer to the second hash value.
+ *
+ * \return 1, -1, or zero, depending on whether \a h1 is greater than,
+ * less than or equal to h2, respectively.
+ */
+_static_inline_ int hash_compare(unsigned char *h1, unsigned char *h2)
+{
+ int i;
+
+ for (i = 0; i < HASH_SIZE; i++) {
+ if (h1[i] < h2[i])
+ return -1;
+ if (h1[i] > h2[i])
+ return 1;
+ }
+ return 0;
+}
+
+/**
+ * Convert a hash value to ascii format.
+ *
+ * \param hash the hash value.
+ * \param asc Result pointer.
+ *
+ * \a asc must point to an area of at least 2 * \p HASH_SIZE + 1 bytes which
+ * will be filled by the function with the ascii representation of the hash
+ * value given by \a hash, and a terminating \p NULL byte.
+ */
+_static_inline_ void hash_to_asc(unsigned char *hash, char *asc)
+{
+ int i;
+ const char hexchar[] = "0123456789abcdef";
+
+ for (i = 0; i < HASH_SIZE; i++) {
+ asc[2 * i] = hexchar[hash[i] >> 4];
+ asc[2 * i + 1] = hexchar[hash[i] & 0xf];
+ }
+ asc[2 * HASH_SIZE] = '\0';
+}