diff options
Diffstat (limited to '')
-rw-r--r-- | third_party/jpeg-xl/lib/jxl/dec_context_map.cc | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/dec_context_map.cc b/third_party/jpeg-xl/lib/jxl/dec_context_map.cc new file mode 100644 index 0000000000..1b291650d7 --- /dev/null +++ b/third_party/jpeg-xl/lib/jxl/dec_context_map.cc @@ -0,0 +1,86 @@ +// 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_context_map.h" + +#include <algorithm> +#include <vector> + +#include "lib/jxl/ans_params.h" +#include "lib/jxl/base/status.h" +#include "lib/jxl/dec_ans.h" +#include "lib/jxl/entropy_coder.h" +#include "lib/jxl/inverse_mtf-inl.h" + +namespace jxl { + +namespace { + +Status VerifyContextMap(const std::vector<uint8_t>& context_map, + const size_t num_htrees) { + std::vector<bool> have_htree(num_htrees); + size_t num_found = 0; + for (const uint8_t htree : context_map) { + if (htree >= num_htrees) { + return JXL_FAILURE("Invalid histogram index in context map."); + } + if (!have_htree[htree]) { + have_htree[htree] = true; + ++num_found; + } + } + if (num_found != num_htrees) { + return JXL_FAILURE("Incomplete context map."); + } + return true; +} + +} // namespace + +Status DecodeContextMap(std::vector<uint8_t>* context_map, size_t* num_htrees, + BitReader* input) { + bool is_simple = input->ReadFixedBits<1>(); + if (is_simple) { + int bits_per_entry = input->ReadFixedBits<2>(); + if (bits_per_entry != 0) { + for (size_t i = 0; i < context_map->size(); i++) { + (*context_map)[i] = input->ReadBits(bits_per_entry); + } + } else { + std::fill(context_map->begin(), context_map->end(), 0); + } + } else { + bool use_mtf = input->ReadFixedBits<1>(); + ANSCode code; + std::vector<uint8_t> dummy_ctx_map; + // Usage of LZ77 is disallowed if decoding only two symbols. This doesn't + // make sense in non-malicious bitstreams, and could cause a stack overflow + // in malicious bitstreams by making every context map require its own + // context map. + JXL_RETURN_IF_ERROR( + DecodeHistograms(input, 1, &code, &dummy_ctx_map, + /*disallow_lz77=*/context_map->size() <= 2)); + ANSSymbolReader reader(&code, input); + size_t i = 0; + while (i < context_map->size()) { + uint32_t sym = reader.ReadHybridUint(0, input, dummy_ctx_map); + if (sym >= kMaxClusters) { + return JXL_FAILURE("Invalid cluster ID"); + } + (*context_map)[i] = sym; + i++; + } + if (!reader.CheckANSFinalState()) { + return JXL_FAILURE("Invalid context map"); + } + if (use_mtf) { + InverseMoveToFrontTransform(context_map->data(), context_map->size()); + } + } + *num_htrees = *std::max_element(context_map->begin(), context_map->end()) + 1; + return VerifyContextMap(*context_map, *num_htrees); +} + +} // namespace jxl |