extend ByteOrder interface to allow converting from a byte slice

internal/utils/byteoder_big_endian_test.go

@@ -9,6 +9,23 @@ import (
 )
 
 var _ = Describe("Big Endian encoding / decoding", func() {
+	Context("converting", func() {
+		It("Uint16", func() {
+			b := []byte{0x13, 0x37}
+			Expect(BigEndian.Uint16(b)).To(Equal(uint16(0x1337)))
+		})
+
+		It("Uint24", func() {
+			b := []byte{0x13, 0x99, 0x37}
+			Expect(BigEndian.Uint24(b)).To(Equal(uint32(0x139937)))
+		})
+
+		It("Uint32", func() {
+			b := []byte{0xde, 0xad, 0xbe, 0xef}
+			Expect(BigEndian.Uint32(b)).To(Equal(uint32(0xdeadbeef)))
+		})
+	})
+
 	Context("ReadUint16", func() {
 		It("reads a big endian", func() {
 			b := []byte{0x13, 0xEF}

internal/utils/byteorder.go

@@ -7,6 +7,10 @@ import (
 
 // A ByteOrder specifies how to convert byte sequences into 16-, 32-, or 64-bit unsigned integers.
 type ByteOrder interface {
+	Uint32([]byte) uint32
+	Uint24([]byte) uint32
+	Uint16([]byte) uint16
+
 	ReadUint32(io.ByteReader) (uint32, error)
 	ReadUint24(io.ByteReader) (uint32, error)
 	ReadUint16(io.ByteReader) (uint16, error)

internal/utils/byteorder_big_endian.go

@@ -2,6 +2,7 @@ package utils
 
 import (
 	"bytes"
+	"encoding/binary"
 	"io"
 )
 
@@ -73,6 +74,19 @@ func (bigEndian) ReadUint16(b io.ByteReader) (uint16, error) {
 	return uint16(b1) + uint16(b2)<<8, nil
 }
 
+func (bigEndian) Uint32(b []byte) uint32 {
+	return binary.BigEndian.Uint32(b)
+}
+
+func (bigEndian) Uint24(b []byte) uint32 {
+	_ = b[2] // bounds check hint to compiler; see golang.org/issue/14808
+	return uint32(b[2]) | uint32(b[1])<<8 | uint32(b[0])<<16
+}
+
+func (bigEndian) Uint16(b []byte) uint16 {
+	return binary.BigEndian.Uint16(b)
+}
+
 // WriteUint32 writes a uint32
 func (bigEndian) WriteUint32(b *bytes.Buffer, i uint32) {
 	b.Write([]byte{uint8(i >> 24), uint8(i >> 16), uint8(i >> 8), uint8(i)})