feat(math): adding Dec.SdkIntTrim (#988)

* feat(math): adding Dec.SdkIntTrim

* adding string benchmark

* Update types/math/dec_bench_test.go

Co-authored-by: Ryan Christoffersen <12519942+ryanchristo@users.noreply.github.com>

Co-authored-by: Ryan Christoffersen <12519942+ryanchristo@users.noreply.github.com>

types/math/dec.go

@@ -5,6 +5,7 @@ import (
 	"math/big"
 
 	"github.com/cockroachdb/apd/v2"
+	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/types/errors"
 )
 
@@ -205,6 +206,27 @@ func (x Dec) BigInt() (*big.Int, error) {
 	return z, nil
 }
 
+// SdkIntTrim rounds decimal number to the integer towards zero and converts it to `sdk.Int`.
+// Panics if x is bigger the SDK Int max value
+func (x Dec) SdkIntTrim() sdk.Int {
+	y, _ := x.Reduce()
+	var r = y.dec.Coeff
+	if y.dec.Exponent != 0 {
+		decs := big.NewInt(10)
+		if y.dec.Exponent > 0 {
+			decs.Exp(decs, big.NewInt(int64(y.dec.Exponent)), nil)
+			r.Mul(&y.dec.Coeff, decs)
+		} else {
+			decs.Exp(decs, big.NewInt(int64(-y.dec.Exponent)), nil)
+			r.Quo(&y.dec.Coeff, decs)
+		}
+	}
+	if x.dec.Negative {
+		r.Neg(&r)
+	}
+	return sdk.NewIntFromBigInt(&r)
+}
+
 func (x Dec) String() string {
 	return x.dec.Text('f')
 }

types/math/dec_bench_test.go

@@ -0,0 +1,61 @@
+package math
+
+import (
+	"testing"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+func BenchmarkSdkIntTrim(b *testing.B) {
+	s := "12345678901234567890.12345678901234567890"
+	d, err := NewDecFromString(s)
+	if err != nil {
+		b.Error("can't convert test number")
+	}
+
+	b.Run("exp", func(b *testing.B) {
+		for n := 0; n < b.N; n++ {
+			d.SdkIntTrim()
+		}
+	})
+
+	b.Run("quo-integer", func(b *testing.B) {
+		for n := 0; n < b.N; n++ {
+			sdkIntTrimQuo(d)
+		}
+	})
+
+	b.Run("string", func(b *testing.B) {
+		for n := 0; n < b.N; n++ {
+			sdkIntTrimNaive(d)
+		}
+	})
+
+}
+
+func sdkIntTrimQuo(d Dec) sdk.Int {
+	d, err := d.QuoInteger(NewDecFromInt64(1))
+	if err != nil {
+		panic(err)
+	}
+
+	i, err := d.BigInt()
+	if err != nil {
+		panic(err)
+	}
+	return sdk.NewIntFromBigInt(i)
+}
+
+func sdkIntTrimNaive(d Dec) sdk.Int {
+	d, err := d.QuoInteger(NewDecFromInt64(1))
+	if err != nil {
+		panic(err)
+	}
+
+	s := d.String()
+	i, ok := sdk.NewIntFromString(s)
+	if !ok {
+		panic("can't convert from string")
+	}
+	return i
+}

types/math/dec_test.go

@@ -644,27 +644,51 @@ func TestQuoExactBad(t *testing.T) {
 }
 
 func TestToBigInt(t *testing.T) {
-	intStr := "1000000000000000000000000000000000000123456789"
-	a, err := NewDecFromString(intStr)
-	require.NoError(t, err)
-	b, err := a.BigInt()
-	require.Equal(t, intStr, b.String())
-
-	intStrWithTrailingZeros := "1000000000000000000000000000000000000123456789.00000000"
-	a, err = NewDecFromString(intStrWithTrailingZeros)
-	require.NoError(t, err)
-	b, err = a.BigInt()
-	require.Equal(t, intStr, b.String())
-
-	intStr2 := "123.456e6"
-	a, err = NewDecFromString(intStr2)
-	require.NoError(t, err)
-	b, err = a.BigInt()
-	require.Equal(t, "123456000", b.String())
+	i1 := "1000000000000000000000000000000000000123456789"
+	tcs := []struct {
+		intStr  string
+		out     string
+		isError error
+	}{
+		{i1, i1, nil},
+		{"1000000000000000000000000000000000000123456789.00000000", i1, nil},
+		{"123.456e6", "123456000", nil},
+		{"12345.6", "", ErrNonIntegeral},
+	}
+	for idx, tc := range tcs {
+		a, err := NewDecFromString(tc.intStr)
+		require.NoError(t, err)
+		b, err := a.BigInt()
+		if tc.isError == nil {
+			require.NoError(t, err, "test_%d", idx)
+			require.Equal(t, tc.out, b.String(), "test_%d", idx)
+		} else {
+			require.ErrorIs(t, err, tc.isError, "test_%d", idx)
+		}
+	}
+}
 
-	intStr3 := "12345.6"
-	a, err = NewDecFromString(intStr3)
-	require.NoError(t, err)
-	_, err = a.BigInt()
-	require.ErrorIs(t, err, ErrNonIntegeral)
+func TestToSdkInt(t *testing.T) {
+	i1 := "1000000000000000000000000000000000000123456789"
+	tcs := []struct {
+		intStr string
+		out    string
+	}{
+		{i1, i1},
+		{"1000000000000000000000000000000000000123456789.00000000", i1},
+		{"123.456e6", "123456000"},
+		{"123.456e1", "1234"},
+		{"123.456", "123"},
+		{"123.956", "123"},
+		{"-123.456", "-123"},
+		{"-123.956", "-123"},
+		{"-0.956", "0"},
+		{"-0.9", "0"},
+	}
+	for idx, tc := range tcs {
+		a, err := NewDecFromString(tc.intStr)
+		require.NoError(t, err)
+		b := a.SdkIntTrim()
+		require.Equal(t, tc.out, b.String(), "test_%d", idx)
+	}
 }