...
Run Format

Source file src/pkg/os/file_unix.go

     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		"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		if !supportsCloseOnExec {
    85			syscall.CloseOnExec(r)
    86		}
    87	
    88		return NewFile(uintptr(r), name), nil
    89	}
    90	
    91	// Close closes the File, rendering it unusable for I/O.
    92	// It returns an error, if any.
    93	func (f *File) Close() error {
    94		if f == nil {
    95			return ErrInvalid
    96		}
    97		return f.file.close()
    98	}
    99	
   100	func (file *file) close() error {
   101		if file == nil || file.fd < 0 {
   102			return syscall.EINVAL
   103		}
   104		var err error
   105		if e := syscall.Close(file.fd); e != nil {
   106			err = &PathError{"close", file.name, e}
   107		}
   108		file.fd = -1 // so it can't be closed again
   109	
   110		// no need for a finalizer anymore
   111		runtime.SetFinalizer(file, nil)
   112		return err
   113	}
   114	
   115	// Stat returns the FileInfo structure describing file.
   116	// If there is an error, it will be of type *PathError.
   117	func (f *File) Stat() (fi FileInfo, err error) {
   118		if f == nil {
   119			return nil, ErrInvalid
   120		}
   121		var stat syscall.Stat_t
   122		err = syscall.Fstat(f.fd, &stat)
   123		if err != nil {
   124			return nil, &PathError{"stat", f.name, err}
   125		}
   126		return fileInfoFromStat(&stat, f.name), nil
   127	}
   128	
   129	// Stat returns a FileInfo describing the named file.
   130	// If there is an error, it will be of type *PathError.
   131	func Stat(name string) (fi FileInfo, err error) {
   132		var stat syscall.Stat_t
   133		err = syscall.Stat(name, &stat)
   134		if err != nil {
   135			return nil, &PathError{"stat", name, err}
   136		}
   137		return fileInfoFromStat(&stat, name), nil
   138	}
   139	
   140	// Lstat returns a FileInfo describing the named file.
   141	// If the file is a symbolic link, the returned FileInfo
   142	// describes the symbolic link.  Lstat makes no attempt to follow the link.
   143	// If there is an error, it will be of type *PathError.
   144	func Lstat(name string) (fi FileInfo, err error) {
   145		var stat syscall.Stat_t
   146		err = syscall.Lstat(name, &stat)
   147		if err != nil {
   148			return nil, &PathError{"lstat", name, err}
   149		}
   150		return fileInfoFromStat(&stat, name), nil
   151	}
   152	
   153	func (f *File) readdir(n int) (fi []FileInfo, err error) {
   154		dirname := f.name
   155		if dirname == "" {
   156			dirname = "."
   157		}
   158		names, err := f.Readdirnames(n)
   159		fi = make([]FileInfo, 0, len(names))
   160		for _, filename := range names {
   161			fip, lerr := lstat(dirname + "/" + filename)
   162			if IsNotExist(lerr) {
   163				// File disappeared between readdir + stat.
   164				// Just treat it as if it didn't exist.
   165				continue
   166			}
   167			if lerr != nil {
   168				return fi, lerr
   169			}
   170			fi = append(fi, fip)
   171		}
   172		return fi, err
   173	}
   174	
   175	// Darwin and FreeBSD can't read or write 2GB+ at a time,
   176	// even on 64-bit systems. See golang.org/issue/7812.
   177	// Use 1GB instead of, say, 2GB-1, to keep subsequent
   178	// reads aligned.
   179	const (
   180		needsMaxRW = runtime.GOOS == "darwin" || runtime.GOOS == "freebsd"
   181		maxRW      = 1 << 30
   182	)
   183	
   184	// read reads up to len(b) bytes from the File.
   185	// It returns the number of bytes read and an error, if any.
   186	func (f *File) read(b []byte) (n int, err error) {
   187		if needsMaxRW && len(b) > maxRW {
   188			b = b[:maxRW]
   189		}
   190		return syscall.Read(f.fd, b)
   191	}
   192	
   193	// pread reads len(b) bytes from the File starting at byte offset off.
   194	// It returns the number of bytes read and the error, if any.
   195	// EOF is signaled by a zero count with err set to nil.
   196	func (f *File) pread(b []byte, off int64) (n int, err error) {
   197		if needsMaxRW && len(b) > maxRW {
