Windows Pipeline (Pipe) is a very important operating system feature that allows data to be passed between different processes. In the Windows system, pipelines are widely used in various scenarios, such as inter-process communication, data processing, and log analysis. In this article, we will discuss in depth the concept, implementation principles, application scenarios and usage methods of Windows pipelines.
1. The concept and implementation principle of Windows pipeline
A Windows pipe is a data transfer mechanism that allows one process to pass output data to another process while another process can read data from the pipe. A Windows pipe is an unnamed pipe that has no name and can only be used to pass data. The realization principle of the Windows pipeline is based on the mechanism of the operating system kernel, which stores data by creating a data buffer, and uses synchronization and mutual exclusion mechanisms to ensure the safe transmission of data when sending and receiving data.
Windows pipes can be divided into two types: anonymous pipes and named pipes. An anonymous pipe is a pipe that can only be used for local inter-process communication. It has no name and can only be created when a process is created. A named pipe is a pipe that can be used for communication between local and network processes. It has a name and can be accessed by name. In this article, we only discuss the use of anonymous pipes.
2. Application scenarios of Windows pipeline
Windows pipelines have a wide range of application scenarios, such as:
1. Inter-process communication: Windows pipes can be used to transfer data between different processes, such as passing the output data of one process to another process for processing.
2. Data processing: Windows pipelines can be used to process data, such as passing the contents of a text file to a pipeline for string matching or sorting operations.
3. Log analysis: Windows pipes can be used to pass the log output of one application to another program for analysis.
3. How to use Windows pipeline
On Windows systems, using Windows pipelines requires the use of some API functions. The following are some commonly used API functions:
1. CreatePipe function: used to create an anonymous pipe, return two file handles, one for reading data, one for writing data.
2. WriteFile function: used to write data into the pipeline.
3. ReadFile function: used to read data from the pipeline.
4. CloseHandle function: used to close the file handle.
Here is a simple example program that demonstrates how to use Windows pipes:
```c++
#include <windows.h>
#include <stdio.h>
int main() {
HANDLE hPipeRead, hPipeWrite;
SECURITY_ATTRIBUTES saAttr;
// Set pipeline attributes
saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
saAttr.bInheritHandle = TRUE;
saAttr.lpSecurityDescriptor = NULL;
// create pipe
if (!CreatePipe(&hPipeRead, &hPipeWrite, &saAttr, 0)) { printf("CreatePipe failed"); return 1; }
// create child process
STARTUPINFO si;
PROCESS_INFORMATION pi;
ZeroMemory(&si, sizeof(si));
si.cb = sizeof(si);
ZeroMemory(&pi, sizeof(pi));
si.hStdInput = hPipeRead;
si.dwFlags |= STARTF_USESTDHANDLES;
if (!CreateProcess(NULL, "child.exe", NULL, NULL, TRUE, 0, NULL, NULL, &si, &pi)) {
printf("CreateProcess failed");
return 1;
}
// Close the read pipe
CloseHandle(hPipeRead);
// 写入数据
char szBuf[] = "Hello, world!";
DWORD dwWritten;
if (!WriteFile(hPipeWrite, szBuf, sizeof(szBuf), &dwWritten, NULL)) {
printf("WriteFile failed");
return 1;
}
// Close the write pipe
CloseHandle(hPipeWrite);
// Wait for the child process to end
WaitForSingleObject(pi.hProcess, INFINITE);
// Close process and thread handles
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
return 0;
}
```
The above program creates an anonymous pipe, writes data to the pipe, and then starts a child process to read the data from the pipe. The code for the subprocess is as follows:
```c++
#include <windows.h>
#include <stdio.h>
int main() {
HANDLE hPipeRead;
char szBuf[1024];
DWORD dwRead;
// Read data from the pipe
hPipeRead = GetStdHandle(STD_INPUT_HANDLE);
if (!ReadFile(hPipeRead, szBuf, sizeof(szBuf), &dwRead, NULL)) { printf("ReadFile failed"); return 1; }
// Output the read data
printf("%s\n", szBuf);
return 0;
}
```
The child process reads data from standard input, that is, reads data from the pipe, and then outputs the read data to the screen. The above program demonstrates how to use Windows pipes for inter-process communication.
Four. Summary
This article introduces the concept, implementation principle, application scenarios and usage methods of Windows pipeline. By understanding the basic knowledge of the Windows pipeline, you can better apply the pipeline mechanism provided by the Windows system and improve the efficiency and reliability of the program.