.. _program_listing_file_include_opentelemetry_trace_propagation_http_trace_context.h:

Program Listing for File http_trace_context.h
=============================================

|exhale_lsh| :ref:`Return to documentation for file <file_include_opentelemetry_trace_propagation_http_trace_context.h>` (``include/opentelemetry/trace/propagation/http_trace_context.h``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   // Copyright 2021, OpenTelemetry 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.
   
   #include "detail/context.h"
   #include "detail/hex.h"
   #include "detail/string.h"
   #include "opentelemetry/trace/default_span.h"
   #include "opentelemetry/trace/propagation/text_map_propagator.h"
   
   OPENTELEMETRY_BEGIN_NAMESPACE
   namespace trace
   {
   namespace propagation
   {
   static const nostd::string_view kTraceParent = "traceparent";
   static const nostd::string_view kTraceState  = "tracestate";
   static const size_t kVersionSize             = 2;
   static const size_t kTraceIdSize             = 32;
   static const size_t kSpanIdSize              = 16;
   static const size_t kTraceFlagsSize          = 2;
   static const size_t kTraceParentSize         = 55;
   
   // The HttpTraceContext provides methods to extract and inject
   // context into headers of HTTP requests with traces.
   // Example:
   //    HttpTraceContext().inject(setter, carrier, context);
   //    HttpTraceContext().extract(getter, carrier, context);
   template <typename T>
   class HttpTraceContext : public TextMapPropagator<T>
   {
   public:
     // 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
     {
       SpanContext span_context = detail::GetCurrentSpan(context);
       if (!span_context.IsValid())
       {
         return;
       }
       InjectImpl(setter, carrier, span_context);
     }
   
     context::Context Extract(Getter getter,
                              const T &carrier,
                              context::Context &context) noexcept override
     {
       SpanContext span_context = ExtractImpl(getter, carrier);
       nostd::shared_ptr<Span> sp{new DefaultSpan(span_context)};
       return context.SetValue(kSpanKey, sp);
     }
   
     static TraceId TraceIdFromHex(nostd::string_view trace_id)
     {
       uint8_t buf[kTraceIdSize / 2];
       detail::HexToBinary(trace_id, buf, sizeof(buf));
       return TraceId(buf);
     }
   
     static SpanId SpanIdFromHex(nostd::string_view span_id)
     {
       uint8_t buf[kSpanIdSize / 2];
       detail::HexToBinary(span_id, buf, sizeof(buf));
       return SpanId(buf);
     }
   
     static TraceFlags TraceFlagsFromHex(nostd::string_view trace_flags)
     {
       uint8_t flags;
       detail::HexToBinary(trace_flags, &flags, sizeof(flags));
       return TraceFlags(flags);
     }
   
   private:
     static constexpr uint8_t kInvalidVersion = 0xFF;
   
     static bool IsValidVersion(nostd::string_view version_hex)
     {
       uint8_t version;
       detail::HexToBinary(version_hex, &version, sizeof(version));
       return version != kInvalidVersion;
     }
   
     static void InjectImpl(Setter setter, T &carrier, const SpanContext &span_context)
     {
       char trace_parent[kTraceParentSize];
       trace_parent[0] = '0';
       trace_parent[1] = '0';
       trace_parent[2] = '-';
       span_context.trace_id().ToLowerBase16({&trace_parent[3], kTraceIdSize});
       trace_parent[kTraceIdSize + 3] = '-';
       span_context.span_id().ToLowerBase16({&trace_parent[kTraceIdSize + 4], kSpanIdSize});
       trace_parent[kTraceIdSize + kSpanIdSize + 4] = '-';
       span_context.trace_flags().ToLowerBase16({&trace_parent[kTraceIdSize + kSpanIdSize + 5], 2});
   
       setter(carrier, kTraceParent, nostd::string_view(trace_parent, sizeof(trace_parent)));
       setter(carrier, kTraceState, span_context.trace_state()->ToHeader());
     }
   
     static SpanContext ExtractContextFromTraceHeaders(nostd::string_view trace_parent,
                                                       nostd::string_view trace_state)
     {
       if (trace_parent.size() != kTraceParentSize)
       {
         return SpanContext::GetInvalid();
       }
   
       std::array<nostd::string_view, 4> fields{};
       if (detail::SplitString(trace_parent, '-', fields.data(), 4) != 4)
       {
         return SpanContext::GetInvalid();
       }
   
       nostd::string_view version_hex     = fields[0];
       nostd::string_view trace_id_hex    = fields[1];
       nostd::string_view span_id_hex     = fields[2];
       nostd::string_view trace_flags_hex = fields[3];
   
       if (version_hex.size() != kVersionSize || trace_id_hex.size() != kTraceIdSize ||
           span_id_hex.size() != kSpanIdSize || trace_flags_hex.size() != kTraceFlagsSize)
       {
         return SpanContext::GetInvalid();
       }
   
       if (!detail::IsValidHex(version_hex) || !detail::IsValidHex(trace_id_hex) ||
           !detail::IsValidHex(span_id_hex) || !detail::IsValidHex(trace_flags_hex))
       {
         return SpanContext::GetInvalid();
       }
   
       if (!IsValidVersion(version_hex))
       {
         return SpanContext::GetInvalid();
       }
   
       TraceId trace_id = TraceIdFromHex(trace_id_hex);
       SpanId span_id   = SpanIdFromHex(span_id_hex);
   
       if (!trace_id.IsValid() || !span_id.IsValid())
       {
         return SpanContext::GetInvalid();
       }
   
       return SpanContext(trace_id, span_id, TraceFlagsFromHex(trace_flags_hex), true,
                          opentelemetry::trace::TraceState::FromHeader(trace_state));
     }
   
     static SpanContext ExtractImpl(Getter getter, const T &carrier)
     {
       nostd::string_view trace_parent = getter(carrier, kTraceParent);
       nostd::string_view trace_state  = getter(carrier, kTraceState);
       if (trace_parent == "")
       {
         return SpanContext::GetInvalid();
       }
   
       return ExtractContextFromTraceHeaders(trace_parent, trace_state);
     }
   };
   }  // namespace propagation
   }  // namespace trace
   OPENTELEMETRY_END_NAMESPACE