2018-03-01 Paul Thomas <pault@gcc.gnu.org>

[official-gcc.git] / libgo / go / os / file_unix.go

// 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.

// +build aix darwin dragonfly freebsd linux nacl netbsd openbsd solaris

package os

import (
        "internal/poll"
        "runtime"
        "syscall"
)

// fixLongPath is a noop on non-Windows platforms.
func fixLongPath(path string) string {
        return path
}

func rename(oldname, newname string) error {
        fi, err := Lstat(newname)
        if err == nil && fi.IsDir() {
                // There are two independent errors this function can return:
                // one for a bad oldname, and one for a bad newname.
                // At this point we've determined the newname is bad.
                // But just in case oldname is also bad, prioritize returning
                // the oldname error because that's what we did historically.
                if _, err := Lstat(oldname); err != nil {
                        if pe, ok := err.(*PathError); ok {
                                err = pe.Err
                        }
                        return &LinkError{"rename", oldname, newname, err}
                }
                return &LinkError{"rename", oldname, newname, syscall.EEXIST}
        }
        err = syscall.Rename(oldname, newname)
        if err != nil {
                return &LinkError{"rename", oldname, newname, err}
        }
        return nil
}

// file is the real representation of *File.
// The extra level of indirection ensures that no clients of os
// can overwrite this data, which could cause the finalizer
// to close the wrong file descriptor.
type file struct {
        pfd         poll.FD
        name        string
        dirinfo     *dirInfo // nil unless directory being read
        nonblock    bool     // whether we set nonblocking mode
        stdoutOrErr bool     // whether this is stdout or stderr
}

// Fd returns the integer Unix file descriptor referencing the open file.
// The file descriptor is valid only until f.Close is called or f is garbage collected.
// On Unix systems this will cause the SetDeadline methods to stop working.
func (f *File) Fd() uintptr {
        if f == nil {
                return ^(uintptr(0))
        }

        // If we put the file descriptor into nonblocking mode,
        // then set it to blocking mode before we return it,
        // because historically we have always returned a descriptor
        // opened in blocking mode. The File will continue to work,
        // but any blocking operation will tie up a thread.
        if f.nonblock {
                f.pfd.SetBlocking()
        }

        return uintptr(f.pfd.Sysfd)
}

// NewFile returns a new File with the given file descriptor and
// name. The returned value will be nil if fd is not a valid file
// descriptor.
func NewFile(fd uintptr, name string) *File {
        return newFile(fd, name, kindNewFile)
}

// newFileKind describes the kind of file to newFile.
type newFileKind int

const (
        kindNewFile newFileKind = iota
        kindOpenFile
        kindPipe
)

// newFile is like NewFile, but if called from OpenFile or Pipe
// (as passed in the kind parameter) it tries to add the file to
// the runtime poller.
func newFile(fd uintptr, name string, kind newFileKind) *File {
        fdi := int(fd)
        if fdi < 0 {
                return nil
        }
        f := &File{&file{
                pfd: poll.FD{
                        Sysfd:         fdi,
                        IsStream:      true,
                        ZeroReadIsEOF: true,
                },
                name:        name,
                stdoutOrErr: fdi == 1 || fdi == 2,
        }}

        // Don't try to use kqueue with regular files on FreeBSD.
        // It crashes the system unpredictably while running all.bash.
        // Issue 19093.
        if runtime.GOOS == "freebsd" && kind == kindOpenFile {
                kind = kindNewFile
        }

        pollable := kind == kindOpenFile || kind == kindPipe
        if err := f.pfd.Init("file", pollable); err != nil {
                // An error here indicates a failure to register
                // with the netpoll system. That can happen for
                // a file descriptor that is not supported by
                // epoll/kqueue; for example, disk files on
                // GNU/Linux systems. We assume that any real error
                // will show up in later I/O.
        } else if pollable {
                // We successfully registered with netpoll, so put
                // the file into nonblocking mode.
                if err := syscall.SetNonblock(fdi, true); err == nil {
                        f.nonblock = true
                }
        }

        runtime.SetFinalizer(f.file, (*file).close)
        return f
}

// Auxiliary information if the File describes a directory
type dirInfo struct {
        buf []byte       // buffer for directory I/O
        dir *syscall.DIR // from opendir
}

// epipecheck raises SIGPIPE if we get an EPIPE error on standard
// output or standard error. See the SIGPIPE docs in os/signal, and
// issue 11845.
func epipecheck(file *File, e error) {
        if e == syscall.EPIPE && file.stdoutOrErr {
                sigpipe()
        }
}

// DevNull is the name of the operating system's ``null device.''
// On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
const DevNull = "/dev/null"

