rclone/vfs/read_write.go

460 lines
10 KiB
Go

package vfs
import (
"fmt"
"io"
"os"
"sync"
"github.com/rclone/rclone/fs"
"github.com/rclone/rclone/fs/log"
"github.com/rclone/rclone/vfs/vfscache"
)
// RWFileHandle is a handle that can be open for read and write.
//
// It will be open to a temporary file which, when closed, will be
// transferred to the remote.
type RWFileHandle struct {
// read only variables
file *File
d *Dir
flags int // open flags
item *vfscache.Item // cached file item
// read write variables protected by mutex
mu sync.Mutex
offset int64 // file pointer offset
closed bool // set if handle has been closed
opened bool
writeCalled bool // if any Write() methods have been called
}
func newRWFileHandle(d *Dir, f *File, flags int) (fh *RWFileHandle, err error) {
defer log.Trace(f.Path(), "")("err=%v", &err)
// get an item to represent this from the cache
item := d.vfs.cache.Item(f.Path())
exists := f.exists() || (item.Exists() && !item.WrittenBack())
// if O_CREATE and O_EXCL are set and if path already exists, then return EEXIST
if flags&(os.O_CREATE|os.O_EXCL) == os.O_CREATE|os.O_EXCL && exists {
return nil, EEXIST
}
fh = &RWFileHandle{
file: f,
d: d,
flags: flags,
item: item,
}
// truncate immediately if O_TRUNC is set or O_CREATE is set and file doesn't exist
if !fh.readOnly() && (fh.flags&os.O_TRUNC != 0 || (fh.flags&os.O_CREATE != 0 && !exists)) {
err = fh.Truncate(0)
if err != nil {
return nil, fmt.Errorf("cache open with O_TRUNC: failed to truncate: %w", err)
}
// we definitely need to write back the item even if we don't write to it
item.Dirty()
}
if !fh.readOnly() {
fh.file.addWriter(fh)
}
return fh, nil
}
// readOnly returns whether flags say fh is read only
func (fh *RWFileHandle) readOnly() bool {
return (fh.flags & accessModeMask) == os.O_RDONLY
}
// writeOnly returns whether flags say fh is write only
func (fh *RWFileHandle) writeOnly() bool {
return (fh.flags & accessModeMask) == os.O_WRONLY
}
// openPending opens the file if there is a pending open
//
// call with the lock held
func (fh *RWFileHandle) openPending() (err error) {
if fh.opened {
return nil
}
defer log.Trace(fh.logPrefix(), "")("err=%v", &err)
fh.file.muRW.Lock()
defer fh.file.muRW.Unlock()
o := fh.file.getObject()
err = fh.item.Open(o)
if err != nil {
return fmt.Errorf("open RW handle failed to open cache file: %w", err)
}
size := fh._size() // update size in file and read size
if fh.flags&os.O_APPEND != 0 {
fh.offset = size
fs.Debugf(fh.logPrefix(), "open at offset %d", fh.offset)
} else {
fh.offset = 0
}
fh.opened = true
fh.d.addObject(fh.file) // make sure the directory has this object in it now
return nil
}
// String converts it to printable
func (fh *RWFileHandle) String() string {
if fh == nil {
return "<nil *RWFileHandle>"
}
if fh.file == nil {
return "<nil *RWFileHandle.file>"
}
return fh.file.String() + " (rw)"
}
// Node returns the Node associated with this - satisfies Noder interface
func (fh *RWFileHandle) Node() Node {
fh.mu.Lock()
defer fh.mu.Unlock()
return fh.file
}
// updateSize updates the size of the file if necessary
//
// Must be called with fh.mu held
func (fh *RWFileHandle) updateSize() {
// If read only or not opened then ignore
if fh.readOnly() || !fh.opened {
return
}
size := fh._size()
fh.file.setSize(size)
}
// close the file handle returning EBADF if it has been
// closed already.
//
// Must be called with fh.mu held.
