C/C++ 文件操作之CreateFile函数、ReadFile函数和WriteFile函数的用法

1.CreateFile最初是专门为文件交互而开发的，但后来被扩展和增强，以包括Windows开发人员可用的大多数其他类型的I / O设备和机制 

　　HANDLE WINAPI CreateFile(   _In_      LPCTSTR lpFileName,                 _In_      DWORD dwDesiredAccess,   _In_      DWORD dwShareMode,   _In_opt_  LPSECURITY_ATTRIBUTES lpSecurityAttributes,   _In_      DWORD dwCreationDisposition,   _In_      DWORD dwFlagsAndAttributes,   _In_opt_  HANDLE hTemplateFile );

#include <stdio.h>
#include <windows.h>
int main()
{
    HANDLE hFILE=CreateFile("1.txt",GENERIC_WRITE,FILE_SHARE_READ,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);
    if(hFILE==INVALID_HANDLE_VALUE)
    {
        printf("CreateFile error
");
        return 0;
    }
    if(SetFilePointer(hFILE,0,NULL,FILE_END)==-1)
    {
        printf("SetFilePointer error
");
        return 0;
    }
    char buff[256]="hello";
    DWORD dwWrite;
    if(!WriteFile(hFILE,&buff,strlen(buff),&dwWrite,NULL))
    {
        printf("WriteFile error
");
        return 0;
    }
    printf("write %d.
",dwWrite);
    printf("done.
");
    CloseHandle(hFILE);
    return 0;
}

2. ReadFile函数 　　从文件指针指向的位置开始将数据读出到一个文件中， 且支持同步和异步操作，如果文件打开方式没有指明FILE_FLAG_OVERLAPPED的话，当程序调用成功时，它将实际读出文件的字节数保存到lpNumberOfBytesRead指明的地址空间中。FILE_FLAG_OVERLAPPED 允许对文件进行重叠操作。

　　BOOL WINAPI ReadFile(   __in          HANDLE hFile,                   // 文件句柄   __out         LPVOID lpBuffer,                // 接收数据用的 buffer   __in          DWORD nNumberOfBytesToRead,     // 要读取的字节数   __out         LPDWORD lpNumberOfBytesRead,    // 实际读取到的字节数   __in          LPOVERLAPPED lpOverlapped       // OVERLAPPED 结构，一般设定为 NULL  );

BOOL Read(char *filePath) {     HANDLE pFile;     DWORD fileSize;     char *buffer,*tmpBuf;     DWORD dwBytesRead,dwBytesToRead,tmpLen;     pFile = CreateFile(filePath,GENERIC_READ,                   FILE_SHARE_READ,         NULL,                        OPEN_EXISTING,        //打开已存在的文件          FILE_ATTRIBUTE_NORMAL,          NULL);     if ( pFile == INVALID_HANDLE_VALUE)     {         printf("open file error!
");         CloseHandle(pFile);         return FALSE;     }     fileSize = GetFileSize(pFile,NULL);          //得到文件的大小     buffer = (char *) malloc(fileSize);     ZeroMemory（buffer,fileSize);     dwBytesToRead = fileSize;     dwBytesRead = 0;     tmpBuf = buffer;     do{                                       //循环读文件，确保读出完整的文件             ReadFile(pFile,tmpBuf,dwBytesToRead,&dwBytesRead,NULL);         if (dwBytesRead == 0)             break;         dwBytesToRead -= dwBytesRead;         tmpBuf += dwBytesRead;         } while (dwBytesToRead > 0);         //  TODO 处理读到的数据 buffer     free(buffer);     CloseHandle(pFile);     return TRUE; }

 3.WriteFile函数 

BOOL WINAPI WriteFile(   __in          HANDLE hFile,                   // 文件句柄   __in          LPCVOID lpBuffer,               // 要写入的数据   __in          DWORD nNumberOfBytesToWrite,    // 要写入的字节数   __out         LPDWORD lpNumberOfBytesWritten, // 实际写入的字节数   __in          LPOVERLAPPED lpOverlapped       // OVERLAPPED 结构，一般设定为 NULL );

BOOL Write(char *buffer, DWORD contentLen) {     HANDLE pFile;     char *tmpBuf;     DWORD dwBytesWrite,dwBytesToWrite;     pFile = CreateFile(filePath,GENERIC_WRITE,                   0,         NULL,                        CREATE_ALWAYS,        //总是创建文件         FILE_ATTRIBUTE_NORMAL,          NULL);     if ( pFile == INVALID_HANDLE_VALUE)     {         printf("create file error!
");         CloseHandle(pFile);         return FALSE;     }     dwBytesToWrite = contentLen;     dwBytesWrite = 0;     tmpBuf = buffer;     do{                                       //循环写文件，确保完整的文件被写入           WriteFile(pFile,tmpBuf,dwBytesToWrite,&dwBytesWrite,NULL);         dwBytesToWrite -= dwBytesWrite;         tmpBuf += dwBytesWrite;         } while (dwBytesToWrite > 0);     CloseHandle(pFile);     return TRUE; }

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将数据写入一个文件。该函数比fwrite函数要灵活的多。也可将这个函数应用于对通信设备、管道、套接字以及邮槽的处理。返回时，TRUE（非零）表示成功，否则返回零。会设置GetLastError

链接：https://www.365jz.com/article/24618
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