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AK: Rewrite the hint-based CircularBuffer::find_copy_in_seekback

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This now searches the memory in blocks, which should be slightly more
efficient. However, it doesn't make much difference (e.g. ~1% in LZMA
compression) in most real-world applications, as the non-hint function
is more expensive by orders of magnitude.
This commit is contained in:
Tim Schumacher 2023-06-02 01:25:56 +02:00 • committed by Linus Groh
parent 3526d67694
commit 42d01b21d8
4 changed files with 36 additions and 51 deletions
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20
Tests/AK/TestCircularBuffer.cpp
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@ -411,25 +411,23 @@ TEST_CASE(find_copy_in_seekback)
}
{
// Find the largest matches with a length between 1 and 2 (selected "AB", everything smaller gets eliminated).
auto matches = MUST(buffer.find_copy_in_seekback(Vector<size_t> { 6ul, 9ul }, 2, 1));
EXPECT_EQ(matches.size(), 2ul);
EXPECT_EQ(matches[0].distance, 6ul);
EXPECT_EQ(matches[0].length, 2ul);
EXPECT_EQ(matches[1].distance, 9ul);
EXPECT_EQ(matches[1].length, 2ul);
// Find the largest match with a length between 1 and 2 (selected "AB", everything smaller gets eliminated).
// Since we have a tie, the first qualified match is preferred.
auto match = buffer.find_copy_in_seekback(Vector<size_t> { 6ul, 9ul }, 2, 1);
EXPECT_EQ(match.value().distance, 6ul);
EXPECT_EQ(match.value().length, 2ul);
}
{
// Check that we don't find anything for hints before the valid range.
auto matches = MUST(buffer.find_copy_in_seekback(Vector<size_t> { 0ul }, 2, 1));
EXPECT_EQ(matches.size(), 0ul);
auto match = buffer.find_copy_in_seekback(Vector<size_t> { 0ul }, 2, 1);
EXPECT(!match.has_value());
}
{
// Check that we don't find anything for hints after the valid range.
auto matches = MUST(buffer.find_copy_in_seekback(Vector<size_t> { 12ul }, 2, 1));
EXPECT_EQ(matches.size(), 0ul);
auto match = buffer.find_copy_in_seekback(Vector<size_t> { 12ul }, 2, 1);
EXPECT(!match.has_value());
}
{