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分享文件的HANDLE如何转化为FILE* ?
win32SDK中操作文件用HANDLE，如何通过HANDLE得到文件的FILE指针呢？
HANDLE hFile = CreateFile(...);
FILE* pFile = xxxx(hFile);
这个xxxx函数如何写呢？
FILE* xxxx(HANDLE hFile)
{
.....
}
HANDLE hFile = CreateFile(...);
FILE* pFile = xxxx(hFile);
这个xxxx函数如何写呢？
FILE* xxxx(HANDLE hFile)
{
.....
}
...全文
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vcmute 2005-10-12
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Do Not Mix Operating System and CRT File Handles
Q139640
--------------------------------------------------------------------------------
The information in this article applies to:
Microsoft Visual C++, versions 2.0, 2.1, 2.2, 4.0
Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0
Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0
Microsoft Visual C++, 32-bit Learning Edition, version 6.0
--------------------------------------------------------------------------------
SUMMARY
In 32-bit Windows-based applications, Windows API functions (OpenFile, CreateFile, and so on) return a file handle that cannot be substituted for a handle returned by a C Runtime Function (_open, _wopen, and so on). You can convert an operating system handle to a CRT handle by using the CRT function _open_osfhandle() as demonstrated in the "Sample Code" section of this article.
NOTE: This distinction is not Win32 specific. However, some programmers using 16-bit products on 16-bit operating systems have mixed operating system and CRT file handles.
MORE INFORMATION
The following sample code shows how to open a file stream from a file handle returned by the OpenFile Windows API function.
Sample Code
/* Compile options needed:none
*/
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
#include <windows.h>
void main( void )
{
HFILE OsFileHandle;
FILE *stream;
int CrtFileHandle;
OFSTRUCT Buffer;
int count = 0;
char inbuf[128];
if ( (OsFileHandle = OpenFile("test.dat", &Buffer, OF_READ))== -1){
printf( "OpenFile Failed");
exit(1);
}
/* convert OS file handle to CRT file pointer */
if ( (CrtFileHandle=_open_osfhandle(OsFileHandle,_O_RDONLY))==-1){
printf( "_open_osfhandle Failed");
exit(1);
}
/* Change handle access to stream access. */
if( (stream = _fdopen( CrtFileHandle, "r" )) == NULL ) {
printf( "_fdopen Failed");
exit( 1 );
}
while( fgets( inbuf, 128, stream ) != NULL )
count++;
/* After _fdopen, close with fclose */
fclose( stream );
printf( "Lines in file: %d\n", count );
}
Q139640
--------------------------------------------------------------------------------
The information in this article applies to:
Microsoft Visual C++, versions 2.0, 2.1, 2.2, 4.0
Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0
Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0
Microsoft Visual C++, 32-bit Learning Edition, version 6.0
--------------------------------------------------------------------------------
SUMMARY
In 32-bit Windows-based applications, Windows API functions (OpenFile, CreateFile, and so on) return a file handle that cannot be substituted for a handle returned by a C Runtime Function (_open, _wopen, and so on). You can convert an operating system handle to a CRT handle by using the CRT function _open_osfhandle() as demonstrated in the "Sample Code" section of this article.
NOTE: This distinction is not Win32 specific. However, some programmers using 16-bit products on 16-bit operating systems have mixed operating system and CRT file handles.
MORE INFORMATION
The following sample code shows how to open a file stream from a file handle returned by the OpenFile Windows API function.
Sample Code
/* Compile options needed:none
*/
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
#include <windows.h>
void main( void )
{
HFILE OsFileHandle;
FILE *stream;
int CrtFileHandle;
OFSTRUCT Buffer;
int count = 0;
char inbuf[128];
if ( (OsFileHandle = OpenFile("test.dat", &Buffer, OF_READ))== -1){
printf( "OpenFile Failed");
exit(1);
}
/* convert OS file handle to CRT file pointer */
if ( (CrtFileHandle=_open_osfhandle(OsFileHandle,_O_RDONLY))==-1){
printf( "_open_osfhandle Failed");
exit(1);
}
/* Change handle access to stream access. */
if( (stream = _fdopen( CrtFileHandle, "r" )) == NULL ) {
printf( "_fdopen Failed");
exit( 1 );
}
while( fgets( inbuf, 128, stream ) != NULL )
count++;
/* After _fdopen, close with fclose */
fclose( stream );
printf( "Lines in file: %d\n", count );
}
力为 2005-10-12
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特别感谢Atry() 、djfu(一马平川)、vcmute(横秋)
djfu 2005-10-11
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楼主，这个函数是没有什么问题的，
int n = fputs("write by FILE*!", pFile);
//执行后返回的结果 n为 0，没有写入文件
这个问题是由于你没有把缓存写入文件，改为：
int n = fputs("write by FILE*!", pFile);
//执行后返回的结果 n为 0，没有写入文件
fflush(pFile);//立即写入文件
即可。
完整测试源码如下：
//////////////////////////////////////////////////////////////////////////////////
#include <windows.h>
#include <io.h>
#include <fcntl.h>
#include <iostream>
using namespace std;
void Test()
{
HANDLE hFile = CreateFile("e:\\test.txt",
GENERIC_READ | GENERIC_WRITE, 0, NULL,
OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
char szText[] = "Hello world!\n";
DWORD dwWritten;
WriteFile(hFile, szText, strlen(szText), &dwWritten, NULL);
FILE* pFile = NULL;
int nHandle = _open_osfhandle((long)hFile, _O_TEXT | _O_APPEND);
if (nHandle != -1)
pFile = _fdopen(nHandle, "wt");
if(pFile)
{
int n = fputs("write by FILE*!", pFile);
fflush(pFile);
//执行后返回的结果 n为 0，没有写入文件
}
CloseHandle(hFile);
}
int main()
{
Test();
return 0;
}
int n = fputs("write by FILE*!", pFile);
//执行后返回的结果 n为 0，没有写入文件
这个问题是由于你没有把缓存写入文件，改为：
int n = fputs("write by FILE*!", pFile);
//执行后返回的结果 n为 0，没有写入文件
fflush(pFile);//立即写入文件
即可。
完整测试源码如下：
//////////////////////////////////////////////////////////////////////////////////
#include <windows.h>
#include <io.h>
#include <fcntl.h>
#include <iostream>
using namespace std;
void Test()
{
HANDLE hFile = CreateFile("e:\\test.txt",
GENERIC_READ | GENERIC_WRITE, 0, NULL,
OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
char szText[] = "Hello world!\n";
DWORD dwWritten;
WriteFile(hFile, szText, strlen(szText), &dwWritten, NULL);
FILE* pFile = NULL;
int nHandle = _open_osfhandle((long)hFile, _O_TEXT | _O_APPEND);
if (nHandle != -1)
pFile = _fdopen(nHandle, "wt");
if(pFile)
{
int n = fputs("write by FILE*!", pFile);
fflush(pFile);
//执行后返回的结果 n为 0，没有写入文件
}
CloseHandle(hFile);
}
int main()
{
Test();
return 0;
}
dxj1234 2005-10-11
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靠，连这种函数都有，什么情况下会用这些C函数啊
力为 2005-10-11
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to Atry:
谢谢你的提示。
但我试了一下不行。测试代码如下.不知问题出在哪里？
void Test()
{
HANDLE hFile = CreateFile("c:\\test.dat",
GENERIC_READ | GENERIC_WRITE, 0, NULL,
OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
char szText[] = "Hello world!\n";
DWORD dwWritten;
WriteFile(hFile, szText, strlen(szText), &dwWritten, NULL);
FILE* pFile = NULL;
int nHandle = _open_osfhandle((long)hFile, _O_TEXT | _O_APPEND);
if (nHandle != -1)
pFile = _fdopen(nHandle, "wt");
if(pFile)
{
int n = fputs("write by FILE*!", pFile);
//执行后返回的结果 n为 0，没有写入文件
}
CloseHandle(hFile);
}
谢谢你的提示。
但我试了一下不行。测试代码如下.不知问题出在哪里？
void Test()
{
HANDLE hFile = CreateFile("c:\\test.dat",
GENERIC_READ | GENERIC_WRITE, 0, NULL,
OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
char szText[] = "Hello world!\n";
DWORD dwWritten;
WriteFile(hFile, szText, strlen(szText), &dwWritten, NULL);
FILE* pFile = NULL;
int nHandle = _open_osfhandle((long)hFile, _O_TEXT | _O_APPEND);
if (nHandle != -1)
pFile = _fdopen(nHandle, "wt");
if(pFile)
{
int n = fputs("write by FILE*!", pFile);
//执行后返回的结果 n为 0，没有写入文件
}
CloseHandle(hFile);
}
pomelowu 2005-10-10
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同意Atry
djfu 2005-10-10
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FILE* xxxx(HANDLE hFile)
{
int nHandle = _open_osfhandle((intptr_t)hFile, _O_TEXT);
if (nHandle != -1)
return _fdopen(nHandle, szMode);
else
return NULL;
}
just try
{
int nHandle = _open_osfhandle((intptr_t)hFile, _O_TEXT);
if (nHandle != -1)
return _fdopen(nHandle, szMode);
else
return NULL;
}
just try
jiajie828 2005-10-10
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呵呵...这个都知道, 厉害厉害!
Atry 2005-10-10
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FILE* xxxx(HANDLE hFile)
{
int nHandle = _open_osfhandle((intptr_t)hFile, _O_TEXT);
if (nHandle != -1)
return _fdopen(nHandle, szMode);
else
return NULL;
}
{
int nHandle = _open_osfhandle((intptr_t)hFile, _O_TEXT);
if (nHandle != -1)
return _fdopen(nHandle, szMode);
else
return NULL;
}
Atry 2005-10-10
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int nHandle = _open_osfhandle((intptr_t)hFile, _O_TEXT);
if (nHandle != -1)
m_pStream = _fdopen(nHandle, szMode);
if (nHandle != -1)
m_pStream = _fdopen(nHandle, szMode);
Atry 2005-10-10
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FILE* xxxx(HANDLE hFile)
{
return _open_osfhandle((intptr_t)hFile, _O_TEXT)
}
{
return _open_osfhandle((intptr_t)hFile, _O_TEXT)
}
legendhui 2005-10-10
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同意楼上
DentistryDoctor 2005-10-10
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不行。
一个是WIN32的文件，一个是C运行时的文件指针。
一个是WIN32的文件，一个是C运行时的文件指针。
