tor-browser

dec_jpeg_data_writer.cc (33652B)

---

// 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.

#include "lib/jxl/jpeg/dec_jpeg_data_writer.h"

#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <cstring> /* for memset, memcpy */
#include <deque>
#include <utility>
#include <vector>

#include "lib/jxl/base/bits.h"
#include "lib/jxl/base/byte_order.h"
#include "lib/jxl/base/common.h"
#include "lib/jxl/base/status.h"
#include "lib/jxl/frame_dimensions.h"
#include "lib/jxl/jpeg/dec_jpeg_serialization_state.h"
#include "lib/jxl/jpeg/jpeg_data.h"

namespace jxl {
namespace jpeg {

namespace {

enum struct SerializationStatus {
 NEEDS_MORE_INPUT,
 NEEDS_MORE_OUTPUT,
 ERROR,
 DONE
};

const int kJpegPrecision = 8;

// JpegBitWriter: buffer size
const size_t kJpegBitWriterChunkSize = 16384;

// Returns non-zero if and only if x has a zero byte, i.e. one of
// x & 0xff, x & 0xff00, ..., x & 0xff00000000000000 is zero.
JXL_INLINE uint64_t HasZeroByte(uint64_t x) {
 return (x - 0x0101010101010101ULL) & ~x & 0x8080808080808080ULL;
}

void JpegBitWriterInit(JpegBitWriter* bw,
                      std::deque<OutputChunk>* output_queue) {
 bw->output = output_queue;
 bw->chunk = OutputChunk(kJpegBitWriterChunkSize);
 bw->pos = 0;
 bw->put_buffer = 0;
 bw->put_bits = 64;
 bw->healthy = true;
 bw->data = bw->chunk.buffer->data();
}

JXL_NOINLINE void SwapBuffer(JpegBitWriter* bw) {
 bw->chunk.len = bw->pos;
 bw->output->emplace_back(std::move(bw->chunk));
 bw->chunk = OutputChunk(kJpegBitWriterChunkSize);
 bw->data = bw->chunk.buffer->data();
 bw->pos = 0;
}

JXL_INLINE void Reserve(JpegBitWriter* bw, size_t n_bytes) {
 if (JXL_UNLIKELY((bw->pos + n_bytes) > kJpegBitWriterChunkSize)) {
   SwapBuffer(bw);
 }
}

/**
* Writes the given byte to the output, writes an extra zero if byte is 0xFF.
*
* This method is "careless" - caller must make sure that there is enough
* space in the output buffer. Emits up to 2 bytes to buffer.
*/
JXL_INLINE void EmitByte(JpegBitWriter* bw, int byte) {
 bw->data[bw->pos] = byte;
 bw->data[bw->pos + 1] = 0;
 bw->pos += (byte != 0xFF ? 1 : 2);
}

JXL_INLINE void DischargeBitBuffer(JpegBitWriter* bw, int nbits,
                                  uint64_t bits) {
 // At this point we are ready to emit the put_buffer to the output.
 // The JPEG format requires that after every 0xff byte in the entropy
 // coded section, there is a zero byte, therefore we first check if any of
 // the 8 bytes of put_buffer is 0xFF.
 bw->put_buffer |= (bits >> -bw->put_bits);
 if (JXL_UNLIKELY(HasZeroByte(~bw->put_buffer))) {
   // We have a 0xFF byte somewhere, examine each byte and append a zero
   // byte if necessary.
   EmitByte(bw, (bw->put_buffer >> 56) & 0xFF);
   EmitByte(bw, (bw->put_buffer >> 48) & 0xFF);
   EmitByte(bw, (bw->put_buffer >> 40) & 0xFF);
   EmitByte(bw, (bw->put_buffer >> 32) & 0xFF);
   EmitByte(bw, (bw->put_buffer >> 24) & 0xFF);
   EmitByte(bw, (bw->put_buffer >> 16) & 0xFF);
   EmitByte(bw, (bw->put_buffer >> 8) & 0xFF);
   EmitByte(bw, (bw->put_buffer) & 0xFF);
 } else {
   // We don't have any 0xFF bytes, output all 8 bytes without checking.
   StoreBE64(bw->put_buffer, bw->data + bw->pos);
   bw->pos += 8;
 }

 bw->put_bits += 64;
 bw->put_buffer = bits << bw->put_bits;
}

JXL_INLINE void WriteBits(JpegBitWriter* bw, int nbits, uint64_t bits) {
 JXL_DASSERT(nbits > 0);
 bw->put_bits -= nbits;
 if (JXL_UNLIKELY(bw->put_bits < 0)) {
   if (JXL_UNLIKELY(nbits > 64)) {
     bw->put_bits += nbits;
     bw->healthy = false;
   } else {
     DischargeBitBuffer(bw, nbits, bits);
   }
 } else {
   bw->put_buffer |= (bits << bw->put_bits);
 }
}

void EmitMarker(JpegBitWriter* bw, int marker) {
 Reserve(bw, 2);
 JXL_DASSERT(marker != 0xFF);
 bw->data[bw->pos++] = 0xFF;
 bw->data[bw->pos++] = marker;
}

