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LibCompress: Use a bit stream for the entire GZIP decompression process

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We currently mix normal and bit streams during GZIP decompression, where
the latter is a wrapper around the former. This isn't causing issues now
as the underlying bit stream buffer is a byte, so the normal stream can
pick up where the bit stream left off.

In order to increase the size of that buffer though, the normal stream
will not be able to assume it can resume reading after the bit stream.
The buffer can easily contain more bits than it was meant to read, so
when the normal stream resumes, there may be N bits leftover in the bit
stream that the normal stream was meant to read.

To avoid weird behavior when mixing streams, this changes the GZIP
decompressor to always read from a bit stream.
This commit is contained in:
Timothy Flynn 2023-03-28 11:28:04 -04:00 • committed by Andreas Kling
parent 9423662107
commit 20aaab47f9
4 changed files with 12 additions and 11 deletions
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7
Userland/Libraries/LibCompress/Gzip.cpp
View file

@ -7,6 +7,7 @@
#include <LibCompress/Gzip.h>
#include <AK/BitStream.h>
#include <AK/DeprecatedString.h>
#include <AK/MemoryStream.h>
#include <LibCore/DateTime.h>
@ -38,9 +39,9 @@ bool BlockHeader::supported_by_implementation() const
return true;
}
ErrorOr<NonnullOwnPtr<GzipDecompressor::Member>> GzipDecompressor::Member::construct(BlockHeader header, Stream& stream)
ErrorOr<NonnullOwnPtr<GzipDecompressor::Member>> GzipDecompressor::Member::construct(BlockHeader header, LittleEndianInputBitStream& stream)
{
auto deflate_stream = TRY(DeflateDecompressor::construct(MaybeOwned<Stream>(stream)));
auto deflate_stream = TRY(DeflateDecompressor::construct(MaybeOwned<LittleEndianInputBitStream>(stream)));
return TRY(adopt_nonnull_own_or_enomem(new (nothrow) Member(header, move(deflate_stream))));
}
@ -51,7 +52,7 @@ GzipDecompressor::Member::Member(BlockHeader header, NonnullOwnPtr<DeflateDecomp
}
GzipDecompressor::GzipDecompressor(NonnullOwnPtr<Stream> stream)
: m_input_stream(move(stream))
: m_input_stream(make<LittleEndianInputBitStream>(move(stream)))
{
}