WriteFile,WriteConsole和_tprintf的一些差别

WriteFile,WriteConsole和_tprintf的一些差别

这几个API都是用于输出的，但都有各自的特点:
1. _tprintf的实现利用了WriteFile和WideCharToMultiByte。
2. WriteFile只接受字节流，没有UNICODE的概念，WriteFile可以实现重定向。
3. WriteConsole有两个版本WriteConsoleA和WriteConsoleW, 可以分别接收ANSI和UNICODE字符串,不支持重定向。

看下面这个简单的程序,编译后再用eXeScope分析一下Import

    1 #include <stdio.h>

    2 

    3 void wmain(int argc, wchar_t* argv[])

    4 {

    5     wprintf(L"Hello World\n");

    6 }

看了eXeScope的输出后，发现wprintf的实现利用了WideCharToMultiByte和WriteFile等API，在写入文件前首先是将UNICODE转换成多字节的。

然后本人试着直接调用API进行输出，分别使用了API WriteConsole和WriteFile

 

    1 #include <windows.h>

    2 

    3 #pragma comment(lib, "User32")

    4 #pragma comment(lib, "Kernel32")

    5 #pragma comment(linker, "/Entry:wmain")

    6 #pragma comment(linker, "/Merge:.rdata=.text")

    7 

    8 void *operator new[](unsigned int size){

    9     return HeapAlloc (GetProcessHeap(), NULL, size);

   10 }

   11 

   12 void operator delete[] (void* memblock){

   13     HeapFree (GetProcessHeap(), NULL, memblock);

   14 }

   15 

   16 bool WINAPI StdOut( wchar_t* lpString)

   17 {

   18     HANDLE hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);

   19     DWORD numOfCharsWritten=0;

   20     WriteConsole(hStdOut, lpString, lstrlen(lpString), &numOfCharsWritten, NULL);

   21 

   22     DWORD dwNum = WideCharToMultiByte(CP_OEMCP,NULL,lpString, -1, NULL, 0, NULL, false);

   23     char *pText = new char[dwNum];

   24     WideCharToMultiByte(CP_OEMCP,NULL,lpString,-1,pText,dwNum,NULL,false);

   25     BOOL bRet = WriteFile(hStdOut, pText, dwNum, &numOfCharsWritten, NULL);

   26     delete[] pText;

   27     return bRet;

   28 }

   29 

   30 void wmain()

   31 {

   32     wchar_t *pChar = L"Hello World!\n";

   33     StdOut(pChar);

   34 }

命令行编译 cl client.cpp /DUNICODE /D_UNICODE /LINK /ALIGN:16

程序执行结果为：

Hello World!

Hello World!

下面的程序Parent.cpp用于输出重定向

    1 #include "stdafx.h"

    2 #include <windows.h>

    3 #include <tchar.h>

    4 #include <stdio.h>

    5 

    6 HANDLE SpawnAndRedirect(LPCTSTR commandLine, HANDLE *hStdOutputReadPipe, LPCTSTR lpCurrentDirectory);

    7 

    8 int _tmain()

    9 {

   10     HANDLE hOutput, hProcess;

   11     hProcess = SpawnAndRedirect(_T("client.exe"), &hOutput, NULL);

   12     if (!hProcess){

   13         _tprintf(_T("Failed to spawn the thread\n"));

   14         return 1;

   15     }

   16 

   17     char buffer[129];

   18     DWORD read;

   19     while(ReadFile(hOutput, buffer, 128, &read, NULL))

   20     {

   21         buffer[read] = '\0';

   22         printf("%s\n", buffer);

   23     }

   24 

   25     CloseHandle(hOutput);

   26     CloseHandle(hProcess);

   27 

   28     return 0;

   29 }

   30 

   31 

   32 // The following function is a shortened variant of Q190351 - HOWTO: Spawn Console Processes with Redirected Standard Handles

   33 // There is no special magic here, and this version doesn't address issues like:

   34 // - redirecting Input handle

   35 // - spawning 16-bits process 

   36 // - command-line limitations (unsafe 1024-char buffer)

   37 // So you might want to use more advanced versions such as the ones you can find on CodeProject

   38 HANDLE SpawnAndRedirect(LPCTSTR commandLine, HANDLE *hStdOutputReadPipe, LPCTSTR lpCurrentDirectory)

   39 {

   40     HANDLE hStdOutputWritePipe, hStdOutput, hStdError;

   41     CreatePipe(hStdOutputReadPipe, &hStdOutputWritePipe, NULL, 0);  // create a non-inheritable pipe

   42     DuplicateHandle(GetCurrentProcess(), hStdOutputWritePipe,

   43         GetCurrentProcess(), &hStdOutput,                           // duplicate the "write" end as inheritable stdout

   44         0, TRUE, DUPLICATE_SAME_ACCESS);

   45     DuplicateHandle(GetCurrentProcess(), hStdOutput,

   46         GetCurrentProcess(), &hStdError,                            // duplicate stdout as inheritable stderr

   47         0, TRUE, DUPLICATE_SAME_ACCESS);

   48     CloseHandle(hStdOutputWritePipe);                               // no longer need the non-inheritable "write" end of the pipe

   49 

   50     PROCESS_INFORMATION pi;

   51     STARTUPINFO si;

   52     ZeroMemory(&si, sizeof(STARTUPINFO));

   53     si.cb = sizeof(STARTUPINFO);

   54     si.dwFlags = STARTF_USESTDHANDLES|STARTF_USESHOWWINDOW;

   55     si.hStdInput  = GetStdHandle(STD_INPUT_HANDLE); // (this is bad on a GUI app)

   56     si.hStdOutput = hStdOutput;

   57     si.hStdError  = hStdError;

   58     si.wShowWindow = SW_HIDE;                       // IMPORTANT: hide subprocess console window

   59     TCHAR commandLineCopy[1024];                    // CreateProcess requires a modifiable buffer

   60     _tcscpy(commandLineCopy, commandLine);

   61     if (!CreateProcess(    NULL, commandLineCopy, NULL, NULL, TRUE,

   62         CREATE_NEW_CONSOLE, NULL, lpCurrentDirectory, &si, &pi))

   63     {

   64         CloseHandle(hStdOutput);

   65         CloseHandle(hStdError);

   66         CloseHandle(*hStdOutputReadPipe);

   67         *hStdOutputReadPipe = INVALID_HANDLE_VALUE;

   68         return NULL;

   69     }

   70 

   71     CloseHandle(pi.hThread);

   72     CloseHandle(hStdOutput);

   73     CloseHandle(hStdError);

   74     return pi.hProcess;

   75 }

调用Parent,这个程序会创建子进程Client，并且通过pipe将Client的输出定向为Parent的输出，程序的执行结果为
Hello World!
在Client中WriteConsole的输出没有重定向过来！