github.com/spotify/syslog-redirector-golang@v0.0.0-20140320174030-4859f03d829a/src/pkg/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 netbsd openbsd 6 7 package os 8 9 import ( 10 "runtime" 11 "sync/atomic" 12 "syscall" 13 ) 14 15 // File represents an open file descriptor. 16 type File struct { 17 *file 18 } 19 20 // file is the real representation of *File. 21 // The extra level of indirection ensures that no clients of os 22 // can overwrite this data, which could cause the finalizer 23 // to close the wrong file descriptor. 24 type file struct { 25 fd int 26 name string 27 dirinfo *dirInfo // nil unless directory being read 28 nepipe int32 // number of consecutive EPIPE in Write 29 } 30 31 // Fd returns the integer Unix file descriptor referencing the open file. 32 func (f *File) Fd() uintptr { 33 if f == nil { 34 return ^(uintptr(0)) 35 } 36 return uintptr(f.fd) 37 } 38 39 // NewFile returns a new File with the given file descriptor and name. 40 func NewFile(fd uintptr, name string) *File { 41 fdi := int(fd) 42 if fdi < 0 { 43 return nil 44 } 45 f := &File{&file{fd: fdi, name: name}} 46 runtime.SetFinalizer(f.file, (*file).close) 47 return f 48 } 49 50 // Auxiliary information if the File describes a directory 51 type dirInfo struct { 52 buf []byte // buffer for directory I/O 53 nbuf int // length of buf; return value from Getdirentries 54 bufp int // location of next record in buf. 55 } 56 57 func epipecheck(file *File, e error) { 58 if e == syscall.EPIPE { 59 if atomic.AddInt32(&file.nepipe, 1) >= 10 { 60 sigpipe() 61 } 62 } else { 63 atomic.StoreInt32(&file.nepipe, 0) 64 } 65 } 66 67 // DevNull is the name of the operating system's ``null device.'' 68 // On Unix-like systems, it is "/dev/null"; on Windows, "NUL". 69 const DevNull = "/dev/null" 70 71 // OpenFile is the generalized open call; most users will use Open 72 // or Create instead. It opens the named file with specified flag 73 // (O_RDONLY etc.) and perm, (0666 etc.) if applicable. If successful, 74 // methods on the returned File can be used for I/O. 75 // If there is an error, it will be of type *PathError. 76 func OpenFile(name string, flag int, perm FileMode) (file *File, err error) { 77 r, e := syscall.Open(name, flag|syscall.O_CLOEXEC, syscallMode(perm)) 78 if e != nil { 79 return nil, &PathError{"open", name, e} 80 } 81 82 // There's a race here with fork/exec, which we are 83 // content to live with. See ../syscall/exec_unix.go. 84 // On OS X 10.6, the O_CLOEXEC flag is not respected. 85 // On OS X 10.7, the O_CLOEXEC flag works. 86 // Without a cheap & reliable way to detect 10.6 vs 10.7 at 87 // runtime, we just always call syscall.CloseOnExec on Darwin. 88 // Once >=10.7 is prevalent, this extra call can removed. 89 if syscall.O_CLOEXEC == 0 || runtime.GOOS == "darwin" { // O_CLOEXEC not supported 90 syscall.CloseOnExec(r) 91 } 92 93 return NewFile(uintptr(r), name), nil 94 } 95 96 // Close closes the File, rendering it unusable for I/O. 97 // It returns an error, if any. 98 func (f *File) Close() error { 99 if f == nil { 100 return ErrInvalid 101 } 102 return f.file.close() 103 } 104 105 func (file *file) close() error { 106 if file == nil || file.fd < 0 { 107 return syscall.EINVAL 108 } 109 var err error 110 if e := syscall.Close(file.fd); e != nil { 111 err = &PathError{"close", file.name, e} 112 } 113 file.fd = -1 // so it can't be closed again 114 115 // no need for a finalizer anymore 116 runtime.SetFinalizer(file, nil) 117 return err 118 } 119 120 // Stat returns the FileInfo structure describing file. 121 // If there is an error, it will be of type *PathError. 