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LibGfx: Store the size of the chunk from start in PNGWriter

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Before this change PNGWriter::add_chunk used to make a copy of
PNGChunk's ByteBuffer to prepend the size of the data.
With this change, 4-byte space is saved from the beginning and written
at the end of the operation. Avoiding this copy yields significant
speed up.
This commit is contained in:
Aziz Berkay Yesilyurt 2021-07-11 21:33:37 +02:00 committed by Andreas Kling
parent db36ddc763
commit b70f2b00a3
Notes: sideshowbarker 2024-07-18 09:03:51 +09:00 
Author: https://github.com/abyesilyurt
Commit: https://github.com/SerenityOS/serenity/commit/b70f2b00a3e
Pull-request: https://github.com/SerenityOS/serenity/pull/8662
Reviewed-by: https://github.com/Hendiadyoin1
2 changed files with 24 additions and 11 deletions
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33
Userland/Libraries/LibGfx/PNGWriter.cpp
View File

@ -1,6 +1,7 @@
/*
* Copyright (c) 2021, Pierre Hoffmeister
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Aziz Berkay Yesilyurt <abyesilyurt@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -14,6 +15,8 @@
namespace Gfx {
class PNGChunk {
using data_length_type = u32;
public:
explicit PNGChunk(String);
auto const& data() const { return m_data; };
@ -29,6 +32,8 @@ public:
void add_u8(u8);
void store_type();
void store_data_length();
u32 crc();
private:
template<typename T>
@ -58,6 +63,7 @@ private:
PNGChunk::PNGChunk(String type)
: m_type(move(type))
{
add<data_length_type>(0);
store_type();
}
@ -68,6 +74,18 @@ void PNGChunk::store_type()
}
}
void PNGChunk::store_data_length()
{
auto data_lenth = BigEndian(m_data.size() - sizeof(data_length_type) - m_type.length());
__builtin_memcpy(m_data.offset_pointer(0), &data_lenth, sizeof(u32));
}
u32 PNGChunk::crc()
{
u32 crc = Crypto::Checksum::CRC32({ m_data.offset_pointer(sizeof(data_length_type)), m_data.size() - sizeof(data_length_type) }).digest();
return crc;
}
template<typename T>
requires(IsUnsigned<T>) void PNGChunk::add(T data)
{
@ -129,17 +147,12 @@ void NonCompressibleBlock::update_adler(u8 data)
m_adler_s2 = (m_adler_s2 + m_adler_s1) % 65521;
}
void PNGWriter::add_chunk(PNGChunk const& png_chunk)
void PNGWriter::add_chunk(PNGChunk& png_chunk)
{
auto crc = BigEndian(Crypto::Checksum::CRC32({ (const u8*)png_chunk.data().data(), png_chunk.data().size() }).digest());
auto data_len = BigEndian(png_chunk.data().size() - png_chunk.type().length());
ByteBuffer buf;
buf.append(&data_len, sizeof(u32));
buf.append(png_chunk.data().data(), png_chunk.data().size());
buf.append(&crc, sizeof(u32));
m_data.append(buf.data(), buf.size());
png_chunk.store_data_length();
u32 crc = png_chunk.crc();
png_chunk.add_as_big_endian(crc);
m_data.append(png_chunk.data().data(), png_chunk.data().size());
}
void PNGWriter::add_png_header()

2
Userland/Libraries/LibGfx/PNGWriter.h
View File

@ -22,7 +22,7 @@ private:
PNGWriter() { }
Vector<u8> m_data;
void add_chunk(PNGChunk const&);
void add_chunk(PNGChunk&);
void add_png_header();
void add_IHDR_chunk(u32 width, u32 height, u8 bit_depth, u8 color_type, u8 compression_method, u8 filter_method, u8 interlace_method);
void add_IDAT_chunk(Gfx::Bitmap const&);