Program Listing for File composite_propagator.h

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#include <initializer_list>
#include <memory>
#include <vector>
#include "opentelemetry/trace/propagation/text_map_propagator.h"

OPENTELEMETRY_BEGIN_NAMESPACE
namespace trace
{
namespace propagation
{

template <typename T>
class CompositePropagator : public TextMapPropagator<T>
{
public:
  CompositePropagator(std::vector<std::unique_ptr<TextMapPropagator<T>>> propagators)
      : propagators_(std::move(propagators))
  {}
  // Rules that manages how context will be extracted from carrier.
  using Getter = nostd::string_view (*)(const T &carrier, nostd::string_view trace_type);

  // Rules that manages how context will be injected to carrier.
  using Setter = void (*)(T &carrier,
                          nostd::string_view trace_type,
                          nostd::string_view trace_description);

  void Inject(Setter setter, T &carrier, const context::Context &context) noexcept override
  {
    for (auto &p : propagators_)
    {
      p->Inject(setter, carrier, context);
    }
  }

  context::Context Extract(Getter getter,
                           const T &carrier,
                           context::Context &context) noexcept override
  {
    auto first = true;
    context::Context tmp_context;
    for (auto &p : propagators_)
    {
      if (first)
      {
        tmp_context = p->Extract(getter, carrier, context);
        first       = false;
      }
      else
      {
        tmp_context = p->Extract(getter, carrier, tmp_context);
      }
    }
    return propagators_.size() ? tmp_context : context;
  }

private:
  std::vector<std::unique_ptr<TextMapPropagator<T>>> propagators_;
};
}  // namespace propagation
}  // namespace trace
OPENTELEMETRY_END_NAMESPACE;