dir_unix.go

Documentation: os

     1  // Copyright 2009 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 aix || dragonfly || freebsd || (js && wasm) || linux || netbsd || openbsd || solaris
     6  // +build aix dragonfly freebsd js,wasm linux netbsd openbsd solaris
     7  
     8  package os
     9  
    10  import (
    11  	"io"
    12  	"runtime"
    13  	"sync"
    14  	"syscall"
    15  	"unsafe"
    16  )
    17  
    18  // Auxiliary information if the File describes a directory
    19  type dirInfo struct {
    20  	buf  *[]byte // buffer for directory I/O
    21  	nbuf int     // length of buf; return value from Getdirentries
    22  	bufp int     // location of next record in buf.
    23  }
    24  
    25  const (
    26  	// More than 5760 to work around https://golang.org/issue/24015.
    27  	blockSize = 8192
    28  )
    29  
    30  var dirBufPool = sync.Pool{
    31  	New: func() interface{} {
    32  		// The buffer must be at least a block long.
    33  		buf := make([]byte, blockSize)
    34  		return &buf
    35  	},
    36  }
    37  
    38  func (d *dirInfo) close() {
    39  	if d.buf != nil {
    40  		dirBufPool.Put(d.buf)
    41  		d.buf = nil
    42  	}
    43  }
    44  
    45  func (f *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEntry, infos []FileInfo, err error) {
    46  	// If this file has no dirinfo, create one.
    47  	if f.dirinfo == nil {
    48  		f.dirinfo = new(dirInfo)
    49  		f.dirinfo.buf = dirBufPool.Get().(*[]byte)
    50  	}
    51  	d := f.dirinfo
    52  
    53  	// Change the meaning of n for the implementation below.
    54  	//
    55  	// The n above was for the public interface of "if n <= 0,
    56  	// Readdir returns all the FileInfo from the directory in a
    57  	// single slice".
    58  	//
    59  	// But below, we use only negative to mean looping until the
    60  	// end and positive to mean bounded, with positive
    61  	// terminating at 0.
    62  	if n == 0 {
    63  		n = -1
    64  	}
    65  
    66  	for n != 0 {
    67  		// Refill the buffer if necessary
    68  		if d.bufp >= d.nbuf {
    69  			d.bufp = 0
    70  			var errno error
    71  			d.nbuf, errno = f.pfd.ReadDirent(*d.buf)
    72  			runtime.KeepAlive(f)
    73  			if errno != nil {
    74  				return names, dirents, infos, &PathError{Op: "readdirent", Path: f.name, Err: errno}
    75  			}
    76  			if d.nbuf <= 0 {
    77  				break // EOF
    78  			}
    79  		}
    80  
    81  		// Drain the buffer
    82  		buf := (*d.buf)[d.bufp:d.nbuf]
    83  		reclen, ok := direntReclen(buf)
    84  		if !ok || reclen > uint64(len(buf)) {
    85  			break
    86  		}
    87  		rec := buf[:reclen]
    88  		d.bufp += int(reclen)
    89  		ino, ok := direntIno(rec)
    90  		if !ok {
    91  			break
    92  		}
    93  		if ino == 0 {
    94  			continue
    95  		}
    96  		const namoff = uint64(unsafe.Offsetof(syscall.Dirent{}.Name))
    97  		namlen, ok := direntNamlen(rec)
    98  		if !ok || namoff+namlen > uint64(len(rec)) {
    99  			break
   100  		}
   101  		name := rec[namoff : namoff+namlen]
   102  		for i, c := range name {
   103  			if c == 0 {
   104  				name = name[:i]
   105  				break
   106  			}
   107  		}
   108  		// Check for useless names before allocating a string.
   109  		if string(name) == "." || string(name) == ".." {
   110  			continue
   111  		}
   112  		if n > 0 { // see 'n == 0' comment above
   113  			n--
   114  		}
   115  		if mode == readdirName {
   116  			names = append(names, string(name))
   117  		} else if mode == readdirDirEntry {
   118  			de, err := newUnixDirent(f.name, string(name), direntType(rec))
   119  			if IsNotExist(err) {
   120  				// File disappeared between readdir and stat.
   121  				// Treat as if it didn't exist.
   122  				continue
   123  			}
   124  			if err != nil {
   125  				return nil, dirents, nil, err
   126  			}
   127  			dirents = append(dirents, de)
   128  		} else {
   129  			info, err := lstat(f.name + "/" + string(name))
   130  			if IsNotExist(err) {
   131  				// File disappeared between readdir + stat.
   132  				// Treat as if it didn't exist.
   133  				continue
   134  			}
   135  			if err != nil {
   136  				return nil, nil, infos, err
   137  			}
   138  			infos = append(infos, info)
   139  		}
   140  	}
   141  
   142  	if n > 0 && len(names)+len(dirents)+len(infos) == 0 {
   143  		return nil, nil, nil, io.EOF
   144  	}
   145  	return names, dirents, infos, nil
   146  }
   147  
   148  // readInt returns the size-bytes unsigned integer in native byte order at offset off.
   149  func readInt(b []byte, off, size uintptr) (u uint64, ok bool) {
   150  	if len(b) < int(off+size) {
   151  		return 0, false
   152  	}
   153  	if isBigEndian {
   154  		return readIntBE(b[off:], size), true
   155  	}
   156  	return readIntLE(b[off:], size), true
   157  }
   158  
   159  func readIntBE(b []byte, size uintptr) uint64 {
   160  	switch size {
   161  	case 1:
   162  		return uint64(b[0])
   163  	case 2:
   164  		_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
   165  		return uint64(b[1]) | uint64(b[0])<<8
   166  	case 4:
   167  		_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
   168  		return uint64(b[3]) | uint64(b[2])<<8 | uint64(b[1])<<16 | uint64(b[0])<<24
   169  	case 8:
   170  		_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
   171  		return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
   172  			uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
   173  	default:
   174  		panic("syscall: readInt with unsupported size")
   175  	}
   176  }
   177  
   178  func readIntLE(b []byte, size uintptr) uint64 {
   179  	switch size {
   180  	case 1:
   181  		return uint64(b[0])
   182  	case 2:
   183  		_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
   184  		return uint64(b[0]) | uint64(b[1])<<8
   185  	case 4:
   186  		_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
   187  		return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24
   188  	case 8:
   189  		_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
   190  		return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
   191  			uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
   192  	default:
   193  		panic("syscall: readInt with unsupported size")
   194  	}
   195  }
   196
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