unix: add test for Getdirentries

Copied and adapted from the respective test in std syscall.

Change-Id: Ia35864e201c8b628dfc21a8da79305d5741d4acc
Reviewed-on: https://go-review.googlesource.com/c/sys/+/183219
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Yuval Pavel Zholkover <paulzhol@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

unix/getdirentries_test.go

@@ -0,0 +1,86 @@
+// Copyright 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.
+
+// +build darwin dragonfly
+
+package unix_test
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"testing"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+func TestGetdirentries(t *testing.T) {
+	for _, count := range []int{10, 1000} {
+		t.Run(fmt.Sprintf("n=%d", count), func(t *testing.T) {
+			testGetdirentries(t, count)
+		})
+	}
+}
+func testGetdirentries(t *testing.T, count int) {
+	if count > 100 && testing.Short() && os.Getenv("GO_BUILDER_NAME") == "" {
+		t.Skip("skipping in -short mode")
+	}
+	d, err := ioutil.TempDir("", "getdirentries-test")
+	if err != nil {
+		t.Fatalf("Tempdir: %v", err)
+	}
+	defer os.RemoveAll(d)
+	var names []string
+	for i := 0; i < count; i++ {
+		names = append(names, fmt.Sprintf("file%03d", i))
+	}
+
+	// Make files in the temp directory
+	for _, name := range names {
+		err := ioutil.WriteFile(filepath.Join(d, name), []byte("data"), 0)
+		if err != nil {
+			t.Fatalf("WriteFile: %v", err)
+		}
+	}
+
+	// Read files using Getdirentries
+	var names2 []string
+	fd, err := unix.Open(d, unix.O_RDONLY, 0)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	defer unix.Close(fd)
+	var base uintptr
+	var buf [2048]byte
+	for {
+		n, err := unix.Getdirentries(fd, buf[:], &base)
+		if err != nil {
+			t.Fatalf("Getdirentries: %v", err)
+		}
+		if n == 0 {
+			break
+		}
+		data := buf[:n]
+		for len(data) > 0 {
+			dirent := (*unix.Dirent)(unsafe.Pointer(&data[0]))
+			data = data[dirent.Reclen:]
+			name := make([]byte, dirent.Namlen)
+			for i := 0; i < int(dirent.Namlen); i++ {
+				name[i] = byte(dirent.Name[i])
+			}
+			names2 = append(names2, string(name))
+		}
+	}
+
+	names = append(names, ".", "..") // Getdirentries returns these also
+	sort.Strings(names)
+	sort.Strings(names2)
+	if strings.Join(names, ":") != strings.Join(names2, ":") {
+		t.Errorf("names don't match\n names: %q\nnames2: %q", names, names2)
+	}
+}