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AK: Use hashing to accelerate searching a CircularBuffer

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Tim Schumacher 2023-06-02 13:37:47 +02:00 • committed by Linus Groh
parent 4a10cf1506
commit 60ac254df6
4 changed files with 269 additions and 101 deletions
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88
Tests/AK/TestCircularBuffer.cpp
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@ -342,72 +342,62 @@ TEST_CASE(find_copy_in_seekback)
auto written_needle_bytes = buffer.write(needle);
VERIFY(written_needle_bytes == needle.size());
// Note: As of now, the preference during a tie is determined by which algorithm found the match.
// Hash-based matching finds the shortest distance first, while memmem finds the greatest distance first.
// A matching TODO can be found in CircularBuffer.cpp.
{
// Find the largest matches with a length between 1 and 1 (all "A").
auto matches = MUST(buffer.find_copy_in_seekback(1, 1));
EXPECT_EQ(matches.size(), 4ul);
EXPECT_EQ(matches[0].distance, 11ul);
EXPECT_EQ(matches[0].length, 1ul);
EXPECT_EQ(matches[1].distance, 9ul);
EXPECT_EQ(matches[1].length, 1ul);
EXPECT_EQ(matches[2].distance, 6ul);
EXPECT_EQ(matches[2].length, 1ul);
EXPECT_EQ(matches[3].distance, 2ul);
EXPECT_EQ(matches[3].length, 1ul);
// Find the largest match with a length between 1 and 1 (all "A").
auto match = buffer.find_copy_in_seekback(1, 1);
EXPECT(match.has_value());
EXPECT_EQ(match.value().distance, 11ul);
EXPECT_EQ(match.value().length, 1ul);
}
{
// Find the largest matches with a length between 1 and 2 (all "AB", everything smaller gets eliminated).
auto matches = MUST(buffer.find_copy_in_seekback(2, 1));
EXPECT_EQ(matches.size(), 4ul);
EXPECT_EQ(matches[0].distance, 11ul);
EXPECT_EQ(matches[0].length, 2ul);
EXPECT_EQ(matches[1].distance, 9ul);
EXPECT_EQ(matches[1].length, 2ul);
EXPECT_EQ(matches[2].distance, 6ul);
EXPECT_EQ(matches[2].length, 2ul);
EXPECT_EQ(matches[3].distance, 2ul);
EXPECT_EQ(matches[3].length, 2ul);
// Find the largest match with a length between 1 and 2 (all "AB", everything smaller gets eliminated).
auto match = buffer.find_copy_in_seekback(2, 1);
EXPECT(match.has_value());
EXPECT_EQ(match.value().distance, 11ul);
EXPECT_EQ(match.value().length, 2ul);
}
{
// Find the largest matches with a length between 1 and 3 (all "ABC", everything smaller gets eliminated).
auto matches = MUST(buffer.find_copy_in_seekback(3, 1));
EXPECT_EQ(matches.size(), 2ul);
EXPECT_EQ(matches[0].distance, 9ul);
EXPECT_EQ(matches[0].length, 3ul);
EXPECT_EQ(matches[1].distance, 6ul);
EXPECT_EQ(matches[1].length, 3ul);
// Find the largest match with a length between 1 and 3 (all "ABC", everything smaller gets eliminated).
auto match = buffer.find_copy_in_seekback(3, 1);
EXPECT(match.has_value());
EXPECT_EQ(match.value().distance, 6ul);
EXPECT_EQ(match.value().length, 3ul);
}
{
// Find the largest matches with a length between 1 and 4 (all "ABCD", everything smaller gets eliminated).
auto matches = MUST(buffer.find_copy_in_seekback(4, 1));
EXPECT_EQ(matches.size(), 1ul);
EXPECT_EQ(matches[0].distance, 6ul);
EXPECT_EQ(matches[0].length, 4ul);
// Find the largest match with a length between 1 and 4 (all "ABCD", everything smaller gets eliminated).
auto match = buffer.find_copy_in_seekback(4, 1);
EXPECT(match.has_value());
EXPECT_EQ(match.value().distance, 6ul);
EXPECT_EQ(match.value().length, 4ul);
}
{
// Find the largest matches with a length between 1 and 5 (all "ABCD", everything smaller gets eliminated, and nothing larger exists).
auto matches = MUST(buffer.find_copy_in_seekback(5, 1));
EXPECT_EQ(matches.size(), 1ul);
EXPECT_EQ(matches[0].distance, 6ul);
EXPECT_EQ(matches[0].length, 4ul);
// Find the largest match with a length between 1 and 5 (all "ABCD", everything smaller gets eliminated, and nothing larger exists).
auto match = buffer.find_copy_in_seekback(5, 1);
EXPECT(match.has_value());
EXPECT_EQ(match.value().distance, 6ul);
EXPECT_EQ(match.value().length, 4ul);
}
{
// Find the largest matches with a length between 4 and 5 (all "ABCD", everything smaller never gets found, nothing larger exists).
auto matches = MUST(buffer.find_copy_in_seekback(5, 4));
EXPECT_EQ(matches.size(), 1ul);
EXPECT_EQ(matches[0].distance, 6ul);
EXPECT_EQ(matches[0].length, 4ul);
// Find the largest match with a length between 4 and 5 (all "ABCD", everything smaller never gets found, nothing larger exists).
auto match = buffer.find_copy_in_seekback(5, 4);
EXPECT(match.has_value());
EXPECT_EQ(match.value().distance, 6ul);
EXPECT_EQ(match.value().length, 4ul);
}
{
// Find the largest matches with a length between 5 and 5 (nothing is found).
auto matches = MUST(buffer.find_copy_in_seekback(5, 5));
EXPECT_EQ(matches.size(), 0ul);
// Find the largest match with a length between 5 and 5 (nothing is found).
auto match = buffer.find_copy_in_seekback(5, 5);
EXPECT(!match.has_value());
}
{
@ -432,8 +422,8 @@ TEST_CASE(find_copy_in_seekback)
{
// Check that we don't find anything for a minimum length beyond the whole buffer size.
auto matches = MUST(buffer.find_copy_in_seekback(12, 13));
EXPECT_EQ(matches.size(), 0ul);
auto match = buffer.find_copy_in_seekback(12, 13);
EXPECT(!match.has_value());
}
}