chromium/third_party/perfetto/src/trace_processor/importers/json/json_trace_tokenizer.h

/*
 * Copyright (C) 2019 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_TRACE_PROCESSOR_IMPORTERS_JSON_JSON_TRACE_TOKENIZER_H_
#define SRC_TRACE_PROCESSOR_IMPORTERS_JSON_JSON_TRACE_TOKENIZER_H_

#include <cstdint>
#include <optional>
#include <string>
#include <vector>

#include "perfetto/base/status.h"
#include "perfetto/ext/base/string_view.h"
#include "src/trace_processor/importers/common/chunked_trace_reader.h"
#include "src/trace_processor/importers/systrace/systrace_line_tokenizer.h"

namespace Json {
class Value;
}

namespace perfetto::trace_processor {

class TraceProcessorContext;

// Visible for testing.
enum class ReadDictRes { … };

// Parses at most one JSON dictionary and returns a pointer to the end of it,
// or nullptr if no dict could be detected.
// This is to avoid decoding the full trace in memory and reduce heap traffic.
// E.g.  input:  { a:1 b:{ c:2, d:{ e:3 } } } , { a:4, ... },
//       output: [   only this is parsed    ] ^return value points here.
// Visible for testing.
ReadDictRes ReadOneJsonDict(const char* start,
                            const char* end,
                            base::StringView* value,
                            const char** next);

enum class ReadKeyRes { … };

// Parses at most one JSON key and returns a pointer to the start of the value
// associated with that key.
// This is to avoid decoding the full trace in memory and reduce heap traffic.
// E.g. input:  a:1 b:{ c:2}}
//     output:    ^ return value points here, key is set to "a".
// Note: even if the whole key may be available, this method will return
// kNeedsMoreData until the first character of the value is available.
// Visible for testing.
ReadKeyRes ReadOneJsonKey(const char* start,
                          const char* end,
                          std::string* key,
                          const char** next);

// Takes as input a JSON dictionary and returns the value associated with
// the provided key (if it exists).
// Implementation note: this method does not currently support dictionaries
// which have arrays as JSON values because current users of this method
// do not require this.
// Visible for testing.
base::Status ExtractValueForJsonKey(base::StringView dict,
                                    const std::string& key,
                                    std::optional<std::string>* value);

enum class ReadSystemLineRes { … };

ReadSystemLineRes ReadOneSystemTraceLine(const char* start,
                                         const char* end,
                                         std::string* line,
                                         const char** next);

// Reads a JSON trace in chunks and extracts top level json objects.
class JsonTraceTokenizer : public ChunkedTraceReader { … };

}  // namespace perfetto::trace_processor

#endif  // SRC_TRACE_PROCESSOR_IMPORTERS_JSON_JSON_TRACE_TOKENIZER_H_