1 files changed, 99 insertions, 0 deletions
diff --git a/src/cmd/link/internal/ld/outbuf_test.go b/src/cmd/link/internal/ld/outbuf_test.go
new file mode 100644
index 0000000..e6643da
--- /dev/null
+++ b/src/cmd/link/internal/ld/outbuf_test.go
@@ -0,0 +1,99 @@
+// Copyright 2020 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 ld
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+)
+
+// TestMMap ensures that we can actually mmap on every supported platform.
+func TestMMap(t *testing.T) {
+	switch runtime.GOOS {
+	default:
+		t.Skip("unsupported OS")
+	case "aix", "darwin", "ios", "dragonfly", "freebsd", "linux", "netbsd", "openbsd", "windows":
+	}
+	dir, err := ioutil.TempDir("", "TestMMap")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+	filename := filepath.Join(dir, "foo.out")
+	ob := NewOutBuf(nil)
+	if err := ob.Open(filename); err != nil {
+		t.Fatalf("error opening file: %v", err)
+	}
+	defer ob.Close()
+	if err := ob.Mmap(1 << 20); err != nil {
+		t.Errorf("error mmapping file %v", err)
+	}
+	if !ob.isMmapped() {
+		t.Errorf("should be mmapped")
+	}
+}
+
+// TestWriteLoc ensures that the math surrounding writeLoc is correct.
+func TestWriteLoc(t *testing.T) {
+	tests := []struct {
+		bufLen          int
+		off             int64
+		heapLen         int
+		lenToWrite      int64
+		expectedHeapLen int
+		writePos        int64
+		addressInHeap   bool
+	}{
+		{100, 0, 0, 100, 0, 0, false},
+		{100, 100, 0, 100, 100, 0, true},
+		{10, 10, 0, 100, 100, 0, true},
+		{10, 20, 10, 100, 110, 10, true},
+		{0, 0, 0, 100, 100, 0, true},
+	}
+
+	for i, test := range tests {
+		ob := &OutBuf{
+			buf:  make([]byte, test.bufLen),
+			off:  test.off,
+			heap: make([]byte, test.heapLen),
+		}
+		pos, buf := ob.writeLoc(test.lenToWrite)
+		if pos != test.writePos {
+			t.Errorf("[%d] position = %d, expected %d", i, pos, test.writePos)
+		}
+		message := "mmapped area"
+		expected := ob.buf
+		if test.addressInHeap {
+			message = "heap"
+			expected = ob.heap
+		}
+		if &buf[0] != &expected[0] {
+			t.Errorf("[%d] expected position to be %q", i, message)
+		}
+		if len(ob.heap) != test.expectedHeapLen {
+			t.Errorf("[%d] expected len(ob.heap) == %d, got %d", i, test.expectedHeapLen, len(ob.heap))
+		}
+	}
+}
+
+func TestIsMmapped(t *testing.T) {
+	tests := []struct {
+		length   int
+		expected bool
+	}{
+		{0, false},
+		{1, true},
+	}
+	for i, test := range tests {
+		ob := &OutBuf{buf: make([]byte, test.length)}
+		if v := ob.isMmapped(); v != test.expected {
+
+			t.Errorf("[%d] isMmapped == %t, expected %t", i, v, test.expected)
+		}
+	}
+}