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// 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/dec_ans.h"
#include <jxl/memory_manager.h>
#include <cstdint>
#include <vector>
#include "lib/jxl/ans_common.h"
#include "lib/jxl/ans_params.h"
#include "lib/jxl/base/bits.h"
#include "lib/jxl/base/printf_macros.h"
#include "lib/jxl/base/status.h"
#include "lib/jxl/dec_context_map.h"
#include "lib/jxl/fields.h"
#include "lib/jxl/memory_manager_internal.h"
namespace jxl {
namespace {
// Decodes a number in the range [0..255], by reading 1 - 11 bits.
inline int DecodeVarLenUint8(BitReader* input) {
if (input->ReadFixedBits<1>()) {
int nbits = static_cast<int>(input->ReadFixedBits<3>());
if (nbits == 0) {
return 1;
} else {
return static_cast<int>(input->ReadBits(nbits)) + (1 << nbits);
}
}
return 0;
}
// Decodes a number in the range [0..65535], by reading 1 - 21 bits.
inline int DecodeVarLenUint16(BitReader* input) {
if (input->ReadFixedBits<1>()) {
int nbits = static_cast<int>(input->ReadFixedBits<4>());
if (nbits == 0) {
return 1;
} else {
return static_cast<int>(input->ReadBits(nbits)) + (1 << nbits);
}
}
return 0;
}
Status ReadHistogram(int precision_bits, std::vector<int32_t>* counts,
BitReader* input) {
int range = 1 << precision_bits;
int simple_code = input->ReadBits(1);
if (simple_code == 1) {
int i;
int symbols[2] = {0};
int max_symbol = 0;
const int num_symbols = input->ReadBits(1) + 1;
for (i = 0; i < num_symbols; ++i) {
symbols[i] = DecodeVarLenUint8(input);
if (symbols[i] > max_symbol) max_symbol = symbols[i];
}
counts->resize(max_symbol + 1);
if (num_symbols == 1) {
(*counts)[symbols[0]] = range;
} else {
if (symbols[0] == symbols[1]) { // corrupt data
return false;
}
(*counts)[symbols[0]] = input->ReadBits(precision_bits);
(*counts)[symbols[1]] = range - (*counts)[symbols[0]];
}
} else {
int is_flat = input->ReadBits(1);
if (is_flat == 1) {
int alphabet_size = DecodeVarLenUint8(input) + 1;
JXL_ENSURE(alphabet_size <= range);
*counts = CreateFlatHistogram(alphabet_size, range);
return true;
}
uint32_t shift;
{
// TODO(veluca): speed up reading with table lookups.
int upper_bound_log = FloorLog2Nonzero(ANS_LOG_TAB_SIZE + 1);
int log = 0;
for (; log < upper_bound_log; log++) {
if (input->ReadFixedBits<1>() == 0) break;
}
shift = (input->ReadBits(log) | (1 << log)) - 1;
if (shift > ANS_LOG_TAB_SIZE + 1) {
return JXL_FAILURE("Invalid shift value");
}
}
int length = DecodeVarLenUint8(input) + 3;
counts->resize(length);
int total_count = 0;
static const uint8_t huff[128][2] = {
{3, 10}, {7, 12}, {3, 7}, {4, 3}, {3, 6}, {3, 8}, {3, 9}, {4, 5},
{3, 10}, {4, 4}, {3, 7}, {4, 1}, {3, 6}, {3, 8}, {3, 9}, {4, 2},
{3, 10}, {5, 0}, {3, 7}, {4, 3}, {3, 6}, {3, 8}, {3, 9}, {4, 5},
{3, 10}, {4, 4}, {3, 7}, {4, 1}, {3, 6}, {3, 8}, {3, 9}, {4, 2},
{3, 10}, {6, 11}, {3, 7}, {4, 3}, {3, 6}, {3, 8}, {3, 9}, {4, 5},
{3, 10}, {4, 4}, {3, 7}, {4, 1}, {3, 6}, {3, 8}, {3, 9}, {4, 2},
{3, 10}, {5, 0}, {3, 7}, {4, 3}, {3, 6}, {3, 8}, {3, 9}, {4, 5},
{3, 10}, {4, 4}, {3, 7}, {4, 1}, {3, 6}, {3, 8}, {3, 9}, {4, 2},
{3, 10}, {7, 13}, {3, 7}, {4, 3}, {3, 6}, {3, 8}, {3, 9}, {4, 5},
{3, 10}, {4, 4}, {3, 7}, {4, 1}, {3, 6}, {3, 8}, {3, 9}, {4, 2},
{3, 10}, {5, 0}, {3, 7}, {4, 3}, {3, 6}, {3, 8}, {3, 9}, {4, 5},
{3, 10}, {4, 4}, {3, 7}, {4, 1}, {3, 6}, {3, 8}, {3, 9}, {4, 2},
{3, 10}, {6, 11}, {3, 7}, {4, 3}, {3, 6}, {3, 8}, {3, 9}, {4, 5},
{3, 10}, {4, 4}, {3, 7}, {4, 1}, {3, 6}, {3, 8}, {3, 9}, {4, 2},
{3, 10}, {5, 0}, {3, 7}, {4, 3}, {3, 6}, {3, 8}, {3, 9}, {4, 5},
{3, 10}, {4, 4}, {3, 7}, {4, 1}, {3, 6}, {3, 8}, {3, 9}, {4, 2},
};
std::vector<int> logcounts(counts->size());
int omit_log = -1;
int omit_pos = -1;
// This array remembers which symbols have an RLE length.
