WriteFile 随机读写文件，怎么做？

[bacy001]

我现在的问题是：每次打开文件都是从头开始写文件（导致老信息被覆盖），而我希望是“打开一个文件，如果存在，新内容添加在文件尾部；如果文件不存在，则创建文件！

	HANDLE m_hLogFile = CreateFile(fname,
		GENERIC_WRITE,
		FILE_SHARE_READ,
		&sa,
		OPEN_ALWAYS,
		FILE_ATTRIBUTE_NORMAL,
		NULL);

	WriteFile(m_hLogFile,buf,lstrlen(buf),&num,NULL);

使用了 SetEndOfFile，也无效！

那位帅哥有经验的，分享下...

[Dreadnought]

SetFilePointer

[lazy_2010]

就是这样用的啊，你打开已经存在的文件之后，调用 SetFilePointerEx 了么？

[bacy001]

如果用 OVERLAPPED 如果实现呢？

[xengine-qyt]

CreateFile(xxxx,FILE_FLAG_OVERLAPPED,NULL);


m_Ol.hEvent = CreateEvent(xxxx);

WriteFile(xxxx&m_Ol); //开始写入数据

读就不用说了把

[anbam]

fopen_s( &pFile, ,"a+")

[xyy410874116]

fOpen()

[yiruirui0507]

SetFilePointer直接将指针定制到文件末尾

[yiruirui0507]

This function moves the file pointer of an open file. A RAPI version of this function exists, called CeSetFilePointer (RAPI).

CopyDWORD SetFilePointer(
HANDLE hFile,
LONG lDistanceToMove,
PLONG lpDistanceToMoveHigh,
DWORD dwMoveMethod
);

Parameters
hFile
[in] Handle to the file whose file pointer is to be moved. The file handle must have been created with GENERIC_READ or GENERIC_WRITE access to the file.
lDistanceToMove
Low-order 32 bits of a signed value that specifies the number of bytes to move the file pointer. A positive value for lDistanceToMove moves the file pointer forward in the file, and a negative value moves the file pointer backward. Note that you cannot use a negative value to move back past beyond the beginning of a file.
lpDistanceToMoveHigh
Not supported; must be NULL or point to a value of zero.
dwMoveMethod
[in] Starting point for the file pointer move. The following table shows possible values for this parameter.
Value Description
FILE_BEGIN Indicates that the starting point is zero or the beginning of the file.
FILE_CURRENT Indicates that the starting point is the current value of the file pointer.
FILE_END Indicates that the starting point is the current EOF position.

[lslsyqyq]

用 OVERLAPPED 的话
写文件 就要设置OVERLAPPED
麻烦的
直接定位到文件末尾多方便

[wyx100]

CreateFile(xxxx,FILE_FLAG_OVERLAPPED,NULL);


m_Ol.hEvent = CreateEvent(xxxx);

WriteFile(xxxx&m_Ol); //开始写入数据

读就不用说了把

[顽固已死_有事烧纸]

那就用 fopen（, "ab"）;

[Lactoferrin]

HANDLE m_hLogFile = CreateFile(fname,
FILE_APPEND_DATA|SYNCHRONIZE,
FILE_SHARE_READ,
&sa,
OPEN_ALWAYS,
FILE_ATTRIBUTE_NORMAL,
NULL);