chromium/third_party/perfetto/src/protozero/filtering/message_tokenizer.h

/*
 * 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_MESSAGE_TOKENIZER_H_
#define SRC_PROTOZERO_FILTERING_MESSAGE_TOKENIZER_H_

#include <stdint.h>

#include "perfetto/base/compiler.h"
#include "perfetto/base/logging.h"
#include "perfetto/protozero/proto_utils.h"

namespace protozero {

// A helper class for schema-less tokenizing of protobuf messages.
// This class takes a stream of proto-encoded bytes, pushed one by one in input
// via Push(octet), and returns a stream of tokens (each Push() call can return
// 0 or 1 token).
// A "token" contains metadata about a field, specifically: its ID, its wire
// type and:
//  - For varint and fixed32/64 fields: its payload.
//  - For string and bytes fields: the length of its payload.
//    In this case the caller is supposed to "eat" those N bytes before calling
//    Push() again.
// Note that this class cannot differentiate between a string/bytes field or
// a submessage, because they are encoded in the same way. The caller is
// supposed to know whether a field can be recursed into by just keep calling
// Push() or is a string that should be skipped.
// This is inline to allow the compiler to see through the Push method and
// avoid a function call for each byte.
class MessageTokenizer { … };

}  // namespace protozero

#endif  // SRC_PROTOZERO_FILTERING_MESSAGE_TOKENIZER_H_