Fix Unicode replacement character appear in parse result

internal/tailer/logstream/decode.go

@@ -17,13 +17,17 @@ import (
 var logLines = expvar.NewMap("log_lines_total")
 
 // decodeAndSend transforms the byte array `b` into unicode in `partial`, sending to the llp as each newline is decoded.
-func decodeAndSend(ctx context.Context, lines chan<- *logline.LogLine, pathname string, n int, b []byte, partial *bytes.Buffer) {
+func decodeAndSend(ctx context.Context, lines chan<- *logline.LogLine, pathname string, n int, b []byte, partial *bytes.Buffer) int {
 	var (
 		r     rune
 		width int
+		count int
 	)
 	for i := 0; i < len(b) && i < n; i += width {
 		r, width = utf8.DecodeRune(b[i:])
+		if r == utf8.RuneError {
+			return count
+		}
 		// Most file-based log sources will end with \n on Unixlike systems.
 		// On Windows they appear to be both \r\n.  syslog disallows \r (and \t
 		// and others) and writes them escaped, per syslog(7).  [RFC
@@ -39,7 +43,9 @@ func decodeAndSend(ctx context.Context, lines chan<- *logline.LogLine, pathname
 		default:
 			partial.WriteRune(r)
 		}
+		count += width
 	}
+	return count
 }
 
 func sendLine(ctx context.Context, pathname string, partial *bytes.Buffer, lines chan<- *logline.LogLine) {

internal/tailer/logstream/filestream.go

@@ -82,6 +82,7 @@ func (fs *fileStream) stream(ctx context.Context, wg *sync.WaitGroup, waker wake
 		glog.V(2).Infof("%v: seeked to end", fd)
 	}
 	b := make([]byte, defaultReadBufferSize)
+	var lastBytes []byte
 	partial := bytes.NewBufferString("")
 	started := make(chan struct{})
 	var total int
@@ -106,7 +107,13 @@ func (fs *fileStream) stream(ctx context.Context, wg *sync.WaitGroup, waker wake
 			if count > 0 {
 				total += count
 				glog.V(2).Infof("%v: decode and send", fd)
-				decodeAndSend(ctx, fs.lines, fs.pathname, count, b[:count], partial)
+				needSend := append(lastBytes, b[:count]...)
+				sendCount := decodeAndSend(ctx, fs.lines, fs.pathname, len(needSend), needSend, partial)
+				if sendCount < len(needSend) {
+					lastBytes = append([]byte{}, needSend[sendCount:]...)
+				} else {
+					lastBytes = []byte{}
+				}
 				fs.mu.Lock()
 				fs.lastReadTime = time.Now()
 				fs.mu.Unlock()