std::vector<int> same(counts->size(), 0);
for (size_t i = 0; i < logcounts.size(); ++i) {
input->Refill(); // for PeekFixedBits + Advance
int idx = input->PeekFixedBits<7>();
input->Consume(huff[idx][0]);
logcounts[i] = huff[idx][1];
// The RLE symbol.
if (logcounts[i] == ANS_LOG_TAB_SIZE + 1) {
int rle_length = DecodeVarLenUint8(input);
same[i] = rle_length + 5;
i += rle_length + 3;
continue;
}
if (logcounts[i] > omit_log) {
omit_log = logcounts[i];
omit_pos = i;
}
}
// Invalid input, e.g. due to invalid usage of RLE.
if (omit_pos < 0) return JXL_FAILURE("Invalid histogram.");
if (static_cast<size_t>(omit_pos) + 1 < logcounts.size() &&
logcounts[omit_pos + 1] == ANS_TAB_SIZE + 1) {
return JXL_FAILURE("Invalid histogram.");
}
int prev = 0;
int numsame = 0;
for (size_t i = 0; i < logcounts.size(); ++i) {
if (same[i]) {
// RLE sequence, let this loop output the same count for the next
// iterations.
numsame = same[i] - 1;
prev = i > 0 ? (*counts)[i - 1] : 0;
}
if (numsame > 0) {
(*counts)[i] = prev;
numsame--;
} else {
unsigned int code = logcounts[i];
// omit_pos may not be negative at this point (checked before).
if (i == static_cast<size_t>(omit_pos)) {
continue;
} else if (code == 0) {
continue;
} else if (code == 1) {
(*counts)[i] = 1;
} else {
int bitcount = GetPopulationCountPrecision(code - 1, shift);
(*counts)[i] = (1u << (code - 1)) +
(input->ReadBits(bitcount) << (code - 1 - bitcount));
}
}
total_count += (*counts)[i];
}
(*counts)[omit_pos] = range - total_count;
if ((*counts)[omit_pos] <= 0) {
// The histogram we've read sums to more than total_count (including at
// least 1 for the omitted value).
return JXL_FAILURE("Invalid histogram count.");
}
}
return true;
}
} // namespace
Status DecodeANSCodes(JxlMemoryManager* memory_manager,
const size_t num_histograms,
const size_t max_alphabet_size, BitReader* in,
ANSCode* result) {
result->memory_manager = memory_manager;
result->degenerate_symbols.resize(num_histograms, -1);
if (result->use_prefix_code) {
JXL_ENSURE(max_alphabet_size <= 1 << PREFIX_MAX_BITS);
result->huffman_data.resize(num_histograms);
std::vector<uint16_t> alphabet_sizes(num_histograms);
for (size_t c = 0; c < num_histograms; c++) {
alphabet_sizes[c] = DecodeVarLenUint16(in) + 1;
if (alphabet_sizes[c] > max_alphabet_size) {
return JXL_FAILURE("Alphabet size is too long: %u", alphabet_sizes[c]);
}
}
for (size_t c = 0; c < num_histograms; c++) {
if (alphabet_sizes[c] > 1) {
if (!result->huffman_data[c].ReadFromBitStream(alphabet_sizes[c], in)) {
if (!in->AllReadsWithinBounds()) {
return JXL_STATUS(StatusCode::kNotEnoughBytes,
"Not enough bytes for huffman code");
}
return JXL_FAILURE("Invalid huffman tree number %" PRIuS
", alphabet size %u",
c, alphabet_sizes[c]);
}
} else {
// 0-bit codes does not require extension tables.
