expressions working

Signed-off-by: Casey Lee <cplee@nektos.com>

vendor/gopkg.in/sourcemap.v1/base64vlq/base64_vlq.go

@@ -0,0 +1,92 @@
+package base64vlq
+
+import (
+	"io"
+)
+
+const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+
+const (
+	vlqBaseShift       = 5
+	vlqBase            = 1 << vlqBaseShift
+	vlqBaseMask        = vlqBase - 1
+	vlqSignBit         = 1
+	vlqContinuationBit = vlqBase
+)
+
+var decodeMap [256]byte
+
+func init() {
+	for i := 0; i < len(encodeStd); i++ {
+		decodeMap[encodeStd[i]] = byte(i)
+	}
+}
+
+func toVLQSigned(n int) int {
+	if n < 0 {
+		return -n<<1 + 1
+	}
+	return n << 1
+}
+
+func fromVLQSigned(n int) int {
+	isNeg := n&vlqSignBit != 0
+	n >>= 1
+	if isNeg {
+		return -n
+	}
+	return n
+}
+
+type Encoder struct {
+	w io.ByteWriter
+}
+
+func NewEncoder(w io.ByteWriter) *Encoder {
+	return &Encoder{
+		w: w,
+	}
+}
+
+func (enc Encoder) Encode(n int) error {
+	n = toVLQSigned(n)
+	for digit := vlqContinuationBit; digit&vlqContinuationBit != 0; {
+		digit = n & vlqBaseMask
+		n >>= vlqBaseShift
+		if n > 0 {
+			digit |= vlqContinuationBit
+		}
+
+		err := enc.w.WriteByte(encodeStd[digit])
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+type Decoder struct {
+	r io.ByteReader
+}
+
+func NewDecoder(r io.ByteReader) *Decoder {
+	return &Decoder{
+		r: r,
+	}
+}
+
+func (dec Decoder) Decode() (n int, err error) {
+	shift := uint(0)
+	for continuation := true; continuation; {
+		c, err := dec.r.ReadByte()
+		if err != nil {
+			return 0, err
+		}
+
+		c = decodeMap[c]
+		continuation = c&vlqContinuationBit != 0
+		n += int(c&vlqBaseMask) << shift
+		shift += vlqBaseShift
+	}
+	return fromVLQSigned(n), nil
+}