Merge d538aec685 into 547861c49b

9007199254740992 converts to float64

decimal.go

@@ -1229,26 +1229,27 @@ func (d Decimal) NumDigits() int {
 		return 1
 	}
 
-	if d.value.IsUint64() {
-		u64 := d.value.Uint64()
-		if u64 < (1 << 53) {
-			if u64 == 0 {
+	if d.value.IsInt64() {
+		i64 := d.value.Int64()
+		if i64 <= (1<<53) && i64 >= -(1<<53) {
+			if i64 == 0 {
 				return 1
 			}
-			return int(math.Log10(float64(u64))) + 1
-		}
-	} else if d.value.IsInt64() {
-		i64 := d.value.Int64()
-		if i64 > -(1 << 53) {
-			return int(math.Log10(float64(-i64))) + 1
+			return int(math.Log10(math.Abs(float64(i64)))) + 1
 		}
 	}
 
-	abs := new(big.Int).Abs(d.value)
-	// lg10 may be off by 1, need to verify
-	lg10 := int(float64(abs.BitLen()) / math.Log2(10))
-	check := big.NewInt(int64(lg10))
-	return lg10 + abs.Cmp(check.Exp(tenInt, check, nil))
+	estimatedNumDigits := int(float64(d.value.BitLen()) / math.Log2(10))
+
+	// estimatedNumDigits (lg10) may be off by 1, need to verify
+	digitsBigInt := big.NewInt(int64(estimatedNumDigits))
+	errorCorrectionUnit := digitsBigInt.Exp(tenInt, digitsBigInt, nil)
+
+	if d.value.CmpAbs(errorCorrectionUnit) >= 0 {
+		return estimatedNumDigits + 1
+	}
+
+	return estimatedNumDigits
 }
 
 // IsInteger returns true when decimal can be represented as an integer value, otherwise, it returns false.
@@ -1801,19 +1802,18 @@ func (d *Decimal) UnmarshalBinary(data []byte) error {
 
 // MarshalBinary implements the encoding.BinaryMarshaler interface.
 func (d Decimal) MarshalBinary() (data []byte, err error) {
-	// Write the exponent first since it's a fixed size
-	v1 := make([]byte, 4)
-	binary.BigEndian.PutUint32(v1, uint32(d.exp))
-
-	// Add the value
-	var v2 []byte
-	if v2, err = d.value.GobEncode(); err != nil {
-		return
+	// exp is written first, but encode value first to know output size
+	var valueData []byte
+	if valueData, err = d.value.GobEncode(); err != nil {
+		return nil, err
 	}
 
+	// Write the exponent in front, since it's a fixed size
+	expData := make([]byte, 4, len(valueData)+4)
+	binary.BigEndian.PutUint32(expData, uint32(d.exp))
+
 	// Return the byte array
-	data = append(v1, v2...)
-	return
+	return append(expData, valueData...), nil
 }
 
 // Scan implements the sql.Scanner interface for database deserialization.