result->huffman_data[c].table_.clear();
result->huffman_data[c].table_.resize(1u << kHuffmanTableBits);
}
for (const auto& h : result->huffman_data[c].table_) {
if (h.bits <= kHuffmanTableBits) {
result->UpdateMaxNumBits(c, h.value);
}
}
}
} else {
JXL_ENSURE(max_alphabet_size <= ANS_MAX_ALPHABET_SIZE);
size_t alloc_size = num_histograms * (1 << result->log_alpha_size) *
sizeof(AliasTable::Entry);
JXL_ASSIGN_OR_RETURN(result->alias_tables,
AlignedMemory::Create(memory_manager, alloc_size));
AliasTable::Entry* alias_tables =
result->alias_tables.address<AliasTable::Entry>();
for (size_t c = 0; c < num_histograms; ++c) {
std::vector<int32_t> counts;
if (!ReadHistogram(ANS_LOG_TAB_SIZE, &counts, in)) {
return JXL_FAILURE("Invalid histogram bitstream.");
}
if (counts.size() > max_alphabet_size) {
return JXL_FAILURE("Alphabet size is too long: %" PRIuS, counts.size());
}
while (!counts.empty() && counts.back() == 0) {
counts.pop_back();
}
for (size_t s = 0; s < counts.size(); s++) {
if (counts[s] != 0) {
result->UpdateMaxNumBits(c, s);
}
}
// InitAliasTable "fixes" empty counts to contain degenerate "0" symbol.
int degenerate_symbol = counts.empty() ? 0 : (counts.size() - 1);
for (int s = 0; s < degenerate_symbol; ++s) {
if (counts[s] != 0) {
degenerate_symbol = -1;
break;
}
}
result->degenerate_symbols[c] = degenerate_symbol;
JXL_RETURN_IF_ERROR(
InitAliasTable(counts, ANS_LOG_TAB_SIZE, result->log_alpha_size,
alias_tables + c * (1 << result->log_alpha_size)));
}
}
return true;
}
Status DecodeUintConfig(size_t log_alpha_size, HybridUintConfig* uint_config,
BitReader* br) {
br->Refill();
size_t split_exponent = br->ReadBits(CeilLog2Nonzero(log_alpha_size + 1));
size_t msb_in_token = 0;
size_t lsb_in_token = 0;
if (split_exponent != log_alpha_size) {
// otherwise, msb/lsb don't matter.
size_t nbits = CeilLog2Nonzero(split_exponent + 1);
msb_in_token = br->ReadBits(nbits);
if (msb_in_token > split_exponent) {
// This could be invalid here already and we need to check this before
// we use its value to read more bits.
return JXL_FAILURE("Invalid HybridUintConfig");
}
nbits = CeilLog2Nonzero(split_exponent - msb_in_token + 1);
lsb_in_token = br->ReadBits(nbits);
}
if (lsb_in_token + msb_in_token > split_exponent) {
return JXL_FAILURE("Invalid HybridUintConfig");
}
*uint_config = HybridUintConfig(split_exponent, msb_in_token, lsb_in_token);
return true;
}
Status DecodeUintConfigs(size_t log_alpha_size,
std::vector<HybridUintConfig>* uint_config,
BitReader* br) {
// TODO(veluca): RLE?
for (auto& cfg : *uint_config) {
JXL_RETURN_IF_ERROR(DecodeUintConfig(log_alpha_size, &cfg, br));
}
return true;
}
LZ77Params::LZ77Params() { Bundle::Init(this); }
Status LZ77Params::VisitFields(Visitor* JXL_RESTRICT visitor) {
JXL_QUIET_RETURN_IF_ERROR(visitor->Bool(false, &enabled));
if (!visitor->Conditional(enabled)) return true;
JXL_QUIET_RETURN_IF_ERROR(visitor->U32(Val(224), Val(512), Val(4096),
BitsOffset(15, 8), 224, &min_symbol));
JXL_QUIET_RETURN_IF_ERROR(visitor->U32(Val(3), Val(4), BitsOffset(2, 5),
BitsOffset(8, 9), 3, &min_length));
return true;
}
void ANSCode::UpdateMaxNumBits(size_t ctx, size_t symbol) {
HybridUintConfig* cfg = &uint_config[ctx];
// LZ77 symbols use a different uint config.
