test mqtt length's encoding

lib_acl_cpp/samples/mqtt/mqtt_length/Makefile

@@ -0,0 +1,4 @@
+all:
+	g++ -o test main.cpp
+clean:
+	rm -f test

lib_acl_cpp/samples/mqtt/mqtt_length/main.cpp

@@ -0,0 +1,71 @@
+/**
+ * Copyright (C) 2015-2018 IQIYI
+ * All rights reserved.
+ *
+ * AUTHOR(S)
+ *   Zheng Shuxin
+ *   E-mail: zhengshuxin@qiyi.com
+ * 
+ * VERSION
+ *   Wed 24 Mar 2021 06:49:23 PM CST
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+static unsigned decode(const unsigned char* buf, unsigned len) {
+	unsigned n = 0;
+	for (unsigned i = 0; i < len; i++) {
+		n |= (unsigned) ((buf[i] & 0x7f) << (7 * i));
+	}
+	return n;
+}
+
+static int encode(unsigned n, unsigned char *buf) {
+	int len = 0;
+	if (n < 128) {
+		buf[len++] = n & 0x7f;
+	} else if (n < 16384) {
+		buf[len++] = ((unsigned char) n & 0x7f) | 0x80;
+		buf[len++] = ((unsigned char) (n >> 7) & 0x7f);
+	} else if (n < 2097152) {
+		buf[len++] = ((unsigned char) n & 0x7f) | 0x80;
+		buf[len++] = ((unsigned char) (n >> 7 ) & 0x7f) | 0x80;
+		buf[len++] = ((unsigned char) (n >> 14) & 0x7f);
+	} else if (n < 268435456) {
+		buf[len++] = ((unsigned char) n & 0x7f) | 0x80;
+		buf[len++] = ((unsigned char) (n >> 7 ) & 0x7f) | 0x80;
+		buf[len++] = ((unsigned char) (n >> 14) & 0x7f) | 0x80;
+		buf[len++] = ((unsigned char) (n >> 21) & 0x7f);
+	} else {
+		printf("invalid dlen_=%u\n", n);
+		return -1;
+	}
+
+	return len;
+}
+
+int main(void) {
+	unsigned char buf[4];
+
+	unsigned i, max= 268435455;
+	for (i = 0; i < max; i++) {
+		int len = encode(i, buf);
+		if (len == -1) {
+			printf("encode i=%u error\r\n", i);
+			break;
+		}
+
+		unsigned n = decode(buf, (unsigned) len);
+		if (n != i) {
+			printf("decode error, n=%u, i=%u\n", n, i);
+			break;
+		}
+		if (i < 10) {
+			printf("ok, i=%u, n=%u\n", i, n);
+		}
+	}
+
+	printf("i=%u, max=%u, status=%s\r\n", i, max, i == max ? "ok" : "error");
+	return 0;
+}

lib_acl_cpp/samples/mqtt/mqtt_pub/main.cpp

@@ -24,7 +24,7 @@ static bool test_publish(acl::mqtt_client& conn, unsigned short id) {
 	publish.set_topic(topic);
 
 	acl::string payload;
-	payload.format("payload-%d", id);
+	payload.format("payload-%ddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd", id);
 	publish.set_payload((unsigned) payload.size(), payload);
 
 	if (!conn.send(publish)) {

lib_acl_cpp/src/mqtt/mqtt_header.cpp

@@ -151,17 +151,17 @@ bool mqtt_header::build_header(string& out) {
 	if (dlen_ < 128) {
 		header[len++] = dlen_ & 0x7f;
 	} else if (dlen_ < 16384) {
-		header[len++] = (unsigned char) dlen_ & 0x7f;
+		header[len++] = ((unsigned char) dlen_ & 0x7f) | 0x80;
-		header[len++] = ((unsigned char) (dlen_ >> 7) & 0x7f) | 0x80;
+		header[len++] = ((unsigned char) (dlen_ >> 7) & 0x7f);
 	} else if (dlen_ < 2097152) {
-		header[len++] = (unsigned char)  dlen_ & 0x7f;
+		header[len++] = ((unsigned char) dlen_ & 0x7f) | 0x80;
 		header[len++] = ((unsigned char) (dlen_ >> 7 ) & 0x7f) | 0x80;
-		header[len++] = ((unsigned char)(dlen_ >> 14) & 0x7f) | 0x80;
+		header[len++] = ((unsigned char) (dlen_ >> 14) & 0x7f);
 	} else if (dlen_ < 268435456) {
-		header[len++] = (unsigned char)  dlen_ & 0x7f;
+		header[len++] = ((unsigned char) dlen_ & 0x7f) | 0x80;
 		header[len++] = ((unsigned char) (dlen_ >> 7 ) & 0x7f) | 0x80;
 		header[len++] = ((unsigned char) (dlen_ >> 14) & 0x7f) | 0x80;
-		header[len++] = ((unsigned char)(dlen_ >> 21) & 0x7f) | 0x80;
+		header[len++] = ((unsigned char) (dlen_ >> 21) & 0x7f);
 	} else {
 		logger_error("invalid dlen_=%u", dlen_);
 		return false;