dirent_test.go

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build unix
     6  
     7  package syscall_test
     8  
     9  import (
    10  	"bytes"
    11  	"fmt"
    12  	"os"
    13  	"path/filepath"
    14  	"runtime"
    15  	"sort"
    16  	"strconv"
    17  	"strings"
    18  	"syscall"
    19  	"testing"
    20  	"unsafe"
    21  )
    22  
    23  func TestDirent(t *testing.T) {
    24  	const (
    25  		direntBufSize   = 2048 // arbitrary? See https://go.dev/issue/37323.
    26  		filenameMinSize = 11
    27  	)
    28  
    29  	d := t.TempDir()
    30  	t.Logf("tmpdir: %s", d)
    31  
    32  	for i, c := range []byte("0123456789") {
    33  		name := string(bytes.Repeat([]byte{c}, filenameMinSize+i))
    34  		err := os.WriteFile(filepath.Join(d, name), nil, 0644)
    35  		if err != nil {
    36  			t.Fatalf("writefile: %v", err)
    37  		}
    38  	}
    39  
    40  	names := make([]string, 0, 10)
    41  
    42  	fd, err := syscall.Open(d, syscall.O_RDONLY, 0)
    43  	if err != nil {
    44  		t.Fatalf("syscall.open: %v", err)
    45  	}
    46  	defer syscall.Close(fd)
    47  
    48  	buf := bytes.Repeat([]byte{0xCD}, direntBufSize)
    49  	for {
    50  		n, err := syscall.ReadDirent(fd, buf)
    51  		if err == syscall.EINVAL {
    52  			// On linux, 'man getdents64' says that EINVAL indicates “result buffer is too small”.
    53  			// Try a bigger buffer.
    54  			t.Logf("ReadDirent: %v; retrying with larger buffer", err)
    55  			buf = bytes.Repeat([]byte{0xCD}, len(buf)*2)
    56  			continue
    57  		}
    58  		if err != nil {
    59  			t.Fatalf("syscall.readdir: %v", err)
    60  		}
    61  		t.Logf("ReadDirent: read %d bytes", n)
    62  		if n == 0 {
    63  			break
    64  		}
    65  
    66  		var consumed, count int
    67  		consumed, count, names = syscall.ParseDirent(buf[:n], -1, names)
    68  		t.Logf("ParseDirent: %d new name(s)", count)
    69  		if consumed != n {
    70  			t.Fatalf("ParseDirent: consumed %d bytes; expected %d", consumed, n)
    71  		}
    72  	}
    73  
    74  	sort.Strings(names)
    75  	t.Logf("names: %q", names)
    76  
    77  	if len(names) != 10 {
    78  		t.Errorf("got %d names; expected 10", len(names))
    79  	}
    80  	for i, name := range names {
    81  		ord, err := strconv.Atoi(name[:1])
    82  		if err != nil {
    83  			t.Fatalf("names[%d] is non-integer %q: %v", i, names[i], err)
    84  		}
    85  		if expected := strings.Repeat(name[:1], filenameMinSize+ord); name != expected {
    86  			t.Errorf("names[%d] is %q (len %d); expected %q (len %d)", i, name, len(name), expected, len(expected))
    87  		}
    88  	}
    89  }
    90  
    91  func TestDirentRepeat(t *testing.T) {
    92  	const N = 100
    93  	// Note: the size of the buffer is small enough that the loop
    94  	// below will need to execute multiple times. See issue #31368.
    95  	size := N * unsafe.Offsetof(syscall.Dirent{}.Name) / 4
    96  	if runtime.GOOS == "freebsd" || runtime.GOOS == "netbsd" {
    97  		if size < 1024 {
    98  			size = 1024 // DIRBLKSIZ, see issue 31403.
    99  		}
   100  	}
   101  
   102  	// Make a directory containing N files
   103  	d := t.TempDir()
   104  
   105  	var files []string
   106  	for i := 0; i < N; i++ {
   107  		files = append(files, fmt.Sprintf("file%d", i))
   108  	}
   109  	for _, file := range files {
   110  		err := os.WriteFile(filepath.Join(d, file), []byte("contents"), 0644)
   111  		if err != nil {
   112  			t.Fatalf("writefile: %v", err)
   113  		}
   114  	}
   115  
   116  	// Read the directory entries using ReadDirent.
   117  	fd, err := syscall.Open(d, syscall.O_RDONLY, 0)
   118  	if err != nil {
   119  		t.Fatalf("syscall.open: %v", err)
   120  	}
   121  	defer syscall.Close(fd)
   122  	var files2 []string
   123  	for {
   124  		buf := make([]byte, size)
   125  		n, err := syscall.ReadDirent(fd, buf)
   126  		if err != nil {
   127  			t.Fatalf("syscall.readdir: %v", err)
   128  		}
   129  		if n == 0 {
   130  			break
   131  		}
   132  		buf = buf[:n]
   133  		for len(buf) > 0 {
   134  			var consumed int
   135  			consumed, _, files2 = syscall.ParseDirent(buf, -1, files2)
   136  			buf = buf[consumed:]
   137  		}
   138  	}
   139  
   140  	// Check results
   141  	sort.Strings(files)
   142  	sort.Strings(files2)
   143  	if strings.Join(files, "|") != strings.Join(files2, "|") {
   144  		t.Errorf("bad file list: want\n%q\ngot\n%q", files, files2)
   145  	}
   146  }
   147
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