go writer 源码
golang writer 代码
文件路径：/src/internal/trace/writer.go
// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package trace
import "bytes"
// Writer is a test trace writer.
type Writer struct {
bytes.Buffer
}
func NewWriter() *Writer {
w := new(Writer)
w.Write([]byte("go 1.9 trace\x00\x00\x00\x00"))
return w
}
// Emit writes an event record to the trace.
// See Event types for valid types and required arguments.
func (w *Writer) Emit(typ byte, args ...uint64) {
nargs := byte(len(args)) - 1
if nargs > 3 {
nargs = 3
}
buf := []byte{typ | nargs<<6}
if nargs == 3 {
buf = append(buf, 0)
}
for _, a := range args {
buf = appendVarint(buf, a)
}
if nargs == 3 {
buf[1] = byte(len(buf) - 2)
}
n, err := w.Write(buf)
if n != len(buf) || err != nil {
panic("failed to write")
}
}
func appendVarint(buf []byte, v uint64) []byte {
for ; v >= 0x80; v >>= 7 {
buf = append(buf, 0x80|byte(v))
}
buf = append(buf, byte(v))
return buf
}
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