1 files changed, 126 insertions, 0 deletions
diff --git a/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/rand/arith128_test.go b/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/rand/arith128_test.go
new file mode 100644
index 0000000..eed655b
--- /dev/null
+++ b/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/rand/arith128_test.go
@@ -0,0 +1,126 @@
+// Copyright 2017 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 rand
+
+import (
+	"math/big"
+	"math/rand"
+	"testing"
+)
+
+var bigMaxUint64 = big.NewInt(0).SetUint64(maxUint64)
+
+func bigInt(xHi, xLo uint64) *big.Int {
+	b := big.NewInt(0).SetUint64(xHi)
+	b.Lsh(b, 64)
+	b.Or(b, big.NewInt(0).SetUint64(xLo))
+	return b
+}
+
+func splitBigInt(b *big.Int) (outHi, outLo uint64) {
+	outHi = big.NewInt(0).Rsh(b, 64).Uint64()
+	outLo = big.NewInt(0).And(b, bigMaxUint64).Uint64()
+	return
+}
+
+func bigMulMod128bits(xHi, xLo, yHi, yLo uint64) (outHi, outLo uint64) {
+	bigX := bigInt(xHi, xLo)
+	bigY := bigInt(yHi, yLo)
+	return splitBigInt(bigX.Mul(bigX, bigY))
+}
+
+func bigAddMod128bits(xHi, xLo, yHi, yLo uint64) (outHi, outLo uint64) {
+	bigX := bigInt(xHi, xLo)
+	bigY := bigInt(yHi, yLo)
+	return splitBigInt(bigX.Add(bigX, bigY))
+}
+
+type arithTest struct {
+	xHi, xLo uint64
+}
+
+const (
+	iLo = increment & maxUint64
+	iHi = (increment >> 64) & maxUint64
+)
+
+var arithTests = []arithTest{
+	{0, 0},
+	{0, 1},
+	{1, 0},
+	{0, maxUint64},
+	{maxUint64, 0},
+	{maxUint64, maxUint64},
+	// Randomly generated 64-bit integers.
+	{3757956613005209672, 17983933746665545631},
+	{511324141977587414, 5626651684620191081},
+	{1534313104606153588, 2415006486399353367},
+	{6873586429837825902, 13854394671140464137},
+	{6617134480561088940, 18421520694158684312},
+}
+
+func TestPCGAdd(t *testing.T) {
+	for i, test := range arithTests {
+		p := &PCGSource{
+			low:  test.xLo,
+			high: test.xHi,
+		}
+		p.add()
+		expectHi, expectLo := bigAddMod128bits(test.xHi, test.xLo, iHi, iLo)
+		if p.low != expectLo || p.high != expectHi {
+			t.Errorf("%d: got hi=%d lo=%d; expect hi=%d lo=%d", i, p.high, p.low, expectHi, expectLo)
+		}
+	}
+}
+
+const (
+	mLo = multiplier & maxUint64
+	mHi = (multiplier >> 64) & maxUint64
+)
+
+func TestPCGMultiply(t *testing.T) {
+	for i, test := range arithTests {
+		p := &PCGSource{
+			low:  test.xLo,
+			high: test.xHi,
+		}
+		p.multiply()
+		expectHi, expectLo := bigMulMod128bits(test.xHi, test.xLo, mHi, mLo)
+		if p.low != expectLo || p.high != expectHi {
+			t.Errorf("%d: got hi=%d lo=%d; expect hi=%d lo=%d", i, p.high, p.low, expectHi, expectLo)
+		}
+	}
+}
+
+func TestPCGMultiplyLong(t *testing.T) {
+	if testing.Short() {
+		return
+	}
+	for i := 0; i < 1e6; i++ {
+		low := rand.Uint64()
+		high := rand.Uint64()
+		p := &PCGSource{
+			low:  low,
+			high: high,
+		}
+		p.multiply()
+		expectHi, expectLo := bigMulMod128bits(high, low, mHi, mLo)
+		if p.low != expectLo || p.high != expectHi {
+			t.Fatalf("%d: (%d,%d): got hi=%d lo=%d; expect hi=%d lo=%d", i, high, low, p.high, p.low, expectHi, expectLo)
+		}
+	}
+}
+
+func BenchmarkPCGMultiply(b *testing.B) {
+	low := rand.Uint64()
+	high := rand.Uint64()
+	p := &PCGSource{
+		low:  low,
+		high: high,
+	}
+	for i := 0; i < b.N; i++ {
+		p.multiply()
+	}
+}