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AK: Implement DuplexMemoryStream::offset_of() in terms of memmem()

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This fixes the FIXME about missing matches that go across chunk
boundaries.
This commit is contained in:
AnotherTest 2020-12-05 04:31:56 +03:30 committed by Andreas Kling
parent 036b39cdfd
commit 602d2ff856
1 changed files with 17 additions and 43 deletions
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60
AK/MemoryStream.h
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@ -222,55 +222,29 @@ public:
return true;
}
// FIXME: Does not read across chunk boundaries
// Perhaps implement AK::memmem() for iterators?
Optional<size_t> offset_of(ReadonlyBytes value) const
{
if (value.size() > size())
return {};
// First, find which chunk we're in.
auto chunk_index = min((m_read_offset - m_base_offset) / chunk_size, m_chunks.size() - 1);
auto last_written_chunk_index = (m_write_offset - m_base_offset) / chunk_size;
auto first_chunk_index = chunk_index;
auto last_written_chunk_offset = m_write_offset % chunk_size;
auto first_chunk_offset = m_read_offset % chunk_size;
size_t last_chunk_offset = 0;
auto found_value = false;
auto chunk_index_max_bound = last_written_chunk_offset > 0 ? last_written_chunk_index + 1 : last_written_chunk_index;
for (; chunk_index < chunk_index_max_bound; ++chunk_index) {
auto& chunk = m_chunks[chunk_index];
auto chunk_bytes = chunk.bytes();
size_t chunk_offset = 0;
if (chunk_index == last_written_chunk_index) {
chunk_bytes = chunk_bytes.slice(0, last_written_chunk_offset);
// We can't directly pass m_chunks to memmem since we have a limited read/write range we want to search in.
Vector<ReadonlyBytes> spans;
auto chunk_index = (m_read_offset - m_base_offset) / chunk_size;
auto chunk_read_offset = (m_read_offset - m_base_offset) % chunk_size;
auto bytes_to_search = m_write_offset - m_read_offset;
for (; bytes_to_search > 0;) {
ReadonlyBytes span = m_chunks[chunk_index];
if (chunk_read_offset) {
span = span.slice(chunk_read_offset);
chunk_read_offset = 0;
}
if (chunk_index == first_chunk_index) {
chunk_bytes = chunk_bytes.slice(first_chunk_offset);
chunk_offset = first_chunk_offset;
if (bytes_to_search < span.size()) {
spans.append(span.slice(0, bytes_to_search));
break;
}
// See if 'value' is in this chunk,
auto position = AK::memmem(chunk_bytes.data(), chunk_bytes.size(), value.data(), value.size());
if (!position)
continue; // Not in this chunk either :(
// We found it!
found_value = true;
last_chunk_offset = (const u8*)position - chunk_bytes.data() + chunk_offset;
break;
bytes_to_search -= span.size();
spans.append(move(span));
++chunk_index;
}
if (found_value) {
if (first_chunk_index == chunk_index)
return last_chunk_offset - first_chunk_offset;
return (chunk_index - first_chunk_index) * chunk_size + last_chunk_offset - first_chunk_offset;
}
// No dice.
return {};
return memmem(spans.begin(), spans.end(), value);
}
size_t read_without_consuming(Bytes bytes) const