utter: use default bytes width if not set

common.go

@@ -231,6 +231,10 @@ func printComplex(w io.Writer, c complex128, floatPrecision int) {
 // hexDump is a modified 'hexdump -C'-like that returns a commented Go syntax
 // byte slice or array.
 func hexDump(w io.Writer, data []byte, indent string, width int, comment, addr bool) {
+	if width <= 0 {
+		width = 16 // This is the width used by hexdump -C, so it makes a reasonable default.
+	}
+
 	var commentBytes []byte
 	if comment {
 		commentBytes = make([]byte, width)

config.go

@@ -54,7 +54,8 @@ type ConfigState struct {
 	Quoting Quoting
 
 	// BytesWidth specifies the number of byte columns to use when dumping a
-	// byte slice or array.
+	// byte slice or array. If this is not set or negative, a value of 16
+	// is used.
 	BytesWidth int
 
 	// CommentBytes specifies whether byte slice or array dumps have ASCII

spew_test.go

@@ -78,6 +78,10 @@ func initSpewTests() {
 	comPtrDefault := utter.NewDefaultConfig()
 	comPtrDefault.CommentPointers = true
 
+	// Byte slice with 8 columns.
+	bs0Default := utter.NewDefaultConfig()
+	bs0Default.BytesWidth = 0
+
 	// Byte slice with 8 columns.
 	bs8Default := utter.NewDefaultConfig()
 	bs8Default.BytesWidth = 8
@@ -191,6 +195,10 @@ func initSpewTests() {
 			"  int( /*%p*/ 5),\n"+
 			"  (*interface{}) /*%[1]p*/ (<already shown>),\n"+
 			"  &int /*%p*/ (5),\n },\n}\n", &c[0], &c[1])},
+		{bs0Default, fCSFdump, []byte{1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5}, "[]uint8{\n" +
+			" 0x01, 0x02, 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, 0x03, 0x04, // |................|\n" +
+			" 0x05, /*                                                                                     */ // |.|\n}\n",
+		},
 		{bs8Default, fCSFdump, []byte{1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3}, "[]uint8{\n" +
 			" 0x01, 0x02, 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, // |........|\n" +
 			" 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, 0x03, /* */ // |.......|\n}\n",