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trace.go
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trace.go
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// Copyright 2022 Google LLC
//
// 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 call
import (
"context"
"go.opentelemetry.io/otel/trace"
)
const traceHeaderLen = 25
// writeTraceContext serializes the trace context (if any) contained in ctx
// into b.
// REQUIRES: len(b) >= traceHeaderLen
func writeTraceContext(ctx context.Context, b []byte) {
sc := trace.SpanContextFromContext(ctx)
if !sc.IsValid() {
return
}
// Send trace information in the header.
// TODO(spetrovic): Confirm that we don't need to bother with TraceState,
// which seems to be used for storing vendor-specific information.
traceID := sc.TraceID()
spanID := sc.SpanID()
copy(b, traceID[:])
copy(b[16:], spanID[:])
b[24] = byte(sc.TraceFlags())
}
// readTraceContext returns a span context with tracing information stored in b.
// REQUIRES: len(b) >= traceHeaderLen
func readTraceContext(b []byte) trace.SpanContext {
cfg := trace.SpanContextConfig{
TraceID: *(*trace.TraceID)(b[:16]),
SpanID: *(*trace.SpanID)(b[16:24]),
TraceFlags: trace.TraceFlags(b[24]),
Remote: true,
}
return trace.NewSpanContext(cfg)
}