1 // Copyright 2021 gRPC authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef GRPC_SRC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_HPACK_ENCODER_TABLE_H 16 #define GRPC_SRC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_HPACK_ENCODER_TABLE_H 17 18 #include <grpc/support/port_platform.h> 19 #include <stddef.h> 20 #include <stdint.h> 21 22 #include <limits> 23 #include <vector> 24 25 #include "src/core/ext/transport/chttp2/transport/hpack_constants.h" 26 27 namespace grpc_core { 28 29 // Tracks the values available in the remote HPACK header table, and their 30 // sizes. 31 class HPackEncoderTable { 32 public: 33 using EntrySize = uint16_t; 34 HPackEncoderTable()35 HPackEncoderTable() : elem_size_(hpack_constants::kInitialTableEntries) {} 36 MaxEntrySize()37 static constexpr size_t MaxEntrySize() { 38 return std::numeric_limits<EntrySize>::max(); 39 } 40 41 // Reserve space in table for the new element, evict entries if needed. 42 // Return the new index of the element. Return 0 to indicate not adding to 43 // table. 44 uint32_t AllocateIndex(size_t element_size); 45 // Set the maximum table size. Return true if it changed. 46 bool SetMaxSize(uint32_t max_table_size); 47 // Get the current max table size max_size()48 uint32_t max_size() const { return max_table_size_; } 49 // Get the current table size test_only_table_size()50 uint32_t test_only_table_size() const { return table_size_; } 51 // Get the number of entries in the table test_only_table_elems()52 uint32_t test_only_table_elems() const { return table_elems_; } 53 54 // Convert an element index into a dynamic index DynamicIndex(uint32_t index)55 uint32_t DynamicIndex(uint32_t index) const { 56 return 1 + hpack_constants::kLastStaticEntry + tail_remote_index_ + 57 table_elems_ - index; 58 } 59 // Check if an element index is convertible to a dynamic index 60 // Note that 0 is always not convertible ConvertibleToDynamicIndex(uint32_t index)61 bool ConvertibleToDynamicIndex(uint32_t index) const { 62 return index > tail_remote_index_; 63 } 64 65 private: 66 void EvictOne(); 67 void Rebuild(uint32_t capacity); 68 69 // one before the lowest usable table index 70 uint32_t tail_remote_index_ = 0; 71 uint32_t max_table_size_ = hpack_constants::kInitialTableSize; 72 uint32_t table_elems_ = 0; 73 uint32_t table_size_ = 0; 74 // The size of each element in the HPACK table. 75 std::vector<EntrySize> elem_size_; 76 }; 77 78 } // namespace grpc_core 79 80 #endif // GRPC_SRC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_HPACK_ENCODER_TABLE_H 81