From c22fa15f5c44a43e291c15f737515e35fb9dc6ba Mon Sep 17 00:00:00 2001
From: Dirk Engling <erdgeist@erdgeist.org>
Date: Sat, 24 Oct 2026 02:00:42 +0200
Subject: Move all code converting between binary and hex representation to its
 own unit

---
 ot_hex.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 ot_hex.c

(limited to 'ot_hex.c')

diff --git a/ot_hex.c b/ot_hex.c
new file mode 100644
index 0000000..17dd1ef
--- /dev/null
+++ b/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.
+
+   $id$ */
+
+/* System */
+#include <stdint.h>
+#include <string.h>
+
+/* Opentracker */
+#include "ot_hex.h"
+
+static int fromhex(unsigned char c) {
+  if (c >= '0' && c <= '9')
+    return c - '0';
+  c |= 0x20; /* fold upper case onto lower, digits are already handled */
+  if (c >= 'a' && c <= 'f')
+    return c - 'a' + 10;
+  return -1;
+}
+
+int hex_isdigit(int c) { return fromhex((unsigned char)c) >= 0; }
+
+char *hex_fromhash(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_tohash(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 = fromhex((unsigned char)src[2 * i])) < 0)
+      return 0;
+    if ((low = fromhex((unsigned char)src[2 * i + 1])) < 0)
+      return 0;
+
+    decoded[i] = (uint8_t)((high << 4) | low);
+  }
+
+  memcpy(hash, decoded, sizeof(decoded));
+  return 1;
+}
-- 
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