   198			b = b[:maxRW]
   199		}
   200		return syscall.Pread(f.fd, b, off)
   201	}
   202	
   203	// write writes len(b) bytes to the File.
   204	// It returns the number of bytes written and an error, if any.
   205	func (f *File) write(b []byte) (n int, err error) {
   206		for {
   207			bcap := b
   208			if needsMaxRW && len(bcap) > maxRW {
   209				bcap = bcap[:maxRW]
   210			}
   211			m, err := syscall.Write(f.fd, bcap)
   212			n += m
   213	
   214			// If the syscall wrote some data but not all (short write)
   215			// or it returned EINTR, then assume it stopped early for
   216			// reasons that are uninteresting to the caller, and try again.
   217			if 0 < m && m < len(bcap) || err == syscall.EINTR {
   218				b = b[m:]
   219				continue
   220			}
   221	
   222			if needsMaxRW && len(bcap) != len(b) && err == nil {
   223				b = b[m:]
   224				continue
   225			}
   226	
   227			return n, err
   228		}
   229	}
   230	
   231	// pwrite writes len(b) bytes to the File starting at byte offset off.
   232	// It returns the number of bytes written and an error, if any.
   233	func (f *File) pwrite(b []byte, off int64) (n int, err error) {
   234		if needsMaxRW && len(b) > maxRW {
   235			b = b[:maxRW]
   236		}
   237		return syscall.Pwrite(f.fd, b, off)
   238	}
   239	
   240	// seek sets the offset for the next Read or Write on file to offset, interpreted
   241	// according to whence: 0 means relative to the origin of the file, 1 means
   242	// relative to the current offset, and 2 means relative to the end.
   243	// It returns the new offset and an error, if any.
   244	func (f *File) seek(offset int64, whence int) (ret int64, err error) {
   245		return syscall.Seek(f.fd, offset, whence)
   246	}
   247	
   248	// Truncate changes the size of the named file.
   249	// If the file is a symbolic link, it changes the size of the link's target.
   250	// If there is an error, it will be of type *PathError.
   251	func Truncate(name string, size int64) error {
   252		if e := syscall.Truncate(name, size); e != nil {
   253			return &PathError{"truncate", name, e}
   254		}
   255		return nil
   256	}
   257	
   258	// Remove removes the named file or directory.
   259	// If there is an error, it will be of type *PathError.
   260	func Remove(name string) error {
   261		// System call interface forces us to know
   262		// whether name is a file or directory.
   263		// Try both: it is cheaper on average than
   264		// doing a Stat plus the right one.
   265		e := syscall.Unlink(name)
   266		if e == nil {
   267			return nil
   268		}
   269		e1 := syscall.Rmdir(name)
   270		if e1 == nil {
   271			return nil
   272		}
   273	
   274		// Both failed: figure out which error to return.
   275		// OS X and Linux differ on whether unlink(dir)
   276		// returns EISDIR, so can't use that.  However,
   277		// both agree that rmdir(file) returns ENOTDIR,
   278		// so we can use that to decide which error is real.
   279		// Rmdir might also return ENOTDIR if given a bad
   280		// file path, like /etc/passwd/foo, but in that case,
   281		// both errors will be ENOTDIR, so it's okay to
   282		// use the error from unlink.
   283		if e1 != syscall.ENOTDIR {
   284			e = e1
   285		}
   286		return &PathError{"remove", name, e}
   287	}
   288	
   289	// basename removes trailing slashes and the leading directory name from path name
   290	func basename(name string) string {
   291		i := len(name) - 1
   292		// Remove trailing slashes
   293		for ; i > 0 && name[i] == '/'; i-- {
   294			name = name[:i]
   295		}
   296		// Remove leading directory name
   297		for i--; i >= 0; i-- {
   298			if name[i] == '/' {
   299				name = name[i+1:]
   300				break
   301			}
   302		}
   303	
   304		return name
   305	}
   306	
   307	// TempDir returns the default directory to use for temporary files.
   308	func TempDir() string {
   309		dir := Getenv("TMPDIR")
   310		if dir == "" {
   311			dir = "/tmp"
   312		}
   313		return dir
   314	}
   315	

View as plain text