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// Copyright (c) 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package edwards25519
import (
"testing"
"testing/quick"
)
func TestScalarAliasing(t *testing.T) {
checkAliasingOneArg := func(f func(v, x *Scalar) *Scalar, v, x Scalar) bool {
x1, v1 := x, x
// Calculate a reference f(x) without aliasing.
if out := f(&v, &x); out != &v || !isReduced(out) {
return false
}
// Test aliasing the argument and the receiver.
if out := f(&v1, &v1); out != &v1 || v1 != v || !isReduced(out) {
return false
}
// Ensure the arguments was not modified.
return x == x1
}
checkAliasingTwoArgs := func(f func(v, x, y *Scalar) *Scalar, v, x, y Scalar) bool {
x1, y1, v1 := x, y, Scalar{}
// Calculate a reference f(x, y) without aliasing.
if out := f(&v, &x, &y); out != &v || !isReduced(out) {
return false
}
// Test aliasing the first argument and the receiver.
v1 = x
if out := f(&v1, &v1, &y); out != &v1 || v1 != v || !isReduced(out) {
return false
}
// Test aliasing the second argument and the receiver.
v1 = y
if out := f(&v1, &x, &v1); out != &v1 || v1 != v || !isReduced(out) {
return false
}
// Calculate a reference f(x, x) without aliasing.
if out := f(&v, &x, &x); out != &v || !isReduced(out) {
return false
}
// Test aliasing the first argument and the receiver.
v1 = x
if out := f(&v1, &v1, &x); out != &v1 || v1 != v || !isReduced(out) {
return false
}
// Test aliasing the second argument and the receiver.
v1 = x
if out := f(&v1, &x, &v1); out != &v1 || v1 != v || !isReduced(out) {
return false
}
// Test aliasing both arguments and the receiver.
v1 = x
if out := f(&v1, &v1, &v1); out != &v1 || v1 != v || !isReduced(out) {
return false
}
// Ensure the arguments were not modified.
return x == x1 && y == y1
}
for name, f := range map[string]any{
"Negate": func(v, x Scalar) bool {
return checkAliasingOneArg((*Scalar).Negate, v, x)
},
"Multiply": func(v, x, y Scalar) bool {
return checkAliasingTwoArgs((*Scalar).Multiply, v, x, y)
},
"Add": func(v, x, y Scalar) bool {
return checkAliasingTwoArgs((*Scalar).Add, v, x, y)
},
"Subtract": func(v, x, y Scalar) bool {
return checkAliasingTwoArgs((*Scalar).Subtract, v, x, y)
},
} {
err := quick.Check(f, &quick.Config{MaxCountScale: 1 << 5})
if err != nil {
t.Errorf("%v: %v", name, err)
}
}
}
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