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LibGfx: Use a FixedArray for the dummy scanline in PNGWriter

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PNGWriter sets up one dummy scanline with the same width as the other
scanlines in order to allow addressing the "previous scanline" without
complicating the code.

By using a FixedArray instead of a VLA, we sidestep the risk of stack
overflow and instead get something that can signal OOM.
This commit is contained in:
Andreas Kling 2022-12-07 19:06:41 +01:00 committed by Sam Atkins
parent e19c8897ee
commit b3b51a5001
Notes: sideshowbarker 2024-07-17 03:38:48 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/b3b51a5001
Pull-request: https://github.com/SerenityOS/serenity/pull/16327
Reviewed-by: https://github.com/AtkinsSJ ✅
Reviewed-by: https://github.com/linusg
1 changed files with 5 additions and 4 deletions
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9
Userland/Libraries/LibGfx/PNGWriter.cpp
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@ -8,6 +8,7 @@
#include <AK/Concepts.h>
#include <AK/DeprecatedString.h>
#include <AK/FixedArray.h>
#include <AK/SIMDExtras.h>
#include <LibCompress/Zlib.h>
#include <LibCrypto/Checksum/CRC32.h>
@ -174,8 +175,8 @@ ErrorOr<void> PNGWriter::add_IDAT_chunk(Gfx::Bitmap const& bitmap)
ByteBuffer uncompressed_block_data;
TRY(uncompressed_block_data.try_ensure_capacity(bitmap.size_in_bytes() + bitmap.height()));
Pixel dummy_scanline[bitmap.width()];
auto const* scanline_minus_1 = dummy_scanline;
auto dummy_scanline = TRY(FixedArray<Pixel>::try_create(bitmap.width()));
auto const* scanline_minus_1 = dummy_scanline.data();
for (int y = 0; y < bitmap.height(); ++y) {
auto* scanline = reinterpret_cast<Pixel const*>(bitmap.scanline(y));
@ -217,8 +218,8 @@ ErrorOr<void> PNGWriter::add_IDAT_chunk(Gfx::Bitmap const& bitmap)
Filter paeth_filter { .type = PNG::FilterType::Paeth };
TRY(paeth_filter.buffer.try_ensure_capacity(sizeof(ARGB32) * bitmap.height()));
auto pixel_x_minus_1 = Pixel::gfx_to_png(*dummy_scanline);
auto pixel_xy_minus_1 = Pixel::gfx_to_png(*dummy_scanline);
auto pixel_x_minus_1 = Pixel::gfx_to_png(dummy_scanline[0]);
auto pixel_xy_minus_1 = Pixel::gfx_to_png(dummy_scanline[0]);
for (int x = 0; x < bitmap.width(); ++x) {
auto pixel = Pixel::gfx_to_png(scanline[x]);