Boost::asio::windows::stream_handle客户端不获取数据
Boost::asio::windows::stream_handle客户端不获取数据
提问于 2022-09-01 09:46:49
我尝试在asio::windows::stream_handle中使用windows管道，但我得到了一种无法理解的行为:客户端不捕获传输的数据，但是服务器端不启动async_write的处理程序。我的密码在下面。Client和Server是两个不同的进程，它们的二进制文件位于同一个目录中。
服务器：
class MessageProcessor
{
private:
HANDLE m_WindowsPipeHandle;
OVERLAPPED m_OverlapWin;
std::unique_ptr<boost::asio::windows::stream_handle> m_Pipe;
public:
MessageProcessor(boost::asio::io_context& asio_ctx, const std::string& pipe_name)
{
if (std::filesystem::exists(pipe_name))
{
std::filesystem::remove(pipe_name);
}
m_WindowsPipeHandle = CreateNamedPipe(
pipe_name.c_str(),
PIPE_ACCESS_OUTBOUND | FILE_FLAG_FIRST_PIPE_INSTANCE | FILE_FLAG_OVERLAPPED,
PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT,
PIPE_UNLIMITED_INSTANCES,
1,
1,
INFINITE,
NULL);
if (m_WindowsPipeHandle == INVALID_HANDLE_VALUE)
{
assert(false && "Pipe");
exit(EXIT_FAILURE);
}
if (ConnectNamedPipe(m_WindowsPipeHandle, &m_OverlapWin) != 0)
{
assert(false && "Connect Pipe");
exit(EXIT_FAILURE);
}
std::this_thread::sleep_for(std::chrono::seconds(1));
m_Pipe = std::make_unique<boost::asio::windows::stream_handle>(asio_ctx, m_WindowsPipeHandle);
}
void AsyncWrite(const std::string& msg)
{
log("Launch async transfer", msg);
boost::asio::async_write(
*m_Pipe,
boost::asio::buffer(msg),
[](const boost::system::error_code& error, size_t bytes_transferred)
{
if (error)
{
log("Pipe transfer error", error);
}
else
{
log("Pipe transfer ok", bytes_transferred);
}
});
}
};AsynWrite被asio::post通过计时器调用延迟
客户端：
class Pipe
{
private:
HANDLE win_handle;
std::unique_ptr<boost::asio::windows::stream_handle> pipe;
std::string read_buf;
std::fstream fs;
public:
Pipe()
{
fs.open("tester.txt", std::ios_base::out);
win_handle = CreateFile(
cfg::PipeName.c_str(),
GENERIC_READ,
0,
NULL,
OPEN_EXISTING,
FILE_FLAG_OVERLAPPED,
NULL);
if (win_handle == INVALID_HANDLE_VALUE)
{
assert(false && "Pipe Client");
exit(EXIT_FAILURE);
}
pipe = std::make_unique<boost::asio::windows::stream_handle>(ctx, win_handle);
}
void Run()
{
fs << "Run launch" << std::endl;
boost::asio::async_read(
*pipe,
boost::asio::buffer(read_buf),
[this](const boost::system::error_code& error, size_t bytes)
{
if (error)
{
fs << error << std::endl;
}
if (!read_buf.empty())
{
fs << "Readed str: " << read_buf << std::endl;
}
else
{
fs << "Empty buf!" << std::endl;
}
boost::asio::post(ctx, boost::bind(&Pipe::Run, this));
});
}
};它总是写‘空buf’：
也许谁知道，为什么我的服务器没有真正通过win管道传输数据？
回答 1
Stack Overflow用户
回答已采纳
发布于 2022-09-01 14:22:41
boost::asio::buffer(read_buf)根据文档
创建一个表示给定字符串的新的可修改缓冲区。 template<类型名称标识，类型名称特征，类型名称Allocator> mutable_buffer缓冲区( std::basic_string< Elem，Allocator>，Allocator >& data)； 返回值 mutable_buffer(data.size()？&data : 0，data.size() * sizeof(Elem))。 备注 对给定的字符串对象调用的任何非const操作都会使缓冲区失效。
因此，您将显式地创建长度为零的缓冲区。缓冲区中没有空间，这是一个async_read。
您可以预先调整缓冲区的大小：
std::string buf;
std::cout << boost::asio::buffer(buf).size() << std::endl;
buf.assign("Hello world!");
std::cout << boost::asio::buffer(buf).size() << std::endl;
buf.resize(1024);
std::cout << boost::asio::buffer(buf).size() << std::endl;打印
0
12
1024如果您想要一个不断增长的缓冲区，您需要使用DynamicBuffer模型。例如streambuf或dynamic_string_buffer等。一个创造性的例子：
住在Coliru
#include <boost/asio.hpp>
#include <iostream>
using namespace std::string_view_literals;
namespace asio = boost::asio;
namespace {
auto poem = R"(
I went to send a missive today
As I have done so oft before
But I forgot to employ that scrap of advice
"Use Signal. Use Tor."
)"sv;
float constexpr crypto[]{
1.3563156e-19, 1.3563156e-19, 1.692641e+22, 1.7563698e+25,
1.6611423e+22, 6.7120163e+22, 4.2902826e+24, 4.524393e+30,
8.398558e-33, 1.3563156e-19, 1.3563156e-19, -2.0796537e-38,
1.2414338e+28, 1.271254e+31, 7.270847e+31, 1.1258676e+24,
2.028251e-19, 7.3782448e+28, 1.172262e-19, 1.3563156e-19,
10.007843, 7.316806e+34, 1.8466762e+20, 7.316806e+34,
1.8466762e+20, 7.316806e+34, 1.8466762e+20, 7.316806e+34,
1.3555985e-19, 1.3563156e-19, 1.6885541e+31, 1.595227e+25,
1.0901187e+27, 1.6885558e+31, 6.5649985e+28, 9.35016e-40};
auto signature = R"(
Manish Goregaokar 2017
)"sv;
} // namespace
template <typename DynBuf> void foo(DynBuf&& buf) {
std::array src{
asio::buffer(poem),
asio::buffer(crypto),
asio::buffer(signature),
};
for (auto in : src) {
for (; auto n = asio::buffer_copy(buf.prepare(90), in); in += n) {
buf.commit(n);
std::cout << "Read " << n << " bytes\n";
}
}
}
int main() {
std::string s;
foo(asio::dynamic_buffer(s));
asio::streambuf sb;
foo(sb);
std::cout << s.length() << " == " << sb.in_avail() << "\n"
<< s << "\n-----\n"
<< &sb;
}打印
Read 90 bytes
Read 75 bytes
Read 90 bytes
Read 54 bytes
Read 45 bytes
Read 90 bytes
Read 75 bytes
Read 90 bytes
Read 54 bytes
Read 45 bytes
444 == 354
I went to send a missive today
As I have done so oft before
But I forgot to employ that scrap of advice
"Use Signal. Use Tor."
Heed this advice, children.
It’s not something to ignore
Always, always, always, always
Use Signal. Use Tor.
Manish Goregaokar 2017
-----
I went to send a missive today
As I have done so oft before
But I forgot to employ that scrap of advice
"Use Signal. Use Tor."
Heed this advice, children.
It’s not something to ignore
Always, always, always, always
Use Signal. Use Tor.
Manish Goregaokar 2017整首诗：https://manishearth.github.io/blog/2017/03/12/use-signal-use-tor/
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/73567330
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