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AK: Correctly calculate size of the last AllocatingMemoryStream chunk

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Tim Schumacher 2023-05-29 11:40:59 +02:00 • committed by Jelle Raaijmakers
parent 52aab50914
commit 58b1d9c319
2 changed files with 37 additions and 1 deletions
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10
AK/MemoryStream.cpp
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@ -210,8 +210,16 @@ ErrorOr<Optional<size_t>> AllocatingMemoryStream::offset_of(ReadonlyBytes needle
search_spans[i] = m_chunks[i].span();
}
auto used_size_of_last_chunk = m_write_offset % CHUNK_SIZE;
// The case where the stored write offset is actually the used space is the only case where a result of zero
// actually is zero. In other cases (i.e. our write offset is beyond the size of a chunk) the write offset
// already points to the beginning of the next chunk, in that case a result of zero indicates "use the last chunk in full".
if (m_write_offset >= CHUNK_SIZE && used_size_of_last_chunk == 0)
used_size_of_last_chunk = CHUNK_SIZE;
// Trimming is done first to ensure that we don't unintentionally shift around if the first and last chunks are the same.
search_spans[chunk_count - 1] = search_spans[chunk_count - 1].trim(m_write_offset % CHUNK_SIZE);
search_spans[chunk_count - 1] = search_spans[chunk_count - 1].trim(used_size_of_last_chunk);
search_spans[0] = search_spans[0].slice(m_read_offset);
return AK::memmem(search_spans.begin(), search_spans.end(), needle);