SHFILEOPSTRUCT and the SHFileOperation

May 3, 2000
By John Z. Czopowik

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Environment: Windows 9x/NT/2K, Version 4.00 (or later) of Shell32.dll

Introduction

The function

SHFileOperation

, enables you to copy, move or delete a file system object. As you can see, this function takes as its sole parameter a pointer to a

SHFILEOPSTRUCT

structure (also shown below).

// SHFileOperation syntax
WINSHELLAPI int WINAPI SHFileOperation(LPSHFILEOPSTRUCT lpFileOp);

// SHFILEOPSTRUCT layout
typedef struct _SHFILEOPSTRUCT{
 HWND		hwnd;
 UINT		wFunc;
 LPCSTR		pFrom;
 LPCSTR		pTo;
 FILEOP_FLAGS	fFlags;
 BOOL		fAnyOperationsAborted;
 LPVOID		hNameMappings;
 LPCSTR		lpszProgressTitle;
} SHFILEOPSTRUCT, FAR *LPSHFILEOPSTRUCT;

Unfortunately, despite this function's obvious usefulness, the Microsoft documentation is very ambiguous regarding the

SHFILEOPSTRUCT

structure and how to fill it out. In fact, there are several pitfalls when using this structure. Therefore, in this article, I'll attempt to address these issues so that those of you using this function for the first time can benefit from my experience as to how to take advantage of this very handy function.

Name Collision Resolution and the hNameMappings member

hNameMappings

is (almost always) an input-only member of

SHFILEOPSTRUCT

In fact, after the call to

SHFileOperation

has returned successfully, this value will be actually be set to

NULL

. The only time that this value will be changed by the

SHFileOperation

function is if you have specified the flags

FOF_RENAMEONCOLLISION

FOF_WANTMAPPINGSHANDLE

in the

FILEOP_FLAGS

member. Then if there were files that had to be renamed due to a name collision, assign a name mapping object will containing their old and new names to the hNameMappings member.

This member can be treated as a void pointer to a continuous memory block. This memory block in turn can be treated as some kind of the structure with int as a first member. Value of this integer indicates how many SHNAMEMAPPING structures follows. This way you can retrieve needed info.

File Name Retrieval

Another pitfall that you need to know about deals with retrieving the names of files.

pszOldPath

and

pszNewPath

members are declared as

LPSTR

. However, they are laid out as

DWORD

; not

char

! Therefore, any string copying function available fails to successfully copy the path strings.

Sample Code

Here is a code snippet illustrating these issues. It can be done differently and is not posted for the purpose of code review. Treat it rather as a suggestion.

CString OldPath;
CString NewPath;
SHFILEOPSTRUCT shFileOp;

//after filling other members:
shFileOp.fFlags = FOF_WANTMAPPINGHANDLE 
                | FOF_RENAMEONCOLLISION;

shFileOp.lpszProgressTitle = "Test";
shFileOp.fAnyOperationsAborted = FALSE;

SHFileOperation(&shFileOp);

if(!shFileOp.hNameMappings) 
 return;	//there is nothing further to do, no file collision

struct TMPMAP
{
int Indx;
SHNAMEMAPPING *pMapping;
};

//this will give you a  pointer to the beginning of the 
//array of SHNAMEMAPPING structures
TMPMAP *pTmpMap = (TMPMAP*)shFileOp.hNameMappings;

for(int in = 0; in < pTmpMap->Indx; in++)
{
 SHNAMEMAPPING *pMap = &pTmpMap->pMapping[in];

 //do the same thing for csOldPath
 /*********************************************************/
 char *buf = csNewPath.GetBufferSetLength(pMap->cchNewPath);

strcpy(buf, (char*)pMap->pszOldPath); //see the result of
this,

for(int dw = 0 ; dw < 2 * pMap->cchNewPath - 1 ; dw+=2)
{
*buf = (pMap->pszNewPath[dw]);
buf++;
}
buf = 0;
csNewPath.ReleaseBuffer();  //and see the result of this.
/**********************************************************/
}

//always free it if requested
SHFreeNameMappings(shFileOp.hNameMappings);

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