// openFileNolog is the Unix implementation of OpenFile.
func openFileNolog(name string, flag int, perm FileMode) (*File, error) {
        chmod := false
        if !supportsCreateWithStickyBit && flag&O_CREATE != 0 && perm&ModeSticky != 0 {
                if _, err := Stat(name); IsNotExist(err) {
                        chmod = true
                }
        }

        var r int
        for {
                var e error
                r, e = syscall.Open(name, flag|syscall.O_CLOEXEC, syscallMode(perm))
                if e == nil {
                        break
                }

                // On OS X, sigaction(2) doesn't guarantee that SA_RESTART will cause
                // open(2) to be restarted for regular files. This is easy to reproduce on
                // fuse file systems (see http://golang.org/issue/11180).
                if runtime.GOOS == "darwin" && e == syscall.EINTR {
                        continue
                }

                return nil, &PathError{"open", name, e}
        }

        // open(2) itself won't handle the sticky bit on *BSD and Solaris
        if chmod {
                Chmod(name, perm)
        }

        // There's a race here with fork/exec, which we are
        // content to live with. See ../syscall/exec_unix.go.
        if !supportsCloseOnExec {
                syscall.CloseOnExec(r)
        }

        return newFile(uintptr(r), name, kindOpenFile), nil
}

// Close closes the File, rendering it unusable for I/O.
// It returns an error, if any.
func (f *File) Close() error {
        if f == nil {
                return ErrInvalid
        }
        return f.file.close()
}

func (file *file) close() error {
        if file == nil {
                return syscall.EINVAL
        }
        var err error
        if e := file.pfd.Close(); e != nil {
                if e == poll.ErrFileClosing {
                        e = ErrClosed
                }
                err = &PathError{"close", file.name, e}
        }

        if file.dirinfo != nil {
                syscall.Entersyscall()
                i := libc_closedir(file.dirinfo.dir)
                errno := syscall.GetErrno()
                syscall.Exitsyscall()
                file.dirinfo = nil
                if i < 0 && err == nil {
                        err = &PathError{"closedir", file.name, errno}
                }
        }

        // no need for a finalizer anymore
        runtime.SetFinalizer(file, nil)
        return err
}

// 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
}

// seek sets the offset for the next Read or Write on file to offset, interpreted
// according to whence: 0 means relative to the origin of the file, 1 means
// relative to the current offset, and 2 means relative to the end.
// It returns the new offset and an error, if any.
func (f *File) seek(offset int64, whence int) (ret int64, err error) {
        ret, err = f.pfd.Seek(offset, whence)
        runtime.KeepAlive(f)
        return ret, err
}

// Truncate changes the size of the named file.
// If the file is a symbolic link, it changes the size of the link's target.
// If there is an error, it will be of type *PathError.
func Truncate(name string, size int64) error {
        if e := syscall.Truncate(name, size); e != nil {
                return &PathError{"truncate", name, e}
        }
        return nil
}

// Remove removes the named file or directory.
// If there is an error, it will be of type *PathError.
func Remove(name string) error {
        // System call interface forces us to know
        // whether name is a file or directory.
        // Try both: it is cheaper on average than
        // doing a Stat plus the right one.
        e := syscall.Unlink(name)
        if e == nil {
                return nil
        }
        e1 := syscall.Rmdir(name)
        if e1 == nil {
                return nil
        }

        // Both failed: figure out which error to return.
        // OS X and Linux differ on whether unlink(dir)
        // returns EISDIR, so can't use that. However,
        // both agree that rmdir(file) returns ENOTDIR,
        // so we can use that to decide which error is real.
        // Rmdir might also return ENOTDIR if given a bad
        // file path, like /etc/passwd/foo, but in that case,
        // both errors will be ENOTDIR, so it's okay to
        // use the error from unlink.
        if e1 != syscall.ENOTDIR {
                e = e1
        }
        return &PathError{"remove", name, e}
}

func tempDir() string {
        dir := Getenv("TMPDIR")
        if dir == "" {
                if runtime.GOOS == "android" {
                        dir = "/data/local/tmp"
                } else {
                        dir = "/tmp"
                }
        }
        return dir
}

// Link creates newname as a hard link to the oldname file.
// If there is an error, it will be of type *LinkError.
func Link(oldname, newname string) error {
        e := syscall.Link(oldname, newname)
        if e != nil {
                return &LinkError{"link", oldname, newname, e}
        }
        return nil
}

// Symlink creates newname as a symbolic link to oldname.
// If there is an error, it will be of type *LinkError.
func Symlink(oldname, newname string) error {
        e := syscall.Symlink(oldname, newname)
        if e != nil {
                return &LinkError{"symlink", oldname, newname, e}
        }
        return nil
}