The RtlDecompressBuffer function decompresses an entire compressed buffer.

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

Parameters

CompressionFormat

Bitmask specifying 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	Specifies that compression should be performed. This value is required.

UncompressedBuffer

Pointer to a caller-allocated buffer (allocated from paged or non-paged pool) receiving 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 containing 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 which 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:

STATUS_SUCCESS

The CompressedBuffer buffer was successfully decompressed.

STATUS_INVALID_PARAMETER

An invalid compression format was specified via 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 via the CompressionFormat parameter. If CompressionFormat is not one of the following, STATUS_UNSUPPORTED_COMPRESSION is returned:

• COMPRESSION_FORMAT_LZNT1
• 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.

Comments

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

Versions: Available in Microsoft Windows XP and later versions of all Windows operating systems.

IRQL: <= APC_LEVEL

Headers: Declared in Ntifs.h. Include Fltkernel.h or Ntifs.h.

Library: Contained in Ntoskrnl.lib.

See Also

FILE_COMPRESSION_INFORMATION, RtlCompressBuffer, RtlDecompressFragment, RtlGetCompressionWorkSpaceSize