fix: #20 parse docker log format

container/docker/docker.go

@@ -367,10 +367,11 @@ func (docker *DockerCli) Close() error {
 }
 
 func (docker *DockerCli) Logs(ctx context.Context, opts types.LogOptions) (io.ReadCloser, error) {
-	return docker.cli.ContainerLogs(ctx, opts.ID, apiTypes.ContainerLogsOptions{
+	rc, err := docker.cli.ContainerLogs(ctx, opts.ID, apiTypes.ContainerLogsOptions{
 		ShowStderr: true,
 		ShowStdout: true,
 		Follow:     opts.Follow,
 		Tail:       opts.Tail,
 	})
+	return parseContainerLog(rc), err
 }

container/docker/log_parser.go

@@ -0,0 +1,81 @@
+package docker
+
+import (
+	"fmt"
+	"io"
+	"strconv"
+)
+
+type logReadCloser struct {
+	io.Closer
+
+	docker io.ReadCloser
+}
+
+// https://ahmet.im/blog/docker-logs-api-binary-format-explained/
+func _dockerStreamFormat(p []byte) bool {
+	if len(p) < 8 {
+		return false
+	}
+	if p[0] != 1 && p[0] != 2 {
+		return false
+	}
+
+	for _, x := range p[1:4] {
+		if x != 0 {
+			return false
+		}
+	}
+
+	return true
+}
+
+func (rc logReadCloser) Read(p []byte) (int, error) {
+	n, err := rc.docker.Read(p)
+	if err != nil {
+		return n, err
+	}
+
+	if !_dockerStreamFormat(p) {
+		return n, err
+	}
+
+	// docker log format
+	var (
+		msgLen int64
+		start  int64
+	)
+	bs := make([]byte, 0, len(p))
+	for start+msgLen < int64(len(p)) {
+		lenHex := fmt.Sprintf("%x", p[start+4:start+8])
+		msgLen, err = strconv.ParseInt(lenHex, 16, 64)
+		if err != nil {
+			return 0, err
+		}
+		if msgLen == 0 {
+			break
+		}
+
+		start += 8
+		line := p[start : start+msgLen]
+		if line[len(line)-1] == '\n' {
+			line[len(line)-1] = '\r'
+			line = append(line, '\n') // must be \r\n
+		}
+		bs = append(bs, line...)
+		start += msgLen
+	}
+
+	copy(p, bs)
+	return len(bs), nil
+}
+
+func parseContainerLog(rc io.ReadCloser) io.ReadCloser {
+	if rc == nil {
+		return nil
+	}
+	return &logReadCloser{
+		Closer: rc,
+		docker: rc,
+	}
+}