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MyFSD_GetFileSize (Compact 2013)

  • Artigo

3/26/2014

This function retrieves the size, in bytes, of the specified file that resides in an installable file system. The application does not call this function directly. Instead, it uses the corresponding standard Win32 function GetFileSize. The File System Disk Manager (FSDMGR) determines the file system type and calls the MyFSD_GetFileSize implementation of the function.

Syntax

DWORD MyFSD_GetFileSize( 
  PFILE pFile, 
  PDWORD pFileSizeHigh
);

Parameters

  • pFile
    [in] Pointer to the value that a file system driver (FSD) passes to the FSDMGR_CreateFileHandle function when creating the file handle.
  • pFileSizeHigh
    [out] Pointer to the variable in which the high-order word of the file size is returned. This parameter can be set to NULL if the application does not require the high-order word.

Return Value

If the function succeeds, the return value is the low-order DWORD of the file size. If lpFileSizeHigh is set to a non-NULL value, the function puts the high-order DWORD of the file size into the variable pointed to by that parameter.

If the function fails and lpFileSizeHigh is set to NULL, the return value is 0xFFFFFFFF. To get extended error information, call GetLastError.

If the function fails and lpFileSizeHigh is set to a non-NULL value, the return value is 0xFFFFFFFF, and GetLastError returns a value other than NO_ERROR.

Remarks

The GetFileSize function obtains the uncompressed size of a file.

An FSD exports this function if it supports the GetFileSize function. All FSD functions can be called on re-entry. Therefore, take this into account when developing an FSD.

FSDMGR is a DLL that manages all OS interaction with installable files systems. Each installable file system requires an FSD, which is a DLL that supports an installable file system. The name of the DLL for an FSD and the names of the functions it exports start with the name of the associated installable file system. For example, if the name of file system is MyFSD, its DLL is MyFSD.dll, and its exported functions are prefaced with MyFSD_*.

FSDMGR provides service functions to FSDs. The FSDMGR_RegisterVolume, FSDMGR_CreateFileHandle, and the FSDMGR_CreateSearchHandle functions record a DWORD of volume-specific data that an FSD associates with a volume. This volume-specific data is passed as the first parameter of these three functions.

Applications that access an installable file system use standard Win32 functions. For example, when an application creates a folder on a device that contains an installable file system, it calls the CreateDirectory function. FSDMGR recognizes that the path is to a device containing an installable file system and calls the appropriate function, which in the case of the MyFSD file system is MyFSD_CreateDirectoryW. That is, the application calls CreateDirectory, causing FSDMGR to call **MyFSD_CreateDirectoryW.

Requirements

Header

fsdmgr.h

Library

Fsdmgr.lib

See Also

Reference

MyFSD Functions
CreateDirectory
GetFileSize
FSDMGR_CreateFileHandle
FSDMGR_CreateSearchHandle
FSDMGR_RegisterVolume
MyFSD_CreateDirectoryW