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ed2658d72c
No behavior change. No measurable performance different either. (I tried `hyperfine 'Build/lagom/bin/image --no-output foo.webp'` for a few input images before and after this change, and I didn't see a difference. I also tried if moving both Gfx::CanonicalCode::read_symbol() and Compress::CanonicalCode::read_symbol() inline, and that didn't help either.)
56 lines
1.5 KiB
C++
56 lines
1.5 KiB
C++
/*
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* Copyright (c) 2024, Nico Weber <thakis@chromium.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <LibCompress/Deflate.h>
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namespace Gfx {
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// WebP-lossless's CanonicalCodes are almost identical to deflate's.
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// One difference is that codes with a single element in webp-lossless consume 0 bits to produce that single element,
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// while they consume 1 bit in Compress::CanonicalCode. This class wraps Compress::CanonicalCode to handle the case
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// where the codes contain just a single element, and dispatches to Compress::CanonicalCode else.
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class CanonicalCode {
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public:
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CanonicalCode()
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: m_code(0)
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{
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}
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static ErrorOr<CanonicalCode> from_bytes(ReadonlyBytes);
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ErrorOr<u32> read_symbol(LittleEndianInputBitStream&) const;
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private:
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explicit CanonicalCode(u32 single_symbol)
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: m_code(single_symbol)
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{
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}
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explicit CanonicalCode(Compress::CanonicalCode code)
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: m_code(move(code))
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{
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}
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Variant<u32, Compress::CanonicalCode> m_code;
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};
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// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#61_overview
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// "From here on, we refer to this set as a prefix code group."
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class PrefixCodeGroup {
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public:
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PrefixCodeGroup() = default;
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PrefixCodeGroup(PrefixCodeGroup&&) = default;
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PrefixCodeGroup(PrefixCodeGroup const&) = delete;
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CanonicalCode& operator[](int i) { return m_codes[i]; }
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CanonicalCode const& operator[](int i) const { return m_codes[i]; }
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private:
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Array<CanonicalCode, 5> m_codes;
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};
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}
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