122 func (f *File) Stat() (fi FileInfo, err error) { 123 if f == nil { 124 return nil, ErrInvalid 125 } 126 var stat syscall.Stat_t 127 err = syscall.Fstat(f.fd, &stat) 128 if err != nil { 129 return nil, &PathError{"stat", f.name, err} 130 } 131 return fileInfoFromStat(&stat, f.name), nil 132 } 133 134 // Stat returns a FileInfo describing the named file. 135 // If there is an error, it will be of type *PathError. 136 func Stat(name string) (fi FileInfo, err error) { 137 var stat syscall.Stat_t 138 err = syscall.Stat(name, &stat) 139 if err != nil { 140 return nil, &PathError{"stat", name, err} 141 } 142 return fileInfoFromStat(&stat, name), nil 143 } 144 145 // Lstat returns a FileInfo describing the named file. 146 // If the file is a symbolic link, the returned FileInfo 147 // describes the symbolic link. Lstat makes no attempt to follow the link. 148 // If there is an error, it will be of type *PathError. 149 func Lstat(name string) (fi FileInfo, err error) { 150 var stat syscall.Stat_t 151 err = syscall.Lstat(name, &stat) 152 if err != nil { 153 return nil, &PathError{"lstat", name, err} 154 } 155 return fileInfoFromStat(&stat, name), nil 156 } 157 158 func (f *File) readdir(n int) (fi []FileInfo, err error) { 159 dirname := f.name 160 if dirname == "" { 161 dirname = "." 162 } 163 dirname += "/" 164 names, err := f.Readdirnames(n) 165 fi = make([]FileInfo, len(names)) 166 for i, filename := range names { 167 fip, lerr := lstat(dirname + filename) 168 if lerr != nil { 169 fi[i] = &fileStat{name: filename} 170 continue 171 } 172 fi[i] = fip 173 } 174 return fi, err 175 } 176 177 // read reads up to len(b) bytes from the File. 178 // It returns the number of bytes read and an error, if any. 179 func (f *File) read(b []byte) (n int, err error) { 180 return syscall.Read(f.fd, b) 181 } 182 183 // pread reads len(b) bytes from the File starting at byte offset off. 184 // It returns the number of bytes read and the error, if any. 185 // EOF is signaled by a zero count with err set to 0. 186 func (f *File) pread(b []byte, off int64) (n int, err error) { 187 return syscall.Pread(f.fd, b, off) 188 } 189 190 // write writes len(b) bytes to the File. 191 // It returns the number of bytes written and an error, if any. 192 func (f *File) write(b []byte) (n int, err error) { 193 for { 194 m, err := syscall.Write(f.fd, b) 195 n += m 196 197 // If the syscall wrote some data but not all (short write) 198 // or it returned EINTR, then assume it stopped early for 199 // reasons that are uninteresting to the caller, and try again. 200 if 0 < m && m < len(b) || err == syscall.EINTR { 201 b = b[m:] 202 continue 203 } 204 205 return n, err 206 } 207 } 208 209 // pwrite writes len(b) bytes to the File starting at byte offset off. 210 // It returns the number of bytes written and an error, if any. 211 func (f *File) pwrite(b []byte, off int64) (n int, err error) { 212 return 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 // basename removes trailing slashes and the leading directory name from path name 265 func basename(name string) string { 266 i := len(name) - 1 267 // Remove trailing slashes 268 for ; i > 0 && name[i] == '/'; i-- { 269 name = name[:i] 270 } 271 // Remove leading directory name 272 for i--; i >= 0; i-- { 273 if name[i] == '/' { 274 name = name[i+1:] 275 break 276 } 277 } 278 279 return name 280 } 281 282 // TempDir returns the default directory to use for temporary files. 283 func TempDir() string { 284 dir := Getenv("TMPDIR") 285 if dir == "" { 286 dir = "/tmp" 287 } 288 return dir 289 }