includes/opentelemetry/trace/trace_flags.h

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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
 
#pragma once
 
#include <cstdint>
 
#include "opentelemetry/nostd/span.h"
#include "opentelemetry/version.h"
 
OPENTELEMETRY_BEGIN_NAMESPACE
namespace trace
{
 
// TraceFlags represents options for a Trace. These options are propagated to all child Spans
// and determine features such as whether a Span should be traced. TraceFlags
// are implemented as a bitmask.
class TraceFlags final
{
public:
  static constexpr uint8_t kIsSampled = 1;
  static constexpr uint8_t kIsRandom  = 2;
 
  static constexpr uint8_t kAllW3CTraceContext1Flags = kIsSampled;
 
  static constexpr uint8_t kAllW3CTraceContext2Flags = kIsSampled | kIsRandom;
 
  TraceFlags() noexcept : rep_{0} {}
 
  explicit TraceFlags(uint8_t flags) noexcept : rep_(flags) {}
 
  bool IsSampled() const noexcept { return rep_ & kIsSampled; }
 
  bool IsRandom() const noexcept { return rep_ & kIsRandom; }
 
  // Populates the buffer with the lowercase base16 representation of the flags.
  void ToLowerBase16(nostd::span<char, 2> buffer) const noexcept
  {
    constexpr char kHex[] = "0123456789ABCDEF";
    buffer[0]             = kHex[(rep_ >> 4) & 0xF];
    buffer[1]             = kHex[(rep_ >> 0) & 0xF];
  }
 
  uint8_t flags() const noexcept { return rep_; }
 
  bool operator==(const TraceFlags &that) const noexcept { return rep_ == that.rep_; }
 
  bool operator!=(const TraceFlags &that) const noexcept { return !(*this == that); }
 
  // Copies the TraceFlags to dest.
  void CopyBytesTo(nostd::span<uint8_t, 1> dest) const noexcept { dest[0] = rep_; }
 
private:
  uint8_t rep_;
};
 
}  // namespace trace
OPENTELEMETRY_END_NAMESPACE