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Tests: Add a test for LZMA repetition lengths beyond the distance

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Tim Schumacher 2023-04-14 17:30:11 +02:00 • committed by Linus Groh
parent 68c313dcd9
commit f47f5ff473
1 changed files with 22 additions and 0 deletions
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Tests/LibCompress/TestLzma.cpp
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@ -9,6 +9,28 @@
#include <AK/MemoryStream.h>
#include <LibCompress/Lzma.h>
TEST_CASE(repetition_length_beyond_distance)
{
// This test exists to ensure correctness when repeating data from the dictionary that has been
// written earlier during the same repetition.
// While this test case is not large enough to testify how well this is optimized, it may still
// be a constellation that is improperly implemented as a whole.
Array<u8, 21> const compressed {
0x5D, // Model properties (lc = 3, lp = 0, pb = 2)
0x00, 0x10, 0x00, 0x00, // Dictionary size (4 KB)
0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Uncompressed size (7)
// Encode a literal 'A' and a literal 'B', followed by a repetition from (real) distance 2 with a (real) length of 5.
0x00, 0x20, 0x90, 0x9F, 0x04, 0x00, 0x00, 0x00
};
auto stream = MUST(try_make<FixedMemoryStream>(compressed));
auto decompressor = MUST(Compress::LzmaDecompressor::create_from_container(move(stream)));
auto buffer = TRY_OR_FAIL(decompressor->read_until_eof(PAGE_SIZE));
EXPECT_EQ("ABABABA"sv.bytes(), buffer.span());
}
// The following tests are based on test files from the LZMA specification, which has been placed in the public domain.
// LZMA Specification Draft (2015): https://www.7-zip.org/a/lzma-specification.7z