diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
---|---|---|
committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
commit | 6bf0a5cb5034a7e684dcc3500e841785237ce2dd (patch) | |
tree | a68f146d7fa01f0134297619fbe7e33db084e0aa /third_party/jpeg-xl/lib/jxl/enc_bit_writer.h | |
parent | Initial commit. (diff) | |
download | thunderbird-6bf0a5cb5034a7e684dcc3500e841785237ce2dd.tar.xz thunderbird-6bf0a5cb5034a7e684dcc3500e841785237ce2dd.zip |
Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/jpeg-xl/lib/jxl/enc_bit_writer.h')
-rw-r--r-- | third_party/jpeg-xl/lib/jxl/enc_bit_writer.h | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/enc_bit_writer.h b/third_party/jpeg-xl/lib/jxl/enc_bit_writer.h new file mode 100644 index 0000000000..d3fac15a68 --- /dev/null +++ b/third_party/jpeg-xl/lib/jxl/enc_bit_writer.h @@ -0,0 +1,129 @@ +// Copyright (c) the JPEG XL Project Authors. All rights reserved. +// +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +#ifndef LIB_JXL_ENC_BIT_WRITER_H_ +#define LIB_JXL_ENC_BIT_WRITER_H_ + +// BitWriter class: unbuffered writes using unaligned 64-bit stores. + +#include <stddef.h> +#include <stdint.h> + +#include <utility> +#include <vector> + +#include "lib/jxl/base/compiler_specific.h" +#include "lib/jxl/base/padded_bytes.h" +#include "lib/jxl/base/span.h" +#include "lib/jxl/base/status.h" +#include "lib/jxl/common.h" + +namespace jxl { + +struct AuxOut; + +struct BitWriter { + // Upper bound on `n_bits` in each call to Write. We shift a 64-bit word by + // 7 bits (max already valid bits in the last byte) and at least 1 bit is + // needed to zero-initialize the bit-stream ahead (i.e. if 7 bits are valid + // and we write 57 bits, then the next write will access a byte that was not + // yet zero-initialized). + static constexpr size_t kMaxBitsPerCall = 56; + + BitWriter() : bits_written_(0) {} + + // Disallow copying - may lead to bugs. + BitWriter(const BitWriter&) = delete; + BitWriter& operator=(const BitWriter&) = delete; + BitWriter(BitWriter&&) = default; + BitWriter& operator=(BitWriter&&) = default; + + size_t BitsWritten() const { return bits_written_; } + + Span<const uint8_t> GetSpan() const { + // Callers must ensure byte alignment to avoid uninitialized bits. + JXL_ASSERT(bits_written_ % kBitsPerByte == 0); + return Span<const uint8_t>(storage_.data(), bits_written_ / kBitsPerByte); + } + + // Example usage: bytes = std::move(writer).TakeBytes(); Useful for the + // top-level encoder which returns PaddedBytes, not a BitWriter. + // *this must be an rvalue reference and is invalid afterwards. + PaddedBytes&& TakeBytes() && { + // Callers must ensure byte alignment to avoid uninitialized bits. + JXL_ASSERT(bits_written_ % kBitsPerByte == 0); + storage_.resize(bits_written_ / kBitsPerByte); + return std::move(storage_); + } + + private: + // Must be byte-aligned before calling. + void AppendByteAligned(const Span<const uint8_t>& span); + + public: + // NOTE: no allotment needed, the other BitWriters have already been charged. + void AppendByteAligned(const BitWriter& other); + void AppendByteAligned(const std::vector<std::unique_ptr<BitWriter>>& others); + void AppendByteAligned(const std::vector<BitWriter>& others); + + class Allotment { + public: + // Expands a BitWriter's storage. Must happen before calling Write or + // ZeroPadToByte. Must call ReclaimUnused after writing to reclaim the + // unused storage so that BitWriter memory use remains tightly bounded. + Allotment(BitWriter* JXL_RESTRICT writer, size_t max_bits); + ~Allotment(); + + size_t MaxBits() const { return max_bits_; } + + // Call after writing a histogram, but before ReclaimUnused. + void FinishedHistogram(BitWriter* JXL_RESTRICT writer); + + size_t HistogramBits() const { + JXL_ASSERT(called_); + return histogram_bits_; + } + + void ReclaimAndCharge(BitWriter* JXL_RESTRICT writer, size_t layer, + AuxOut* JXL_RESTRICT aux_out); + + private: + void PrivateReclaim(BitWriter* JXL_RESTRICT writer, + size_t* JXL_RESTRICT used_bits, + size_t* JXL_RESTRICT unused_bits); + + size_t prev_bits_written_; + const size_t max_bits_; + size_t histogram_bits_ = 0; + bool called_ = false; + Allotment* parent_; + }; + + // Writes bits into bytes in increasing addresses, and within a byte + // least-significant-bit first. + // + // The function can write up to 56 bits in one go. + void Write(size_t n_bits, uint64_t bits); + + // This should only rarely be used - e.g. when the current location will be + // referenced via byte offset (TOCs point to groups), or byte-aligned reading + // is required for speed. + void ZeroPadToByte() { + const size_t remainder_bits = + RoundUpBitsToByteMultiple(bits_written_) - bits_written_; + if (remainder_bits == 0) return; + Write(remainder_bits, 0); + JXL_ASSERT(bits_written_ % kBitsPerByte == 0); + } + + private: + size_t bits_written_; + PaddedBytes storage_; + Allotment* current_allotment_ = nullptr; +}; + +} // namespace jxl + +#endif // LIB_JXL_ENC_BIT_WRITER_H_ |