src/os/file_posix.go - go - Git at Google

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 //go:build unix || (js && wasm) || wasip1 || windows

 package os

 import (
 	"runtime"
 	"syscall"
 	"time"
 )

 // Close closes the [File], rendering it unusable for I/O.
 // On files that support [File.SetDeadline], any pending I/O operations will
 // be canceled and return immediately with an [ErrClosed] error.
 // Close will return an error if it has already been called.
 func (f *File) Close() error {
 	if f == nil {
 		return ErrInvalid
 	}
 	return f.file.close()
 }

 // read reads up to len(b) bytes from the File.
 // It returns the number of bytes read and an error, if any.
 func (f *File) read(b []byte) (n int, err error) {
 	n, err = f.pfd.Read(b)
 	runtime.KeepAlive(f)
 	return n, err
 }

 // pread reads len(b) bytes from the File starting at byte offset off.
 // It returns the number of bytes read and the error, if any.
 // EOF is signaled by a zero count with err set to nil.
 func (f *File) pread(b []byte, off int64) (n int, err error) {
 	n, err = f.pfd.Pread(b, off)
 	runtime.KeepAlive(f)
 	return n, err
 }

 // write writes len(b) bytes to the File.
 // It returns the number of bytes written and an error, if any.
 func (f *File) write(b []byte) (n int, err error) {
 	n, err = f.pfd.Write(b)
 	runtime.KeepAlive(f)
 	return n, err
 }

 // pwrite writes len(b) bytes to the File starting at byte offset off.
 // It returns the number of bytes written and an error, if any.
 func (f *File) pwrite(b []byte, off int64) (n int, err error) {
 	n, err = f.pfd.Pwrite(b, off)
 	runtime.KeepAlive(f)
 	return n, err
 }

 // syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
 func syscallMode(i FileMode) (o uint32) {
 	o |= uint32(i.Perm())
 	if i&ModeSetuid != 0 {
 		o |= syscall.S_ISUID
 	}
 	if i&ModeSetgid != 0 {
 		o |= syscall.S_ISGID
 	}
 	if i&ModeSticky != 0 {
 		o |= syscall.S_ISVTX
 	}
 	// No mapping for Go's ModeTemporary (plan9 only).
 	return
 }

 // See docs in file.go:Chmod.
 func chmod(name string, mode FileMode) error {
 	longName := fixLongPath(name)
 	e := ignoringEINTR(func() error {
 		return syscall.Chmod(longName, syscallMode(mode))
 	})
 	if e != nil {
 		return &PathError{Op: "chmod", Path: name, Err: e}
 	}
 	return nil
 }

 // See docs in file.go:(*File).Chmod.
 func (f *File) chmod(mode FileMode) error {
 	if err := f.checkValid("chmod"); err != nil {
 		return err
 	}
 	if e := f.pfd.Fchmod(syscallMode(mode)); e != nil {
 		return f.wrapErr("chmod", e)
 	}
 	return nil
 }

 // Chown changes the numeric uid and gid of the named file.
 // If the file is a symbolic link, it changes the uid and gid of the link's target.
 // A uid or gid of -1 means to not change that value.
 // If there is an error, it will be of type [*PathError].
 //
 // On Windows or Plan 9, Chown always returns the [syscall.EWINDOWS] or
 // EPLAN9 error, wrapped in *PathError.
 func Chown(name string, uid, gid int) error {
 	e := ignoringEINTR(func() error {
 		return syscall.Chown(name, uid, gid)
 	})
 	if e != nil {
 		return &PathError{Op: "chown", Path: name, Err: e}
 	}
 	return nil
 }

 // Lchown changes the numeric uid and gid of the named file.
 // If the file is a symbolic link, it changes the uid and gid of the link itself.
 // If there is an error, it will be of type [*PathError].
 //
 // On Windows, it always returns the [syscall.EWINDOWS] error, wrapped
 // in *PathError.
 func Lchown(name string, uid, gid int) error {
 	e := ignoringEINTR(func() error {
 		return syscall.Lchown(name, uid, gid)
 	})
 	if e != nil {
 		return &PathError{Op: "lchown", Path: name, Err: e}
 	}
 	return nil
 }

