toc.cc (3777B)
1 // Copyright (c) the JPEG XL Project Authors. All rights reserved. 2 // 3 // Use of this source code is governed by a BSD-style 4 // license that can be found in the LICENSE file. 5 6 #include "lib/jxl/toc.h" 7 8 #include <stdint.h> 9 10 #include "lib/jxl/base/common.h" 11 #include "lib/jxl/coeff_order.h" 12 #include "lib/jxl/coeff_order_fwd.h" 13 #include "lib/jxl/fields.h" 14 15 namespace jxl { 16 size_t MaxBits(const size_t num_sizes) { 17 const size_t entry_bits = U32Coder::MaxEncodedBits(kTocDist) * num_sizes; 18 // permutation bit (not its tokens!), padding, entries, padding. 19 return 1 + kBitsPerByte + entry_bits + kBitsPerByte; 20 } 21 22 Status ReadToc(size_t toc_entries, BitReader* JXL_RESTRICT reader, 23 std::vector<uint32_t>* JXL_RESTRICT sizes, 24 std::vector<coeff_order_t>* JXL_RESTRICT permutation) { 25 if (toc_entries > 65536) { 26 // Prevent out of memory if invalid JXL codestream causes a bogus amount 27 // of toc_entries such as 2720436919446 to be computed. 28 // TODO(lode): verify whether 65536 is a reasonable upper bound 29 return JXL_FAILURE("too many toc entries"); 30 } 31 32 sizes->clear(); 33 sizes->resize(toc_entries); 34 if (reader->TotalBitsConsumed() >= reader->TotalBytes() * kBitsPerByte) { 35 return JXL_STATUS(StatusCode::kNotEnoughBytes, "Not enough bytes for TOC"); 36 } 37 const auto check_bit_budget = [&](size_t num_entries) -> Status { 38 // U32Coder reads 2 bits to recognize variant and kTocDist cheapest variant 39 // is Bits(10), this way at least 12 bits are required per toc-entry. 40 size_t minimal_bit_cost = num_entries * (2 + 10); 41 size_t bit_budget = reader->TotalBytes() * 8; 42 size_t expenses = reader->TotalBitsConsumed(); 43 if ((expenses <= bit_budget) && 44 (minimal_bit_cost <= bit_budget - expenses)) { 45 return true; 46 } 47 return JXL_STATUS(StatusCode::kNotEnoughBytes, "Not enough bytes for TOC"); 48 }; 49 50 JXL_DASSERT(toc_entries > 0); 51 if (reader->ReadFixedBits<1>() == 1) { 52 JXL_RETURN_IF_ERROR(check_bit_budget(toc_entries)); 53 permutation->resize(toc_entries); 54 JXL_RETURN_IF_ERROR(DecodePermutation(/*skip=*/0, toc_entries, 55 permutation->data(), reader)); 56 } 57 JXL_RETURN_IF_ERROR(reader->JumpToByteBoundary()); 58 JXL_RETURN_IF_ERROR(check_bit_budget(toc_entries)); 59 for (size_t i = 0; i < toc_entries; ++i) { 60 (*sizes)[i] = U32Coder::Read(kTocDist, reader); 61 } 62 JXL_RETURN_IF_ERROR(reader->JumpToByteBoundary()); 63 JXL_RETURN_IF_ERROR(check_bit_budget(0)); 64 return true; 65 } 66 67 Status ReadGroupOffsets(size_t toc_entries, BitReader* JXL_RESTRICT reader, 68 std::vector<uint64_t>* JXL_RESTRICT offsets, 69 std::vector<uint32_t>* JXL_RESTRICT sizes, 70 uint64_t* total_size) { 71 std::vector<coeff_order_t> permutation; 72 JXL_RETURN_IF_ERROR(ReadToc(toc_entries, reader, sizes, &permutation)); 73 74 offsets->clear(); 75 offsets->resize(toc_entries); 76 77 // Prefix sum starting with 0 and ending with the offset of the last group 78 uint64_t offset = 0; 79 for (size_t i = 0; i < toc_entries; ++i) { 80 if (offset + (*sizes)[i] < offset) { 81 return JXL_FAILURE("group offset overflow"); 82 } 83 (*offsets)[i] = offset; 84 offset += (*sizes)[i]; 85 } 86 if (total_size) { 87 *total_size = offset; 88 } 89 90 if (!permutation.empty()) { 91 std::vector<uint64_t> permuted_offsets; 92 std::vector<uint32_t> permuted_sizes; 93 permuted_offsets.reserve(toc_entries); 94 permuted_sizes.reserve(toc_entries); 95 for (coeff_order_t index : permutation) { 96 permuted_offsets.push_back((*offsets)[index]); 97 permuted_sizes.push_back((*sizes)[index]); 98 } 99 std::swap(*offsets, permuted_offsets); 100 std::swap(*sizes, permuted_sizes); 101 } 102 103 return true; 104 } 105 } // namespace jxl