Add LineBufferSize option field

To support configuring the line buffer size a new field LineBufferSize is added
to the cmd.Options struct. This allows configuring the line buffer size to the
callers needs instead of relying on the DEFAULT_LINE_BUFFER_SIZE.

Author: Crevil

cmd.go

@@ -157,6 +157,12 @@ type Options struct {
 	// the real command. These functions can be used to customize the underlying
 	// os/exec.Cmd. For example, to set SysProcAttr.
 	BeforeExec []func(cmd *exec.Cmd)
+
+	// LineBufferSize sets the size of the OutputStream line buffer. The default
+	// value DEFAULT_LINE_BUFFER_SIZE is usually sufficient, but if
+	// ErrLineBufferOverflow errors occur, try increasing the size with this
+	// field.
+	LineBufferSize int
 }
 
 // NewCmdOptions creates a new Cmd with options. The command is not started
@@ -178,6 +184,10 @@ func NewCmdOptions(options Options, name string, args ...string) *Cmd {
 		doneChan: make(chan struct{}),
 	}
 
+	if options.LineBufferSize == 0 {
+		options.LineBufferSize = DEFAULT_LINE_BUFFER_SIZE
+	}
+
 	if options.Buffered {
 		c.stdoutBuf = NewOutputBuffer()
 		c.stderrBuf = NewOutputBuffer()
@@ -186,9 +196,11 @@ func NewCmdOptions(options Options, name string, args ...string) *Cmd {
 	if options.Streaming {
 		c.Stdout = make(chan string, DEFAULT_STREAM_CHAN_SIZE)
 		c.stdoutStream = NewOutputStream(c.Stdout)
+		c.stdoutStream.SetLineBufferSize(options.LineBufferSize)
 
 		c.Stderr = make(chan string, DEFAULT_STREAM_CHAN_SIZE)
 		c.stderrStream = NewOutputStream(c.Stderr)
+		c.stderrStream.SetLineBufferSize(options.LineBufferSize)
 	}
 
 	if len(options.BeforeExec) > 0 {

cmd_test.go

@@ -1167,3 +1167,63 @@ func TestOptionsBeforeExec(t *testing.T) {
 		t.Error("exec cmd option not applied")
 	}
 }
+
+func TestCmdLineBufferIncrease(t *testing.T) {
+	lineContent := cmd.DEFAULT_LINE_BUFFER_SIZE * 2
+	longLine := make([]byte, lineContent) // "AAA..."
+	for i := 0; i < lineContent; i++ {
+		longLine[i] = 'A'
+	}
+
+	tmpfile, err := ioutil.TempFile("", "cmd.TestCmdLineBufferIncrease")
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		os.Remove(tmpfile.Name())
+	})
+	if _, err := tmpfile.Write(longLine); err != nil {
+		t.Fatal(err)
+	}
+	if err := tmpfile.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	timeout := time.After(10 * time.Second) // test timeout
+
+	catStdout := cmd.NewCmdOptions(cmd.Options{
+		Streaming:      true,
+		LineBufferSize: cmd.DEFAULT_LINE_BUFFER_SIZE * 2,
+	}, "./test/cat", tmpfile.Name(), "1")
+
+	catStdoutStatus := catStdout.Start()
+
+	select {
+	case curLine := <-catStdout.Stdout:
+		t.Logf("got stdout bytes: %d", len(curLine))
+		if len(curLine) <= cmd.DEFAULT_LINE_BUFFER_SIZE {
+			t.Error("Unable to read more than default line buffer from stdout")
+		}
+	case <-timeout:
+		t.Fatal("timeout reading streaming output")
+	}
+	<-catStdoutStatus
+
+	catStderr := cmd.NewCmdOptions(cmd.Options{
+		Streaming:      true,
+		LineBufferSize: cmd.DEFAULT_LINE_BUFFER_SIZE * 2,
+	}, "./test/cat", tmpfile.Name(), "2")
+
+	catStderrStatus := catStderr.Start()
+
+	select {
+	case curLine := <-catStderr.Stderr:
+		t.Logf("got stderr bytes: %d", len(curLine))
+		if len(curLine) <= cmd.DEFAULT_LINE_BUFFER_SIZE {
+			t.Error("Unable to read more than default line buffer from stderr")
+		}
+	case <-timeout:
+		t.Fatal("timeout reading streaming output")
+	}
+	<-catStderrStatus
+}

test/cat

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+cat $1 >&$2