bool JumpToByteBoundary(JpegBitWriter* bw, const uint8_t** pad_bits,
                       const uint8_t* pad_bits_end) {
 size_t n_bits = bw->put_bits & 7u;
 uint8_t dangling_bits = 0;
 uint8_t pad_pattern;
 if (*pad_bits == nullptr) {
   pad_pattern = (1u << n_bits) - 1;
 } else {
   pad_pattern = 0;
   const uint8_t* src = *pad_bits;
   // TODO(eustas): bitwise reading looks insanely ineffective!
   while (n_bits--) {
     pad_pattern <<= 1;
     if (src >= pad_bits_end) return false;
     uint8_t bit = *src;
     src++;
     dangling_bits |= bit;
     pad_pattern |= bit;
   }
   *pad_bits = src;
 }
 if ((dangling_bits & ~1) != 0) return false;

 Reserve(bw, 16);

 while (bw->put_bits <= 56) {
   int c = (bw->put_buffer >> 56) & 0xFF;
   EmitByte(bw, c);
   bw->put_buffer <<= 8;
   bw->put_bits += 8;
 }
 if (bw->put_bits < 64) {
   int pad_mask = 0xFFu >> (64 - bw->put_bits);
   int c = ((bw->put_buffer >> 56) & ~pad_mask) | pad_pattern;
   EmitByte(bw, c);
 }
 bw->put_buffer = 0;
 bw->put_bits = 64;

 return true;
}

void JpegBitWriterFinish(JpegBitWriter* bw) {
 if (bw->pos == 0) return;
 bw->chunk.len = bw->pos;
 bw->output->emplace_back(std::move(bw->chunk));
 bw->chunk = OutputChunk(nullptr, 0);
 bw->data = nullptr;
 bw->pos = 0;
}

void DCTCodingStateInit(DCTCodingState* s) {
 s->eob_run_ = 0;
 s->cur_ac_huff_ = nullptr;
 s->refinement_bits_.clear();
 s->refinement_bits_.reserve(64);
}

JXL_INLINE void WriteSymbol(int symbol, HuffmanCodeTable* table,
                           JpegBitWriter* bw) {
 WriteBits(bw, table->depth[symbol], table->code[symbol]);
}

JXL_INLINE void WriteSymbolBits(int symbol, HuffmanCodeTable* table,
                               JpegBitWriter* bw, int nbits, uint64_t bits) {
 WriteBits(bw, nbits + table->depth[symbol],
           bits | (table->code[symbol] << nbits));
}

// Emit all buffered data to the bit stream using the given Huffman code and
// bit writer.
JXL_INLINE void Flush(DCTCodingState* s, JpegBitWriter* bw) {
 if (s->eob_run_ > 0) {
   Reserve(bw, 16);
   int nbits = FloorLog2Nonzero<uint32_t>(s->eob_run_);
   int symbol = nbits << 4u;
   WriteSymbol(symbol, s->cur_ac_huff_, bw);
   if (nbits > 0) {
     WriteBits(bw, nbits, s->eob_run_ & ((1 << nbits) - 1));
   }
   s->eob_run_ = 0;
 }
 const size_t kStride = 124;  // (515 - 16) / 2 / 2
 size_t num_words = s->refinement_bits_count_ >> 4;
 size_t i = 0;
 while (i < num_words) {
   size_t limit = std::min(i + kStride, num_words);
   Reserve(bw, 512);
   for (; i < limit; ++i) {
     WriteBits(bw, 16, s->refinement_bits_[i]);
   }
 }
 Reserve(bw, 16);
 size_t tail = s->refinement_bits_count_ & 0xF;
 if (tail) {
   WriteBits(bw, tail, s->refinement_bits_.back());
 }
 s->refinement_bits_.clear();
 s->refinement_bits_count_ = 0;
}

// Buffer some more data at the end-of-band (the last non-zero or newly
// non-zero coefficient within the [Ss, Se] spectral band).
JXL_INLINE void BufferEndOfBand(DCTCodingState* s, HuffmanCodeTable* ac_huff,
                               const int* new_bits_array,
                               size_t new_bits_count, JpegBitWriter* bw) {
 if (s->eob_run_ == 0) {
   s->cur_ac_huff_ = ac_huff;
 }
 ++s->eob_run_;
 if (new_bits_count) {
   uint64_t new_bits = 0;
   for (size_t i = 0; i < new_bits_count; ++i) {
     new_bits = (new_bits << 1) | new_bits_array[i];
   }
   size_t tail = s->refinement_bits_count_ & 0xF;
   if (tail) {  // First stuff the tail item
     size_t stuff_bits_count = std::min(16 - tail, new_bits_count);
     uint16_t stuff_bits = new_bits >> (new_bits_count - stuff_bits_count);
     stuff_bits &= ((1u << stuff_bits_count) - 1);
     s->refinement_bits_.back() =
         (s->refinement_bits_.back() << stuff_bits_count) | stuff_bits;
     new_bits_count -= stuff_bits_count;
     s->refinement_bits_count_ += stuff_bits_count;
   }
   while (new_bits_count >= 16) {
     s->refinement_bits_.push_back(new_bits >> (new_bits_count - 16));
     new_bits_count -= 16;
     s->refinement_bits_count_ += 16;
   }
   if (new_bits_count) {
     s->refinement_bits_.push_back(new_bits & ((1u << new_bits_count) - 1));
     s->refinement_bits_count_ += new_bits_count;
   }
 }

