1 files changed, 159 insertions, 0 deletions
diff --git a/vendor/go.opentelemetry.io/otel/propagation/trace_context.go b/vendor/go.opentelemetry.io/otel/propagation/trace_context.go
new file mode 100644
index 000000000..902692da0
--- /dev/null
+++ b/vendor/go.opentelemetry.io/otel/propagation/trace_context.go
@@ -0,0 +1,159 @@
+// Copyright The 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.
+
+package propagation // import "go.opentelemetry.io/otel/propagation"
+
+import (
+	"context"
+	"encoding/hex"
+	"fmt"
+	"regexp"
+
+	"go.opentelemetry.io/otel/trace"
+)
+
+const (
+	supportedVersion  = 0
+	maxVersion        = 254
+	traceparentHeader = "traceparent"
+	tracestateHeader  = "tracestate"
+)
+
+// TraceContext is a propagator that supports the W3C Trace Context format
+// (https://www.w3.org/TR/trace-context/)
+//
+// This propagator will propagate the traceparent and tracestate headers to
+// guarantee traces are not broken. It is up to the users of this propagator
+// to choose if they want to participate in a trace by modifying the
+// traceparent header and relevant parts of the tracestate header containing
+// their proprietary information.
+type TraceContext struct{}
+
+var _ TextMapPropagator = TraceContext{}
+var traceCtxRegExp = regexp.MustCompile("^(?P<version>[0-9a-f]{2})-(?P<traceID>[a-f0-9]{32})-(?P<spanID>[a-f0-9]{16})-(?P<traceFlags>[a-f0-9]{2})(?:-.*)?$")
+
+// Inject set tracecontext from the Context into the carrier.
+func (tc TraceContext) Inject(ctx context.Context, carrier TextMapCarrier) {
+	sc := trace.SpanContextFromContext(ctx)
+	if !sc.IsValid() {
+		return
+	}
+
+	if ts := sc.TraceState().String(); ts != "" {
+		carrier.Set(tracestateHeader, ts)
+	}
+
+	// Clear all flags other than the trace-context supported sampling bit.
+	flags := sc.TraceFlags() & trace.FlagsSampled
+
+	h := fmt.Sprintf("%.2x-%s-%s-%s",
+		supportedVersion,
+		sc.TraceID(),
+		sc.SpanID(),
+		flags)
+	carrier.Set(traceparentHeader, h)
+}
+
+// Extract reads tracecontext from the carrier into a returned Context.
+//
+// The returned Context will be a copy of ctx and contain the extracted
+// tracecontext as the remote SpanContext. If the extracted tracecontext is
+// invalid, the passed ctx will be returned directly instead.
+func (tc TraceContext) Extract(ctx context.Context, carrier TextMapCarrier) context.Context {
+	sc := tc.extract(carrier)
+	if !sc.IsValid() {
+		return ctx
+	}
+	return trace.ContextWithRemoteSpanContext(ctx, sc)
+}
+
+func (tc TraceContext) extract(carrier TextMapCarrier) trace.SpanContext {
+	h := carrier.Get(traceparentHeader)
+	if h == "" {
+		return trace.SpanContext{}
+	}
+
+	matches := traceCtxRegExp.FindStringSubmatch(h)
+
+	if len(matches) == 0 {
+		return trace.SpanContext{}
+	}
+
+	if len(matches) < 5 { // four subgroups plus the overall match
+		return trace.SpanContext{}
+	}
+
+	if len(matches[1]) != 2 {
+		return trace.SpanContext{}
+	}
+	ver, err := hex.DecodeString(matches[1])
+	if err != nil {
+		return trace.SpanContext{}
+	}
+	version := int(ver[0])
+	if version > maxVersion {
+		return trace.SpanContext{}
+	}
+
+	if version == 0 && len(matches) != 5 { // four subgroups plus the overall match
+		return trace.SpanContext{}
+	}
+
+	if len(matches[2]) != 32 {
+		return trace.SpanContext{}
+	}
+
+	var scc trace.SpanContextConfig
+
+	scc.TraceID, err = trace.TraceIDFromHex(matches[2][:32])
+	if err != nil {
+		return trace.SpanContext{}
+	}
+
+	if len(matches[3]) != 16 {
+		return trace.SpanContext{}
+	}
+	scc.SpanID, err = trace.SpanIDFromHex(matches[3])
+	if err != nil {
+		return trace.SpanContext{}
+	}
+
+	if len(matches[4]) != 2 {
+		return trace.SpanContext{}
+	}
+	opts, err := hex.DecodeString(matches[4])
+	if err != nil || len(opts) < 1 || (version == 0 && opts[0] > 2) {
+		return trace.SpanContext{}
+	}
+	// Clear all flags other than the trace-context supported sampling bit.
+	scc.TraceFlags = trace.TraceFlags(opts[0]) & trace.FlagsSampled
+
+	// Ignore the error returned here. Failure to parse tracestate MUST NOT
+	// affect the parsing of traceparent according to the W3C tracecontext
+	// specification.
+	scc.TraceState, _ = trace.ParseTraceState(carrier.Get(tracestateHeader))
+	scc.Remote = true
+
+	sc := trace.NewSpanContext(scc)
+	if !sc.IsValid() {
+		return trace.SpanContext{}
+	}
+
+	return sc
+}
+
+// Fields returns the keys who's values are set with Inject.
+func (tc TraceContext) Fields() []string {
+	return []string{traceparentHeader, tracestateHeader}
+}