dir.go

     1  // Copyright 2016 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  package os
     6  
     7  import (
     8  	"internal/bytealg"
     9  	"internal/filepathlite"
    10  	"io"
    11  	"io/fs"
    12  	"slices"
    13  )
    14  
    15  type readdirMode int
    16  
    17  const (
    18  	readdirName readdirMode = iota
    19  	readdirDirEntry
    20  	readdirFileInfo
    21  )
    22  
    23  // Readdir reads the contents of the directory associated with file and
    24  // returns a slice of up to n [FileInfo] values, as would be returned
    25  // by [Lstat], in directory order. Subsequent calls on the same file will yield
    26  // further FileInfos.
    27  //
    28  // If n > 0, Readdir returns at most n FileInfo structures. In this case, if
    29  // Readdir returns an empty slice, it will return a non-nil error
    30  // explaining why. At the end of a directory, the error is [io.EOF].
    31  //
    32  // If n <= 0, Readdir returns all the FileInfo from the directory in
    33  // a single slice. In this case, if Readdir succeeds (reads all
    34  // the way to the end of the directory), it returns the slice and a
    35  // nil error. If it encounters an error before the end of the
    36  // directory, Readdir returns the FileInfo read until that point
    37  // and a non-nil error.
    38  //
    39  // Most clients are better served by the more efficient ReadDir method.
    40  func (f *File) Readdir(n int) ([]FileInfo, error) {
    41  	if f == nil {
    42  		return nil, ErrInvalid
    43  	}
    44  	_, _, infos, err := f.readdir(n, readdirFileInfo)
    45  	if infos == nil {
    46  		// Readdir has historically always returned a non-nil empty slice, never nil,
    47  		// even on error (except misuse with nil receiver above).
    48  		// Keep it that way to avoid breaking overly sensitive callers.
    49  		infos = []FileInfo{}
    50  	}
    51  	return infos, err
    52  }
    53  
    54  // Readdirnames reads the contents of the directory associated with file
    55  // and returns a slice of up to n names of files in the directory,
    56  // in directory order. Subsequent calls on the same file will yield
    57  // further names.
    58  //
    59  // If n > 0, Readdirnames returns at most n names. In this case, if
    60  // Readdirnames returns an empty slice, it will return a non-nil error
    61  // explaining why. At the end of a directory, the error is [io.EOF].
    62  //
    63  // If n <= 0, Readdirnames returns all the names from the directory in
    64  // a single slice. In this case, if Readdirnames succeeds (reads all
    65  // the way to the end of the directory), it returns the slice and a
    66  // nil error. If it encounters an error before the end of the
    67  // directory, Readdirnames returns the names read until that point and
    68  // a non-nil error.
    69  func (f *File) Readdirnames(n int) (names []string, err error) {
    70  	if f == nil {
    71  		return nil, ErrInvalid
    72  	}
    73  	names, _, _, err = f.readdir(n, readdirName)
    74  	if names == nil {
    75  		// Readdirnames has historically always returned a non-nil empty slice, never nil,
    76  		// even on error (except misuse with nil receiver above).
    77  		// Keep it that way to avoid breaking overly sensitive callers.
    78  		names = []string{}
    79  	}
    80  	return names, err
    81  }
    82  
    83  // A DirEntry is an entry read from a directory
    84  // (using the [ReadDir] function or a [File.ReadDir] method).
    85  type DirEntry = fs.DirEntry
    86  
    87  // ReadDir reads the contents of the directory associated with the file f
    88  // and returns a slice of [DirEntry] values in directory order.
    89  // Subsequent calls on the same file will yield later DirEntry records in the directory.
    90  //
    91  // If n > 0, ReadDir returns at most n DirEntry records.
    92  // In this case, if ReadDir returns an empty slice, it will return an error explaining why.
    93  // At the end of a directory, the error is [io.EOF].