 if (s->eob_run_ == 0x7FFF) {
   Flush(s, bw);
 }
}

bool BuildHuffmanCodeTable(const JPEGHuffmanCode& huff,
                          HuffmanCodeTable* table) {
 int huff_code[kJpegHuffmanAlphabetSize];
 // +1 for a sentinel element.
 uint32_t huff_size[kJpegHuffmanAlphabetSize + 1];
 int p = 0;
 for (size_t l = 1; l <= kJpegHuffmanMaxBitLength; ++l) {
   int i = huff.counts[l];
   if (p + i > kJpegHuffmanAlphabetSize + 1) {
     return false;
   }
   while (i--) huff_size[p++] = l;
 }

 if (p == 0) {
   return true;
 }

 // Reuse sentinel element.
 int last_p = p - 1;
 huff_size[last_p] = 0;

 int code = 0;
 uint32_t si = huff_size[0];
 p = 0;
 while (huff_size[p]) {
   while ((huff_size[p]) == si) {
     huff_code[p++] = code;
     code++;
   }
   code <<= 1;
   si++;
 }
 for (p = 0; p < last_p; p++) {
   int i = huff.values[p];
   table->depth[i] = huff_size[p];
   table->code[i] = huff_code[p];
 }
 return true;
}

bool EncodeSOI(SerializationState* state) {
 state->output_queue.push_back(OutputChunk({0xFF, 0xD8}));
 return true;
}

bool EncodeEOI(const JPEGData& jpg, SerializationState* state) {
 state->output_queue.push_back(OutputChunk({0xFF, 0xD9}));
 state->output_queue.emplace_back(jpg.tail_data);
 return true;
}

bool EncodeSOF(const JPEGData& jpg, uint8_t marker, SerializationState* state) {
 if (marker <= 0xC2) state->is_progressive = (marker == 0xC2);

 const size_t n_comps = jpg.components.size();
 const size_t marker_len = 8 + 3 * n_comps;
 state->output_queue.emplace_back(marker_len + 2);
 uint8_t* data = state->output_queue.back().buffer->data();
 size_t pos = 0;
 data[pos++] = 0xFF;
 data[pos++] = marker;
 data[pos++] = marker_len >> 8u;
 data[pos++] = marker_len & 0xFFu;
 data[pos++] = kJpegPrecision;
 data[pos++] = jpg.height >> 8u;
 data[pos++] = jpg.height & 0xFFu;
 data[pos++] = jpg.width >> 8u;
 data[pos++] = jpg.width & 0xFFu;
 data[pos++] = n_comps;
 for (size_t i = 0; i < n_comps; ++i) {
   data[pos++] = jpg.components[i].id;
   data[pos++] = ((jpg.components[i].h_samp_factor << 4u) |
                  (jpg.components[i].v_samp_factor));
   const size_t quant_idx = jpg.components[i].quant_idx;
   if (quant_idx >= jpg.quant.size()) return false;
   data[pos++] = jpg.quant[quant_idx].index;
 }
 return true;
}

bool EncodeSOS(const JPEGData& jpg, const JPEGScanInfo& scan_info,
              SerializationState* state) {
 const size_t n_scans = scan_info.num_components;
 const size_t marker_len = 6 + 2 * n_scans;
 state->output_queue.emplace_back(marker_len + 2);
 uint8_t* data = state->output_queue.back().buffer->data();
 size_t pos = 0;
 data[pos++] = 0xFF;
 data[pos++] = 0xDA;
 data[pos++] = marker_len >> 8u;
 data[pos++] = marker_len & 0xFFu;
 data[pos++] = n_scans;
 for (size_t i = 0; i < n_scans; ++i) {
   const JPEGComponentScanInfo& si = scan_info.components[i];
   if (si.comp_idx >= jpg.components.size()) return false;
   data[pos++] = jpg.components[si.comp_idx].id;
   data[pos++] = (si.dc_tbl_idx << 4u) + si.ac_tbl_idx;
 }
 data[pos++] = scan_info.Ss;
 data[pos++] = scan_info.Se;
 data[pos++] = ((scan_info.Ah << 4u) | (scan_info.Al));
 return true;
}

bool EncodeDHT(const JPEGData& jpg, SerializationState* state) {
 const std::vector<JPEGHuffmanCode>& huffman_code = jpg.huffman_code;

