2.3.32 FSCTL_GET_RETRIEVAL_POINTERS Reply
The FSCTL_GET_RETRIEVAL_POINTERS reply message returns the results of the FSCTL_GET_RETRIEVAL_POINTERS request as a variably sized data element, RETRIEVAL_POINTERS_BUFFER, that specifies the allocation and location on disk of a specific file.
The FSCTL_GET_RETRIEVAL_POINTERS reply returns the extent locations (that is, locations of allocated regions of disk space) of nonresident data. A file system MAY allow resident data, which is data that can be written to disk within the file's directory record. Because resident data requires no additional disk space allocation, no extent locations are associated with resident data.<31>
The RETRIEVAL_POINTERS_BUFFER data element is as follows.
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ExtentCount |
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Unused |
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StartingVcn |
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Extents (variable) |
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ExtentCount (4 bytes): A 32-bit unsigned integer that contains the number of EXTENTS data elements in the Extents array. This number can be zero if there are no clusters allocated at (or beyond) the specified StartingVcn.
Unused (4 bytes): Reserved for alignment. This field can contain any value and MUST be ignored.
StartingVcn (8 bytes): A 64-bit signed integer that contains the starting virtual cluster number (VCN) returned by the FSCTL_GET_RETRIEVAL_POINTERS reply. This is not necessarily the VCN requested by the FSCTL_GET_RETRIEVAL_POINTERS request, as the file system driver might return the starting VCN of the extent containing the requested starting VCN. This value MUST be greater than or equal to 0.
Extents (variable): An array of zero or more EXTENTS data elements. For the number of EXTENTS data elements in the array, see ExtentCount.