Merge c31da0254a into 645a76e5b0

* Drop support for Go versions older than 1.10
* Remove 1.18 from test suite

.github/workflows/ci.yml

@@ -1,11 +1,15 @@
 name: ci
-on: [push]
+on:
+  push:
+    branches:
+      - master
+  pull_request:
 jobs:
   ci-job:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: [ '1.7.x', '1.18', '1.19', '1.20', '1.21', '1.x' ]
+        go: [ '1.10.x', '1.19', '1.20', '1.21', '1.22', '1.x' ]
     name: Go ${{ matrix.go }}
     steps:
       - uses: actions/checkout@v4

README.md

@@ -22,7 +22,7 @@ Run `go get github.com/shopspring/decimal`
 
 ## Requirements 
 
-Decimal library requires Go version `>=1.7`
+Decimal library requires Go version `>=1.10`
 
 ## Usage
 

decimal.go

@@ -1224,14 +1224,33 @@ 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.
@@ -1387,9 +1406,7 @@ func (d Decimal) IntPart() int64 {
 // BigInt returns integer component of the decimal as a BigInt.
 func (d Decimal) BigInt() *big.Int {
 	scaledD := d.rescale(0)
-	i := &big.Int{}
-	i.SetString(scaledD.String(), 10)
-	return i
+	return scaledD.value
 }
 
 // BigFloat returns decimal as BigFloat.
@@ -1443,6 +1460,73 @@ func (d Decimal) String() string {
 	return d.string(true)
 }
 
+// Format formats a decimal.
+// thousandsSeparator can be empty, in which case the integer value will be displayed without separation.
+// if decimalSeparator is empty and the value is a decimal this will panic.
+func (d Decimal) Format(thousandsSeparator string, decimalSeparator string, trimTrailingZeros bool) string {
+	if d.exp >= 0 {
+		d = d.rescale(0)
+	}
+
+	abs := new(big.Int).Abs(d.value)
+	str := abs.String()
+
+	var intPart, fractionalPart string
+
+	// NOTE(vadim): this cast to int will cause bugs if d.exp == INT_MIN
+	// and you are on a 32-bit machine. Won't fix this super-edge case.
+	dExpInt := int(d.exp)
+	if len(str) > -dExpInt {
+		intPart = str[:len(str)+dExpInt]
+		fractionalPart = str[len(str)+dExpInt:]
+	} else {
+		intPart = "0"
+
+		num0s := -dExpInt - len(str)
+		fractionalPart = strings.Repeat("0", num0s) + str
+	}
+
+	if thousandsSeparator != "" {
+		parts := 1 + (len(intPart)-1)/3
+		if parts > 1 {
+			intParts := make([]string, 1+(len(intPart)-1)/3)
+			offset := len(intPart) - (len(intParts)-1)*3
+			for i := 0; i < len(intParts); i++ {
+				if i == 0 {
+					intParts[i] = intPart[0:offset]
+				} else {
+					intParts[i] = intPart[(i-1)*3+offset : i*3+offset]
+				}
+			}
+			intPart = strings.Join(intParts, thousandsSeparator)
+		}
+	}
+
+	if trimTrailingZeros {
+		i := len(fractionalPart) - 1
+		for ; i >= 0; i-- {
+			if fractionalPart[i] != '0' {
+				break
+			}
+		}
+		fractionalPart = fractionalPart[:i+1]
+	}
+	if fractionalPart != "" && decimalSeparator == "" {
+		panic("no decimal separator for non-integer")
+	}
+
+	number := intPart
+	if len(fractionalPart) > 0 {
+		number += decimalSeparator + fractionalPart
+	}
+
+	if d.value.Sign() < 0 {
+		return "-" + number
+	}
+
+	return number
+}
+
 // StringFixed returns a rounded fixed-point string with places digits after
 // the decimal point.
 //
@@ -1872,48 +1956,7 @@ func (d Decimal) StringScaled(exp int32) string {
 }
 
 func (d Decimal) string(trimTrailingZeros bool) string {
-	if d.exp >= 0 {
-		return d.rescale(0).value.String()
-	}
-
-	abs := new(big.Int).Abs(d.value)
-	str := abs.String()
-
-	var intPart, fractionalPart string
-
-	// NOTE(vadim): this cast to int will cause bugs if d.exp == INT_MIN
-	// and you are on a 32-bit machine. Won't fix this super-edge case.
-	dExpInt := int(d.exp)
-	if len(str) > -dExpInt {
-		intPart = str[:len(str)+dExpInt]
-		fractionalPart = str[len(str)+dExpInt:]
-	} else {
-		intPart = "0"
-
-		num0s := -dExpInt - len(str)
-		fractionalPart = strings.Repeat("0", num0s) + str
-	}
-
-	if trimTrailingZeros {
-		i := len(fractionalPart) - 1
-		for ; i >= 0; i-- {
-			if fractionalPart[i] != '0' {
-				break
-			}
-		}
-		fractionalPart = fractionalPart[:i+1]
-	}
-
-	number := intPart
-	if len(fractionalPart) > 0 {
-		number += "." + fractionalPart
-	}
-
-	if d.value.Sign() < 0 {
-		return "-" + number
-	}
-
-	return number
+	return d.Format("", ".", trimTrailingZeros)
 }
 
 func (d *Decimal) ensureInitialized() {

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

@@ -1513,6 +1513,47 @@ func TestDecimal_RoundDownAndStringFixed(t *testing.T) {
 	}
 }
 
+func TestDecimal_Format(t *testing.T) {
+	type testData struct {
+		input              string
+		thousandsSeparator string
+		decimalSeparator   string
+		trimTrailingZeros  bool
+		expected           string
+	}
+	tests := []testData{
+		{"0", ",", ".", false, "0"},
+		{"0", ",", ".", true, "0"},
+		{"999", ",", ".", true, "999"},
+		{"1000", ",", ".", true, "1,000"},
+		{"123", ",", ".", true, "123"},
+		{"1234", ",", ".", true, "1,234"},
+		{"12345.67", "", ".", true, "12345.67"},
+		{"12345.00", ",", ".", true, "12,345"},
+		{"12345.00", ",", ".", false, "12,345.00"},
+		{"123456.00", ",", ".", false, "123,456.00"},
+		{"1234567.00", ",", ".", false, "1,234,567.00"},
+		{"1234567.00", ".", ",", false, "1.234.567,00"},
+		{"1234567.00", "_", ".", true, "1_234_567"},
+		{"-12.00", "_", ".", true, "-12"},
+		{"-123.00", "_", ".", true, "-123"},
+		{"-1234.00", "_", ".", true, "-1_234"},
+	}
+
+	for _, test := range tests {
+		d, err := NewFromString(test.input)
+		if err != nil {
+			panic(err)
+		}
+
+		got := d.Format(test.thousandsSeparator, test.decimalSeparator, test.trimTrailingZeros)
+		if got != test.expected {
+			t.Errorf("Format %s got %s, expected %s",
+				d, got, test.expected)
+		}
+	}
+}
+
 func TestDecimal_BankRoundAndStringFixed(t *testing.T) {
 	type testData struct {
 		input         string

go.mod

@@ -1,3 +1,3 @@
 module github.com/shopspring/decimal
 
-go 1.7
+go 1.10