better algorithms

skeletons/ber_tlv_length.c

@@ -20,7 +20,7 @@ ber_fetch_length(int _is_constructed, void *bufptr, size_t size,
 		/*
 		 * Short definite length.
 		 */
-		*len_r = (oct & 0x7F);
+		*len_r = oct;	/* & 0x7F */
 		return 1;
 	} else {
 		ber_tlv_len_t len;
@@ -38,7 +38,7 @@ ber_fetch_length(int _is_constructed, void *bufptr, size_t size,
 
 		oct &= 0x7F;	/* Leave only the 7 LS bits */
 		for(len = 0, buf++, skipped = 1;
-			oct && (++skipped < size); buf++, oct--) {
+			oct && (++skipped <= size); buf++, oct--) {
 
 			len = (len << 8) | *buf;
 			if(len < 0
@@ -118,10 +118,10 @@ ber_skip_length(int _is_constructed, void *ptr, size_t size) {
 
 ssize_t
 der_tlv_length_serialize(ber_tlv_len_t len, void *bufp, size_t size) {
-	size_t computed_size;	/* Size of len encoding */
+	size_t required_size;	/* Size of len encoding */
 	uint8_t *buf = (uint8_t *)bufp;
 	uint8_t *end;
-	int i;
+	size_t i;
 
 	if(len <= 127) {
 		/* Encoded in 1 octet */
@@ -132,28 +132,25 @@ der_tlv_length_serialize(ber_tlv_len_t len, void *bufp, size_t size) {
 	/*
 	 * Compute the size of the subsequent bytes.
 	 */
-	computed_size = sizeof(len);	/* assert(sizeof(len)<128), n.p. */
-	for(i = (8*(sizeof(len)-1)); i > 0; i -= 8) {
-		if((len >> i) & 0xFF) break;
-		computed_size--;
+	for(required_size = 1, i = 8; i < 8 * sizeof(len); i += 8) {
+		if(len >> i)
+			required_size++;
+		else
+			break;
 	}
 
-	if(size) {
-		*buf++ = 0x80 | computed_size;	/* Length of the encoding */
-		size--;
-	}
+	if(size < required_size)
+		return required_size + 1;
+
+	*buf++ = 0x80 | required_size;	/* Length of the encoding */
 
 	/*
 	 * Produce the len encoding, space permitting.
 	 */
-	if(size > computed_size)
-		end = buf + computed_size;
-	else
-		end = buf + size;
-	for((void)i /* Reuse bits count */; buf < end; i -= 8, buf++) {
-		*buf = (len >> i) & 0xFF;
-	}
+	end = buf + required_size;
+	for(i -= 8; buf < end; i -= 8, buf++)
+		*buf = (len >> i);
 
-	return computed_size + 1;
+	return required_size + 1;
 }