Add integer attribute type.

Merges some common code between integer and enum.
Enum can now bw a set.
Add valuer must take a interface{} in addValue since it can be different types.

packages/ipp/integer_test.go

@@ -0,0 +1,38 @@
+package ipp
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUnMarshalSinglePositiveInteger(T *testing.T) {
+	testdata := []byte{
+		0x00, 0x04,
+		0x66, 0x6c, 0x6f, 0x70, //flop
+		0x00, 0x04,
+		0x00, 0x0, 0x0, 0x4,
+	}
+
+	buf := bytes.NewBuffer(testdata)
+
+	n, v := unmarshalSingleInteger(buf)
+	assert.Equal(T, "flop", n, "Should be equal")
+	assert.Equal(T, int32(4), v, "Should be equal")
+}
+
+func TestUnMarshalSingleNegativeInteger(T *testing.T) {
+	testdata := []byte{
+		0x00, 0x04,
+		0x66, 0x6c, 0x6f, 0x70, //flop
+		0x00, 0x04,
+		0xff, 0xff, 0xff, 0xfc,
+	}
+
+	buf := bytes.NewBuffer(testdata)
+
+	n, v := unmarshalSingleInteger(buf)
+	assert.Equal(T, "flop", n, "Should be equal")
+	assert.Equal(T, int32(-4), v, "Should be equal")
+}