RtlDecompressFragment function (ntifs.h)
The RtlDecompressFragment function is used to decompress part of a compressed buffer (that is, a buffer "fragment").
Syntax
NT_RTL_COMPRESS_API NTSTATUS RtlDecompressFragment(
[in] USHORT CompressionFormat,
[out] PUCHAR UncompressedFragment,
[in] ULONG UncompressedFragmentSize,
[in] PUCHAR CompressedBuffer,
[in] ULONG CompressedBufferSize,
[in] ULONG FragmentOffset,
[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.
[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 RtlDecompressFragment function during decompression. Use the RtlGetCompressionWorkSpaceSize function to determine the correct work space buffer size.
Return value
RtlDecompressFragmentreturns 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. |
Remarks
Relative to the RtlDecompressBuffer function, RtlDecompressFragment is used for decompressing a portion of the data from a compressed buffer (as opposed to the entire buffer).
To determine the correct buffer size for the WorkSpace parameter, use the RtlGetCompressionWorkSpaceSize function (that is, the value returned by the RtlGetCompressionWorkSpaceSize parameter).
To compress an uncompressed buffer, use the RtlCompressBuffer function.
To decompress an entire compressed buffer, use the RtlDecompressBuffer function.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows XP |
| Target Platform | Universal |
| Header | ntifs.h (include Fltkernel.h, Ntifs.h) |
| Library | NtosKrnl.lib |
| DLL | NtosKrnl.exe |
| IRQL | <= APC_LEVEL |