 // Chown changes the numeric uid and gid of the named file.
 // If there is an error, it will be of type [*PathError].
 //
 // On Windows, it always returns the [syscall.EWINDOWS] error, wrapped
 // in *PathError.
 func (f *File) Chown(uid, gid int) error {
 	if err := f.checkValid("chown"); err != nil {
 		return err
 	}
 	if e := f.pfd.Fchown(uid, gid); e != nil {
 		return f.wrapErr("chown", e)
 	}
 	return nil
 }

 // Truncate changes the size of the file.
 // It does not change the I/O offset.
 // If there is an error, it will be of type [*PathError].
 func (f *File) Truncate(size int64) error {
 	if err := f.checkValid("truncate"); err != nil {
 		return err
 	}
 	if e := f.pfd.Ftruncate(size); e != nil {
 		return f.wrapErr("truncate", e)
 	}
 	return nil
 }

 // Sync commits the current contents of the file to stable storage.
 // Typically, this means flushing the file system's in-memory copy
 // of recently written data to disk.
 func (f *File) Sync() error {
 	if err := f.checkValid("sync"); err != nil {
 		return err
 	}
 	if e := f.pfd.Fsync(); e != nil {
 		return f.wrapErr("sync", e)
 	}
 	return nil
 }

 // Chtimes changes the access and modification times of the named
 // file, similar to the Unix utime() or utimes() functions.
 // A zero [time.Time] value will leave the corresponding file time unchanged.
 //
 // The underlying filesystem may truncate or round the values to a
 // less precise time unit.
 // If there is an error, it will be of type [*PathError].
 func Chtimes(name string, atime time.Time, mtime time.Time) error {
 	var utimes [2]syscall.Timespec
 	set := func(i int, t time.Time) {
 		if t.IsZero() {
 			utimes[i] = syscall.Timespec{Sec: _UTIME_OMIT, Nsec: _UTIME_OMIT}
 		} else {
 			utimes[i] = syscall.NsecToTimespec(t.UnixNano())
 		}
 	}
 	set(0, atime)
 	set(1, mtime)
 	if e := syscall.UtimesNano(fixLongPath(name), utimes[0:]); e != nil {
 		return &PathError{Op: "chtimes", Path: name, Err: e}
 	}
 	return nil
 }

 // Chdir changes the current working directory to the file,
 // which must be a directory.
 // If there is an error, it will be of type [*PathError].
 func (f *File) Chdir() error {
 	if err := f.checkValid("chdir"); err != nil {
 		return err
 	}
 	if e := f.pfd.Fchdir(); e != nil {
 		return f.wrapErr("chdir", e)
 	}
 	return nil
 }

 // setDeadline sets the read and write deadline.
 func (f *File) setDeadline(t time.Time) error {
 	if err := f.checkValid("SetDeadline"); err != nil {
 		return err
 	}
 	return f.pfd.SetDeadline(t)
 }

 // setReadDeadline sets the read deadline.
 func (f *File) setReadDeadline(t time.Time) error {
 	if err := f.checkValid("SetReadDeadline"); err != nil {
 		return err
 	}
 	return f.pfd.SetReadDeadline(t)
 }

 // setWriteDeadline sets the write deadline.
 func (f *File) setWriteDeadline(t time.Time) error {
 	if err := f.checkValid("SetWriteDeadline"); err != nil {
 		return err
 	}
 	return f.pfd.SetWriteDeadline(t)
 }

 // checkValid checks whether f is valid for use.
 // If not, it returns an appropriate error, perhaps incorporating the operation name op.
 func (f *File) checkValid(op string) error {
 	if f == nil {
 		return ErrInvalid
 	}
 	return nil
 }

 // ignoringEINTR makes a function call and repeats it if it returns an
 // EINTR error. This appears to be required even though we install all
 // signal handlers with SA_RESTART: see #22838, #38033, #38836, #40846.
 // Also #20400 and #36644 are issues in which a signal handler is
 // installed without setting SA_RESTART. None of these are the common case,
 // but there are enough of them that it seems that we can't avoid
 // an EINTR loop.
 func ignoringEINTR(fn func() error) error {
 	for {
 		err := fn()
 		if err != syscall.EINTR {
 			return err
 		}
 	}
 }
	// Copyright 2009 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	//go:build unix \|\| (js && wasm) \|\| wasip1 \|\| windows

	package os

	import (
	"runtime"
	"syscall"
	"time"
	)

