1 files changed, 56 insertions, 0 deletions

diff --git a/src/ot_hex.c b/src/ot_hex.c
new file mode 100644
index 0000000..b537094
--- /dev/null
+++ b/src/ot_hex.c
@@ -0,0 +1,56 @@
+/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
+   It is considered beerware. Prost. Skol. Cheers or whatever. */
+
+/* System */
+#include <stdint.h>
+#include <string.h>
+
+/* Opentracker */
+#include "ot_hex.h"
+
+int hex_value(int c) {
+  unsigned char u = (unsigned char)c;
+
+  if (u >= '0' && u <= '9')
+    return u - '0';
+  u |= 0x20; /* fold upper case onto lower, digits are already handled */
+  if (u >= 'a' && u <= 'f')
+    return u - 'a' + 10;
+  return -1;
+}
+
+int hex_isdigit(int c) { return hex_value(c) >= 0; }
+
+char *hex_from_hash(char *dest, const uint8_t *hash) {
+  static const char digits[] = "0123456789ABCDEF";
+  char             *d        = dest;
+  size_t            i;
+
+  for (i = 0; i < sizeof(ot_hash); ++i) {
+    *d++ = digits[hash[i] >> 4];
+    *d++ = digits[hash[i] & 15];
+  }
+  *d = 0;
+  return dest;
+}
+
+int hex_to_hash(ot_hash hash, const char *src) {
+  uint8_t decoded[sizeof(ot_hash)];
+  size_t  i;
+
+  for (i = 0; i < sizeof(ot_hash); ++i) {
+    int high, low;
+
+    /* Tested one character at a time so that a string ending early stops us
+       at its terminator rather than one byte past it */
+    if ((high = hex_value((unsigned char)src[2 * i])) < 0)
+      return 0;
+    if ((low = hex_value((unsigned char)src[2 * i + 1])) < 0)
+      return 0;
+
+    decoded[i] = (uint8_t)((high << 4) | low);
+  }
+
+  memcpy(hash, decoded, sizeof(decoded));
+  return 1;
+}