Checkin initial version

from:
http://www.reddit.com/r/golang/comments/2s1zn1/how_can_i_improve_the_performance_of_my_xxd_port/

xxd.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"unicode/utf8"
+)
+
+const (
+	byteOffsetInit = 8
+	charOffsetInt  = 39
+	line_length    = 50
+)
+
+func main() {
+	line_offset := 0
+
+	if len(os.Args) != 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s [file]\n", os.Args[0])
+		os.Exit(1)
+	}
+
+	f, err := os.Open(os.Args[1])
+	if err != nil {
+		panic(err)
+	}
+	defer f.Close()
+
+	r := bufio.NewReader(f)
+	buf := make([]byte, 16)
+	for {
+		n, err := r.Read(buf)
+		if n == 0 || err == io.EOF {
+			break
+		}
+
+		// Line offset
+		fmt.Printf("%06x0: ", line_offset)
+		line_offset++
+
+		// Hex values
+		for i := 0; i < n; i++ {
+			fmt.Printf("%02x", buf[i])
+
+			if i%2 == 1 {
+				fmt.Print(" ")
+			}
+		}
+		if n < len(buf) {
+			for i := n; i < len(buf); i++ {
+				fmt.Printf("  ")
+				if i%2 == 1 {
+					fmt.Print(" ")
+				}
+			}
+		}
+
+		fmt.Printf(" ")
+
+		// Character values
+		b := buf[:n]
+		for len(b) > 0 {
+			r, size := utf8.DecodeRune(b)
+
+			if int(r) > 0x1f && int(r) < 0x7f {
+				fmt.Printf("%v", string(r))
+			} else {
+				fmt.Printf(".")
+			}
+			b = b[size:]
+		}
+
+		fmt.Printf("\n")
+	}
+}