ladybird/AK/MemoryStream.cpp
Lucas CHOLLET 44bedf7844 AK: Don't reuse chunks in AllocatingMemoryStream
As confusing as it may sound, reusing them is terrible performance wise.
When profiling the PNG decoder, the result (which is dominated by the
Zlib decompression) shows that the `cleanup_unused_chunks()` function
represented 14.26% of the profile before this patch and only 7.7%
afterward.

On a 6.5 MB PNG image, it reduces the decompression time by more than
5%.
2023-07-10 21:35:10 -04:00

284 lines
7.9 KiB
C++

/*
* Copyright (c) 2021, kleines Filmröllchen <filmroellchen@serenityos.org>.
* Copyright (c) 2022, Tim Schumacher <timschumi@gmx.de>.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/ByteBuffer.h>
#include <AK/FixedArray.h>
#include <AK/MemMem.h>
#include <AK/MemoryStream.h>
namespace AK {
FixedMemoryStream::FixedMemoryStream(Bytes bytes)
: m_bytes(bytes)
{
}
FixedMemoryStream::FixedMemoryStream(ReadonlyBytes bytes)
: m_bytes({ const_cast<u8*>(bytes.data()), bytes.size() })
, m_writing_enabled(false)
{
}
bool FixedMemoryStream::is_eof() const
{
return m_offset >= m_bytes.size();
}
bool FixedMemoryStream::is_open() const
{
return true;
}
void FixedMemoryStream::close()
{
// FIXME: It doesn't make sense to close a memory stream. Therefore, we don't do anything here. Is that fine?
}
ErrorOr<void> FixedMemoryStream::truncate(size_t)
{
return Error::from_errno(EBADF);
}
ErrorOr<Bytes> FixedMemoryStream::read_some(Bytes bytes)
{
auto to_read = min(remaining(), bytes.size());
if (to_read == 0)
return Bytes {};
m_bytes.slice(m_offset, to_read).copy_to(bytes);
m_offset += to_read;
return bytes.trim(to_read);
}
ErrorOr<void> FixedMemoryStream::read_until_filled(AK::Bytes bytes)
{
if (remaining() < bytes.size())
return Error::from_string_view_or_print_error_and_return_errno("Can't read past the end of the stream memory"sv, EINVAL);
m_bytes.slice(m_offset).copy_trimmed_to(bytes);
m_offset += bytes.size();
return {};
}
ErrorOr<size_t> FixedMemoryStream::seek(i64 offset, SeekMode seek_mode)
{
switch (seek_mode) {
case SeekMode::SetPosition:
if (offset > static_cast<i64>(m_bytes.size()))
return Error::from_string_view_or_print_error_and_return_errno("Offset past the end of the stream memory"sv, EINVAL);
m_offset = offset;
break;
case SeekMode::FromCurrentPosition:
if (offset + static_cast<i64>(m_offset) > static_cast<i64>(m_bytes.size()))
return Error::from_string_view_or_print_error_and_return_errno("Offset past the end of the stream memory"sv, EINVAL);
m_offset += offset;
break;
case SeekMode::FromEndPosition:
if (offset > static_cast<i64>(m_bytes.size()))
return Error::from_string_view_or_print_error_and_return_errno("Offset past the start of the stream memory"sv, EINVAL);
m_offset = m_bytes.size() - offset;
break;
}
return m_offset;
}
ErrorOr<size_t> FixedMemoryStream::write_some(ReadonlyBytes bytes)
{
VERIFY(m_writing_enabled);
// FIXME: Can this not error?
auto const nwritten = bytes.copy_trimmed_to(m_bytes.slice(m_offset));
m_offset += nwritten;
return nwritten;
}
ErrorOr<void> FixedMemoryStream::write_until_depleted(ReadonlyBytes bytes)
{
if (remaining() < bytes.size())
return Error::from_string_view_or_print_error_and_return_errno("Write of entire buffer ends past the memory area"sv, EINVAL);
