RtlDecompressFragmentEx - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _NTRTL_H
#if (PHNT_VERSION >= PHNT_WINBLUE)

NTSYSAPI
NTSTATUS
NTAPI
RtlDecompressFragmentEx(
    _In_ USHORT CompressionFormat,
    _Out_writes_bytes_to_(UncompressedFragmentSize, *FinalUncompressedSize) PUCHAR UncompressedFragment,
    _In_ ULONG UncompressedFragmentSize,
    _In_reads_bytes_(CompressedBufferSize) PUCHAR CompressedBuffer,
    _In_ ULONG CompressedBufferSize,
    _In_range_(<, CompressedBufferSize) ULONG FragmentOffset,
    _In_ ULONG UncompressedChunkSize,
    _Out_ PULONG FinalUncompressedSize,
    _In_ PVOID WorkSpace
    );

#endif
#endif

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This function is documented in Windows Driver Kit.