//
// Note that we leave the file around in the cache on error conditions
// to give the user a chance to recover it.
func (fh *RWFileHandle) close() (err error) {
defer log.Trace(fh.logPrefix(), "")("err=%v", &err)
fh.file.muRW.Lock()
defer fh.file.muRW.Unlock()
if fh.closed {
return ECLOSED
}
fh.closed = true
fh.updateSize()
if fh.opened {
err = fh.item.Close(fh.file.setObject)
fh.opened = false
} else {
// apply any pending mod times if any
_ = fh.file.applyPendingModTime()
}
if !fh.readOnly() {
fh.file.delWriter(fh)
}
return err
}
// Close closes the file
func (fh *RWFileHandle) Close() error {
fh.mu.Lock()
defer fh.mu.Unlock()
return fh.close()
}
// Flush is called each time the file or directory is closed.
// Because there can be multiple file descriptors referring to a
// single opened file, Flush can be called multiple times.
func (fh *RWFileHandle) Flush() error {
fh.mu.Lock()
fs.Debugf(fh.logPrefix(), "RWFileHandle.Flush")
fh.updateSize()
fh.mu.Unlock()
return nil
}
// Release is called when we are finished with the file handle
//
// It isn't called directly from userspace so the error is ignored by
// the kernel
func (fh *RWFileHandle) Release() error {
fh.mu.Lock()
defer fh.mu.Unlock()
fs.Debugf(fh.logPrefix(), "RWFileHandle.Release")
if fh.closed {
// Don't return an error if called twice
return nil
}
err := fh.close()
if err != nil {
fs.Errorf(fh.logPrefix(), "RWFileHandle.Release error: %v", err)
}
return err
}
// _size returns the size of the underlying file and also sets it in
// the owning file
//
// call with the lock held
func (fh *RWFileHandle) _size() int64 {
size, err := fh.item.GetSize()
if err != nil {
o := fh.file.getObject()
if o != nil {
size = o.Size()
} else {
fs.Errorf(fh.logPrefix(), "Couldn't read size of file")
size = 0
}
}
fh.file.setSize(size)
return size
}
// Size returns the size of the underlying file
func (fh *RWFileHandle) Size() int64 {
fh.mu.Lock()
defer fh.mu.Unlock()
return fh._size()
}
// Stat returns info about the file
func (fh *RWFileHandle) Stat() (os.FileInfo, error) {
fh.mu.Lock()
defer fh.mu.Unlock()
return fh.file, nil
}
// _readAt bytes from the file at off
//
// if release is set then it releases the mutex just before doing the IO
//
// call with lock held
func (fh *RWFileHandle) _readAt(b []byte, off int64, release bool) (n int, err error) {
defer log.Trace(fh.logPrefix(), "size=%d, off=%d", len(b), off)("n=%d, err=%v", &n, &err)
if fh.closed {
return n, ECLOSED
}
if fh.writeOnly() {
return n, EBADF
}
if off >= fh._size() {
return n, io.EOF
}
if err = fh.openPending(); err != nil {
return n, err
}
if release {
// Do the writing with fh.mu unlocked
fh.mu.Unlock()
}
n, err = fh.item.ReadAt(b, off)
if release {
fh.mu.Lock()
}
return n, err
}
// ReadAt bytes from the file at off
func (fh *RWFileHandle) ReadAt(b []byte, off int64) (n int, err error) {
fh.mu.Lock()
defer fh.mu.Unlock()
return fh._readAt(b, off, true)
}
// Read bytes from the file
func (fh *RWFileHandle) Read(b []byte) (n int, err error) {
fh.mu.Lock()
defer fh.mu.Unlock()
n, err = fh._readAt(b, fh.offset, false)
fh.offset += int64(n)
return n, err
}
// Seek to new file position
func (fh *RWFileHandle) Seek(offset int64, whence int) (ret int64, err error) {
fh.mu.Lock()
defer fh.mu.Unlock()
if fh.closed {
return 0, ECLOSED
}
if !fh.opened && offset == 0 && whence != 2 {
return 0, nil
}
if err = fh.openPending(); err != nil {
return ret, err
}
switch whence {
case io.SeekStart:
fh.offset = 0
case io.SeekEnd:
fh.offset = fh._size()
}
fh.offset += offset
// we don't check the offset - the next Read will
return fh.offset, nil
}
// _writeAt bytes to the file at off
//
// if release is set then it releases the mutex just before doing the IO
//
// call with lock held
func (fh *RWFileHandle) _writeAt(b []byte, off int64, release bool) (n int, err error) {
defer log.Trace(fh.logPrefix(), "size=%d, off=%d", len(b), off)("n=%d, err=%v", &n, &err)
if fh.closed {
return n, ECLOSED
}
if fh.readOnly() {
return n, EBADF
}
if err = fh.openPending(); err != nil {
return n, err
}
if fh.flags&os.O_APPEND != 0 {
// From open(2): Before each write(2), the file offset is
// positioned at the end of the file, as if with lseek(2).
