Question

我试图通过设置好的管道通过注入的.dll将来自外部进程的一些数据管道传输到我的程序。但是，ReadFile（）仅在退出外部程序后才返回（此后它将给出正确的输出）。这是标准行为，还是我在使用管道（或其他方式）错误？

下面是该代码的相关部分（为简洁起见，省略了一些部分）：

main.cpp：

int main() {
    // Create a duplex pipe-based communication channel
    STARTUPINFO startupInfo = {};
    HANDLE parent_IN, parent_OUT;
    if (!IntraProcessComms(startupInfo, parent_IN, parent_OUT)) {
        std::cout << "Could not set up communication necessities" << std::endl;
        return 1;
    }

    // Launch program and obtain the handle
    PROCESS_INFORMATION processInfo = {};
    if (!CreateProcess(
            nullptr,                                                        // path
            LPSTR("[the program path]"),                                    // commands
            nullptr,                                                        // handler inheritable
            nullptr,                                                        // thread inheritable
            true,                                                           // handler inheritance from caller
            0,                                                              // creation flag
            nullptr,                                                        // environment
            nullptr,                                                        // directory
            &startupInfo,                                                   // startup info
            &processInfo)) {                                                // process info
        std::cout << "Could not launch program" << std::endl;
        return 2;
    }

    // Inject the DLL (omitted here; it is injected successfully)
    if (!InjectDLL(processInfo.hProcess, "scraper.dll")) {
        std::cout << "Could not inject DLL" << std::endl;
        return 3;
    }

    CloseHandle(processInfo.hProcess);
    CloseHandle(processInfo.hThread);
    std::cout << "Successfully set up" << std::endl;

    char buffer[BUFSIZ];
    ZeroMemory(buffer, BUFSIZ);
    ReadFile(parent_IN, buffer, sizeof(buffer), nullptr, nullptr);
    std::cout << "Read: \"" << buffer << "\"" << std::endl;
    return 0;
}

bool IntraProcessComms(STARTUPINFO &si, HANDLE &parent_IN, HANDLE &parent_OUT) {
    HANDLE child_IN, child_OUT;
    SECURITY_ATTRIBUTES securityAttr {
        sizeof(SECURITY_ATTRIBUTES),                                        // size
        nullptr,                                                            // security
        true                                                                // inheritable
    };

    // Create pipes from the child to the parent and vice-versa
    if (!CreatePipe(
            &parent_IN,
            &child_OUT,
            &securityAttr,
            0)
    || !CreatePipe(
            &child_IN,
            &parent_OUT,
            &securityAttr,
            0))
        return false;

    // Ensure only the correct handles are inherited
    if (!SetHandleInformation(
            parent_IN,
            HANDLE_FLAG_INHERIT,
            0)
    || !SetHandleInformation(
            parent_OUT,
            HANDLE_FLAG_INHERIT,
            0))
        return false;

    // Set up startupinfo
    si.cb = sizeof(STARTUPINFO);
    si.hStdError = child_OUT;
    si.hStdOutput = child_OUT;
    si.hStdInput = child_IN;
    si.dwFlags = STARTF_USESTDHANDLES;

    return true;
}

scraper.dll：

BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpReserved) {
    if (fdwReason == DLL_PROCESS_ATTACH) {
        // stdout was redirected by IntraProcessComms()
        std::cout << "Send from .dll";
    }
    return true;
}

（可能存在一些明显的错误/奇怪的做法，我是C ++的新手）

Answer 1

写入std::cout的内容将在内部缓存，直到缓冲区已满或刷新为止。直到发生刷新，管道才会看到任何写入的数据。

您可以在写入数据后调用std::cout.flush()，或在输出语句后附加<< std::endl以添加换行符并刷新缓冲区。如果您仅要发送完整的消息（即，一个<<到cout，而不是几个来编写消息），则可以在流中使用unitbuf标志来刷新输出在每次输出操作（std::cout << std::unitbuf << "Send from .dll";之后，您可以使用nounitbuf重新打开缓冲。

从注入的.dll冻结直到进程终止的管道

1 个答案: