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AK: Handle empty trailing chunks in AllocatingMemoryStream::offset_of

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Tim Schumacher 2023-05-29 11:14:08 +02:00 committed by Jelle Raaijmakers
parent 9a7ae52b31
commit 52aab50914
Notes: sideshowbarker 2024-07-17 01:28:15 +09:00 
Author: https://github.com/timschumi
Commit: https://github.com/SerenityOS/serenity/commit/52aab50914
Pull-request: https://github.com/SerenityOS/serenity/pull/19122
Reviewed-by: https://github.com/alimpfard ✅
Reviewed-by: https://github.com/gmta ✅
2 changed files with 37 additions and 3 deletions
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7
AK/MemoryStream.cpp
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@ -198,11 +198,12 @@ ErrorOr<Optional<size_t>> AllocatingMemoryStream::offset_of(ReadonlyBytes needle
if (m_chunks.size() == 0)
return Optional<size_t> {};
// Ensure that we don't have to trim away more than one block.
// Ensure that we don't have empty chunks at the beginning of the stream. Our trimming implementation
// assumes this to be the case, since this should be held up by `cleanup_unused_chunks()` at all times.
VERIFY(m_read_offset < CHUNK_SIZE);
VERIFY(m_chunks.size() * CHUNK_SIZE - m_write_offset < CHUNK_SIZE);
auto chunk_count = m_chunks.size();
auto empty_chunks_at_end = ((m_chunks.size() * CHUNK_SIZE - m_write_offset) / CHUNK_SIZE);
auto chunk_count = m_chunks.size() - empty_chunks_at_end;
auto search_spans = TRY(FixedArray<ReadonlyBytes>::create(chunk_count));
for (size_t i = 0; i < chunk_count; i++) {

33
Tests/AK/TestMemoryStream.cpp
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@ -90,3 +90,36 @@ TEST_CASE(allocating_memory_stream_offset_of_oob)
EXPECT(!offset.has_value());
}
}
TEST_CASE(allocating_memory_stream_offset_of_after_chunk_reorder)
{
AllocatingMemoryStream stream;
// First, fill exactly one chunk (in groups of 16 bytes). This chunk will be reordered.
for (size_t i = 0; i < AllocatingMemoryStream::CHUNK_SIZE / 16; ++i)
MUST(stream.write_until_depleted("AAAAAAAAAAAAAAAA"sv.bytes()));
// Append a few additional bytes to create a second chunk.
MUST(stream.write_until_depleted("BCDEFGHIJKLMNOPQ"sv.bytes()));
// Read back the first chunk, which should reorder it to the end of the list.
// The chunk that we wrote to the second time is now the first one.
MUST(stream.discard(AllocatingMemoryStream::CHUNK_SIZE));
{
auto offset = MUST(stream.offset_of("A"sv.bytes()));
EXPECT(!offset.has_value());
}
{
auto offset = MUST(stream.offset_of("B"sv.bytes()));
EXPECT(offset.has_value());
EXPECT_EQ(offset.value(), 0ul);
}
{
auto offset = MUST(stream.offset_of("Q"sv.bytes()));
EXPECT(offset.has_value());
EXPECT_EQ(offset.value(), 15ul);
}
}