BLI_md5: add a utility function to 'translate' raw 16bytes digest into a nice 32chars hexadecimal string.

That kind of stuff belongs to BLI, not specialized code like thumbs.c

source/blender/blenlib/BLI_md5.h

@@ -41,5 +41,7 @@ void *md5_buffer(const char *buffer, size_t len, void *resblock);
 
 int md5_stream(FILE *stream, void *resblock);
 
+char *md5_to_hexdigest(void *resblock, char r_hex_digest[33]);
+
 #endif
 

source/blender/blenlib/intern/md5.c

@@ -389,3 +389,20 @@ void *md5_buffer(const char *buffer, size_t len, void *resblock)
 	/* Put result in desired memory area. */
 	return md5_read_ctx(&ctx, resblock);
 }
+
+char *md5_to_hexdigest(void *resblock, char r_hex_digest[33])
+{
+	static const char hex_map[17] = "0123456789abcdef";
+	const unsigned char *p;
+	char *q;
+	short len;
+
+	for (q = r_hex_digest, p = (const unsigned char *)resblock, len = 0; len < 16; ++p, ++len) {
+		const unsigned char c = *p;
+		*q++ = hex_map[c >> 4];
+		*q++ = hex_map[c & 15];
+	}
+	*q = '\0';
+
+	return r_hex_digest;
+}

source/blender/imbuf/intern/thumbs.c

@@ -258,9 +258,7 @@ static void thumbname_from_uri(const char *uri, char *thumb, const int thumb_len
 
 	md5_buffer(uri, strlen(uri), digest);
 	hexdigest[0] = '\0';
-	to_hex_char(hexdigest, digest, 16);
-	hexdigest[32] = '\0';
-	BLI_snprintf(thumb, thumb_len, "%s.png", hexdigest);
+	BLI_snprintf(thumb, thumb_len, "%s.png", md5_to_hexdigest(digest, hexdigest));
 
 	// printf("%s: '%s' --> '%s'\n", __func__, uri, thumb);
 }