WriteFile的内容，如何刷新到硬盘上?

Question

我的小程序是这样的:1.在main里面CreateFile打开一个文件
2.启动一个新的线程来Write一个字符串helloworld
3.在main里面等待线程完成，把内容读出来。但是Write的内容好像没有被写入硬盘，程序打印Read的内容为空。程序结束以后也没有磁盘文件生成。这到底是为什么呢? 我要求程序不要多次CreateFile/OpenFile，只打开一次，不同的线程执行读/写操作。
我应该如何修改? 请指点。程序代码如下:#include "stdafx.h"
#include<windows.h>
#include<stdio.h>
HANDLE hFile;
void* fun(void*){
char hw[]="helloworld";
DWORD dwWriten;
if(!WriteFile(hFile,(LPVOID)hw,sizeof(hw),&dwWriten,NULL)){//ERROR_ACCESS_DENIED(5)
printf("WriteFile failed:%d\n",GetLastError());
}
return NULL;
}
int _tmain(int argc, _TCHAR* argv[])
{
hFile=CreateFile("d:\\my.txt",
GENERIC_READ|GENERIC_WRITE,
FILE_SHARE_WRITE|FILE_SHARE_READ,
NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_HIDDEN,
NULL);
if(INVALID_HANDLE_VALUE==hFile){
printf("CreateFile failed:%d\n",GetLastError());
return 1;
}
HANDLE hThread=CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)fun,NULL,0,NULL);
if(NULL==hThread){
printf("CreateThread failed:%d\n",GetLastError());
return 1;
}
WaitForSingleObject(hThread,INFINITE);
char buf[20]={0};
DWORD dwRead;
if(!ReadFile(hFile,(LPVOID)buf,20,&dwRead,NULL)){
printf("ReadFile failed:%d\n",GetLastError());
return 1;
}
printf("content read:%s\n",buf);
CloseHandle(hFile);
return 0;
}

Answer 1

每次写完close文件 然后读

Answer 2

#include "stdafx.h"
#include<windows.h>
#include<stdio.h>
HANDLE hFile;
void* fun(void*){
TCHAR hw[]= _T("helloworld");
DWORD dwWriten;
if(!WriteFile(hFile,(LPVOID)hw,sizeof(hw),&dwWriten,NULL)){//ERROR_ACCESS_DENIED(5)
printf("WriteFile failed:%d\n",GetLastError());
}
return NULL;
}
int _tmain(int argc, _TCHAR* argv[])
{
hFile=CreateFile(_T("F:\\my.txt"),
GENERIC_READ|GENERIC_WRITE,
FILE_SHARE_WRITE|FILE_SHARE_READ,
NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_HIDDEN,
NULL);
if(INVALID_HANDLE_VALUE==hFile){
printf("CreateFile failed:%d\n",GetLastError());
return 1;
}
HANDLE hThread=CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)fun,NULL,0,NULL);
if(NULL==hThread){
printf("CreateThread failed:%d\n",GetLastError());
return 1;
}
WaitForSingleObject(hThread,INFINITE);
CloseHandle(hFile); TCHAR buf[20]={0};
DWORD dwRead;
hFile=CreateFile(_T("F:\\my.txt"),
GENERIC_READ,
FILE_SHARE_READ,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_HIDDEN,
NULL);
if(!ReadFile(hFile,(LPVOID)buf,sizeof(buf),&dwRead,NULL)){
printf("ReadFile failed:%d\n",GetLastError());
return 1;
}
_tprintf(_T("content read:%s\n"),buf);
CloseHandle(hFile);
return 0;
}

Answer 3

FlushFileBuffers(HANDLE)HANDLE CReateFile();有这么个函数，没用过~Cfile的话就直接用CFile::Flush();了

Answer 4

大虾，可不可以，不需要两次CreateFile,CloseHandle,就完成我的需求呢?

Answer 5

我的需求说白了就是，同一个文件句柄，被不同线程来执行读/写。不要多次CreateFile来得到不同的Handle.我修改了一下代码，加入了FlushFileBuffers，但是还是一样的运行结果。现在的代码是:#include "stdafx.h"
#include<windows.h>
#include<stdio.h>
HANDLE hFile;
void* fun(void*){
char hw[]="helloworld";
DWORD dwWriten;
if(!WriteFile(hFile,(LPVOID)hw,sizeof(hw),&dwWriten,NULL)){//ERROR_ACCESS_DENIED(5)
printf("WriteFile failed:%d\n",GetLastError());
}
if(!FlushFileBuffers(hFile)){
printf("Flush failed\n");
}
return NULL;
}
int _tmain(int argc, _TCHAR* argv[])
{
hFile=CreateFile("d:\\my.txt",
GENERIC_READ|GENERIC_WRITE,
FILE_SHARE_WRITE|FILE_SHARE_READ,
NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_NORMAL,
NULL);
if(INVALID_HANDLE_VALUE==hFile){
printf("CreateFile failed:%d\n",GetLastError());
return 1;
}
HANDLE hThread=CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)fun,NULL,0,NULL);
if(NULL==hThread){
printf("CreateThread failed:%d\n",GetLastError());
return 1;
}
WaitForSingleObject(hThread,INFINITE);
char buf[20]={0};
DWORD dwRead;
if(!ReadFile(hFile,(LPVOID)buf,20,&dwRead,NULL)){
printf("ReadFile failed:%d\n",GetLastError());
return 1;
}
printf("content read:%s\n",buf);
CloseHandle(hFile);
return 0;
}

Answer 6

#include "stdafx.h"#include<windows.h>
#include<stdio.h>
HANDLE hFile;
void* fun(void*){
char hw[]="helloworld";
DWORD dwWriten;
if(!WriteFile(hFile,(LPVOID)hw,sizeof(hw),&dwWriten,NULL)){//ERROR_ACCESS_DENIED(5)
printf("WriteFile failed:%d\n",GetLastError());
}
if(!FlushFileBuffers(hFile)){
printf("Flush failed\n");
}
return NULL;
}
int _tmain(int argc, _TCHAR* argv[])
{
hFile=CreateFile(_T("F:\\my.txt"),
GENERIC_READ|GENERIC_WRITE,
FILE_SHARE_WRITE|FILE_SHARE_READ,
NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_NORMAL,
NULL);
if(INVALID_HANDLE_VALUE==hFile){
printf("CreateFile failed:%d\n",GetLastError());
return 1;
}
HANDLE hThread=CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)fun,NULL,0,NULL);
if(NULL==hThread){
printf("CreateThread failed:%d\n",GetLastError());
return 1;
}
WaitForSingleObject(hThread,INFINITE); SetFilePointer(hFile, 0, 0, FILE_BEGIN); char buf[20]={0};
DWORD dwRead;
if(!ReadFile(hFile,(LPVOID)buf,20,&dwRead,NULL)){
printf("ReadFile failed:%d\n",GetLastError());
return 1;
}
printf("content read:%s\n",buf);
CloseHandle(hFile);
return 0;
}

Answer 7

WaitForSingleObject(hThread,INFINITE);
后面加上这句
SetFilePointer(hFile, 0, 0, FILE_BEGIN);

Answer 8

Bingo，这个就能搞定！谢谢！