 size_t marker_len = 2;
 for (size_t i = state->dht_index; i < huffman_code.size(); ++i) {
   const JPEGHuffmanCode& huff = huffman_code[i];
   marker_len += kJpegHuffmanMaxBitLength;
   for (uint32_t count : huff.counts) {
     marker_len += count;
   }
   if (huff.is_last) break;
 }
 state->output_queue.emplace_back(marker_len + 2);
 uint8_t* data = state->output_queue.back().buffer->data();
 size_t pos = 0;
 data[pos++] = 0xFF;
 data[pos++] = 0xC4;
 data[pos++] = marker_len >> 8u;
 data[pos++] = marker_len & 0xFFu;
 while (true) {
   const size_t huffman_code_index = state->dht_index++;
   if (huffman_code_index >= huffman_code.size()) {
     return false;
   }
   const JPEGHuffmanCode& huff = huffman_code[huffman_code_index];
   size_t index = huff.slot_id;
   HuffmanCodeTable* huff_table;
   if (index & 0x10) {
     index -= 0x10;
     huff_table = &state->ac_huff_table[index];
   } else {
     huff_table = &state->dc_huff_table[index];
   }
   // TODO(eustas): cache
   huff_table->InitDepths(127);
   if (!BuildHuffmanCodeTable(huff, huff_table)) {
     return false;
   }
   huff_table->initialized = true;
   size_t total_count = 0;
   size_t max_length = 0;
   for (size_t i = 0; i < huff.counts.size(); ++i) {
     if (huff.counts[i] != 0) {
       max_length = i;
     }
     total_count += huff.counts[i];
   }
   --total_count;
   data[pos++] = huff.slot_id;
   for (size_t i = 1; i <= kJpegHuffmanMaxBitLength; ++i) {
     data[pos++] = (i == max_length ? huff.counts[i] - 1 : huff.counts[i]);
   }
   for (size_t i = 0; i < total_count; ++i) {
     data[pos++] = huff.values[i];
   }
   if (huff.is_last) break;
 }
 return true;
}

bool EncodeDQT(const JPEGData& jpg, SerializationState* state) {
 int marker_len = 2;
 for (size_t i = state->dqt_index; i < jpg.quant.size(); ++i) {
   const JPEGQuantTable& table = jpg.quant[i];
   marker_len += 1 + (table.precision ? 2 : 1) * kDCTBlockSize;
   if (table.is_last) break;
 }
 state->output_queue.emplace_back(marker_len + 2);
 uint8_t* data = state->output_queue.back().buffer->data();
 size_t pos = 0;
 data[pos++] = 0xFF;
 data[pos++] = 0xDB;
 data[pos++] = marker_len >> 8u;
 data[pos++] = marker_len & 0xFFu;
 while (true) {
   const size_t idx = state->dqt_index++;
   if (idx >= jpg.quant.size()) {
     return false;  // corrupt input
   }
   const JPEGQuantTable& table = jpg.quant[idx];
   data[pos++] = (table.precision << 4u) + table.index;
   for (size_t i = 0; i < kDCTBlockSize; ++i) {
     int val_idx = kJPEGNaturalOrder[i];
     int val = table.values[val_idx];
     if (table.precision) {
       data[pos++] = val >> 8u;
     }
     data[pos++] = val & 0xFFu;
   }
   if (table.is_last) break;
 }
 return true;
}

bool EncodeDRI(const JPEGData& jpg, SerializationState* state) {
 state->seen_dri_marker = true;
 OutputChunk dri_marker = {0xFF,
                           0xDD,
                           0,
                           4,
                           static_cast<uint8_t>(jpg.restart_interval >> 8),
                           static_cast<uint8_t>(jpg.restart_interval & 0xFF)};
 state->output_queue.push_back(std::move(dri_marker));
 return true;
}

bool EncodeRestart(uint8_t marker, SerializationState* state) {
 state->output_queue.push_back(OutputChunk({0xFF, marker}));
 return true;
}

bool EncodeAPP(const JPEGData& jpg, uint8_t marker, SerializationState* state) {
 // TODO(eustas): check that marker corresponds to payload?
 (void)marker;

 size_t app_index = state->app_index++;
 if (app_index >= jpg.app_data.size()) return false;
 state->output_queue.push_back(OutputChunk({0xFF}));
 state->output_queue.emplace_back(jpg.app_data[app_index]);
 return true;
}

bool EncodeCOM(const JPEGData& jpg, SerializationState* state) {
 size_t com_index = state->com_index++;
 if (com_index >= jpg.com_data.size()) return false;
 state->output_queue.push_back(OutputChunk({0xFF}));
 state->output_queue.emplace_back(jpg.com_data[com_index]);
 return true;
}

bool EncodeInterMarkerData(const JPEGData& jpg, SerializationState* state) {
 size_t index = state->data_index++;
 if (index >= jpg.inter_marker_data.size()) return false;
 state->output_queue.emplace_back(jpg.inter_marker_data[index]);
 return true;
}

bool EncodeDCTBlockSequential(const coeff_t* coeffs, HuffmanCodeTable* dc_huff,
                             HuffmanCodeTable* ac_huff, int num_zero_runs,
                             coeff_t* last_dc_coeff, JpegBitWriter* bw) {
 coeff_t temp2;
 coeff_t temp;
 coeff_t litmus = 0;
 temp2 = coeffs[0];
 temp = temp2 - *last_dc_coeff;
 *last_dc_coeff = temp2;
 temp2 = temp >> (8 * sizeof(coeff_t) - 1);
 temp += temp2;
 temp2 ^= temp;

