examples/sha1: implement full hash and test

examples/sha1/sha1.go

@@ -0,0 +1,44 @@
+package sha1
+
+import (
+	"encoding/binary"
+)
+
+const (
+	Size      = 20
+	BlockSize = 64
+)
+
+func Sum(data []byte) [Size]byte {
+	n := len(data)
+	h := [5]uint32{0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0}
+
+	// Consume full blocks.
+	for len(data) >= BlockSize {
+		block(&h, data)
+		data = data[BlockSize:]
+	}
+
+	// Final block.
+	tmp := make([]byte, BlockSize)
+	copy(tmp[:], data)
+	tmp[len(data)] = 0x80
+
+	if len(data) >= 56 {
+		block(&h, tmp)
+		for i := 0; i < BlockSize; i++ {
+			tmp[i] = 0
+		}
+	}
+
+	binary.BigEndian.PutUint64(tmp[56:], uint64(8*n))
+	block(&h, tmp)
+
+	// Write into byte array.
+	var digest [Size]byte
+	for i := 0; i < 5; i++ {
+		binary.BigEndian.PutUint32(digest[4*i:], h[i])
+	}
+
+	return digest
+}