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-rw-r--r--src/internal/trace/writer.go49
1 files changed, 49 insertions, 0 deletions
diff --git a/src/internal/trace/writer.go b/src/internal/trace/writer.go
new file mode 100644
index 0000000..dd0b9f1
--- /dev/null
+++ b/src/internal/trace/writer.go
@@ -0,0 +1,49 @@
+// 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
+}