    94  //
    95  // If n <= 0, ReadDir returns all the DirEntry records remaining in the directory.
    96  // When it succeeds, it returns a nil error (not io.EOF).
    97  func (f *File) ReadDir(n int) ([]DirEntry, error) {
    98  	if f == nil {
    99  		return nil, ErrInvalid
   100  	}
   101  	_, dirents, _, err := f.readdir(n, readdirDirEntry)
   102  	if dirents == nil {
   103  		// Match Readdir and Readdirnames: don't return nil slices.
   104  		dirents = []DirEntry{}
   105  	}
   106  	return dirents, err
   107  }
   108  
   109  // testingForceReadDirLstat forces ReadDir to call Lstat, for testing that code path.
   110  // This can be difficult to provoke on some Unix systems otherwise.
   111  var testingForceReadDirLstat bool
   112  
   113  // ReadDir reads the named directory,
   114  // returning all its directory entries sorted by filename.
   115  // If an error occurs reading the directory,
   116  // ReadDir returns the entries it was able to read before the error,
   117  // along with the error.
   118  func ReadDir(name string) ([]DirEntry, error) {
   119  	f, err := openDir(name)
   120  	if err != nil {
   121  		return nil, err
   122  	}
   123  	defer f.Close()
   124  
   125  	dirs, err := f.ReadDir(-1)
   126  	slices.SortFunc(dirs, func(a, b DirEntry) int {
   127  		return bytealg.CompareString(a.Name(), b.Name())
   128  	})
   129  	return dirs, err
   130  }
   131  
   132  // CopyFS copies the file system fsys into the directory dir,
   133  // creating dir if necessary.
   134  //
   135  // Files are created with mode 0o666 plus any execute permissions
   136  // from the source, and directories are created with mode 0o777
   137  // (before umask).
   138  //
   139  // CopyFS will not overwrite existing files. If a file name in fsys
   140  // already exists in the destination, CopyFS will return an error
   141  // such that errors.Is(err, fs.ErrExist) will be true.
   142  //
   143  // Symbolic links in fsys are not supported. A *PathError with Err set
   144  // to ErrInvalid is returned when copying from a symbolic link.
   145  //
   146  // Symbolic links in dir are followed.
   147  //
   148  // Copying stops at and returns the first error encountered.
   149  func CopyFS(dir string, fsys fs.FS) error {
   150  	return fs.WalkDir(fsys, ".", func(path string, d fs.DirEntry, err error) error {
   151  		if err != nil {
   152  			return err
   153  		}
   154  
   155  		fpath, err := filepathlite.Localize(path)
   156  		if err != nil {
   157  			return err
   158  		}
   159  		newPath := joinPath(dir, fpath)
   160  		if d.IsDir() {
   161  			return MkdirAll(newPath, 0777)
   162  		}
   163  
   164  		// TODO(panjf2000): handle symlinks with the help of fs.ReadLinkFS
   165  		// 		once https://go.dev/issue/49580 is done.
   166  		//		we also need filepathlite.IsLocal from https://go.dev/cl/564295.
   167  		if !d.Type().IsRegular() {
   168  			return &PathError{Op: "CopyFS", Path: path, Err: ErrInvalid}
   169  		}
   170  
   171  		r, err := fsys.Open(path)
   172  		if err != nil {
   173  			return err
   174  		}
   175  		defer r.Close()
   176  		info, err := r.Stat()
   177  		if err != nil {
   178  			return err
   179  		}
   180  		w, err := OpenFile(newPath, O_CREATE|O_EXCL|O_WRONLY, 0666|info.Mode()&0777)
   181  		if err != nil {
   182  			return err
   183  		}
   184  
   185  		if _, err := io.Copy(w, r); err != nil {
   186  			w.Close()
   187  			return &PathError{Op: "Copy", Path: newPath, Err: err}
   188  		}
   189  		return w.Close()
   190  	})
   191  }
   192
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