CcCanIWrite function (ntifs.h)

The CcCanIWrite routine determines whether the caller can write to a cached file.

Syntax

BOOLEAN CcCanIWrite(
  [in] PFILE_OBJECT FileObject,
  [in] ULONG        BytesToWrite,
  [in] BOOLEAN      Wait,
  [in] UCHAR        Retrying
);

[in] FileObject

Pointer to a file object for the cached file.

[in] BytesToWrite

Number of bytes to be written.

[in] Wait

Set to TRUE if the caller can be put into a wait state until it can write to the cached file, FALSE otherwise.

[in] Retrying

Set to FALSE if this is the first time CcCanIWrite is being called for this write request, TRUE otherwise.

CcCanIWrite returns TRUE if the cache manager can accept the write request, FALSE otherwise.

CcCanIWrite should be called before calling CcCopyWrite or CcFastCopyWrite.

If CcCanIWrite returns TRUE, the caller can immediately call CcCopyWrite or CcFastCopyWrite.

If CcCanIWrite returns FALSE, the caller must instead call CcDeferWrite to defer the write request.

Generally speaking, the cache manager can accept a write request if the following conditions are true:

The amount of data to be written is not too large.
There is enough memory to perform the write operation.
The number of dirty pages in the system cache does not exceed the dirty page threshold (CcDirtyPageThreshold).
If a per-file dirty page threshold exists for this file, it is not exceeded by the number of dirty pages for this file in the system cache.