added WriteReadVarSize test, added PutVarSize/GetVarSize and test

little/little.go

@@ -29,9 +29,10 @@ var (
 	// ErrNegativeReadCount shows 100% bug in the source reader
 	ErrNegativeReadCount = errors.New("bin: reader returned negative 'n'")
 
-	ErrNoSpace = errors.New("bin: no space")
-	ErrTooLong = errors.New("bin: too long") // слишком длинная строка или массив байт
-	ErrRange   = errors.New("bin: out of range")
+	ErrNoSpace      = errors.New("bin: no space")
+	ErrTooLong      = errors.New("bin: too long") // слишком длинная строка или массив байт
+	ErrRange        = errors.New("bin: out of range")
+	ErrNegativeSize = errors.New("bin: negative size")
 )
 
 func ReadByteAsInt(r io.Reader) (i int, err error) {
@@ -1013,10 +1014,16 @@ func ReadBool(src io.Reader) (bool, error) {
 	return b == 1, nil
 }
 
-// uint64
+// READ/WRITE VAR SIZE
+
 func WriteVarSize(w io.Writer, n int) (int, error) {
-	num := uint64(n)
-	a := make([]byte, 9)
+	if n < 0 {
+		return 0, ErrNegativeSize
+	}
+	var (
+		num = uint64(n)
+		a   = make([]byte, 9)
+	)
 	for i := 0; i < 8; i++ {
 		a[i] = byte(num & 127)
 		num >>= 7
@@ -1100,3 +1107,55 @@ func CountVarSize(n int) int {
 	}
 	return 9
 }
+
+// PUT/GET VAR SIZE
+
+func PutVarSize(a []byte, n int) (int, error) {
+	if n < 0 {
+		return 0, ErrNegativeSize
+	}
+	var (
+		num = uint64(n)
+		tmp = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0}
+	)
+	for i := 0; i < 8; i++ {
+		if i < len(a) {
+			if num < 128 {
+				tmp[i] = byte(num) | 128
+				q := i + 1
+				copy(a, tmp[:q])
+				return q, nil
+			}
+			tmp[i] = byte(num & 127)
+			num >>= 7
+		} else {
+			return 0, ErrNoSpace
+		}
+	}
+	if len(a) < 9 {
+		return 0, ErrNoSpace
+	}
+	tmp[8] = byte(num)
+	copy(a, tmp)
+	return 9, nil
+}
+
+func GetVarSize(a []byte) (int, error) {
+	var num uint64
+	for i := 0; i < 8; i++ {
+		if i < len(a) {
+			b := a[i]
+			num |= uint64(b&127) << uint(i*7)
+			if b >= 128 {
+				return int(num), nil
+			}
+		} else {
+			return 0, ErrNoSpace
+		}
+	}
+	if len(a) < 9 {
+		return 0, ErrNoSpace
+	}
+	num |= uint64(a[8]) << 56
+	return int(num), nil
+}