 int dc_nbits = (temp2 == 0) ? 0 : (FloorLog2Nonzero<uint32_t>(temp2) + 1);
 WriteSymbol(dc_nbits, dc_huff, bw);
#if JXL_FALSE
 // If the input is corrupt, this could be triggered. Checking is
 // costly though, so it makes more sense to avoid this branch.
 // (producing a corrupt JPEG when the input is corrupt, instead
 // of catching it and returning error)
 if (dc_nbits >= 12) return false;
#endif
 if (dc_nbits) {
   WriteBits(bw, dc_nbits, temp & ((1u << dc_nbits) - 1));
 }
 int16_t r = 0;

 for (size_t i = 1; i < 64; i++) {
   temp = coeffs[kJPEGNaturalOrder[i]];
   if (temp == 0) {
     r++;
   } else {
     temp2 = temp >> (8 * sizeof(coeff_t) - 1);
     temp += temp2;
     temp2 ^= temp;
     if (JXL_UNLIKELY(r > 15)) {
       WriteSymbol(0xf0, ac_huff, bw);
       r -= 16;
       if (r > 15) {
         WriteSymbol(0xf0, ac_huff, bw);
         r -= 16;
       }
       if (r > 15) {
         WriteSymbol(0xf0, ac_huff, bw);
         r -= 16;
       }
     }
     litmus |= temp2;
     int ac_nbits =
         FloorLog2Nonzero<uint32_t>(static_cast<uint16_t>(temp2)) + 1;
     int symbol = (r << 4u) + ac_nbits;
     WriteSymbolBits(symbol, ac_huff, bw, ac_nbits,
                     temp & ((1 << ac_nbits) - 1));
     r = 0;
   }
 }

 for (int i = 0; i < num_zero_runs; ++i) {
   WriteSymbol(0xf0, ac_huff, bw);
   r -= 16;
 }
 if (r > 0) {
   WriteSymbol(0, ac_huff, bw);
 }
 return (litmus >= 0);
}

bool EncodeDCTBlockProgressive(const coeff_t* coeffs, HuffmanCodeTable* dc_huff,
                              HuffmanCodeTable* ac_huff, int Ss, int Se,
                              int Al, int num_zero_runs,
                              DCTCodingState* coding_state,
                              coeff_t* last_dc_coeff, JpegBitWriter* bw) {
 bool eob_run_allowed = Ss > 0;
 coeff_t temp2;
 coeff_t temp;
 if (Ss == 0) {
   temp2 = coeffs[0] >> Al;
   temp = temp2 - *last_dc_coeff;
   *last_dc_coeff = temp2;
   temp2 = temp;
   if (temp < 0) {
     temp = -temp;
     if (temp < 0) return false;
     temp2--;
   }
   int nbits = (temp == 0) ? 0 : (FloorLog2Nonzero<uint32_t>(temp) + 1);
   WriteSymbol(nbits, dc_huff, bw);
   if (nbits) {
     WriteBits(bw, nbits, temp2 & ((1 << nbits) - 1));
   }
   ++Ss;
 }
 if (Ss > Se) {
   return true;
 }
 int r = 0;
 for (int k = Ss; k <= Se; ++k) {
   temp = coeffs[kJPEGNaturalOrder[k]];
   if (temp == 0) {
     r++;
     continue;
   }
   if (temp < 0) {
     temp = -temp;
     if (temp < 0) return false;
     temp >>= Al;
     temp2 = ~temp;
   } else {
     temp >>= Al;
     temp2 = temp;
   }
   if (temp == 0) {
     r++;
     continue;
   }
   Flush(coding_state, bw);
   while (r > 15) {
     WriteSymbol(0xf0, ac_huff, bw);
     r -= 16;
   }
   int nbits = FloorLog2Nonzero<uint32_t>(temp) + 1;
   int symbol = (r << 4u) + nbits;
   WriteSymbol(symbol, ac_huff, bw);
   WriteBits(bw, nbits, temp2 & ((1 << nbits) - 1));
   r = 0;
 }
 if (num_zero_runs > 0) {
   Flush(coding_state, bw);
   for (int i = 0; i < num_zero_runs; ++i) {
     WriteSymbol(0xf0, ac_huff, bw);
     r -= 16;
   }
 }
 if (r > 0) {
   BufferEndOfBand(coding_state, ac_huff, nullptr, 0, bw);
   if (!eob_run_allowed) {
     Flush(coding_state, bw);
   }
 }
 return true;
}

