move utils.go to its own package so that it's available for aeads

utils/utils.go

@@ -0,0 +1,84 @@
+package utils
+
+import (
+	"bytes"
+	"io"
+)
+
+// ReadUintN reads N bytes
+func ReadUintN(b io.ByteReader, length uint8) (uint64, error) {
+	var res uint64
+	for i := uint8(0); i < length; i++ {
+		bt, err := b.ReadByte()
+		if err != nil {
+			return 0, err
+		}
+		res = res<<8 + uint64(bt)
+	}
+	return res, nil
+}
+
+// ReadUint32 reads a uint32
+func ReadUint32(b io.ByteReader) (uint32, error) {
+	var b1, b2, b3, b4 uint8
+	var err error
+	if b1, err = b.ReadByte(); err != nil {
+		return 0, err
+	}
+	if b2, err = b.ReadByte(); err != nil {
+		return 0, err
+	}
+	if b3, err = b.ReadByte(); err != nil {
+		return 0, err
+	}
+	if b4, err = b.ReadByte(); err != nil {
+		return 0, err
+	}
+	return uint32(b1) + uint32(b2)<<8 + uint32(b3)<<16 + uint32(b4)<<24, nil
+}
+
+// ReadUint16 reads a uint16
+func ReadUint16(b io.ByteReader) (uint16, error) {
+	var b1, b2 uint8
+	var err error
+	if b1, err = b.ReadByte(); err != nil {
+		return 0, err
+	}
+	if b2, err = b.ReadByte(); err != nil {
+		return 0, err
+	}
+	return uint16(b1) + uint16(b2)<<8, nil
+}
+
+// WriteUint64 writes a uint64
+func WriteUint64(b *bytes.Buffer, i uint64) {
+	b.WriteByte(uint8(i & 0xff))
+	b.WriteByte(uint8((i >> 8) & 0xff))
+	b.WriteByte(uint8((i >> 16) & 0xff))
+	b.WriteByte(uint8((i >> 24) & 0xff))
+	b.WriteByte(uint8((i >> 32) & 0xff))
+	b.WriteByte(uint8((i >> 40) & 0xff))
+	b.WriteByte(uint8((i >> 48) & 0xff))
+	b.WriteByte(uint8((i >> 56) & 0xff))
+}
+
+// WriteUint32 writes a uint32
+func WriteUint32(b *bytes.Buffer, i uint32) {
+	b.WriteByte(uint8(i & 0xff))
+	b.WriteByte(uint8((i >> 8) & 0xff))
+	b.WriteByte(uint8((i >> 16) & 0xff))
+	b.WriteByte(uint8((i >> 24) & 0xff))
+}
+
+// WriteUint16 writes a uint16
+func WriteUint16(b *bytes.Buffer, i uint16) {
+	b.WriteByte(uint8(i & 0xff))
+	b.WriteByte(uint8((i >> 8) & 0xff))
+}
+
+// Uint32Slice attaches the methods of sort.Interface to []uint32, sorting in increasing order.
+type Uint32Slice []uint32
+
+func (s Uint32Slice) Len() int           { return len(s) }
+func (s Uint32Slice) Less(i, j int) bool { return s[i] < s[j] }
+func (s Uint32Slice) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }