added random reader

I thought this one might be slow but it gets 400Mb/s on my mac.

cmd/trash/main.go

@@ -25,6 +25,8 @@ func main() {
 		r = trash.HiLo
 	case "lohi", "55", "5":
 		r = trash.LoHi
+	case "rand", "random":
+		r = trash.Random
 	default:
 		fmt.Fprintf(os.Stderr, "unsupported algorithm: %v\ntry one of 'lo(w)', 'hi(gh)', 'hilo', 'lohi', 'trash'\n", *algo)
 		os.Exit(1)

trash.go

@@ -3,6 +3,7 @@ package trash
 
 import (
 	"io"
+	"math/rand"
 	"time"
 )
 
@@ -12,6 +13,7 @@ func init() {
 	Fs = &reader{0xff}
 	HiLo = &reader{0xaa}
 	LoHi = &reader{0x55}
+	Random = rand.New(rand.NewSource(time.Now().UnixNano()))
 }
 
 // Reader provides a steady stream of trash (non-random bytes) when read from
@@ -29,6 +31,8 @@ var HiLo io.Reader
 // LoHi provides a steady stream of 0x55
 var LoHi io.Reader
 
+var Random io.Reader
+
 // TimeoutReader returns a reader that returns io.EOF after dur.
 func TimeoutReader(dur time.Duration) io.Reader {
 	return &timeoutReader{timeout: time.Now().Add(dur)}