helper: Code cleanup for hexify()

Simplify hexify() and do not longer use 0 as special case for the
parameter 'count' to determine the string length of the binary input.
Instead, use strlen() outside of the function if needed.
Additionally, fix the return value and return the length of the
converted string. The old function always returned 2 * count.

Also, use more appropriate data types for the function parameters and
add a small documentation.

Change-Id: I133a8ab786b8f7c1296afcaf9c0a0b43881e5112
Signed-off-by: Marc Schink <openocd-dev@marcschink.de>
Reviewed-on: http://openocd.zylin.com/3793
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>

1 files changed, 29 insertions, 8 deletions

diff --git a/src/helper/binarybuffer.c b/src/helper/binarybuffer.c
index 26aa8cc..76f657f 100644
--- a/src/helper/binarybuffer.c
+++ b/src/helper/binarybuffer.c
@@ -45,6 +45,11 @@ static const unsigned char bit_reverse_table256[] = {
 	0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF, 0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF
 };
 
+static const char hex_digits[] = {
+	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+	'a', 'b', 'c', 'd', 'e', 'f'
+};
+
 void *buf_cpy(const void *from, void *_to, unsigned size)
 {
 	if (NULL == from || NULL == _to)
@@ -407,18 +412,34 @@ size_t unhexify(uint8_t *bin, const char *hex, size_t count)
 	return i / 2;
 }
 
-int hexify(char *hex, const char *bin, int count, int out_maxlen)
+/**
+ * Convert binary data into a string of hexadecimal pairs.
+ *
+ * @param[out] hex Buffer to store string of hexadecimal pairs. The buffer size
+ *                 must be at least @p length.
+ * @param[in] bin Buffer with binary data to convert into hexadecimal pairs.
+ * @param[in] count Number of bytes to convert.
+ * @param[in] length Maximum number of characters, including null-terminator,
+ *                   to store into @p hex.
+ *
+ * @returns The length of the converted string excluding null-terminator.
+ */
+size_t hexify(char *hex, const uint8_t *bin, size_t count, size_t length)
 {
-	int i, cmd_len = 0;
+	size_t i;
+	uint8_t tmp;
 
-	/* May use a length, or a null-terminated string as input. */
-	if (count == 0)
-		count = strlen(bin);
+	if (!length)
+		return 0;
 
-	for (i = 0; i < count; i++)
-		cmd_len += snprintf(hex + cmd_len, out_maxlen - cmd_len, "%02x", bin[i] & 0xff);
+	for (i = 0; i < length - 1 && i < 2 * count; i++) {
+		tmp = (bin[i / 2] >> (4 * ((i + 1) % 2))) & 0x0f;
+		hex[i] = hex_digits[tmp];
+	}
 
-	return cmd_len;
+	hex[i] = 0;
+
+	return i;
 }
 
 void buffer_shr(void *_buf, unsigned buf_len, unsigned count)