unix: merge implementation for ReadDirent

Provide common implementation for ReadDirent based on Getdents for
aix, *bsd and linux.

Add Getdents on aix as a wrapper around getdirent.

Keep the implementation for ReadDirent based on Getdirentries for
darwin and dragonfly.

Change-Id: I09094156a1452118ba48af4f14dfe44b1ab745d3
Reviewed-on: https://go-review.googlesource.com/c/sys/+/182321
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>

unix/dirent_test.go

@@ -0,0 +1,150 @@
+// 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 aix darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package unix_test
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"runtime"
+	"sort"
+	"strconv"
+	"strings"
+	"testing"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+func TestDirent(t *testing.T) {
+	const (
+		direntBufSize   = 2048
+		filenameMinSize = 11
+	)
+
+	d, err := ioutil.TempDir("", "dirent-test")
+	if err != nil {
+		t.Fatalf("tempdir: %v", err)
+	}
+	defer os.RemoveAll(d)
+	t.Logf("tmpdir: %s", d)
+
+	for i, c := range []byte("0123456789") {
+		name := string(bytes.Repeat([]byte{c}, filenameMinSize+i))
+		err = ioutil.WriteFile(filepath.Join(d, name), nil, 0644)
+		if err != nil {
+			t.Fatalf("writefile: %v", err)
+		}
+	}
+
+	buf := bytes.Repeat([]byte("DEADBEAF"), direntBufSize/8)
+	fd, err := unix.Open(d, unix.O_RDONLY, 0)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	defer unix.Close(fd)
+	n, err := unix.ReadDirent(fd, buf)
+	if err != nil {
+		t.Fatalf("ReadDirent: %v", err)
+	}
+	buf = buf[:n]
+
+	names := make([]string, 0, 10)
+	for len(buf) > 0 {
+		var bc int
+		bc, _, names = unix.ParseDirent(buf, -1, names)
+		if bc == 0 && len(buf) > 0 {
+			t.Fatal("no progress")
+		}
+		buf = buf[bc:]
+	}
+
+	sort.Strings(names)
+	t.Logf("names: %q", names)
+
+	if len(names) != 10 {
+		t.Errorf("got %d names; expected 10", len(names))
+	}
+	for i, name := range names {
+		ord, err := strconv.Atoi(name[:1])
+		if err != nil {
+			t.Fatalf("names[%d] is non-integer %q: %v", i, names[i], err)
+		}
+		if expected := string(strings.Repeat(name[:1], filenameMinSize+ord)); name != expected {
+			t.Errorf("names[%d] is %q (len %d); expected %q (len %d)", i, name, len(name), expected, len(expected))
+		}
+	}
+}
+
+func TestDirentRepeat(t *testing.T) {
+	const N = 100
+	// Note: the size of the buffer is small enough that the loop
+	// below will need to execute multiple times. See issue #31368.
+	size := N * unsafe.Offsetof(unix.Dirent{}.Name) / 4
+	if runtime.GOOS == "freebsd" || runtime.GOOS == "netbsd" {
+		if size < 1024 {
+			size = 1024 // DIRBLKSIZ, see issue 31403.
+		}
+		if runtime.GOOS == "freebsd" {
+			t.Skip("need to fix issue 31416 first")
+		}
+	}
+
+	// Make a directory containing N files
+	d, err := ioutil.TempDir("", "direntRepeat-test")
+	if err != nil {
+		t.Fatalf("tempdir: %v", err)
+	}
+	defer os.RemoveAll(d)
+
+	var files []string
+	for i := 0; i < N; i++ {
+		files = append(files, fmt.Sprintf("file%d", i))
+	}
+	for _, file := range files {
+		err = ioutil.WriteFile(filepath.Join(d, file), []byte("contents"), 0644)
+		if err != nil {
+			t.Fatalf("writefile: %v", err)
+		}
+	}
+
+	// Read the directory entries using ReadDirent.
+	fd, err := unix.Open(d, unix.O_RDONLY, 0)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	defer unix.Close(fd)
+	var files2 []string
+	for {
+		buf := make([]byte, size)
+		n, err := unix.ReadDirent(fd, buf)
+		if err != nil {
+			t.Fatalf("ReadDirent: %v", err)
+		}
+		if n == 0 {
+			break
+		}
+		buf = buf[:n]
+		for len(buf) > 0 {
+			var consumed int
+			consumed, _, files2 = unix.ParseDirent(buf, -1, files2)
+			if consumed == 0 && len(buf) > 0 {
+				t.Fatal("no progress")
+			}
+			buf = buf[consumed:]
+		}
+	}
+
+	// Check results
+	sort.Strings(files)
+	sort.Strings(files2)
+	if strings.Join(files, "|") != strings.Join(files2, "|") {
+		t.Errorf("bad file list: want\n%q\ngot\n%q", files, files2)
+	}
+}