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RtlDecompressFragmentEx function (ntifs.h)

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The RtlDecompressFragmentEx function is used to decompress part of a compressed buffer (that is, a buffer "fragment"), using multiple processors where possible.

Syntax

NT_RTL_COMPRESS_API NTSTATUS RtlDecompressFragmentEx(
  [in]  USHORT CompressionFormat,
  [out] PUCHAR UncompressedFragment,
  [in]  ULONG  UncompressedFragmentSize,
  [in]  PUCHAR CompressedBuffer,
  [in]  ULONG  CompressedBufferSize,
  [in]  ULONG  FragmentOffset,
  [in]  ULONG  UncompressedChunkSize,
  [out] PULONG FinalUncompressedSize,
  [in]  PVOID  WorkSpace
);

Parameters

[in] 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.

[out] UncompressedFragment

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.

[in] UncompressedFragmentSize

The size, in bytes, of the UncompressedFragment buffer.

[in] CompressedBuffer

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

[in] CompressedBufferSize

The size, in bytes, of the CompressedBuffer buffer.

[in] FragmentOffset

The zero-based offset, in bytes, where the uncompressed fragment is being extract from. This offset value is the position within the original uncompressed buffer.

[in] UncompressedChunkSize

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

[out] FinalUncompressedSize

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

[in] WorkSpace

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

Return value

RtlDecompressFragmentEx returns an appropriate NTSTATUS code, such as one of the following:

Return code Description
STATUS_SUCCESS The CompressedBuffer buffer was successfully decompressed into UncompressedFragment.
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
STATUS_BAD_COMPRESSION_BUFFER UncompressedFragment is not large enough to contain the uncompressed data.

Requirements

Requirement Value
Minimum supported client 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

RtlCompressBuffer

RtlDecompressBuffer

RtlDecompressBufferEx

RtlDecompressBufferEx2

RtlDecompressFragment