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Add DivMod() #113

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merged 1 commit into from
Mar 25, 2022
Merged

Add DivMod() #113

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16 changes: 14 additions & 2 deletions uint256.go
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Original file line number Diff line number Diff line change
Expand Up @@ -588,8 +588,20 @@ func (z *Int) Mod(x, y *Int) *Int {
}

var quot Int
rem := udivrem(quot[:], x[:], y)
return z.Set(&rem)
*z = udivrem(quot[:], x[:], y)
return z
}

// DivMod sets z to the quotient x div y and m to the modulus x mod y and returns the pair (z, m) for y != 0.
// If y == 0, both z and m are set to 0 (OBS: differs from the big.Int)
func (z *Int) DivMod(x, y, m *Int) (*Int, *Int) {
if y.IsZero() {
return z.Clear(), m.Clear()
}
var quot Int
*m = udivrem(quot[:], x[:], y)
*z = quot
return z, m
}

// SMod interprets x and y as two's complement signed integers,
Expand Down
17 changes: 17 additions & 0 deletions uint256_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -260,6 +260,8 @@ func TestRandomBinOp(t *testing.T) {
t.Run("Mod", func(t *testing.T) { testRandomOp(t, (*Int).Mod, bigMod) })
t.Run("SDiv", func(t *testing.T) { testRandomOp(t, (*Int).SDiv, bigSDiv) })
t.Run("SMod", func(t *testing.T) { testRandomOp(t, (*Int).SMod, bigSMod) })
t.Run("DivMod/Div", func(t *testing.T) { testRandomOp(t, divModDiv, bigDiv) })
t.Run("DivMod/Mod", func(t *testing.T) { testRandomOp(t, divModMod, bigMod) })
t.Run("udivrem/Div", func(t *testing.T) { testRandomOp(t, udivremDiv, bigDiv) })
t.Run("udivrem/Mod", func(t *testing.T) { testRandomOp(t, udivremMod, bigMod) })
}
Expand Down Expand Up @@ -298,6 +300,19 @@ func TestRandomSquare(t *testing.T) {
)
}

// divModDiv wraps DivMod and returns quotient only
func divModDiv(z, x, y *Int) *Int {
var m Int
z.DivMod(x, y, &m)
return z
}

// divModMod wraps DivMod and returns modulus only
func divModMod(z, x, y *Int) *Int {
new(Int).DivMod(x, y, z)
return z
}

// udivremDiv wraps udivrem and returns quotient
func udivremDiv(z, x, y *Int) *Int {
var quot Int
Expand Down Expand Up @@ -1243,6 +1258,8 @@ func TestBinOp(t *testing.T) {
t.Run("Mod", func(t *testing.T) { proc(t, (*Int).Mod, bigMod) })
t.Run("SDiv", func(t *testing.T) { proc(t, (*Int).SDiv, bigSDiv) })
t.Run("SMod", func(t *testing.T) { proc(t, (*Int).SMod, bigSMod) })
t.Run("DivMod/Div", func(t *testing.T) { proc(t, divModDiv, bigDiv) })
t.Run("DivMod/Mod", func(t *testing.T) { proc(t, divModMod, bigMod) })
t.Run("udivrem/Div", func(t *testing.T) { proc(t, udivremDiv, bigDiv) })
t.Run("udivrem/Mod", func(t *testing.T) { proc(t, udivremMod, bigMod) })
t.Run("Exp", func(t *testing.T) { proc(t, (*Int).Exp, bigExp) })
Expand Down