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如何在不拖尾字节的情况下发送不同长度的消息 \x00？
c++zeromq
浏览量:61
编辑于:2023-04-12 22:59:46
在下面的代码中，内部与之后是什么意思？20``message()``20``message.data(),
zmq::message_t message(20);
snprintf ((char *) message.data(), 20 ,"%05d %d %d", zipcode, temperature, relhumidity);
publisher.send(message);
从阅读文档开始，将消息初始化为 20 字节长。后做什么？message(20)``20``message.data(),
如何更改消息的大小以发送不带尾随字节的消息？是否可以在外部声明，并且该变量的长度用于启动消息并发送它？\x00``"%05d %d %d", zipcode, temperature, relhumidity
解决方案:
在为数据分配空间之前，您可以使用限制为零来测量数据的大小：snprintf()
auto length = std::snprintf(nullptr, 0, "%05d %d %d", zipcode, temperature, relhumidity) + 1;
// +1 to account for null terminating character.
zmq::message_t message(length);
std::snprintf(
static_cast<char *>(message.data()), length,
"%05d %d %d", zipcode, temperature, relhumidity
);
publisher.send(message);
You could also format into a local buffer that you know is large enough, measure the string's length, then copy it:
char buffer[64];
auto length = std::snprintf(buffer, 64, "%05d %d %d", zipcode, temperature, relhumidity) + 1;
zmq::message_t message(length);
std::copy(buffer, buffer + length, static_cast<char *>(message.data());
publisher.send(message);
