reorder to try to use go modules

broadcast.go

@@ -0,0 +1,69 @@
+package pathway
+
+import (
+	"io"
+)
+
+type broadcastWriter struct {
+	writers []io.Writer
+}
+
+func (t *broadcastWriter) Close() (err error) {
+	for i := 0; i < len(t.writers); i++ {
+		if w, ok := t.writers[i].(io.WriteCloser); ok {
+			if e := w.Close(); e != nil {
+				err = e
+			}
+		}
+	}
+	return
+}
+
+func (t *broadcastWriter) Write(p []byte) (n int, err error) {
+	for i := 0; i < len(t.writers); i++ {
+		n, err = t.writers[i].Write(p)
+
+		if err == nil && n != len(p) {
+			err = io.ErrShortWrite
+		}
+
+		if err != nil {
+			// if not at the end, move last to here and redo this
+			if i < len(t.writers)-1 {
+				// close the writer if it implements WriteCloser
+				if w, ok := t.writers[i].(io.WriteCloser); ok {
+					defer w.Close()
+				}
+				t.writers[i] = t.writers[len(t.writers)-1]
+				i = i - 1
+			}
+			// always shorten list by one to drop the last one
+			t.writers = t.writers[:len(t.writers)-1]
+		}
+	}
+	if len(t.writers) <= 0 {
+		return 0, err
+	}
+
+	return len(p), nil
+}
+
+// BroadcastWriter creates a writer that duplicates its writes to all the
+// provided writers, similar to the Unix tee(1) command.
+//
+// Each write is written to each listed writer, one at a time.
+// If a listed writer returns an error, that overall write operation
+// continues and the offending writer is dropped from the list.
+//
+// Only if all writers are dropped, the last error is returned at the end.
+func BroadcastWriter(writers ...io.Writer) io.WriteCloser {
+	allWriters := make([]io.Writer, 0, len(writers))
+	for _, w := range writers {
+		if bw, ok := w.(*broadcastWriter); ok {
+			allWriters = append(allWriters, bw.writers...)
+		} else {
+			allWriters = append(allWriters, w)
+		}
+	}
+	return &broadcastWriter{allWriters}
+}