crypto/sha512: provide top-level Sum512 and Sum384 functions

Makes it easy to ask the simple question, what is the hash of this data?
Also fix the commentary and prints in Sum256.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/10630043

src/pkg/crypto/sha256/sha256.go

@@ -179,7 +179,7 @@ func (d *digest) checkSum() [Size]byte {
 	return digest
 }
 
-// Sum returns the SHA256 checksum of the data.
+// Sum256 returns the SHA256 checksum of the data.
 func Sum256(data []byte) [Size]byte {
 	var d digest
 	d.Reset()

src/pkg/crypto/sha256/sha256_test.go

@@ -90,7 +90,7 @@ func TestGolden(t *testing.T) {
 		g := golden[i]
 		s := fmt.Sprintf("%x", Sum256([]byte(g.in)))
 		if s != g.out {
-			t.Fatalf("Sum function: sha256(%s) = %s want %s", g.in, s, g.out)
+			t.Fatalf("Sum256 function: sha256(%s) = %s want %s", g.in, s, g.out)
 		}
 		c := New()
 		for j := 0; j < 3; j++ {

src/pkg/crypto/sha512/sha512.go

@@ -135,7 +135,14 @@ func (d0 *digest) Sum(in []byte) []byte {
 	// Make a copy of d0 so that caller can keep writing and summing.
 	d := new(digest)
 	*d = *d0
+	hash := d.checkSum()
+	if d.is384 {
+		return append(in, hash[:Size384]...)
+	}
+	return append(in, hash[:]...)
+}
 
+func (d *digest) checkSum() [Size]byte {
 	// Padding.  Add a 1 bit and 0 bits until 112 bytes mod 128.
 	len := d.len
 	var tmp [128]byte
@@ -158,10 +165,8 @@ func (d0 *digest) Sum(in []byte) []byte {
 	}
 
 	h := d.h[:]
-	size := Size
 	if d.is384 {
 		h = d.h[:6]
-		size = Size384
 	}
 
 	var digest [Size]byte
@@ -176,5 +181,24 @@ func (d0 *digest) Sum(in []byte) []byte {
 		digest[i*8+7] = byte(s)
 	}
 
-	return append(in, digest[:size]...)
+	return digest
+}
+
+// Sum returns the SHA512 checksum of the data.
+func Sum512(data []byte) [Size]byte {
+	var d digest
+	d.Reset()
+	d.Write(data)
+	return d.checkSum()
+}
+
+// Sum384 returns the SHA384 checksum of the data.
+func Sum384(data []byte) (sum384 [Size384]byte) {
+	var d digest
+	d.is384 = true
+	d.Reset()
+	d.Write(data)
+	sum := d.checkSum()
+	copy(sum384[:], sum[:Size384])
+	return
 }

src/pkg/crypto/sha512/sha512_test.go

@@ -88,6 +88,10 @@ var golden384 = []sha512Test{
 func TestGolden(t *testing.T) {
 	for i := 0; i < len(golden); i++ {
 		g := golden[i]
+		s := fmt.Sprintf("%x", Sum512([]byte(g.in)))
+		if s != g.out {
+			t.Fatalf("Sum512 function: sha512(%s) = %s want %s", g.in, s, g.out)
+		}
 		c := New()
 		for j := 0; j < 3; j++ {
 			if j < 2 {
@@ -106,6 +110,10 @@ func TestGolden(t *testing.T) {
 	}
 	for i := 0; i < len(golden384); i++ {
 		g := golden384[i]
+		s := fmt.Sprintf("%x", Sum384([]byte(g.in)))
+		if s != g.out {
+			t.Fatalf("Sum384 function: sha384(%s) = %s want %s", g.in, s, g.out)
+		}
 		c := New384()
 		for j := 0; j < 3; j++ {
 			if j < 2 {