size := fh._size()
fh.offset = size
off = fh.offset
}
fh.writeCalled = true
if release {
// Do the writing with fh.mu unlocked
fh.mu.Unlock()
}
n, err = fh.item.WriteAt(b, off)
if release {
fh.mu.Lock()
}
if err != nil {
return n, err
}
_ = fh._size()
return n, err
}
// WriteAt bytes to the file at off
func (fh *RWFileHandle) WriteAt(b []byte, off int64) (n int, err error) {
fh.mu.Lock()
n, err = fh._writeAt(b, off, true)
if fh.flags&os.O_APPEND != 0 {
fh.offset += int64(n)
}
fh.mu.Unlock()
return n, err
}
// Write bytes to the file
func (fh *RWFileHandle) Write(b []byte) (n int, err error) {
fh.mu.Lock()
defer fh.mu.Unlock()
n, err = fh._writeAt(b, fh.offset, false)
fh.offset += int64(n)
return n, err
}
// WriteString a string to the file
func (fh *RWFileHandle) WriteString(s string) (n int, err error) {
return fh.Write([]byte(s))
}
// Truncate file to given size
//
// Call with mutex held
func (fh *RWFileHandle) _truncate(size int64) (err error) {
if size == fh._size() {
return nil
}
fh.file.setSize(size)
return fh.item.Truncate(size)
}
// Truncate file to given size
func (fh *RWFileHandle) Truncate(size int64) (err error) {
fh.mu.Lock()
defer fh.mu.Unlock()
if fh.closed {
return ECLOSED
}
if err = fh.openPending(); err != nil {
return err
}
return fh._truncate(size)
}
// 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 (fh *RWFileHandle) Sync() error {
fh.mu.Lock()
defer fh.mu.Unlock()
if fh.closed {
return ECLOSED
}
if !fh.opened {
return nil
}
if fh.readOnly() {
return nil
}
return fh.item.Sync()
}
func (fh *RWFileHandle) logPrefix() string {
return fmt.Sprintf("%s(%p)", fh.file.Path(), fh)
}
// Chdir changes the current working directory to the file, which must
// be a directory.
func (fh *RWFileHandle) Chdir() error {
return ENOSYS
}
// Chmod changes the mode of the file to mode.
func (fh *RWFileHandle) Chmod(mode os.FileMode) error {
return ENOSYS
}
// Chown changes the numeric uid and gid of the named file.
func (fh *RWFileHandle) Chown(uid, gid int) error {
return ENOSYS
}
// Fd returns the integer Unix file descriptor referencing the open file.
func (fh *RWFileHandle) Fd() uintptr {
return 0xdeadbeef // FIXME
}
// Name returns the name of the file from the underlying Object.
func (fh *RWFileHandle) Name() string {
return fh.file.String()
}
// Readdir reads the contents of the directory associated with file.
func (fh *RWFileHandle) Readdir(n int) ([]os.FileInfo, error) {
return nil, ENOSYS
}
// Readdirnames reads the contents of the directory associated with file.
func (fh *RWFileHandle) Readdirnames(n int) (names []string, err error) {
return nil, ENOSYS
}