	// Close closes the [File], rendering it unusable for I/O.
	// On files that support [File.SetDeadline], any pending I/O operations will
	// be canceled and return immediately with an [ErrClosed] error.
	// Close will return an error if it has already been called.
	func (f *File) Close() error {
	if f == nil {
	return ErrInvalid
	}
	return f.file.close()
	}

	// read reads up to len(b) bytes from the File.
	// It returns the number of bytes read and an error, if any.
	func (f *File) read(b []byte) (n int, err error) {
	n, err = f.pfd.Read(b)
	runtime.KeepAlive(f)
	return n, err
	}

	// pread reads len(b) bytes from the File starting at byte offset off.
	// It returns the number of bytes read and the error, if any.
	// EOF is signaled by a zero count with err set to nil.
	func (f *File) pread(b []byte, off int64) (n int, err error) {
	n, err = f.pfd.Pread(b, off)
	runtime.KeepAlive(f)
	return n, err
	}

	// write writes len(b) bytes to the File.
	// It returns the number of bytes written and an error, if any.
	func (f *File) write(b []byte) (n int, err error) {
	n, err = f.pfd.Write(b)
	runtime.KeepAlive(f)
	return n, err
	}

	// pwrite writes len(b) bytes to the File starting at byte offset off.
	// It returns the number of bytes written and an error, if any.
	func (f *File) pwrite(b []byte, off int64) (n int, err error) {
	n, err = f.pfd.Pwrite(b, off)
	runtime.KeepAlive(f)
	return n, err
	}

	// syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
	func syscallMode(i FileMode) (o uint32) {
	o \|= uint32(i.Perm())
	if i&ModeSetuid != 0 {
	o \|= syscall.S_ISUID
	}
	if i&ModeSetgid != 0 {
	o \|= syscall.S_ISGID
	}
	if i&ModeSticky != 0 {
	o \|= syscall.S_ISVTX
	}
	// No mapping for Go's ModeTemporary (plan9 only).
	return
	}

	// See docs in file.go:Chmod.
	func chmod(name string, mode FileMode) error {
	longName := fixLongPath(name)
	e := ignoringEINTR(func() error {
	return syscall.Chmod(longName, syscallMode(mode))
	})
	if e != nil {
	return &PathError{Op: "chmod", Path: name, Err: e}
	}
	return nil
	}

	// See docs in file.go:(*File).Chmod.
	func (f *File) chmod(mode FileMode) error {
	if err := f.checkValid("chmod"); err != nil {
	return err
	}
	if e := f.pfd.Fchmod(syscallMode(mode)); e != nil {
	return f.wrapErr("chmod", e)
	}
	return nil
	}

	// Chown changes the numeric uid and gid of the named file.
	// If the file is a symbolic link, it changes the uid and gid of the link's target.
	// A uid or gid of -1 means to not change that value.
	// If there is an error, it will be of type [*PathError].
	//
	// On Windows or Plan 9, Chown always returns the [syscall.EWINDOWS] or
	// EPLAN9 error, wrapped in *PathError.
	func Chown(name string, uid, gid int) error {
	e := ignoringEINTR(func() error {
	return syscall.Chown(name, uid, gid)
	})
	if e != nil {
	return &PathError{Op: "chown", Path: name, Err: e}
	}
	return nil
	}

	// Lchown changes the numeric uid and gid of the named file.
	// If the file is a symbolic link, it changes the uid and gid of the link itself.
	// If there is an error, it will be of type [*PathError].
	//
	// On Windows, it always returns the [syscall.EWINDOWS] error, wrapped
	// in *PathError.
	func Lchown(name string, uid, gid int) error {
	e := ignoringEINTR(func() error {
	return syscall.Lchown(name, uid, gid)
	})
	if e != nil {
	return &PathError{Op: "lchown", Path: name, Err: e}
	}
	return nil
	}

