如何写一个boost :: asio :: mutable_buffer？

Question

我有一些代码为我提供了一个指向缓冲区的指针,以及我需要填充数据的缓冲区大小.我用一个boost::asio::mutable_buffer实例表示这个缓冲区,但是我如何正确使用这个缓冲区(例如,给它写一个字符串,......)并且增强强制执行缓冲区边界？

这是一些伪代码:

size_t some_callback(void *ptr, size_t) {
    // this function is called by 3rd party
    return our_handler(boost::asio::mutable_buffer(ptr, size));
}

size_t our_handler(const boost::asio::mutable_buffer &buffer)
{
    const std::string test("test");
    // How do I write this string into my buffer?
    return test.size();
}

Answer 1

boost::asio::buffer_cast<>()是你应该用来访问缓冲区使用的指针. boost::asio::buffer_size()是你应该用来访问所用大小的.

例如

const std::string test("test");
const size_t len = std::min(boost::asio::buffer_size(mybuf), test.length());
memcpy(boost::asio::buffer_cast<void *>(mybuf),
    test.c_str(),
    len);
const std::string test2("test");
boost::asio::mutable_buffer offset = mybuf + len;
const size_t len2 = std::min(boost::asio::buffer_size(offset), test2.length());
memcpy(boost::asio::buffer_cast<void *>(offset),
    test.c_str(),
    len2);

boost::asio::mutable_buffer offset2 = offset + len2;

也可以看看:

• buffer_cast()
• buffer_size()