Selective export (#770)

vendor/github.com/rs/zerolog/writer.go

@@ -0,0 +1,100 @@
+package zerolog
+
+import (
+	"io"
+	"sync"
+)
+
+// LevelWriter defines as interface a writer may implement in order
+// to receive level information with payload.
+type LevelWriter interface {
+	io.Writer
+	WriteLevel(level Level, p []byte) (n int, err error)
+}
+
+type levelWriterAdapter struct {
+	io.Writer
+}
+
+func (lw levelWriterAdapter) WriteLevel(l Level, p []byte) (n int, err error) {
+	return lw.Write(p)
+}
+
+type syncWriter struct {
+	mu sync.Mutex
+	lw LevelWriter
+}
+
+// SyncWriter wraps w so that each call to Write is synchronized with a mutex.
+// This syncer can be the call to writer's Write method is not thread safe.
+// Note that os.File Write operation is using write() syscall which is supposed
+// to be thread-safe on POSIX systems. So there is no need to use this with
+// os.File on such systems as zerolog guaranties to issue a single Write call
+// per log event.
+func SyncWriter(w io.Writer) io.Writer {
+	if lw, ok := w.(LevelWriter); ok {
+		return &syncWriter{lw: lw}
+	}
+	return &syncWriter{lw: levelWriterAdapter{w}}
+}
+
+// Write implements the io.Writer interface.
+func (s *syncWriter) Write(p []byte) (n int, err error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.lw.Write(p)
+}
+
+// WriteLevel implements the LevelWriter interface.
+func (s *syncWriter) WriteLevel(l Level, p []byte) (n int, err error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.lw.WriteLevel(l, p)
+}
+
+type multiLevelWriter struct {
+	writers []LevelWriter
+}
+
+func (t multiLevelWriter) Write(p []byte) (n int, err error) {
+	for _, w := range t.writers {
+		n, err = w.Write(p)
+		if err != nil {
+			return
+		}
+		if n != len(p) {
+			err = io.ErrShortWrite
+			return
+		}
+	}
+	return len(p), nil
+}
+
+func (t multiLevelWriter) WriteLevel(l Level, p []byte) (n int, err error) {
+	for _, w := range t.writers {
+		n, err = w.WriteLevel(l, p)
+		if err != nil {
+			return
+		}
+		if n != len(p) {
+			err = io.ErrShortWrite
+			return
+		}
+	}
+	return len(p), nil
+}
+
+// MultiLevelWriter creates a writer that duplicates its writes to all the
+// provided writers, similar to the Unix tee(1) command. If some writers
+// implement LevelWriter, their WriteLevel method will be used instead of Write.
+func MultiLevelWriter(writers ...io.Writer) LevelWriter {
+	lwriters := make([]LevelWriter, 0, len(writers))
+	for _, w := range writers {
+		if lw, ok := w.(LevelWriter); ok {
+			lwriters = append(lwriters, lw)
+		} else {
+			lwriters = append(lwriters, levelWriterAdapter{w})
+		}
+	}
+	return multiLevelWriter{lwriters}
+}