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-rw-r--r--src/testing/iotest/writer.go35
1 files changed, 35 insertions, 0 deletions
diff --git a/src/testing/iotest/writer.go b/src/testing/iotest/writer.go
new file mode 100644
index 0000000..af61ab8
--- /dev/null
+++ b/src/testing/iotest/writer.go
@@ -0,0 +1,35 @@
+// Copyright 2009 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 iotest
+
+import "io"
+
+// TruncateWriter returns a Writer that writes to w
+// but stops silently after n bytes.
+func TruncateWriter(w io.Writer, n int64) io.Writer {
+ return &truncateWriter{w, n}
+}
+
+type truncateWriter struct {
+ w io.Writer
+ n int64
+}
+
+func (t *truncateWriter) Write(p []byte) (n int, err error) {
+ if t.n <= 0 {
+ return len(p), nil
+ }
+ // real write
+ n = len(p)
+ if int64(n) > t.n {
+ n = int(t.n)
+ }
+ n, err = t.w.Write(p[0:n])
+ t.n -= int64(n)
+ if err == nil {
+ n = len(p)
+ }
+ return
+}