utter: add byte index keys to byte slice dumps

common.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"io"
 	"math"
+	"math/bits"
 	"reflect"
 	"sort"
 	"strconv"
@@ -229,15 +230,22 @@ 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 bool) {
+func hexDump(w io.Writer, data []byte, indent string, width int, comment, addr bool) {
 	var commentBytes []byte
 	if comment {
 		commentBytes = make([]byte, width)
 	}
 
+	var addrFmt string
+	if addr {
+		addrFmt = fmt.Sprintf("%%#0%dx: ", (bits.Len(uint(len(data)))+3)/4)
+	}
 	for i, v := range data {
 		if i%width == 0 {
 			fmt.Fprint(w, indent)
+			if addr {
+				fmt.Fprintf(w, addrFmt, i)
+			}
 		} else {
 			w.Write(spaceBytes)
 		}

config.go

@@ -61,6 +61,10 @@ type ConfigState struct {
 	// comment annotations.
 	CommentBytes bool
 
+	// AddressBytes specifies whether byte slice or array dumps have index
+	// annotations.
+	AddressBytes bool
+
 	// CommentPointers specifies whether pointer information will be added
 	// as comments.
 	CommentPointers bool
@@ -133,10 +137,10 @@ pointer addresses used to indirect to the final value.  It provides the
 following features over the built-in printing facilities provided by the fmt
 package:
 
-	* Pointers are dereferenced and followed
-	* Circular data structures are detected and handled properly
-	* Byte arrays and slices are dumped in a way similar to the hexdump -C command
-	  which includes byte values in hex, and ASCII output
+  - Pointers are dereferenced and followed
+  - Circular data structures are detected and handled properly
+  - Byte arrays and slices are dumped in a way similar to the hexdump -C command
+    which includes byte values in hex, and ASCII output
 
 The configuration options are controlled by modifying the public members
 of c.  See ConfigState for options documentation.
@@ -158,15 +162,15 @@ func (c *ConfigState) Sdump(a interface{}) string {
 
 // NewDefaultConfig returns a ConfigState with the following default settings.
 //
-// 	Indent: " "
-//  NumericWidth: 1,
-//  StringWidth: 1,
-// 	BytesWidth: 16
-// 	CommentBytes: true
-// 	CommentPointers: false
-//  IgnoreUnexported: false
-//  ElideType: false
-// 	SortKeys: false
+//		Indent: " "
+//	 NumericWidth: 1,
+//	 StringWidth: 1,
+//		BytesWidth: 16
+//		CommentBytes: true
+//		CommentPointers: false
+//	 IgnoreUnexported: false
+//	 ElideType: false
+//		SortKeys: false
 func NewDefaultConfig() *ConfigState {
 	return &ConfigState{
 		Indent:       " ",

dump.go

@@ -300,7 +300,7 @@ func (d *dumpState) dumpSlice(v reflect.Value, canElideCompound bool) {
 	// Hexdump the entire slice as needed.
 	if doHexDump {
 		indent := strings.Repeat(d.cs.Indent, d.depth)
-		hexDump(d.w, buf, indent, d.cs.BytesWidth, d.cs.CommentBytes)
+		hexDump(d.w, buf, indent, d.cs.BytesWidth, d.cs.CommentBytes, d.cs.AddressBytes)
 		return
 	}
 
@@ -785,10 +785,10 @@ pointer addresses used to indirect to the final value.  It provides the
 following features over the built-in printing facilities provided by the fmt
 package:
 
-	* Pointers are dereferenced and followed
-	* Circular data structures are detected and annotated
-	* Byte arrays and slices are dumped in a way similar to the hexdump -C command,
-	  which includes byte values in hex, and ASCII output
+  - Pointers are dereferenced and followed
+  - Circular data structures are detected and annotated
+  - Byte arrays and slices are dumped in a way similar to the hexdump -C command,
+    which includes byte values in hex, and ASCII output
 
 The configuration options are controlled by an exported package global,
 utter.Config.  See ConfigState for options documentation.

spew_test.go

@@ -82,6 +82,11 @@ func initSpewTests() {
 	bs8Default := utter.NewDefaultConfig()
 	bs8Default.BytesWidth = 8
 
+	// Byte slice with 8 columns and an address.
+	bsa8Default := utter.NewDefaultConfig()
+	bsa8Default.BytesWidth = 8
+	bsa8Default.AddressBytes = true
+
 	// Numeric slice with 4 columns.
 	num4elideDefault := utter.NewDefaultConfig()
 	num4elideDefault.ElideType = true
@@ -205,6 +210,30 @@ func initSpewTests() {
 		{bs8Default, fCSFdump, []byte{1, 2, 3, 4, 5, 0, 1}, "[]uint8{\n" +
 			" 0x01, 0x02, 0x03, 0x04, 0x05, 0x00, 0x01, // |.......|\n}\n",
 		},
+		{bsa8Default, fCSFdump, []byte{1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3}, "[]uint8{\n" +
+			" 0x0: 0x01, 0x02, 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, // |........|\n" +
+			" 0x8: 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, 0x03, /* */ // |.......|\n}\n",
+		},
+		{bsa8Default, fCSFdump, []byte{1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 0, 1, 2}, "[]uint8{\n" +
+			" 0x0: 0x01, 0x02, 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, // |........|\n" +
+			" 0x8: 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, /*       */ // |......|\n}\n",
+		},
+		{bsa8Default, fCSFdump, []byte{1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 0, 1}, "[]uint8{\n" +
+			" 0x0: 0x01, 0x02, 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, // |........|\n" +
+			" 0x8: 0x03, 0x04, 0x05, 0x00, 0x01, /*             */ // |.....|\n}\n",
+		},
+		{bsa8Default, fCSFdump, []byte{1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 0}, "[]uint8{\n" +
+			" 0x0: 0x01, 0x02, 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, // |........|\n" +
+			" 0x8: 0x03, 0x04, 0x05, 0x00, /*                   */ // |....|\n}\n",
+		},
+		{bsa8Default, fCSFdump, []byte{1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 0}, "[]uint8{\n" +
+			" 0x00: 0x01, 0x02, 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, // |........|\n" +
+			" 0x08: 0x03, 0x04, 0x05, 0x00, 0x01, 0x02, 0x03, 0x04, // |........|\n" +
+			" 0x10: 0x05, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x00, // |........|\n}\n",
+		},
+		{bsa8Default, fCSFdump, []byte{1, 2, 3, 4, 5, 0, 1}, "[]uint8{\n" +
+			" 0x0: 0x01, 0x02, 0x03, 0x04, 0x05, 0x00, 0x01, // |.......|\n}\n",
+		},
 		{ignUnexDefault, fCSFdump, Foo{Bar{flag: 1}, map[interface{}]interface{}{"one": true}},
 			"utter_test.Foo{\n ExportedField: map[interface{}]interface{}{\n  string(\"one\"): bool(true),\n },\n}\n",
 		},