Difference between revisions of "Unit NTFSUtils"

Revision as of 03:02, 20 October 2016

Source	Source buffer contains the uncompressed data on entry Source buffer must always be a full compression unit in size
Dest	Dest buffer will contain the compressed data on exit Dest buffer must always be a full compression unit in size
Size	Size is the size of a cluster
Shift	Shift is the cluster to compression unit shift count (Usually 4)
Start	Start is the starting cluster for the compression (zero to start at the first cluster)
Count	Count is the number of clusters to be compressed
Total	Total is the number of bytes to be compressed (from start) (may be less than a full unit)
Note	Compress block will detect an uncompressable block as the final length after compression will be greater than 4096 in length. If compress block reaches the end of the dest buffer then it will fail the compress block and compress unit and the whole unit will be considered as uncompressable. If the data available for the block is less then 4096 then it may grow after compression but will not be marked as uncompressed unless it exceeds 4096 bytes.

function NTFSDecompressUnit(ASource,ADest:Pointer; ASize,AShift,AStart,ACount,ATotal:LongWord):Boolean;

Description: Decompress a unit (or partial unit) of data from source to dest buffers

Source	Source buffer contains the compressed data on entry Source buffer must always be a full compression unit in size
Dest	Dest buffer will contain the uncompressed data on exit Dest buffer must always be a full compression unit in size
Size	Size is the size of a cluster
Shift	Shift is the cluster to compression unit shift count (Usually 4)
Start	Start is the starting cluster for the decompression (zero to start at the first cluster)
Count	Count is the number of blocks to be decompressed
Total	Total is the number of bytes to be decompressed (from start) (may be less than a full unit)
Note	Caller must have confirmed that the unit is compressed

function NTFSGetBlockShift(ASize:LongWord):LongWord;

Description: Get the shift count for cluster to 4k block conversion

Size	Size is the size of a cluster

function NTFSCompressBlock(ASource,ADest:Pointer; ASize,ATotal:LongWord):Boolean;

Description: Compress a 4k block of data from source to dest buffers

Source	Source buffer contains the uncompressed data on entry Source buffer must have at least one 4k block available
Dest	Dest buffer will contain the compressed data on exit
Size	Size is the available bytes in the dest buffer
Total	Total is the number of bytes to be compressed (may be less than a full block)
Note	Compress block will detect an uncompressable block as the final length after compression will be greater than 4096 in length. If compress block reaches the end of the dest buffer then it will fail the compress block and compress unit and the whole unit will be considered as uncompressable. If the data available for the block is less then 4096 then it may grow after compression but will not be marked as uncompressed unless it exceeds 4096 bytes.

function NTFSDecompressBlock(ASource,ADest:Pointer; ASize:LongWord):Boolean;

Description: Decompress a 4k block of data from source to dest buffers

Source	Source buffer contains the compressed data on entry
Dest	Dest buffer will contain the uncompressed data on exit Dest buffer must have at least one 4k block available
Size	Size is the available bytes in the source buffer

function NTFSGetTagShiftMask(AOffset:LongWord; var AMask,AShift:Word):Boolean;

Description: Get the Mask bits and Shift count for Tag encode and decode based on the offset

Offset	Offset is the offset into the uncompressed data at the point of the tag

NTFS string functions

function NTFSBufferToString(ABuffer:Pointer; AOffset:LongWord; ALength:LongWord):String;