bool EncodeRefinementBits(const coeff_t* coeffs, HuffmanCodeTable* ac_huff,
                         int Ss, int Se, int Al, DCTCodingState* coding_state,
                         JpegBitWriter* bw) {
 bool eob_run_allowed = Ss > 0;
 if (Ss == 0) {
   // Emit next bit of DC component.
   WriteBits(bw, 1, (coeffs[0] >> Al) & 1);
   ++Ss;
 }
 if (Ss > Se) {
   return true;
 }
 int abs_values[kDCTBlockSize];
 int eob = 0;
 for (int k = Ss; k <= Se; k++) {
   const coeff_t abs_val = std::abs(coeffs[kJPEGNaturalOrder[k]]);
   abs_values[k] = abs_val >> Al;
   if (abs_values[k] == 1) {
     eob = k;
   }
 }
 int r = 0;
 int refinement_bits[kDCTBlockSize];
 size_t refinement_bits_count = 0;
 for (int k = Ss; k <= Se; k++) {
   if (abs_values[k] == 0) {
     r++;
     continue;
   }
   while (r > 15 && k <= eob) {
     Flush(coding_state, bw);
     WriteSymbol(0xf0, ac_huff, bw);
     r -= 16;
     for (size_t i = 0; i < refinement_bits_count; ++i) {
       WriteBits(bw, 1, refinement_bits[i]);
     }
     refinement_bits_count = 0;
   }
   if (abs_values[k] > 1) {
     refinement_bits[refinement_bits_count++] = abs_values[k] & 1u;
     continue;
   }
   Flush(coding_state, bw);
   int symbol = (r << 4u) + 1;
   int new_non_zero_bit = (coeffs[kJPEGNaturalOrder[k]] < 0) ? 0 : 1;
   WriteSymbol(symbol, ac_huff, bw);
   WriteBits(bw, 1, new_non_zero_bit);
   for (size_t i = 0; i < refinement_bits_count; ++i) {
     WriteBits(bw, 1, refinement_bits[i]);
   }
   refinement_bits_count = 0;
   r = 0;
 }
 if (r > 0 || refinement_bits_count) {
   BufferEndOfBand(coding_state, ac_huff, refinement_bits,
                   refinement_bits_count, bw);
   if (!eob_run_allowed) {
     Flush(coding_state, bw);
   }
 }
 return true;
}

template <int kMode>
SerializationStatus JXL_NOINLINE DoEncodeScan(const JPEGData& jpg,
                                             SerializationState* state) {
 const JPEGScanInfo& scan_info = jpg.scan_info[state->scan_index];
 EncodeScanState& ss = state->scan_state;

 const int restart_interval =
     state->seen_dri_marker ? jpg.restart_interval : 0;

 const auto get_next_extra_zero_run_index = [&ss, &scan_info]() -> int {
   if (ss.extra_zero_runs_pos < scan_info.extra_zero_runs.size()) {
     return scan_info.extra_zero_runs[ss.extra_zero_runs_pos].block_idx;
   } else {
     return -1;
   }
 };

 const auto get_next_reset_point = [&ss, &scan_info]() -> int {
   if (ss.next_reset_point_pos < scan_info.reset_points.size()) {
     return scan_info.reset_points[ss.next_reset_point_pos++];
   } else {
     return -1;
   }
 };

 if (ss.stage == EncodeScanState::HEAD) {
   if (!EncodeSOS(jpg, scan_info, state)) return SerializationStatus::ERROR;
   JpegBitWriterInit(&ss.bw, &state->output_queue);
   DCTCodingStateInit(&ss.coding_state);
   ss.restarts_to_go = restart_interval;
   ss.next_restart_marker = 0;
   ss.block_scan_index = 0;
   ss.extra_zero_runs_pos = 0;
   ss.next_extra_zero_run_index = get_next_extra_zero_run_index();
   ss.next_reset_point_pos = 0;
   ss.next_reset_point = get_next_reset_point();
   ss.mcu_y = 0;
   memset(ss.last_dc_coeff, 0, sizeof(ss.last_dc_coeff));
   ss.stage = EncodeScanState::BODY;
 }
 JpegBitWriter* bw = &ss.bw;
 DCTCodingState* coding_state = &ss.coding_state;

 if (ss.stage != EncodeScanState::BODY) return SerializationStatus::ERROR;

 // "Non-interleaved" means color data comes in separate scans, in other words
 // each scan can contain only one color component.
 const bool is_interleaved = (scan_info.num_components > 1);
 int MCUs_per_row = 0;
 int MCU_rows = 0;
 jpg.CalculateMcuSize(scan_info, &MCUs_per_row, &MCU_rows);
 const bool is_progressive = state->is_progressive;
 const int Al = is_progressive ? scan_info.Al : 0;
 const int Ss = is_progressive ? scan_info.Ss : 0;
 const int Se = is_progressive ? scan_info.Se : 63;

 // DC-only is defined by [0..0] spectral range.
 const bool want_ac = ((Ss != 0) || (Se != 0));
 const bool want_dc = (Ss == 0);
 // TODO(user): support streaming decoding again.
 const bool complete_ac = true;
 const bool has_ac = true;
 if (want_ac && !has_ac) return SerializationStatus::NEEDS_MORE_INPUT;

 // |has_ac| implies |complete_dc| but not vice versa; for the sake of
 // simplicity we pretend they are equal, because they are separated by just a
 // few bytes of input.
 const bool complete_dc = has_ac;
 const bool complete = want_ac ? complete_ac : complete_dc;
 // When "incomplete" |ac_dc| tracks information about current ("incomplete")
 // band parsing progress.

