1 files changed, 97 insertions, 0 deletions
diff --git a/src/runtime/rand_test.go b/src/runtime/rand_test.go
new file mode 100644
index 0000000..baecb69
--- /dev/null
+++ b/src/runtime/rand_test.go
@@ -0,0 +1,97 @@
+// 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 runtime_test
+
+import (
+	. "runtime"
+	"strconv"
+	"testing"
+	_ "unsafe" // for go:linkname
+)
+
+func TestReadRandom(t *testing.T) {
+	if *ReadRandomFailed {
+		switch GOOS {
+		default:
+			t.Fatalf("readRandom failed at startup")
+		case "plan9":
+			// ok
+		}
+	}
+}
+
+func BenchmarkFastrand(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Fastrand()
+		}
+	})
+}
+
+func BenchmarkFastrand64(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Fastrand64()
+		}
+	})
+}
+
+func BenchmarkFastrandHashiter(b *testing.B) {
+	var m = make(map[int]int, 10)
+	for i := 0; i < 10; i++ {
+		m[i] = i
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			for range m {
+				break
+			}
+		}
+	})
+}
+
+var sink32 uint32
+
+func BenchmarkFastrandn(b *testing.B) {
+	for n := uint32(2); n <= 5; n++ {
+		b.Run(strconv.Itoa(int(n)), func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				sink32 = Fastrandn(n)
+			}
+		})
+	}
+}
+
+//go:linkname fastrand runtime.fastrand
+func fastrand() uint32
+
+//go:linkname fastrandn runtime.fastrandn
+func fastrandn(uint32) uint32
+
+//go:linkname fastrand64 runtime.fastrand64
+func fastrand64() uint64
+
+func TestLegacyFastrand(t *testing.T) {
+	// Testing mainly that the calls work at all,
+	// but check that all three don't return the same number (1 in 2^64 chance)
+	{
+		x, y, z := fastrand(), fastrand(), fastrand()
+		if x == y && y == z {
+			t.Fatalf("fastrand three times = %#x, %#x, %#x, want different numbers", x, y, z)
+		}
+	}
+	{
+		x, y, z := fastrandn(1e9), fastrandn(1e9), fastrandn(1e9)
+		if x == y && y == z {
+			t.Fatalf("fastrandn three times = %#x, %#x, %#x, want different numbers", x, y, z)
+		}
+	}
+	{
+		x, y, z := fastrand64(), fastrand64(), fastrand64()
+		if x == y && y == z {
+			t.Fatalf("fastrand64 three times = %#x, %#x, %#x, want different numbers", x, y, z)
+		}
+	}
+}