github.com/freddyisaac/sicortex-golang@v0.0.0-20231019035217-e03519e66f60/src/os/file_unix.go (about) 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 // +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris 6 7 package os 8 9 import ( 10 "runtime" 11 "syscall" 12 ) 13 14 // fixLongPath is a noop on non-Windows platforms. 15 func fixLongPath(path string) string { 16 return path 17 } 18 19 func rename(oldname, newname string) error { 20 fi, err := Lstat(newname) 21 if err == nil && fi.IsDir() { 22 return &LinkError{"rename", oldname, newname, syscall.EEXIST} 23 } 24 e := syscall.Rename(oldname, newname) 25 if e != nil { 26 return &LinkError{"rename", oldname, newname, e} 27 } 28 return nil 29 } 30 31 // file is the real representation of *File. 32 // The extra level of indirection ensures that no clients of os 33 // can overwrite this data, which could cause the finalizer 34 // to close the wrong file descriptor. 35 type file struct { 36 fd int 37 name string 38 dirinfo *dirInfo // nil unless directory being read 39 } 40 41 // Fd returns the integer Unix file descriptor referencing the open file. 42 // The file descriptor is valid only until f.Close is called or f is garbage collected. 43 func (f *File) Fd() uintptr { 44 if f == nil { 45 return ^(uintptr(0)) 46 } 47 return uintptr(f.fd) 48 } 49 50 // NewFile returns a new File with the given file descriptor and name. 51 func NewFile(fd uintptr, name string) *File { 52 fdi := int(fd) 53 if fdi < 0 { 54 return nil 55 } 56 f := &File{&file{fd: fdi, name: name}} 57 runtime.SetFinalizer(f.file, (*file).close) 58 return f 59 } 60 61 // Auxiliary information if the File describes a directory 62 type dirInfo struct { 63 buf []byte // buffer for directory I/O 64 nbuf int // length of buf; return value from Getdirentries 65 bufp int // location of next record in buf. 66 } 67 68 // epipecheck raises SIGPIPE if we get an EPIPE error on standard 69 // output or standard error. See the SIGPIPE docs in os/signal, and 70 // issue 11845. 71 func epipecheck(file *File, e error) { 72 if e == syscall.EPIPE && (file.fd == 1 || file.fd == 2) { 73 sigpipe() 74 } 75 } 76 77 // DevNull is the name of the operating system's ``null device.'' 78 // On Unix-like systems, it is "/dev/null"; on Windows, "NUL". 79 const DevNull = "/dev/null" 80 81 // OpenFile is the generalized open call; most users will use Open 82 // or Create instead. It opens the named file with specified flag 83 // (O_RDONLY etc.) and perm, (0666 etc.) if applicable. If successful, 84 // methods on the returned File can be used for I/O. 85 // If there is an error, it will be of type *PathError. 86 func OpenFile(name string, flag int, perm FileMode) (*File, error) { 87 chmod := false 88 if !supportsCreateWithStickyBit && flag&O_CREATE != 0 && perm&ModeSticky != 0 { 89 if _, err := Stat(name); IsNotExist(err) { 90 chmod = true 91 } 92 } 93 94 var r int 95 for { 96 var e error 97 r, e = syscall.Open(name, flag|syscall.O_CLOEXEC, syscallMode(perm)) 98 if e == nil { 99 break 100 } 101 102 // On OS X, sigaction(2) doesn't guarantee that SA_RESTART will cause 103 // open(2) to be restarted for regular files. This is easy to reproduce on 104 // fuse file systems (see http://golang.org/issue/11180). 105 if runtime.GOOS == "darwin" && e == syscall.EINTR { 106 continue 107 } 108 109 return nil, &PathError{"open", name, e} 110 } 111 112 // open(2) itself won't handle the sticky bit on *BSD and Solaris 113 if chmod { 114 Chmod(name, perm) 115 } 116 117 // There's a race here with fork/exec, which we are 118 // content to live with. See ../syscall/exec_unix.go. 119 if !supportsCloseOnExec { 120 syscall.CloseOnExec(r) 121 } 122 123 return NewFile(uintptr(r), name), nil 124 } 125 126 // Close closes the File, rendering it unusable for I/O. 127 // It returns an error, if any. 128 func (f *File) Close() error { 129 if f == nil { 130 return ErrInvalid 131 } 132 return f.file.close() 133 } 134 135 func (file *file) close() error { 136 if file == nil || file.fd == badFd { 137 return syscall.EINVAL 138 } 139 var err error 140 if e := syscall.Close(file.fd); e != nil { 141 err = &PathError{"close", file.name, e} 142 } 143 file.fd = -1 // so it can't be closed again 144 145 // no need for a finalizer anymore 146 runtime.SetFinalizer(file, nil) 147 return err 148 } 149 150 // Darwin and FreeBSD can't read or write 2GB+ at a time, 151 // even on 64-bit systems. See golang.org/issue/7812. 152 // Use 1GB instead of, say, 2GB-1, to keep subsequent 153 // reads aligned. 