decoder.h

// Copyright 2025 The Pigweed Authors
//
// 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
//
//     https://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.
 
#pragma once
 
#include <optional>
#include <string>
#include <vector>
 
#include "pw_result/result.h"
#include "pw_stream/stream.h"
#include "pw_tokenizer/detokenize.h"
#include "pw_trace_tokenized/trace_tokenized.h"
 
namespace pw::trace {
 
 
struct DecodedEvent {
  EventType type = EventType::PW_TRACE_EVENT_TYPE_INVALID;
  // TODO: https://pwbug.dev/448489618 - The 'flag' field in the token is
  // ostensibly a decimal integer string, but could actually be any arbitrary C
  // expression that evaluates to an integer. Rather than try to parse it and
  // risk failing, simply return it as a string for now.
  std::string flags_str;
  std::string module;
  std::string group;
  std::string label;
  std::string data_fmt;
  uint64_t timestamp_usec{};
  std::optional<uint64_t> trace_id;
  std::vector<std::byte> data;
};
 
class TokenizedDecoder {
 public:
  TokenizedDecoder(tokenizer::Detokenizer& detokenizer, uint64_t ticks_per_sec)
      : detokenizer_(detokenizer), ticks_per_sec_(ticks_per_sec) {}
 
  void SetTimeOffset(uint64_t time_offset) { last_timestamp_us_ = time_offset; }
 
  Result<DecodedEvent> ReadSizePrefixed(stream::Reader& reader);
 
  Result<DecodedEvent> Decode(ConstByteSpan data);
 
 private:
  tokenizer::Detokenizer& detokenizer_;
  const uint64_t ticks_per_sec_;
  uint64_t last_timestamp_us_ = 0;
 
  uint64_t usec_per_tick() const { return 1'000'000 / ticks_per_sec_; }
};
 
 
}  // namespace pw::trace