RtlDecompressBuffer function

The RtlDecompressBuffer function decompresses an entire compressed buffer.

Syntax

NT_RTL_COMPRESS_API NTSTATUS RtlDecompressBuffer(
  USHORT CompressionFormat,
  PUCHAR UncompressedBuffer,
  ULONG  UncompressedBufferSize,
  PUCHAR CompressedBuffer,
  ULONG  CompressedBufferSize,
  PULONG FinalUncompressedSize
);

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.

UncompressedBuffer

A pointer to a caller-allocated buffer (allocated from 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.

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.

Return Value

RtlDecompressBuffer 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_NONE (in this case, STATUS_INVALID_PARAMETER is returned).
  • COMPRESSION_FORMAT_DEFAULT (in this case, STATUS_INVALID_PARAMETER is returned).
STATUS_BAD_COMPRESSION_BUFFER
UncompressedBuffer is not large enough to contain the uncompressed data.

Remarks

The RtlDecompressBuffer 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

   
Minimum supported client Available starting in Windows XP.
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

RtlCompressBuffer

RtlDecompressBufferEx

RtlDecompressBufferEx2

RtlDecompressFragment

RtlDecompressFragmentEx