RtlDecompressBufferEx2 function

The RtlDecompressBufferEx2 function decompresses an entire compressed buffer, using multiple processors where possible. Multiple processor support is only implemented for kernel mode callers.

Syntax

NT_RTL_COMPRESS_API NTSTATUS RtlDecompressBufferEx2(
  USHORT CompressionFormat,
  PUCHAR UncompressedBuffer,
  ULONG  UncompressedBufferSize,
  PUCHAR CompressedBuffer,
  ULONG  CompressedBufferSize,
  ULONG  UncompressedChunkSize,
  PULONG FinalUncompressedSize,
  PVOID  WorkSpace
);

Parameters

CompressionFormat

A bitmask that specifies the compression format of the compressed buffer. This parameter must be set to COMPRESSION_FORMAT_LZNT1. The meaning of this and other related compression format values are as follows.

Value Meaning
COMPRESSION_FORMAT_NONE
Not supported by this function.
COMPRESSION_FORMAT_DEFAULT
Not supported by this function.
COMPRESSION_FORMAT_LZNT1
The function will perform LZ decompression.
COMPRESSION_FORMAT_XPRESS
The function will perform Xpress decompression.
COMPRESSION_FORMAT_XPRESS_HUFF
The function will perform Xpress Huffman decompression.

UncompressedBuffer

A pointer to a caller-allocated buffer (allocated from a paged or non-paged pool) that receives the decompressed data from CompressedBuffer. This parameter is required and cannot be NULL.

UncompressedBufferSize

The size, in bytes, of the UncompressedBuffer buffer.

CompressedBuffer

A pointer to the buffer that contains the data to decompress. This parameter is required and cannot be NULL.

CompressedBufferSize

The size, in bytes, of the CompressedBuffer buffer.

UncompressedChunkSize

The size, in bytes, of each chunk within the compression buffer. Valid values are 512, 1024, 2048 and 4096.

FinalUncompressedSize

A pointer to a caller-allocated variable that receives the size, in bytes, of the decompressed data stored in UncompressedBuffer. This parameter is required and cannot be NULL.

WorkSpace

A pointer to a caller-allocated work space buffer used by the RtlDecompressBufferEx2 function during decompression. Use the RtlGetCompressionWorkSpaceSize function to determine the correct work space buffer size.

Return Value

RtlDecompressBufferEx2 returns an appropriate error status value, such as one of the following.

Return code Description
STATUS_SUCCESS
The CompressedBuffer buffer was successfully decompressed.
STATUS_INVALID_PARAMETER
An invalid compression format was specified through the CompressionFormat parameter. If CompressionFormat is either COMPRESSION_FORMAT_NONE or COMPRESSION_FORMAT_DEFAULT (but not both), this value is returned.
STATUS_UNSUPPORTED_COMPRESSION
An invalid compression format was specified through the CompressionFormat parameter. If CompressionFormat is not one of the following, STATUS_UNSUPPORTED_COMPRESSION is returned:
  • COMPRESSION_FORMAT_LZNT1
  • COMPRESSION_FORMAT_XPRESS
  • COMPRESSION_FORMAT_XPRESS_HUFF
  • COMPRESSION_FORMAT_NONE
  • COMPRESSION_FORMAT_DEFAULT
STATUS_BAD_COMPRESSION_BUFFER
UncompressedBuffer is not large enough to contain the uncompressed data.

Remarks

The RtlDecompressBufferEx2 function takes as input an entire compressed buffer and produces its decompressed equivalent provided that the uncompressed data fits within the specified destination buffer.

To decompress only a portion of a compressed buffer (that is, a "fragment" of the buffer), use the RtlDecompressFragment function.

To compress an uncompressed buffer, use the RtlCompressBuffer function.

Requirements

   
Windows version Available in starting in Windows 10.
Target Platform Universal
Header ntifs.h (include Fltkernel.h, Ntifs.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe
IRQL "<= APC_LEVEL"

See Also

FILE_COMPRESSION_INFORMATION

RtlDecompressBuffer

RtlDecompressBufferEx

RtlDecompressFragment

RtlDecompressFragmentEx