Distr-PR-2 Truncate Decimal Functionality (#2379)

PENDING.md

@@ -129,6 +129,7 @@ IMPROVEMENTS
     * [simulation] Logs get written to file if large, and also get printed on panics \#2285
     * [gaiad] \#1992 Add optional flag to `gaiad testnet` to make config directory of daemon (default `gaiad`) and cli (default `gaiacli`) configurable
     * [x/stake] Add stake `Queriers` for Gaia-lite endpoints. This increases the staking endpoints performance by reusing the staking `keeper` logic for queries. [#2249](https://github.com/cosmos/cosmos-sdk/pull/2149)
+    * [types/decimal] \#2378 - Added truncate functionality to decimal
 
 * Tendermint
 

types/decimal.go

@@ -325,6 +325,32 @@ func (d Dec) RoundInt() Int {
 
 //___________________________________________________________________________________
 
+// similar to chopPrecisionAndRound, but always rounds down
+func chopPrecisionAndTruncate(d *big.Int) *big.Int {
+	return d.Quo(d, precisionReuse)
+}
+
+func chopPrecisionAndTruncateNonMutative(d *big.Int) *big.Int {
+	tmp := new(big.Int).Set(d)
+	return chopPrecisionAndTruncate(tmp)
+}
+
+// TruncateInt64 truncates the decimals from the number and returns an int64
+func (d Dec) TruncateInt64() int64 {
+	chopped := chopPrecisionAndTruncateNonMutative(d.Int)
+	if !chopped.IsInt64() {
+		panic("Int64() out of bound")
+	}
+	return chopped.Int64()
+}
+
+// TruncateInt truncates the decimals from the number and returns an Int
+func (d Dec) TruncateInt() Int {
+	return NewIntFromBigInt(chopPrecisionAndTruncateNonMutative(d.Int))
+}
+
+//___________________________________________________________________________________
+
 // reuse nil values
 var (
 	nilAmino string

types/decimal_test.go

@@ -202,6 +202,32 @@ func TestBankerRoundChop(t *testing.T) {
 	}
 }
 
+func TestTruncate(t *testing.T) {
+	tests := []struct {
+		d1  Dec
+		exp int64
+	}{
+		{mustNewDecFromStr(t, "0"), 0},
+		{mustNewDecFromStr(t, "0.25"), 0},
+		{mustNewDecFromStr(t, "0.75"), 0},
+		{mustNewDecFromStr(t, "1"), 1},
+		{mustNewDecFromStr(t, "1.5"), 1},
+		{mustNewDecFromStr(t, "7.5"), 7},
+		{mustNewDecFromStr(t, "7.6"), 7},
+		{mustNewDecFromStr(t, "7.4"), 7},
+		{mustNewDecFromStr(t, "100.1"), 100},
+		{mustNewDecFromStr(t, "1000.1"), 1000},
+	}
+
+	for tcIndex, tc := range tests {
+		resNeg := tc.d1.Neg().TruncateInt64()
+		require.Equal(t, -1*tc.exp, resNeg, "negative tc %d", tcIndex)
+
+		resPos := tc.d1.TruncateInt64()
+		require.Equal(t, tc.exp, resPos, "positive tc %d", tcIndex)
+	}
+}
+
 func TestToLeftPadded(t *testing.T) {
 	tests := []struct {
 		dec    Dec