154 const ( 155 needsMaxRW = runtime.GOOS == "darwin" || runtime.GOOS == "freebsd" 156 maxRW = 1 << 30 157 ) 158 159 // read reads up to len(b) bytes from the File. 160 // It returns the number of bytes read and an error, if any. 161 func (f *File) read(b []byte) (n int, err error) { 162 if needsMaxRW && len(b) > maxRW { 163 b = b[:maxRW] 164 } 165 return fixCount(syscall.Read(f.fd, b)) 166 } 167 168 // pread reads len(b) bytes from the File starting at byte offset off. 169 // It returns the number of bytes read and the error, if any. 170 // EOF is signaled by a zero count with err set to nil. 171 func (f *File) pread(b []byte, off int64) (n int, err error) { 172 if needsMaxRW && len(b) > maxRW { 173 b = b[:maxRW] 174 } 175 return fixCount(syscall.Pread(f.fd, b, off)) 176 } 177 178 // write writes len(b) bytes to the File. 179 // It returns the number of bytes written and an error, if any. 180 func (f *File) write(b []byte) (n int, err error) { 181 for { 182 bcap := b 183 if needsMaxRW && len(bcap) > maxRW { 184 bcap = bcap[:maxRW] 185 } 186 m, err := fixCount(syscall.Write(f.fd, bcap)) 187 n += m 188 189 // If the syscall wrote some data but not all (short write) 190 // or it returned EINTR, then assume it stopped early for 191 // reasons that are uninteresting to the caller, and try again. 192 if 0 < m && m < len(bcap) || err == syscall.EINTR { 193 b = b[m:] 194 continue 195 } 196 197 if needsMaxRW && len(bcap) != len(b) && err == nil { 198 b = b[m:] 199 continue 200 } 201 202 return n, err 203 } 204 } 205 206 // pwrite writes len(b) bytes to the File starting at byte offset off. 207 // It returns the number of bytes written and an error, if any. 208 func (f *File) pwrite(b []byte, off int64) (n int, err error) { 209 if needsMaxRW && len(b) > maxRW { 210 b = b[:maxRW] 211 } 212 return fixCount(syscall.Pwrite(f.fd, b, off)) 213 } 214 215 // seek sets the offset for the next Read or Write on file to offset, interpreted 216 // according to whence: 0 means relative to the origin of the file, 1 means 217 // relative to the current offset, and 2 means relative to the end. 218 // It returns the new offset and an error, if any. 219 func (f *File) seek(offset int64, whence int) (ret int64, err error) { 220 return syscall.Seek(f.fd, offset, whence) 221 } 222 223 // Truncate changes the size of the named file. 224 // If the file is a symbolic link, it changes the size of the link's target. 225 // If there is an error, it will be of type *PathError. 226 func Truncate(name string, size int64) error { 227 if e := syscall.Truncate(name, size); e != nil { 228 return &PathError{"truncate", name, e} 229 } 230 return nil 231 } 232 233 // Remove removes the named file or directory. 234 // If there is an error, it will be of type *PathError. 235 func Remove(name string) error { 236 // System call interface forces us to know 237 // whether name is a file or directory. 238 // Try both: it is cheaper on average than 239 // doing a Stat plus the right one. 240 e := syscall.Unlink(name) 241 if e == nil { 242 return nil 243 } 244 e1 := syscall.Rmdir(name) 245 if e1 == nil { 246 return nil 247 } 248 249 // Both failed: figure out which error to return. 250 // OS X and Linux differ on whether unlink(dir) 251 // returns EISDIR, so can't use that. However, 252 // both agree that rmdir(file) returns ENOTDIR, 253 // so we can use that to decide which error is real. 254 // Rmdir might also return ENOTDIR if given a bad 255 // file path, like /etc/passwd/foo, but in that case, 256 // both errors will be ENOTDIR, so it's okay to 257 // use the error from unlink. 258 if e1 != syscall.ENOTDIR { 259 e = e1 260 } 261 return &PathError{"remove", name, e} 262 } 263 264 // TempDir returns the default directory to use for temporary files. 265 func TempDir() string { 266 dir := Getenv("TMPDIR") 267 if dir == "" { 268 if runtime.GOOS == "android" { 269 dir = "/data/local/tmp" 270 } else { 271 dir = "/tmp" 272 } 273 } 274 return dir 275 } 276 277 // Link creates newname as a hard link to the oldname file. 278 // If there is an error, it will be of type *LinkError. 279 func Link(oldname, newname string) error { 280 e := syscall.Link(oldname, newname) 281 if e != nil { 282 return &LinkError{"link", oldname, newname, e} 283 } 284 return nil 285 } 286 287 // Symlink creates newname as a symbolic link to oldname. 288 // If there is an error, it will be of type *LinkError. 289 func Symlink(oldname, newname string) error { 290 e := syscall.Symlink(oldname, newname) 291 if e != nil { 292 return &LinkError{"symlink", oldname, newname, e} 293 } 294 return nil 295 }