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/*
* Copyright (C) 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef SRC_PROTOZERO_FILTERING_FILTER_BYTECODE_GENERATOR_H_
#define SRC_PROTOZERO_FILTERING_FILTER_BYTECODE_GENERATOR_H_
#include <stddef.h>
#include <stdint.h>
#include <string>
#include <vector>
namespace protozero {
// Creates a filter bytecode that can be passed to the FilterBytecodeParser.
// This class is typically only used by offline tools (e.g. the proto_filter
// cmdline tool). See go/trace-filtering for the full filtering design.
class FilterBytecodeGenerator {
public:
FilterBytecodeGenerator();
~FilterBytecodeGenerator();
// Call at the end of every message. It implicitly starts a new message, there
// is no corresponding BeginMessage().
void EndMessage();
// All the methods below must be called in monotonic field_id order or the
// generator will CHECK() and crash.
// Allows a simple field (varint, fixed32/64, string or bytes).
void AddSimpleField(uint32_t field_id);
// Allows a range of simple fields. |range_start| is the id of the first field
// in range, |range_len| the number of fields in the range.
// AddSimpleFieldRange(N,1) is semantically equivalent to AddSimpleField(N)
// (but it takes 2 words to encode, rather than just one).
void AddSimpleFieldRange(uint32_t range_start, uint32_t range_len);
// Adds a nested field. |message_index| is the index of the message that the
// parser must recurse into. This implies that at least |message_index| calls
// to Begin/EndMessage will be made.
// The Serialize() method will fail if any field points to an index that is
// out of range (e.g., if message_index = 5 but only 3 EndMessage() calls were
// made).
void AddNestedField(uint32_t field_id, uint32_t message_index);
// Returns the filter bytecode, which is a buffer containing a sequence of
// varints and a checksum. The returned string can be passed to
// FilterBytecodeParser.Load().
std::string Serialize();
private:
uint32_t num_messages_ = 0;
uint32_t last_field_id_ = 0;
uint32_t max_msg_index_ = 0;
bool endmessage_called_ = false;
std::vector<uint32_t> bytecode_;
};
} // namespace protozero
#endif // SRC_PROTOZERO_FILTERING_FILTER_BYTECODE_GENERATOR_H_
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