Opentracing support

vendor/github.com/openzipkin/zipkin-go-opentracing/wire/carrier.go

@@ -0,0 +1,65 @@
+package wire
+
+import (
+	"github.com/openzipkin/zipkin-go-opentracing/flag"
+	"github.com/openzipkin/zipkin-go-opentracing/types"
+)
+
+// ProtobufCarrier is a DelegatingCarrier that uses protocol buffers as the
+// the underlying datastructure. The reason for implementing DelagatingCarrier
+// is to allow for end users to serialize the underlying protocol buffers using
+// jsonpb or any other serialization forms they want.
+type ProtobufCarrier TracerState
+
+// SetState set's the tracer state.
+func (p *ProtobufCarrier) SetState(traceID types.TraceID, spanID uint64, parentSpanID *uint64, sampled bool, flags flag.Flags) {
+	p.TraceId = traceID.Low
+	p.TraceIdHigh = traceID.High
+	p.SpanId = spanID
+	if parentSpanID == nil {
+		flags |= flag.IsRoot
+		p.ParentSpanId = 0
+	} else {
+		flags &^= flag.IsRoot
+		p.ParentSpanId = *parentSpanID
+	}
+	flags |= flag.SamplingSet
+	if sampled {
+		flags |= flag.Sampled
+		p.Sampled = sampled
+	} else {
+		flags &^= flag.Sampled
+	}
+	p.Flags = uint64(flags)
+}
+
+// State returns the tracer state.
+func (p *ProtobufCarrier) State() (traceID types.TraceID, spanID uint64, parentSpanID *uint64, sampled bool, flags flag.Flags) {
+	traceID.Low = p.TraceId
+	traceID.High = p.TraceIdHigh
+	spanID = p.SpanId
+	sampled = p.Sampled
+	flags = flag.Flags(p.Flags)
+	if flags&flag.IsRoot == 0 {
+		parentSpanID = &p.ParentSpanId
+	}
+	return traceID, spanID, parentSpanID, sampled, flags
+}
+
+// SetBaggageItem sets a baggage item.
+func (p *ProtobufCarrier) SetBaggageItem(key, value string) {
+	if p.BaggageItems == nil {
+		p.BaggageItems = map[string]string{key: value}
+		return
+	}
+
+	p.BaggageItems[key] = value
+}
+
+// GetBaggage iterates over each baggage item and executes the callback with
+// the key:value pair.
+func (p *ProtobufCarrier) GetBaggage(f func(k, v string)) {
+	for k, v := range p.BaggageItems {
+		f(k, v)
+	}
+}