[libs] Implement Update MD5

cores/common/base/api/lt_utils.c

@@ -39,3 +39,36 @@ void hexdump(const uint8_t *buf, size_t len, uint32_t offset, uint8_t width) {
 		pos += lineWidth;
 	}
 }
+
+char *lt_btox(const uint8_t *src, int len, char *dest) {
+	// https://stackoverflow.com/a/53966346
+	const char hex[] = "0123456789abcdef";
+	len *= 2;
+	dest[len] = '\0';
+	while (--len >= 0)
+		dest[len] = hex[(src[len >> 1] >> ((1 - (len & 1)) << 2)) & 0xF];
+	return dest;
+}
+
+uint8_t *lt_xtob(const char *src, int len, uint8_t *dest) {
+	// https://gist.github.com/vi/dd3b5569af8a26b97c8e20ae06e804cb
+
+	// mapping of ASCII characters to hex values
+	// (16-byte swapped to reduce XOR 0x10 operation)
+	const uint8_t mapping[] = {
+		0x00, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x00, // @ABCDEFG
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // HIJKLMNO
+		0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, // 01234567
+		0x08, 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 89:;<=>?
+	};
+
+	int j = 0;
+	uint8_t idx0;
+	uint8_t idx1;
+	for (int i = 0; i < len; i += 2) {
+		idx0	  = ((uint8_t)src[i + 0] & 0x1F);
+		idx1	  = ((uint8_t)src[i + 1] & 0x1F);
+		dest[j++] = (mapping[idx0] << 4) | (mapping[idx1] << 0);
+	}
+	return dest;
+}

cores/common/base/api/lt_utils.h

@@ -45,3 +45,23 @@ void hexdump(
 	uint8_t width
 #endif
 );
+
+/**
+ * @brief Convert a byte array to hexadecimal string.
+ *
+ * @param src source byte array
+ * @param len source length (bytes)
+ * @param dest destination string
+ * @return destination string
+ */
+char *lt_btox(const uint8_t *src, int len, char *dest);
+
+/**
+ * @brief Convert a hexadecimal string to byte array.
+ *
+ * @param src source string
+ * @param len source length (chars)
+ * @param dest destination byte array
+ * @return destination byte array
+ */
+uint8_t *lt_xtob(const char *src, int len, uint8_t *dest);