84 lines
2.4 KiB
Go
84 lines
2.4 KiB
Go
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// Copyright 2017 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package tracecontext provides encoders and decoders for Stackdriver Trace contexts.
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package tracecontext
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import "encoding/binary"
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const (
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versionID = 0
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traceIDField = 0
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spanIDField = 1
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optsField = 2
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traceIDLen = 16
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spanIDLen = 8
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optsLen = 1
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// Len represents the length of trace context.
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Len = 1 + 1 + traceIDLen + 1 + spanIDLen + 1 + optsLen
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)
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// Encode encodes trace ID, span ID and options into dst. The number of bytes
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// written will be returned. If len(dst) isn't big enough to fit the trace context,
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// a negative number is returned.
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func Encode(dst []byte, traceID []byte, spanID uint64, opts byte) (n int) {
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if len(dst) < Len {
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return -1
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}
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var offset = 0
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putByte := func(b byte) { dst[offset] = b; offset++ }
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putUint64 := func(u uint64) { binary.LittleEndian.PutUint64(dst[offset:], u); offset += 8 }
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putByte(versionID)
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putByte(traceIDField)
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for _, b := range traceID {
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putByte(b)
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}
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putByte(spanIDField)
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putUint64(spanID)
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putByte(optsField)
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putByte(opts)
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return offset
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}
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// Decode decodes the src into a trace ID, span ID and options. If src doesn't
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// contain a valid trace context, ok = false is returned.
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func Decode(src []byte) (traceID []byte, spanID uint64, opts byte, ok bool) {
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if len(src) < Len {
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return traceID, spanID, 0, false
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}
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var offset = 0
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readByte := func() byte { b := src[offset]; offset++; return b }
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readUint64 := func() uint64 { v := binary.LittleEndian.Uint64(src[offset:]); offset += 8; return v }
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if readByte() != versionID {
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return traceID, spanID, 0, false
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}
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for offset < len(src) {
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switch readByte() {
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case traceIDField:
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traceID = src[offset : offset+traceIDLen]
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offset += traceIDLen
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case spanIDField:
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spanID = readUint64()
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case optsField:
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opts = readByte()
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}
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}
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return traceID, spanID, opts, true
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}
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