[api] Add hexdump() utility

arduino/libretuya/core/LibreTuyaAPI.cpp

@@ -8,7 +8,13 @@ String ipToString(const IPAddress &ip) {
 	return String(szRet);
 }
 
-static void lt_random_bytes(uint8_t *buf, size_t len) {
+/**
+ * @brief Generate random bytes using rand().
+ *
+ * @param buf destination pointer
+ * @param len how many bytes to generate
+ */
+void lt_rand_bytes(uint8_t *buf, size_t len) {
 	int *data = (int *)buf;
 	size_t i;
 	for (i = 0; len >= sizeof(int); len -= sizeof(int)) {
@@ -20,3 +26,36 @@ static void lt_random_bytes(uint8_t *buf, size_t len) {
 		memcpy(buf + i * sizeof(int), pRem, len);
 	}
 }
+
+/**
+ * @brief Print data pointed to by buf in hexdump-like format (hex+ASCII).
+ *
+ * @param buf source pointer
+ * @param len how many bytes to print
+ * @param offset increment printed offset by this value
+ * @param width how many bytes on a line
+ */
+void hexdump(uint8_t *buf, size_t len, uint32_t offset = 0, uint8_t width = 16) {
+	uint16_t pos = 0;
+	while (pos < len) {
+		// print hex offset
+		printf("%06x ", offset + pos);
+		// calculate current line width
+		uint8_t lineWidth = min(width, len - pos);
+		// print hexadecimal representation
+		for (uint8_t i = 0; i < lineWidth; i++) {
+			if (i % 8 == 0) {
+				printf(" ");
+			}
+			printf("%02x ", buf[pos + i]);
+		}
+		// print ascii representation
+		printf(" |");
+		for (uint8_t i = 0; i < lineWidth; i++) {
+			char c = buf[pos + i];
+			printf("%c", isprint(c) ? c : '.');
+		}
+		printf("|\n");
+		pos += lineWidth;
+	}
+}

arduino/libretuya/core/LibreTuyaAPI.h

@@ -43,10 +43,9 @@ extern "C" {
 #define FPSTR(pstr_pointer) (reinterpret_cast<const __FlashStringHelper *>(pstr_pointer))
 #define PGM_VOID_P			const void *
 
-// C functions
 void lt_rand_bytes(uint8_t *buf, size_t len);
+void hexdump(uint8_t *buf, size_t len, uint32_t offset = 0, uint8_t width = 16);
 
-// C++ only functions
 #ifdef __cplusplus
 String ipToString(const IPAddress &ip);
 #endif