add thread safe writer

1 files changed, 20 insertions, 0 deletions

diff --git a/skate/xio/util.go b/skate/xio/util.go
index 4fc8905..49f38a3 100644
--- a/skate/xio/util.go
+++ b/skate/xio/util.go
@@ -6,8 +6,28 @@ import (
 	"io"
 	"os"
 	"strings"
+	"sync"
 )
 
+// SingleWriter makes any writer thread safe.
+type SingleWriter struct {
+	sync.Mutex
+	w io.Writer
+}
+
+// NewSingleWriter returns an io.Writer that can be safely accessed by multiple
+// goroutines.
+func NewSingleWriter(w io.Writer) *SingleWriter {
+	return &SingleWriter{w: w}
+}
+
+// Write wraps the underlying writer and gives exclusive access.
+func (w *SingleWriter) Write(p []byte) (n int, err error) {
+	w.Lock()
+	defer w.Unlock()
+	return w.w.Write(p)
+}
+
 // OpenTwo opens two files. The caller needs to check for a single error only.
 func OpenTwo(f0, f1 string) (g0, g1 *os.File, err error) {
 	if g0, err = os.Open(f0); err != nil {