package trace
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import "bytes"
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// Writer is a test trace writer.
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type Writer struct {
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bytes.Buffer
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}
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func NewWriter() *Writer {
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w := new(Writer)
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w.Write([]byte("go 1.9 trace\x00\x00\x00\x00"))
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return w
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}
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// Emit writes an event record to the trace.
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// See Event types for valid types and required arguments.
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func (w *Writer) Emit(typ byte, args ...uint64) {
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nargs := byte(len(args)) - 1
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if nargs > 3 {
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nargs = 3
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}
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buf := []byte{typ | nargs<<6}
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if nargs == 3 {
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buf = append(buf, 0)
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}
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for _, a := range args {
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buf = appendVarint(buf, a)
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}
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if nargs == 3 {
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buf[1] = byte(len(buf) - 2)
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}
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n, err := w.Write(buf)
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if n != len(buf) || err != nil {
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panic("failed to write")
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}
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}
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func appendVarint(buf []byte, v uint64) []byte {
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for ; v >= 0x80; v >>= 7 {
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buf = append(buf, 0x80|byte(v))
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}
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buf = append(buf, byte(v))
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return buf
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}
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