1 /* 2 * Copyright (C) 2021 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef SRC_PROTOZERO_FILTERING_FILTER_BYTECODE_GENERATOR_H_ 18 #define SRC_PROTOZERO_FILTERING_FILTER_BYTECODE_GENERATOR_H_ 19 20 #include <stddef.h> 21 #include <stdint.h> 22 23 #include <string> 24 #include <vector> 25 26 namespace protozero { 27 28 // Creates a filter bytecode that can be passed to the FilterBytecodeParser. 29 // This class is typically only used by offline tools (e.g. the proto_filter 30 // cmdline tool). See go/trace-filtering for the full filtering design. 31 class FilterBytecodeGenerator { 32 public: 33 FilterBytecodeGenerator(); 34 ~FilterBytecodeGenerator(); 35 36 // Call at the end of every message. It implicitly starts a new message, there 37 // is no corresponding BeginMessage(). 38 void EndMessage(); 39 40 // All the methods below must be called in monotonic field_id order or the 41 // generator will CHECK() and crash. 42 43 // Allows a simple field (varint, fixed32/64, string or bytes). 44 void AddSimpleField(uint32_t field_id); 45 46 // Allows a range of simple fields. |range_start| is the id of the first field 47 // in range, |range_len| the number of fields in the range. 48 // AddSimpleFieldRange(N,1) is semantically equivalent to AddSimpleField(N) 49 // (but it takes 2 words to encode, rather than just one). 50 void AddSimpleFieldRange(uint32_t range_start, uint32_t range_len); 51 52 // Adds a nested field. |message_index| is the index of the message that the 53 // parser must recurse into. This implies that at least |message_index| calls 54 // to Begin/EndMessage will be made. 55 // The Serialize() method will fail if any field points to an index that is 56 // out of range (e.g., if message_index = 5 but only 3 EndMessage() calls were 57 // made). 58 void AddNestedField(uint32_t field_id, uint32_t message_index); 59 60 // Returns the filter bytecode, which is a buffer containing a sequence of 61 // varints and a checksum. The returned string can be passed to 62 // FilterBytecodeParser.Load(). 63 std::string Serialize(); 64 65 private: 66 uint32_t num_messages_ = 0; 67 uint32_t last_field_id_ = 0; 68 uint32_t max_msg_index_ = 0; 69 bool endmessage_called_ = false; 70 71 std::vector<uint32_t> bytecode_; 72 }; 73 74 } // namespace protozero 75 76 #endif // SRC_PROTOZERO_FILTERING_FILTER_BYTECODE_GENERATOR_H_ 77