 // FIXME: Is this always complete?
 // const int last_mcu_y =
 //     complete ? MCU_rows : parsing_state.internal->ac_dc.next_mcu_y *
 //     v_group;
 (void)complete;
 const int last_mcu_y = complete ? MCU_rows : 0;

 for (; ss.mcu_y < last_mcu_y; ++ss.mcu_y) {
   for (int mcu_x = 0; mcu_x < MCUs_per_row; ++mcu_x) {
     // Possibly emit a restart marker.
     if (restart_interval > 0 && ss.restarts_to_go == 0) {
       Flush(coding_state, bw);
       if (!JumpToByteBoundary(bw, &state->pad_bits, state->pad_bits_end)) {
         return SerializationStatus::ERROR;
       }
       EmitMarker(bw, 0xD0 + ss.next_restart_marker);
       ss.next_restart_marker += 1;
       ss.next_restart_marker &= 0x7;
       ss.restarts_to_go = restart_interval;
       memset(ss.last_dc_coeff, 0, sizeof(ss.last_dc_coeff));
     }

     // Encode one MCU
     for (size_t i = 0; i < scan_info.num_components; ++i) {
       const JPEGComponentScanInfo& si = scan_info.components[i];
       const JPEGComponent& c = jpg.components[si.comp_idx];
       size_t dc_tbl_idx = si.dc_tbl_idx;
       size_t ac_tbl_idx = si.ac_tbl_idx;
       HuffmanCodeTable* dc_huff = &state->dc_huff_table[dc_tbl_idx];
       HuffmanCodeTable* ac_huff = &state->ac_huff_table[ac_tbl_idx];
       if (want_dc && !dc_huff->initialized) {
         return SerializationStatus::ERROR;
       }
       if (want_ac && !ac_huff->initialized) {
         return SerializationStatus::ERROR;
       }
       int n_blocks_y = is_interleaved ? c.v_samp_factor : 1;
       int n_blocks_x = is_interleaved ? c.h_samp_factor : 1;
       for (int iy = 0; iy < n_blocks_y; ++iy) {
         for (int ix = 0; ix < n_blocks_x; ++ix) {
           int block_y = ss.mcu_y * n_blocks_y + iy;
           int block_x = mcu_x * n_blocks_x + ix;
           int block_idx = block_y * c.width_in_blocks + block_x;
           if (ss.block_scan_index == ss.next_reset_point) {
             Flush(coding_state, bw);
             ss.next_reset_point = get_next_reset_point();
           }
           int num_zero_runs = 0;
           if (ss.block_scan_index == ss.next_extra_zero_run_index) {
             num_zero_runs = scan_info.extra_zero_runs[ss.extra_zero_runs_pos]
                                 .num_extra_zero_runs;
             ++ss.extra_zero_runs_pos;
             ss.next_extra_zero_run_index = get_next_extra_zero_run_index();
           }
           const coeff_t* coeffs = &c.coeffs[block_idx << 6];
           bool ok;
           // compressed size per block cannot be more than 512 bytes
           Reserve(bw, 512);
           if (kMode == 0) {
             ok = EncodeDCTBlockSequential(coeffs, dc_huff, ac_huff,
                                           num_zero_runs,
                                           ss.last_dc_coeff + si.comp_idx, bw);
           } else if (kMode == 1) {
             ok = EncodeDCTBlockProgressive(
                 coeffs, dc_huff, ac_huff, Ss, Se, Al, num_zero_runs,
                 coding_state, ss.last_dc_coeff + si.comp_idx, bw);
           } else {
             ok = EncodeRefinementBits(coeffs, ac_huff, Ss, Se, Al,
                                       coding_state, bw);
           }
           if (!ok) return SerializationStatus::ERROR;
           ++ss.block_scan_index;
         }
       }
     }
     --ss.restarts_to_go;
   }
 }
 if (ss.mcu_y < MCU_rows) {
   if (!bw->healthy) return SerializationStatus::ERROR;
   return SerializationStatus::NEEDS_MORE_INPUT;
 }
 Flush(coding_state, bw);
 if (!JumpToByteBoundary(bw, &state->pad_bits, state->pad_bits_end)) {
   return SerializationStatus::ERROR;
 }
 JpegBitWriterFinish(bw);
 ss.stage = EncodeScanState::HEAD;
 state->scan_index++;
 if (!bw->healthy) return SerializationStatus::ERROR;

 return SerializationStatus::DONE;
}

SerializationStatus JXL_INLINE EncodeScan(const JPEGData& jpg,
                                         SerializationState* state) {
 const JPEGScanInfo& scan_info = jpg.scan_info[state->scan_index];
 const bool is_progressive = state->is_progressive;
 const int Al = is_progressive ? scan_info.Al : 0;
 const int Ah = is_progressive ? scan_info.Ah : 0;
 const int Ss = is_progressive ? scan_info.Ss : 0;
 const int Se = is_progressive ? scan_info.Se : 63;
 const bool need_sequential =
     !is_progressive || (Ah == 0 && Al == 0 && Ss == 0 && Se == 63);
 if (need_sequential) {
   return DoEncodeScan<0>(jpg, state);
 } else if (Ah == 0) {
   return DoEncodeScan<1>(jpg, state);
 } else {
   return DoEncodeScan<2>(jpg, state);
 }
}