if (lz77.enabled && lz77.nonserialized_distance_context != ctx &&
symbol >= lz77.min_symbol) {
symbol -= lz77.min_symbol;
cfg = &lz77.length_uint_config;
}
size_t split_token = cfg->split_token;
size_t msb_in_token = cfg->msb_in_token;
size_t lsb_in_token = cfg->lsb_in_token;
size_t split_exponent = cfg->split_exponent;
if (symbol < split_token) {
max_num_bits = std::max(max_num_bits, split_exponent);
return;
}
uint32_t n_extra_bits =
split_exponent - (msb_in_token + lsb_in_token) +
((symbol - split_token) >> (msb_in_token + lsb_in_token));
size_t total_bits = msb_in_token + lsb_in_token + n_extra_bits + 1;
max_num_bits = std::max(max_num_bits, total_bits);
}
Status DecodeHistograms(JxlMemoryManager* memory_manager, BitReader* br,
size_t num_contexts, ANSCode* code,
std::vector<uint8_t>* context_map, bool disallow_lz77) {
JXL_RETURN_IF_ERROR(Bundle::Read(br, &code->lz77));
if (code->lz77.enabled) {
num_contexts++;
JXL_RETURN_IF_ERROR(DecodeUintConfig(/*log_alpha_size=*/8,
&code->lz77.length_uint_config, br));
}
if (code->lz77.enabled && disallow_lz77) {
return JXL_FAILURE("Using LZ77 when explicitly disallowed");
}
size_t num_histograms = 1;
context_map->resize(num_contexts);
if (num_contexts > 1) {
JXL_RETURN_IF_ERROR(
DecodeContextMap(memory_manager, context_map, &num_histograms, br));
}
JXL_DEBUG_V(
4, "Decoded context map of size %" PRIuS " and %" PRIuS " histograms",
num_contexts, num_histograms);
code->lz77.nonserialized_distance_context = context_map->back();
code->use_prefix_code = static_cast<bool>(br->ReadFixedBits<1>());
if (code->use_prefix_code) {
code->log_alpha_size = PREFIX_MAX_BITS;
} else {
code->log_alpha_size = br->ReadFixedBits<2>() + 5;
}
code->uint_config.resize(num_histograms);
JXL_RETURN_IF_ERROR(
DecodeUintConfigs(code->log_alpha_size, &code->uint_config, br));
const size_t max_alphabet_size = 1 << code->log_alpha_size;
JXL_RETURN_IF_ERROR(DecodeANSCodes(memory_manager, num_histograms,
max_alphabet_size, br, code));
return true;
}
StatusOr<ANSSymbolReader> ANSSymbolReader::Create(const ANSCode* code,
BitReader* JXL_RESTRICT br,
size_t distance_multiplier) {
AlignedMemory lz77_window_storage;
if (code->lz77.enabled) {
JxlMemoryManager* memory_manager = code->memory_manager;
JXL_ASSIGN_OR_RETURN(
lz77_window_storage,
AlignedMemory::Create(memory_manager, kWindowSize * sizeof(uint32_t)));
}
return ANSSymbolReader(code, br, distance_multiplier,
std::move(lz77_window_storage));
}
ANSSymbolReader::ANSSymbolReader(const ANSCode* code,
BitReader* JXL_RESTRICT br,
size_t distance_multiplier,
AlignedMemory&& lz77_window_storage)
: alias_tables_(code->alias_tables.address<AliasTable::Entry>()),
huffman_data_(code->huffman_data.data()),
use_prefix_code_(code->use_prefix_code),
configs(code->uint_config.data()),
lz77_window_storage_(std::move(lz77_window_storage)) {
if (!use_prefix_code_) {
state_ = static_cast<uint32_t>(br->ReadFixedBits<32>());
log_alpha_size_ = code->log_alpha_size;
log_entry_size_ = ANS_LOG_TAB_SIZE - code->log_alpha_size;
entry_size_minus_1_ = (1 << log_entry_size_) - 1;
} else {
state_ = (ANS_SIGNATURE << 16u);
}
if (!code->lz77.enabled) return;
lz77_window_ = lz77_window_storage_.address<uint32_t>();
lz77_ctx_ = code->lz77.nonserialized_distance_context;
lz77_length_uint_ = code->lz77.length_uint_config;
lz77_threshold_ = code->lz77.min_symbol;
lz77_min_length_ = code->lz77.min_length;
num_special_distances_ = distance_multiplier == 0 ? 0 : kNumSpecialDistances;
for (size_t i = 0; i < num_special_distances_; i++) {
special_distances_[i] = SpecialDistance(i, distance_multiplier);
}
}
} // namespace jxl