Go: Add base32 support library

Our base32 uses 0-9a-v with no padding. The length is hard coded to
20 bytes (and 32 characters)

go/hash/base32.go

@@ -0,0 +1,18 @@
+// Copyright 2016 The Noms Authors. All rights reserved.
+// Licensed under the Apache License, version 2.0:
+// http://www.apache.org/licenses/LICENSE-2.0
+
+package hash
+
+import "encoding/base32"
+
+var encoding = base32.NewEncoding("0123456789abcdefghijklmnopqrstuv")
+
+func encode(data []byte) string {
+	return encoding.EncodeToString(data[:20]) // We only use the first remove trailing padding
+}
+
+func decode(s string) []byte {
+	slice, _ := encoding.DecodeString(s)
+	return slice
+}

go/hash/base32_test.go

@@ -0,0 +1,66 @@
+// Copyright 2016 The Noms Authors. All rights reserved.
+// Licensed under the Apache License, version 2.0:
+// http://www.apache.org/licenses/LICENSE-2.0
+
+package hash
+
+import (
+	"testing"
+
+	"github.com/attic-labs/testify/assert"
+)
+
+func TestBase32Encode(t *testing.T) {
+	assert := assert.New(t)
+
+	d := make([]byte, 20, 20)
+	assert.Equal("00000000000000000000000000000000", encode(d))
+	d[19] = 1
+	assert.Equal("00000000000000000000000000000001", encode(d))
+	d[19] = 10
+	assert.Equal("0000000000000000000000000000000a", encode(d))
+	d[19] = 20
+	assert.Equal("0000000000000000000000000000000k", encode(d))
+	d[19] = 31
+	assert.Equal("0000000000000000000000000000000v", encode(d))
+	d[19] = 32
+	assert.Equal("00000000000000000000000000000010", encode(d))
+	d[19] = 63
+	assert.Equal("0000000000000000000000000000001v", encode(d))
+	d[19] = 64
+	assert.Equal("00000000000000000000000000000020", encode(d))
+
+	// Largest!
+	for i := 0; i < 20; i++ {
+		d[i] = 0xff
+	}
+	assert.Equal("vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv", encode(d))
+}
+
+func TestBase32Decode(t *testing.T) {
+	assert := assert.New(t)
+
+	d := make([]byte, 20, 20)
+	assert.Equal(d, decode("00000000000000000000000000000000"))
+
+	d[19] = 1
+	assert.Equal(d, decode("00000000000000000000000000000001"))
+	d[19] = 10
+	assert.Equal(d, decode("0000000000000000000000000000000a"))
+	d[19] = 20
+	assert.Equal(d, decode("0000000000000000000000000000000k"))
+	d[19] = 31
+	assert.Equal(d, decode("0000000000000000000000000000000v"))
+	d[19] = 32
+	assert.Equal(d, decode("00000000000000000000000000000010"))
+	d[19] = 63
+	assert.Equal(d, decode("0000000000000000000000000000001v"))
+	d[19] = 64
+	assert.Equal(d, decode("00000000000000000000000000000020"))
+
+	// Largest!
+	for i := 0; i < 20; i++ {
+		d[i] = 0xff
+	}
+	assert.Equal(d, decode("vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv"))
+}