Merge dd34943dc4 into 0e69d5cd53

.github/workflows/ci.yml

@@ -1,5 +1,9 @@
 name: ci
-on: [push]
+on:
+  push:
+    branches:
+      - master
+  pull_request:
 jobs:
   ci-job:
     runs-on: ubuntu-latest

decimal.go

@@ -130,6 +130,18 @@ func NewFromInt32(value int32) Decimal {
 	}
 }
 
+// NewFromUint64 converts an uint64 to Decimal.
+//
+// Example:
+//
+//	NewFromUint64(123).String() // output: "123"
+func NewFromUint64(value uint64) Decimal {
+	return Decimal{
+		value: new(big.Int).SetUint64(value),
+		exp:   0,
+	}
+}
+
 // NewFromBigInt returns a new Decimal from a big.Int, value * 10 ^ exp
 func NewFromBigInt(value *big.Int, exp int32) Decimal {
 	return Decimal{
@@ -1224,14 +1236,33 @@ func (d Decimal) Ln(precision int32) (Decimal, error) {
 }
 
 // NumDigits returns the number of digits of the decimal coefficient (d.Value)
-// Note: Current implementation is extremely slow for large decimals and/or decimals with large fractional part
 func (d Decimal) NumDigits() int {
-	d.ensureInitialized()
-	// Note(mwoss): It can be optimized, unnecessary cast of big.Int to string
-	if d.IsNegative() {
-		return len(d.value.String()) - 1
+	if d.value == nil {
+		return 1
 	}
-	return len(d.value.String())
+
+	if d.value.IsInt64() {
+		i64 := d.value.Int64()
+		// restrict fast path to integers with exact conversion to float64
+		if i64 <= (1<<53) && i64 >= -(1<<53) {
+			if i64 == 0 {
+				return 1
+			}
+			return int(math.Log10(math.Abs(float64(i64)))) + 1
+		}
+	}
+
+	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.

decimal_bench_test.go

@@ -121,6 +121,34 @@ func BenchmarkDecimal_RoundCash_Five(b *testing.B) {
 	}
 }
 
+func numDigits(b *testing.B, want int, val Decimal) {
+	b.Helper()
+	for i := 0; i < b.N; i++ {
+		if have := val.NumDigits(); have != want {
+			b.Fatalf("\nHave: %d\nWant: %d", have, want)
+		}
+	}
+}
+
+func BenchmarkDecimal_NumDigits10(b *testing.B) {
+	numDigits(b, 10, New(3478512345, -3))
+}
+
+func BenchmarkDecimal_NumDigits100(b *testing.B) {
+	s := make([]byte, 102)
+	for i := range s {
+		s[i] = byte('0' + i%10)
+	}
+	s[0] = '-'
+	s[100] = '.'
+	d, err := NewFromString(string(s))
+	if err != nil {
+		b.Log(d)
+		b.Error(err)
+	}
+	numDigits(b, 100, d)
+}
+
 func Benchmark_Cmp(b *testing.B) {
 	decimals := DecimalSlice([]Decimal{})
 	for i := 0; i < 1000000; i++ {
@@ -132,7 +160,7 @@ func Benchmark_Cmp(b *testing.B) {
 	}
 }
 
-func Benchmark_decimal_Decimal_Add_different_precision(b *testing.B) {
+func BenchmarkDecimal_Add_different_precision(b *testing.B) {
 	d1 := NewFromFloat(1000.123)
 	d2 := NewFromFloat(500).Mul(NewFromFloat(0.12))
 
@@ -143,7 +171,7 @@ func Benchmark_decimal_Decimal_Add_different_precision(b *testing.B) {
 	}
 }
 
-func Benchmark_decimal_Decimal_Sub_different_precision(b *testing.B) {
+func BenchmarkDecimal_Sub_different_precision(b *testing.B) {
 	d1 := NewFromFloat(1000.123)
 	d2 := NewFromFloat(500).Mul(NewFromFloat(0.12))
 
@@ -154,7 +182,7 @@ func Benchmark_decimal_Decimal_Sub_different_precision(b *testing.B) {
 	}
 }
 
-func Benchmark_decimal_Decimal_Add_same_precision(b *testing.B) {
+func BenchmarkDecimal_Add_same_precision(b *testing.B) {
 	d1 := NewFromFloat(1000.123)
 	d2 := NewFromFloat(500.123)
 
@@ -165,7 +193,7 @@ func Benchmark_decimal_Decimal_Add_same_precision(b *testing.B) {
 	}
 }
 
-func Benchmark_decimal_Decimal_Sub_same_precision(b *testing.B) {
+func BenchmarkDecimal_Sub_same_precision(b *testing.B) {
 	d1 := NewFromFloat(1000.123)
 	d2 := NewFromFloat(500.123)
 

decimal_test.go

@@ -476,10 +476,11 @@ func TestNewFromFloatWithExponent(t *testing.T) {
 
 func TestNewFromInt(t *testing.T) {
 	tests := map[int64]string{
-		0:                   "0",
-		1:                   "1",
-		323412345:           "323412345",
-		9223372036854775807: "9223372036854775807",
+		0:                    "0",
+		1:                    "1",
+		323412345:            "323412345",
+		9223372036854775807:  "9223372036854775807",
+		-9223372036854775808: "-9223372036854775808",
 	}
 
 	// add negatives
@@ -501,10 +502,11 @@ func TestNewFromInt(t *testing.T) {
 
 func TestNewFromInt32(t *testing.T) {
 	tests := map[int32]string{
-		0:          "0",
-		1:          "1",
-		323412345:  "323412345",
-		2147483647: "2147483647",
+		0:           "0",
+		1:           "1",
+		323412345:   "323412345",
+		2147483647:  "2147483647",
+		-2147483648: "-2147483648",
 	}
 
 	// add negatives
@@ -524,6 +526,25 @@ func TestNewFromInt32(t *testing.T) {
 	}
 }
 
+func TestNewFromUint64(t *testing.T) {
+	tests := map[uint64]string{
+		0:                    "0",
+		1:                    "1",
+		323412345:            "323412345",
+		9223372036854775807:  "9223372036854775807",
+		18446744073709551615: "18446744073709551615",
+	}
+
+	for input, s := range tests {
+		d := NewFromUint64(input)
+		if d.String() != s {
+			t.Errorf("expected %s, got %s (%s, %d)",
+				s, d.String(),
+				d.value.String(), d.exp)
+		}
+	}
+}
+
 func TestNewFromBigIntWithExponent(t *testing.T) {
 	type Inp struct {
 		val *big.Int