SerializationStatus SerializeSection(uint8_t marker, SerializationState* state,
                                    const JPEGData& jpg) {
 const auto to_status = [](bool result) {
   return result ? SerializationStatus::DONE : SerializationStatus::ERROR;
 };
 // TODO(eustas): add and use marker enum
 switch (marker) {
   case 0xC0:
   case 0xC1:
   case 0xC2:
   case 0xC9:
   case 0xCA:
     return to_status(EncodeSOF(jpg, marker, state));

   case 0xC4:
     return to_status(EncodeDHT(jpg, state));

   case 0xD0:
   case 0xD1:
   case 0xD2:
   case 0xD3:
   case 0xD4:
   case 0xD5:
   case 0xD6:
   case 0xD7:
     return to_status(EncodeRestart(marker, state));

   case 0xD9:
     return to_status(EncodeEOI(jpg, state));

   case 0xDA:
     return EncodeScan(jpg, state);

   case 0xDB:
     return to_status(EncodeDQT(jpg, state));

   case 0xDD:
     return to_status(EncodeDRI(jpg, state));

   case 0xE0:
   case 0xE1:
   case 0xE2:
   case 0xE3:
   case 0xE4:
   case 0xE5:
   case 0xE6:
   case 0xE7:
   case 0xE8:
   case 0xE9:
   case 0xEA:
   case 0xEB:
   case 0xEC:
   case 0xED:
   case 0xEE:
   case 0xEF:
     return to_status(EncodeAPP(jpg, marker, state));

   case 0xFE:
     return to_status(EncodeCOM(jpg, state));

   case 0xFF:
     return to_status(EncodeInterMarkerData(jpg, state));

   default:
     return SerializationStatus::ERROR;
 }
}

// TODO(veluca): add streaming support again.
Status WriteJpegInternal(const JPEGData& jpg, const JPEGOutput& out,
                        SerializationState* ss) {
 const auto maybe_push_output = [&]() -> Status {
   if (ss->stage != SerializationState::STAGE_ERROR) {
     while (!ss->output_queue.empty()) {
       auto& chunk = ss->output_queue.front();
       size_t num_written = out(chunk.next, chunk.len);
       if (num_written == 0 && chunk.len > 0) {
         return StatusMessage(Status(StatusCode::kNotEnoughBytes),
                              "Failed to write output");
       }
       chunk.len -= num_written;
       if (chunk.len == 0) {
         ss->output_queue.pop_front();
       }
     }
   }
   return true;
 };

 while (true) {
   switch (ss->stage) {
     case SerializationState::STAGE_INIT: {
       // Valid Brunsli requires, at least, 0xD9 marker.
       // This might happen on corrupted stream, or on unconditioned JPEGData.
       // TODO(eustas): check D9 in the only one and is the last one.
       if (jpg.marker_order.empty()) {
         ss->stage = SerializationState::STAGE_ERROR;
         break;
       }
       ss->dc_huff_table.resize(kMaxHuffmanTables);
       ss->ac_huff_table.resize(kMaxHuffmanTables);
       if (jpg.has_zero_padding_bit) {
         ss->pad_bits = jpg.padding_bits.data();
         ss->pad_bits_end = ss->pad_bits + jpg.padding_bits.size();
       }

       EncodeSOI(ss);
       JXL_QUIET_RETURN_IF_ERROR(maybe_push_output());
       ss->stage = SerializationState::STAGE_SERIALIZE_SECTION;
       break;
     }

     case SerializationState::STAGE_SERIALIZE_SECTION: {
       if (ss->section_index >= jpg.marker_order.size()) {
         ss->stage = SerializationState::STAGE_DONE;
         break;
       }
       uint8_t marker = jpg.marker_order[ss->section_index];
       SerializationStatus status = SerializeSection(marker, ss, jpg);
       if (status == SerializationStatus::ERROR) {
         JXL_WARNING("Failed to encode marker 0x%.2x", marker);
         ss->stage = SerializationState::STAGE_ERROR;
         break;
       }
       JXL_QUIET_RETURN_IF_ERROR(maybe_push_output());
       if (status == SerializationStatus::NEEDS_MORE_INPUT) {
         return JXL_FAILURE("Incomplete serialization data");
       } else if (status != SerializationStatus::DONE) {
         ss->stage = SerializationState::STAGE_ERROR;
         return JXL_FAILURE("Internal logic error");
         break;
       }
       ++ss->section_index;
       break;
     }

     case SerializationState::STAGE_DONE:
       JXL_ENSURE(ss->output_queue.empty());
       if (ss->pad_bits != nullptr && ss->pad_bits != ss->pad_bits_end) {
         return JXL_FAILURE("Invalid number of padding bits.");
       }
       return true;

     case SerializationState::STAGE_ERROR:
       return JXL_FAILURE("JPEG serialization error");
   }
 }
}

}  // namespace

Status WriteJpeg(const JPEGData& jpg, const JPEGOutput& out) {
 auto ss = jxl::make_unique<SerializationState>();
 return WriteJpegInternal(jpg, out, ss.get());
}

}  // namespace jpeg
}  // namespace jxl