Revert "WIP2"

This reverts commit 1a03842.

Author: sjaeckel

src/omemo/omemo.c

@@ -1700,29 +1700,28 @@ omemo_encrypt_file(FILE* in, FILE* out, off_t file_size, int* gcry_res)
     return fragment;
 }
 
-int
-_bytes_from_hex(const char* hex,
-                unsigned char* bytes, size_t* size)
+void
+_bytes_from_hex(const char* hex, size_t hex_size,
+                unsigned char* bytes, size_t bytes_size)
 {
     const unsigned char ht[] = {
         0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, // 01234567
         0x08, 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 89:;<=>?
         0x00, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x00, // @ABCDEFG
     };
     const size_t ht_size = sizeof(ht);
-    size_t wr = 0;
-    const char* h = hex;
-    unsigned char* out = bytes;
 
     unsigned char b0;
     unsigned char b1;
 
-    for (; *h && *(h + 1); h += 2) {
-        b0 = ((unsigned char)*h & 0x1f) ^ 0x10;
-        b1 = ((unsigned char)*(h + 1) & 0x1f) ^ 0x10;
+    memset(bytes, 0, bytes_size);
+
+    for (int i = 0; (i < hex_size) && (i / 2 < bytes_size); i += 2) {
+        b0 = ((unsigned char)hex[i + 0] & 0x1f) ^ 0x10;
+        b1 = ((unsigned char)hex[i + 1] & 0x1f) ^ 0x10;
 
-        if (wr < *size && b0 <= ht_size && b1 <= ht_size) {
-            bytes[wr++] = (unsigned char)(ht[b0] << 4) | ht[b1];
+        if (b0 <= ht_size && b1 <= ht_size) {
+            bytes[i / 2] = (unsigned char)(ht[b0] << 4) | ht[b1];
         }
     }
 }