trace_context.h

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/*
 * Copyright 2026 The A11 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
 *
 *     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 A11_OBS_TRACE_CONTEXT_H_
#define A11_OBS_TRACE_CONTEXT_H_
 
#include <cstdint>
#include <optional>
#include <string>
#include <string_view>
#include <vector>
 
#include <absl/status/status.h>
#include <absl/status/statusor.h>
 
#include "a11/data/types.h"
 
namespace a11::obs {
 
inline constexpr std::string_view kTraceparentHeader = "x-otel-traceparent";
inline constexpr std::string_view kTracestateHeader = "x-otel-tracestate";
inline constexpr std::string_view kBaggageHeader = "x-otel-baggage";
 
struct BaggageEntry {
  std::string key;    
  std::string value;  
  std::string properties;  
 
  friend bool operator==(const BaggageEntry&, const BaggageEntry&) = default;
};
 
struct TraceContext {
  std::string trace_id;               
  std::string span_id;                
  std::uint8_t trace_flags = 0;       
  std::string tracestate;             
  std::vector<BaggageEntry> baggage;  
 
  [[nodiscard]] bool sampled() const { return (trace_flags & 0x01U) != 0; }
 
  friend bool operator==(const TraceContext&, const TraceContext&) = default;
};
 
absl::StatusOr<std::optional<TraceContext>> ExtractTraceContext(
    const data::ByteMap& headers);
 
absl::Status InjectTraceContext(const TraceContext& context,
                                data::ByteMap& headers);
 
}  // namespace a11::obs
 
#endif  // A11_OBS_TRACE_CONTEXT_H_