[英]Deadlock while using ReadFile and WriteFile
我正在做一个学校项目,试图在子进程的StdOut上显示在父StdIn中编写的内容。 反之亦然,也就是说,在父StdOut上显示子进程StdIn上写的内容,但是我在ReadFile和WriteFile操作中陷入了僵局。
从我在研究此主题期间收集到的信息来看,这是使用同步管道时常见的问题。
是否应该通过事件来同步管道操作的读写? 您是否建议其他方法? 任何建议,将不胜感激,在此先感谢。
Parent.cpp
#include <windows.h>
#include <iostream>
#include <stdio.h>
//read handle pipe1
HANDLE r1 = NULL;
//write handle pip1
HANDLE w1 = NULL;
//read handle pipe2
HANDLE r2 = NULL;
//write handle for pipe2
HANDLE w2 = NULL;
#define BUFSIZE 4096
void CreateChildProcess() {
TCHAR applicationName[] = TEXT("Child");
PROCESS_INFORMATION pi;
STARTUPINFO si;
BOOL success = FALSE;
ZeroMemory(&pi, sizeof(PROCESS_INFORMATION));
ZeroMemory(&si, sizeof(STARTUPINFO));
si.cb = sizeof(STARTUPINFO);
si.hStdError = w1;
si.hStdOutput = w1;
si.hStdInput = r2;
si.dwFlags |= STARTF_USESTDHANDLES;
success = CreateProcess(NULL, applicationName, NULL, NULL, TRUE, CREATE_NEW_CONSOLE, NULL, NULL, &si, &pi);
if (!success) {
printf("Error creating child process \n");
}
else {
printf("Child process successfuly created \n");
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
}
}
void WriteToPipe() {
DWORD read, written;
CHAR chBuf[BUFSIZE];
BOOL success = FALSE;
HANDLE pStdIn = GetStdHandle(STD_INPUT_HANDLE);
for (;;)
{
success = ReadFile(pStdIn, chBuf, BUFSIZE, &read, NULL);
if (!success || read == 0) break;
success = WriteFile(w2, chBuf, read, &written, NULL);
if (!success) break;
}
}
void ReadFromPipe() {
DWORD read, written;
CHAR chBuf[BUFSIZE];
BOOL success = FALSE;
HANDLE pStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
for (;;)
{
success = ReadFile(r1, chBuf, BUFSIZE, &read, NULL);
if (!success || read == 0) break;
success = WriteFile(pStdOut, chBuf, read, &written, NULL);
if (!success) break;
}
}
int main()
{
DWORD dRead, dWritten;
CHAR chBuf[BUFSIZE];
BOOL bSuccess = FALSE;
SECURITY_ATTRIBUTES secAttr;
secAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
secAttr.bInheritHandle = TRUE;
secAttr.lpSecurityDescriptor = NULL;
printf("Creating first pipe\n");
if (!CreatePipe(&r1, &w1, &secAttr, 0)) {
printf("\nError creating first pipe\n");
}
printf("Creating second pipe\n");
if (!CreatePipe(&r2, &w2, &secAttr, 0)) {
printf("Error creating second pipe \n");
}
if (!SetHandleInformation(r1, HANDLE_FLAG_INHERIT, 0)) {
printf("r1 SetHandleInformation \n");
}
if (!SetHandleInformation(w2, HANDLE_FLAG_INHERIT, 0)) {
printf("w2 SetHandleInformation \n");
}
printf("\nCreating child process..... \n");
CreateChildProcess();
WriteToPipe();
ReadFromPipe();
return 0;
}
Child.cpp
#include <windows.h>
#include <stdio.h>
#include "pch.h"
#define BUFSIZE 4096
int main()
{
DWORD dRead, dWritten;
CHAR chBuf[BUFSIZE];
BOOL success = FALSE;
HANDLE stdIn = GetStdHandle(STD_INPUT_HANDLE);
HANDLE stdOut = GetStdHandle(STD_OUTPUT_HANDLE);
if (stdIn == INVALID_HANDLE_VALUE || stdOut == INVALID_HANDLE_VALUE) {
ExitProcess(1);
}
for (;;) {
success = ReadFile(stdIn, chBuf, BUFSIZE, &dRead, NULL);
if (!success || dRead == 0) break;
success = WriteFile(stdOut, chBuf, dRead, &dWritten, NULL);
if (!success) break;
}
return 0;
}
您将无法显示在父级StdOut上的子进程StdIn上写的内容,因为子级的stdIn Handle设置为“ r2”。 因此,您将无法在子进程中手动插入任何内容。 我建议使用namepipe ,以便child的std句柄不会与其他pipe句柄混合。
for(;;)等于while(1),并且ReadFile()在接收到数据之前不会返回,因此,如果不发生异常(不包括未传入数据),则循环将永不中断,并且代码将不会中断。 t继续阅读ReadFromPipe();
使用名称管道的重叠模式,或尝试创建2个线程和2个名称管道,一个从名称管道读取然后打印出来,另一个从stdin读取然后写入名称管道(在两个进程中)。
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