	// Chown changes the numeric uid and gid of the named file.
	// If there is an error, it will be of type [*PathError].
	//
	// On Windows, it always returns the [syscall.EWINDOWS] error, wrapped
	// in *PathError.
	func (f *File) Chown(uid, gid int) error {
	if err := f.checkValid("chown"); err != nil {
	return err
	}
	if e := f.pfd.Fchown(uid, gid); e != nil {
	return f.wrapErr("chown", e)
	}
	return nil
	}

	// Truncate changes the size of the file.
	// It does not change the I/O offset.
	// If there is an error, it will be of type [*PathError].
	func (f *File) Truncate(size int64) error {
	if err := f.checkValid("truncate"); err != nil {
	return err
	}
	if e := f.pfd.Ftruncate(size); e != nil {
	return f.wrapErr("truncate", e)
	}
	return nil
	}

	// Sync commits the current contents of the file to stable storage.
	// Typically, this means flushing the file system's in-memory copy
	// of recently written data to disk.
	func (f *File) Sync() error {
	if err := f.checkValid("sync"); err != nil {
	return err
	}
	if e := f.pfd.Fsync(); e != nil {
	return f.wrapErr("sync", e)
	}
	return nil
	}

	// Chtimes changes the access and modification times of the named
	// file, similar to the Unix utime() or utimes() functions.
	// A zero [time.Time] value will leave the corresponding file time unchanged.
	//
	// The underlying filesystem may truncate or round the values to a
	// less precise time unit.
	// If there is an error, it will be of type [*PathError].
	func Chtimes(name string, atime time.Time, mtime time.Time) error {
	var utimes [2]syscall.Timespec
	set := func(i int, t time.Time) {
	if t.IsZero() {
	utimes[i] = syscall.Timespec{Sec: _UTIME_OMIT, Nsec: _UTIME_OMIT}
	} else {
	utimes[i] = syscall.NsecToTimespec(t.UnixNano())
	}
	}
	set(0, atime)
	set(1, mtime)
	if e := syscall.UtimesNano(fixLongPath(name), utimes[0:]); e != nil {
	return &PathError{Op: "chtimes", Path: name, Err: e}
	}
	return nil
	}

	// Chdir changes the current working directory to the file,
	// which must be a directory.
	// If there is an error, it will be of type [*PathError].
	func (f *File) Chdir() error {
	if err := f.checkValid("chdir"); err != nil {
	return err
	}
	if e := f.pfd.Fchdir(); e != nil {
	return f.wrapErr("chdir", e)
	}
	return nil
	}

	// setDeadline sets the read and write deadline.
	func (f *File) setDeadline(t time.Time) error {
	if err := f.checkValid("SetDeadline"); err != nil {
	return err
	}
	return f.pfd.SetDeadline(t)
	}

	// setReadDeadline sets the read deadline.
	func (f *File) setReadDeadline(t time.Time) error {
	if err := f.checkValid("SetReadDeadline"); err != nil {
	return err
	}
	return f.pfd.SetReadDeadline(t)
	}

	// setWriteDeadline sets the write deadline.
	func (f *File) setWriteDeadline(t time.Time) error {
	if err := f.checkValid("SetWriteDeadline"); err != nil {
	return err
	}
	return f.pfd.SetWriteDeadline(t)
	}

	// checkValid checks whether f is valid for use.
	// If not, it returns an appropriate error, perhaps incorporating the operation name op.
	func (f *File) checkValid(op string) error {
	if f == nil {
	return ErrInvalid
	}
	return nil
	}

	// ignoringEINTR makes a function call and repeats it if it returns an
	// EINTR error. This appears to be required even though we install all
	// signal handlers with SA_RESTART: see #22838, #38033, #38836, #40846.
	// Also #20400 and #36644 are issues in which a signal handler is
	// installed without setting SA_RESTART. None of these are the common case,
	// but there are enough of them that it seems that we can't avoid
	// an EINTR loop.
	func ignoringEINTR(fn func() error) error {
	for {
	err := fn()
	if err != syscall.EINTR {
	return err
	}
	}
	}