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) {
+var varUint32Cutoffs = []uint32{
-	b, err := ReadByte(src)
+	1 << 7,
-	if err != nil {
+	1 << 14,
-		return false, err
+	1 << 21,
-	}
+	1 << 28,
-	return b == 1, nil
+}
+
+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
 }

little/little_test.go

@@ -703,6 +703,96 @@ func TestWriteReadBool(t *testing.T) {
 	}
 }
 
+// VAR SIZE COUNT
+
+func TestCountVarUint32(t *testing.T) {
+	var testCases = []struct {
+		Num   uint32
+		Count int
+	}{
+		{Num: (1 << 7) - 1, Count: 1},
+		{Num: (1 << 7), Count: 2},
+		{Num: (1 << 14) - 1, Count: 2},
+		{Num: (1 << 14), Count: 3},
+		{Num: (1 << 21) - 1, Count: 3},
+		{Num: (1 << 21), Count: 4},
+		{Num: (1 << 28) - 1, Count: 4},
+		{Num: (1 << 28), Count: 5},
+		{Num: (1 << 32) - 1, Count: 5},
+	}
+	for _, testCase := range testCases {
+		count := CountVarUint32(testCase.Num)
+		if count != testCase.Count {
+			t.Fatalf("calculated count %d is not equal %d for num %d\n",
+				count, testCase.Count, testCase.Num)
+		}
+	}
+}
+
+func TestCountVarUint64(t *testing.T) {
+	var testCases = []struct {
+		Num   uint64
+		Count int
+	}{
+		{Num: (1 << 7) - 1, Count: 1},
+		{Num: (1 << 7), Count: 2},
+		{Num: (1 << 14) - 1, Count: 2},
+		{Num: (1 << 14), Count: 3},
+		{Num: (1 << 21) - 1, Count: 3},
+		{Num: (1 << 21), Count: 4},
+		{Num: (1 << 28) - 1, Count: 4},
+		{Num: (1 << 28), Count: 5},
+		{Num: (1 << 35) - 1, Count: 5},
+		{Num: (1 << 35), Count: 6},
+		{Num: (1 << 42) - 1, Count: 6},
+		{Num: (1 << 42), Count: 7},
+		{Num: (1 << 49) - 1, Count: 7},
+		{Num: (1 << 49), Count: 8},
+		{Num: (1 << 56) - 1, Count: 8},
+		{Num: (1 << 56), Count: 9},
+		{Num: (1 << 64) - 1, Count: 9},
+	}
+	for _, testCase := range testCases {
+		count := CountVarUint64(testCase.Num)
+		if count != testCase.Count {
+			t.Fatalf("calculated count %d is not equal %d for num %d\n",
+				count, testCase.Count, testCase.Num)
+		}
+	}
+}
+
+func TestCountVarSize(t *testing.T) {
+	var testCases = []struct {
+		Num   int
+		Count int
+	}{
+		{Num: (1 << 7) - 1, Count: 1},
+		{Num: (1 << 7), Count: 2},
+		{Num: (1 << 14) - 1, Count: 2},
+		{Num: (1 << 14), Count: 3},
+		{Num: (1 << 21) - 1, Count: 3},
+		{Num: (1 << 21), Count: 4},
+		{Num: (1 << 28) - 1, Count: 4},
+		{Num: (1 << 28), Count: 5},
+		{Num: (1 << 35) - 1, Count: 5},
+		{Num: (1 << 35), Count: 6},
+		{Num: (1 << 42) - 1, Count: 6},
+		{Num: (1 << 42), Count: 7},
+		{Num: (1 << 49) - 1, Count: 7},
+		{Num: (1 << 49), Count: 8},
+		{Num: (1 << 56) - 1, Count: 8},
+		{Num: (1 << 56), Count: 9},
+		{Num: (1 << 63) - 1, Count: 9},
+	}
+	for _, testCase := range testCases {
+		count := CountVarSize(testCase.Num)
+		if count != testCase.Count {
+			t.Fatalf("calculated count %d is not equal %d for num %d\n",
+				count, testCase.Count, testCase.Num)
+		}
+	}
+}
+
 // HELPERS
 
 const letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"