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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