Add a simple sha3sum utility.

sha3sum/main.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/magical/keccak"
+)
+
+func main() {
+	flag.Parse()
+	var sum [keccak.Size]byte
+	h := keccak.New256()
+	files := flag.Args()
+	for _, filename := range files {
+		f, err := os.Open(filename)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			continue
+		}
+		h.Reset()
+		_, err = io.Copy(h, f)
+		f.Close()
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			continue
+		}
+		h.Sum(sum[:0])
+		fmt.Printf("%x %s\n", sum, filename)
+	}
+}