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LibCore: Add AllocatingMemoryStream::offset_of

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This commit is contained in:
Tim Schumacher 2023-01-13 13:41:14 +01:00 • committed by Ali Mohammad Pur
parent ecc202c59d
commit 156b6e83cd
3 changed files with 76 additions and 0 deletions
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27
Userland/Libraries/LibCore/MemoryStream.cpp
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@ -5,6 +5,8 @@
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/FixedArray.h>
#include <AK/MemMem.h>
#include <LibCore/MemoryStream.h>
namespace Core::Stream {
@ -198,6 +200,31 @@ size_t AllocatingMemoryStream::used_buffer_size() const
return m_write_offset - m_read_offset;
}
ErrorOr<Optional<size_t>> AllocatingMemoryStream::offset_of(ReadonlyBytes needle) const
{
VERIFY(m_write_offset >= m_read_offset);
if (m_chunks.size() == 0)
return Optional<size_t> {};
// Ensure that we don't have to trim away more than one block.
VERIFY(m_read_offset < chunk_size);
VERIFY(m_chunks.size() * chunk_size - m_write_offset < chunk_size);
auto chunk_count = m_chunks.size();
auto search_spans = TRY(FixedArray<ReadonlyBytes>::try_create(chunk_count));
for (size_t i = 0; i < chunk_count; i++) {
search_spans[i] = m_chunks[i].span();
}
// 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(chunk_count * chunk_size - m_write_offset);
search_spans[0] = search_spans[0].slice(m_read_offset);
return AK::memmem(search_spans.begin(), search_spans.end(), needle);
}
ErrorOr<ReadonlyBytes> AllocatingMemoryStream::next_read_range()
{
VERIFY(m_write_offset >= m_read_offset);