升压：如何创建一个线程，这样就可以控制所有的标准输出，标准错误？

问题描述

我C语言创建一个Win32控制台应用程序++。我使用一些API（不是我的，我不能修改其源）。这是写，这样它写入一些信息上的控制台屏幕不问......每次我把它（每秒48次），所以我想放入一些线和限制其输出能力，但我需要得到通知时，该线程将尝试一些输出信息这对我很重要。我有标准的字符串消息文本。如何做这样的事情在C ++使用boost？

I create a win32 console app in C++. I use some API (not mine, and I can not modify its sources). It Is written so that it writes some of its info onto console screen not asking... each time I call it (48 times per second) So I want to put it into some thread and limit its output capabilities, but I need to get notified when that thread will try to output some message which is important for me. I have message text in standard string. How to do such thing in C++ using boost?

推荐答案

这功能不存在升压。你可以，但是，使用来代替标准输出描述：

That feature does not exist in Boost. You can, however, use _dup2 to replace the standard out descriptor:

#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <io.h>
#include <iostream>
#include <windows.h>

int main()
{
    HANDLE h = CreateFile(TEXT("test.txt"), GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
    if (0 == SetStdHandle(STD_OUTPUT_HANDLE, h)) {
        std::fprintf(stderr, "`SetStdHandle` failed with error %d\n", (int)GetLastError());
        return EXIT_FAILURE;
    }

    int h_desc = _open_osfhandle((long)h, 0);
    _dup2(h_desc, STDOUT_FILENO);

    std::printf("test\r\n"); // This actually writes to `h`.
    std::fflush(stdout);

    std::cout << "another test" << std::endl; // Also writes to `h`

    CloseHandle(h);
    return EXIT_SUCCESS;
}

从本质上讲这是什么招确实是让你重定向所有写入标准输出，的std :: COUT ，和 GetStdHandle（STD_OUTPUT_HANDLE）到您选择的一个可写的句柄（ ^ h ）。当然，你可以使用来创建可写的句柄（ ^ h ），并在另一个线程读取结尾阅读。

Essentially what this trick does is allow you to redirect all writes to stdout, std::cout, and GetStdHandle(STD_OUTPUT_HANDLE) to a writable handle of your choosing (h). Of course, you can use CreatePipe to create the writable handle (h) and read from the readable end in another thread.

编辑：如果您正在寻找一个跨平台的解决方案，请注意，这一招是POSIX兼容的系统更容易，因为的是在 unistd.h中和可写处理已描述符。

If you are looking for a cross-platform solution, note that this trick is even easier on POSIX-compatible systems because dup2 is a standard function in unistd.h and "writable handles" are already descriptors.

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