forked from TrueCloudLab/restic
83 lines
2.4 KiB
Go
83 lines
2.4 KiB
Go
// Copyright 2017 Google Inc. All Rights Reserved.
|
|
//
|
|
// 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 tracecontext provides encoders and decoders for Stackdriver Trace contexts.
|
|
package tracecontext
|
|
|
|
import "encoding/binary"
|
|
|
|
const (
|
|
versionID = 0
|
|
traceIDField = 0
|
|
spanIDField = 1
|
|
optsField = 2
|
|
|
|
traceIDLen = 16
|
|
spanIDLen = 8
|
|
optsLen = 1
|
|
|
|
// Len represents the length of trace context.
|
|
Len = 1 + 1 + traceIDLen + 1 + spanIDLen + 1 + optsLen
|
|
)
|
|
|
|
// Encode encodes trace ID, span ID and options into dst. The number of bytes
|
|
// written will be returned. If len(dst) isn't big enough to fit the trace context,
|
|
// a negative number is returned.
|
|
func Encode(dst []byte, traceID []byte, spanID uint64, opts byte) (n int) {
|
|
if len(dst) < Len {
|
|
return -1
|
|
}
|
|
var offset = 0
|
|
putByte := func(b byte) { dst[offset] = b; offset++ }
|
|
putUint64 := func(u uint64) { binary.LittleEndian.PutUint64(dst[offset:], u); offset += 8 }
|
|
|
|
putByte(versionID)
|
|
putByte(traceIDField)
|
|
for _, b := range traceID {
|
|
putByte(b)
|
|
}
|
|
putByte(spanIDField)
|
|
putUint64(spanID)
|
|
putByte(optsField)
|
|
putByte(opts)
|
|
|
|
return offset
|
|
}
|
|
|
|
// Decode decodes the src into a trace ID, span ID and options. If src doesn't
|
|
// contain a valid trace context, ok = false is returned.
|
|
func Decode(src []byte) (traceID []byte, spanID uint64, opts byte, ok bool) {
|
|
if len(src) < Len {
|
|
return traceID, spanID, 0, false
|
|
}
|
|
var offset = 0
|
|
readByte := func() byte { b := src[offset]; offset++; return b }
|
|
readUint64 := func() uint64 { v := binary.LittleEndian.Uint64(src[offset:]); offset += 8; return v }
|
|
|
|
if readByte() != versionID {
|
|
return traceID, spanID, 0, false
|
|
}
|
|
for offset < len(src) {
|
|
switch readByte() {
|
|
case traceIDField:
|
|
traceID = src[offset : offset+traceIDLen]
|
|
offset += traceIDLen
|
|
case spanIDField:
|
|
spanID = readUint64()
|
|
case optsField:
|
|
opts = readByte()
|
|
}
|
|
}
|
|
return traceID, spanID, opts, true
|
|
}
|