/
binary_propagator.go
80 lines (71 loc) · 2.16 KB
/
binary_propagator.go
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// Copyright 2019, 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 propagators
import (
"go.opentelemetry.io/otel/api/core"
)
// BinaryFormat is an interface that specifies methods to convert SpanContext
// to/from byte array.
type BinaryFormat interface {
// ToBytes serializes span context into a byte array and returns the array.
ToBytes(sc core.SpanContext) []byte
// FromBytes de-serializes byte array into span context and returns the span context.
FromBytes([]byte) core.SpanContext
}
var _ BinaryFormat = binary{}
type binary struct{}
// Binary creates a new propagator. The propagator implements
// ToBytes and FromBytes method to transform SpanContext to/from byte array.
func Binary() BinaryFormat {
return binary{}
}
// ToBytes implements ToBytes method of propagators.BinaryFormat.
// It serializes core.SpanContext into a byte array.
func (bp binary) ToBytes(sc core.SpanContext) []byte {
if sc == core.EmptySpanContext() {
return nil
}
var b [29]byte
copy(b[2:18], sc.TraceID[:])
b[18] = 1
copy(b[19:27], sc.SpanID[:])
b[27] = 2
b[28] = sc.TraceFlags
return b[:]
}
// FromBytes implements FromBytes method of propagators.BinaryFormat.
// It de-serializes bytes into core.SpanContext.
func (bp binary) FromBytes(b []byte) (sc core.SpanContext) {
if len(b) == 0 {
return core.EmptySpanContext()
}
b = b[1:]
if len(b) >= 17 && b[0] == 0 {
copy(sc.TraceID[:], b[1:17])
b = b[17:]
} else {
return core.EmptySpanContext()
}
if len(b) >= 9 && b[0] == 1 {
copy(sc.SpanID[:], b[1:9])
b = b[9:]
}
if len(b) >= 2 && b[0] == 2 {
sc.TraceFlags = b[1]
}
if sc.IsValid() {
return sc
}
return core.EmptySpanContext()
}