TRY(write_some(bytes));
return {};
}
Bytes FixedMemoryStream::bytes()
{
VERIFY(m_writing_enabled);
return m_bytes;
}
ReadonlyBytes FixedMemoryStream::bytes() const
{
return m_bytes;
}
size_t FixedMemoryStream::offset() const
{
return m_offset;
}
size_t FixedMemoryStream::remaining() const
{
return m_bytes.size() - m_offset;
}
ErrorOr<Bytes> AllocatingMemoryStream::read_some(Bytes bytes)
{
size_t read_bytes = 0;
while (read_bytes < bytes.size()) {
VERIFY(m_write_offset >= m_read_offset);
auto range = TRY(next_read_range());
if (range.size() == 0)
break;
auto copied_bytes = range.copy_trimmed_to(bytes.slice(read_bytes));
read_bytes += copied_bytes;
m_read_offset += copied_bytes;
}
cleanup_unused_chunks();
return bytes.trim(read_bytes);
}
ErrorOr<size_t> AllocatingMemoryStream::write_some(ReadonlyBytes bytes)
{
size_t written_bytes = 0;
while (written_bytes < bytes.size()) {
VERIFY(m_write_offset >= m_read_offset);
auto range = TRY(next_write_range());
auto copied_bytes = bytes.slice(written_bytes).copy_trimmed_to(range);
written_bytes += copied_bytes;
m_write_offset += copied_bytes;
}
return written_bytes;
}
ErrorOr<void> AllocatingMemoryStream::discard(size_t count)
{
VERIFY(m_write_offset >= m_read_offset);
if (count > used_buffer_size())
return Error::from_string_view_or_print_error_and_return_errno("Number of discarded bytes is higher than the number of allocated bytes"sv, EINVAL);
m_read_offset += count;
cleanup_unused_chunks();
return {};
}
bool AllocatingMemoryStream::is_eof() const
{
return used_buffer_size() == 0;
}
bool AllocatingMemoryStream::is_open() const
{
return true;
}
void AllocatingMemoryStream::close()
{
}
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 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);
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++) {
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(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);
}
ErrorOr<ReadonlyBytes> AllocatingMemoryStream::next_read_range()
{
VERIFY(m_write_offset >= m_read_offset);
size_t const chunk_index = m_read_offset / CHUNK_SIZE;
size_t const chunk_offset = m_read_offset % CHUNK_SIZE;
size_t const read_size = min(CHUNK_SIZE - m_read_offset % CHUNK_SIZE, m_write_offset - m_read_offset);
if (read_size == 0)
return ReadonlyBytes { static_cast<u8*>(nullptr), 0 };
VERIFY(chunk_index < m_chunks.size());
return ReadonlyBytes { m_chunks[chunk_index].data() + chunk_offset, read_size };
}
ErrorOr<Bytes> AllocatingMemoryStream::next_write_range()
{
VERIFY(m_write_offset >= m_read_offset);
size_t const chunk_index = m_write_offset / CHUNK_SIZE;
size_t const chunk_offset = m_write_offset % CHUNK_SIZE;
size_t const write_size = CHUNK_SIZE - m_write_offset % CHUNK_SIZE;
if (chunk_index >= m_chunks.size())
TRY(m_chunks.try_append(TRY(Chunk::create_uninitialized(CHUNK_SIZE))));
VERIFY(chunk_index < m_chunks.size());
return Bytes { m_chunks[chunk_index].data() + chunk_offset, write_size };
}
void AllocatingMemoryStream::cleanup_unused_chunks()
{
// FIXME: Move these all at once.
while (m_read_offset >= CHUNK_SIZE) {
VERIFY(m_write_offset >= m_read_offset);
auto buffer = m_chunks.take_first();
m_read_offset -= CHUNK_SIZE;
m_write_offset -= CHUNK_SIZE;
}
}
}