CcCopyRead function (ntifs.h)

The CcCopyRead routine copies data from a cached file to a user buffer.


  [in]  PFILE_OBJECT     FileObject,
  [in]  PLARGE_INTEGER   FileOffset,
  [in]  ULONG            Length,
  [in]  BOOLEAN          Wait,
  [out] PVOID            Buffer,
  [out] PIO_STATUS_BLOCK IoStatus


[in] FileObject

A pointer to a file object for the cached file from which the data is to be read.

[in] FileOffset

A pointer to a variable that specifies the starting byte offset within the cached file.

[in] Length

The length in bytes of the data to be read.

[in] Wait

Set to TRUE if the caller can be put into a wait state until all the data has been copied, FALSE otherwise.

[out] Buffer

A pointer to a buffer into which the data is to be copied.

[out] IoStatus

A pointer to a caller-allocated structure that receives the final completion status and information about the operation. If not all of the data is copied successfully, IoStatus.Information contains the actual number of bytes that were copied.

Return value

The CcCopyRead routine returns TRUE if the data was copied successfully, FALSE otherwise.


If Wait is TRUE, CcCopyRead is guaranteed to complete the copy request and return TRUE. If the required pages of the cached file are already resident in memory, the data will be copied immediately and no blocking will occur. If any needed pages are not resident, the caller will be put in a wait state until all required pages have been made resident and the data can be copied.

If Wait is FALSE, CcCopyRead will refuse to block, and will return FALSE, if the required pages of the cached file are not already resident in memory.

FileOffset plus Length must be less than or equal to the size of the cached file, or an assertion failure will occur.

If any failure occurs, CcCopyRead raises a status exception for that particular failure. For example, if a pool allocation failure occurs, CcCopyRead raises a STATUS_INSUFFICIENT_RESOURCES exception; if an I/O error occurs, CcCopyRead raises the status exception of the I/O error. Therefore, to gain control if a failure occurs, the driver should wrap the call to CcCopyRead in a try-except or try-finally statement.

To cache a file, use CcInitializeCacheMap.


Requirement Value
Minimum supported client Windows 2000
Target Platform Universal
Header ntifs.h (include Ntifs.h, FltKernel.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe

See also