added CountVarUint64, CountVarUint32, CountVarSize

little/little.go

@@ -996,6 +996,24 @@ func ReadVarUint64(src io.Reader) (num uint64, err error) {
 	return
 }
 
+func WriteBool(w io.Writer, flag bool) (err error) {
+	var b byte
+	if flag {
+		b = 1
+	}
+	_, err = w.Write([]byte{b})
+	return
+}
+
+func ReadBool(src io.Reader) (bool, error) {
+	b, err := ReadByte(src)
+	if err != nil {
+		return false, err
+	}
+	return b == 1, nil
+}
+
+// uint64
 func WriteVarSize(w io.Writer, n int) (int, error) {
 	num := uint64(n)
 	a := make([]byte, 9)
@@ -1013,15 +1031,6 @@ func WriteVarSize(w io.Writer, n int) (int, error) {
 	return w.Write(a)
 }
 
-func WriteBool(w io.Writer, flag bool) (err error) {
-	var b byte
-	if flag {
-		b = 1
-	}
-	_, err = w.Write([]byte{b})
-	return
-}
-
 func ReadVarSize(src io.Reader) (_ int, err error) {
 	var (
 		b   byte
@@ -1047,10 +1056,47 @@ func ReadVarSize(src io.Reader) (_ int, err error) {
 	return int(num), nil
 }
 
-func ReadBool(src io.Reader) (bool, error) {
-	b, err := ReadByte(src)
-	if err != nil {
-		return false, err
-	}
-	return b == 1, nil
+var varUint32Cutoffs = []uint32{
+	1 << 7,
+	1 << 14,
+	1 << 21,
+	1 << 28,
+}
+
+func CountVarUint32(n uint32) int {
+	for i, cutoff := range varUint32Cutoffs {
+		if n < cutoff {
+			return i + 1
+		}
+	}
+	return 5
+}
+
+var varUint64Cutoffs = []uint64{
+	1 << 7,
+	1 << 14,
+	1 << 21,
+	1 << 28,
+	1 << 35,
+	1 << 42,
+	1 << 49,
+	1 << 56,
+}
+
+func CountVarUint64(n uint64) int {
+	for i, cutoff := range varUint64Cutoffs {
+		if n < cutoff {
+			return i + 1
+		}
+	}
+	return 9
+}
+func CountVarSize(n int) int {
+	u64 := uint64(n)
+	for i, cutoff := range varUint64Cutoffs {
+		if u64 < cutoff {
+			return i + 1
+		}
+	}
+	return 9
 }