Trace context propagation.

src/trace_context.hpp

@@ -1,7 +1,9 @@
 #pragma once
 
+#include <array>
 #include <opentelemetry/trace/trace_id.h>
 #include <opentelemetry/trace/span_id.h>
+#include <opentelemetry/trace/propagation/http_trace_context.h>
 #include <opentelemetry/sdk/trace/random_id_generator.h>
 
 #include "str_view.hpp"
@@ -12,6 +14,9 @@ struct TraceContext {
     bool sampled;
     StrView state;
 
+    static const auto Size =
+        opentelemetry::trace::propagation::kTraceParentSize;
+
     static TraceContext generate(bool sampled, TraceContext parent = {})
     {
         opentelemetry::sdk::trace::RandomIdGenerator idGen;
@@ -22,4 +27,60 @@ struct TraceContext {
                 sampled,
                 parent.state};
     }
+
+    static TraceContext parse(StrView trace, StrView state)
+    {
+        using namespace opentelemetry::trace::propagation;
+
+        std::array<StrView, 4> parts;
+        if (detail::SplitString(trace, '-', parts.data(), 4) != 4) {
+            return TraceContext{};
+        }
+
+        auto version = parts[0];
+        auto traceId = parts[1];
+        auto spanId = parts[2];
+        auto flags = parts[3];
+
+        if (version != "00") {
+            return TraceContext{};
+        }
+
+        if (traceId.size() != kTraceIdSize || spanId.size() != kSpanIdSize ||
+            flags.size() != kTraceFlagsSize)
+        {
+            return TraceContext{};
+        }
+
+        if (!detail::IsValidHex(traceId) || !detail::IsValidHex(spanId) ||
+            !detail::IsValidHex(flags))
+        {
+            return TraceContext{};
+        }
+
+        return {HttpTraceContext::TraceIdFromHex(traceId),
+                HttpTraceContext::SpanIdFromHex(spanId),
+                HttpTraceContext::TraceFlagsFromHex(flags).IsSampled(),
+                state};
+    }
+
+    static void serialize(const TraceContext& tc, char* out)
+    {
+        using namespace opentelemetry::trace::propagation;
+
+        *out++ = '0';
+        *out++ = '0';
+        *out++ = '-';
+
+        tc.traceId.ToLowerBase16({out, kTraceIdSize});
+        out += kTraceIdSize;
+        *out++ = '-';
+
+        tc.spanId.ToLowerBase16({out, kSpanIdSize});
+        out += kSpanIdSize;
+        *out++ = '-';
+
+        *out++ = '0';
+        *out++ = tc.sampled ? '1' : '0';
+    }
 };