rclone/cmd/mountlib/file.go

221 lines
4.9 KiB
Go
Raw Normal View History

package mountlib
import (
"path"
"sync"
"sync/atomic"
"time"
"github.com/ncw/rclone/fs"
"github.com/pkg/errors"
)
// File represents a file
type File struct {
inode uint64 // inode number
size int64 // size of file - read and written with atomic int64 - must be 64 bit aligned
d *Dir // parent directory - read only
mu sync.RWMutex // protects the following
o fs.Object // NB o may be nil if file is being written
leaf string // leaf name of the object
writers int // number of writers for this file
pendingModTime time.Time // will be applied once o becomes available, i.e. after file was written
}
// newFile creates a new File
func newFile(d *Dir, o fs.Object, leaf string) *File {
return &File{
d: d,
o: o,
leaf: leaf,
inode: NewInode(),
}
}
// String converts it to printable
func (f *File) String() string {
if f == nil {
return "<nil *File>"
}
return path.Join(f.d.path, f.leaf)
}
// IsFile returns true for File - satisfies Node interface
func (f *File) IsFile() bool {
return true
}
// Inode returns the inode number - satisfies Node interface
func (f *File) Inode() uint64 {
return f.inode
}
// Node returns the Node assocuated with this - satisfies Noder interface
func (f *File) Node() Node {
return f
}
// rename should be called to update f.o and f.d after a rename
func (f *File) rename(d *Dir, o fs.Object) {
f.mu.Lock()
f.o = o
f.d = d
f.mu.Unlock()
}
// addWriters increments or decrements the writers
func (f *File) addWriters(n int) {
f.mu.Lock()
f.writers += n
f.mu.Unlock()
}
// Attr fills out the attributes for the file
func (f *File) Attr(noModTime bool) (modTime time.Time, Size, Blocks uint64, err error) {
f.mu.Lock()
defer f.mu.Unlock()
// if o is nil it isn't valid yet or there are writers, so return the size so far
if f.o == nil || f.writers != 0 {
Size = uint64(atomic.LoadInt64(&f.size))
if !noModTime && !f.pendingModTime.IsZero() {
modTime = f.pendingModTime
}
} else {
Size = uint64(f.o.Size())
if !noModTime {
modTime = f.o.ModTime()
}
}
Blocks = (Size + 511) / 512
// fs.Debugf(f.o, "File.Attr modTime=%v, Size=%d, Blocks=%v", modTime, Size, Blocks)
return
}
// SetModTime sets the modtime for the file
func (f *File) SetModTime(modTime time.Time) error {
if f.d.fsys.readOnly {
return EROFS
}
f.mu.Lock()
defer f.mu.Unlock()
f.pendingModTime = modTime
if f.o != nil {
return f.applyPendingModTime()
}
// queue up for later, hoping f.o becomes available
return nil
}
// call with the mutex held
func (f *File) applyPendingModTime() error {
defer func() { f.pendingModTime = time.Time{} }()
if f.pendingModTime.IsZero() {
return nil
}
if f.o == nil {
return errors.New("Cannot apply ModTime, file object is not available")
}
err := f.o.SetModTime(f.pendingModTime)
switch err {
case nil:
fs.Debugf(f.o, "File.applyPendingModTime OK")
case fs.ErrorCantSetModTime:
// do nothing, in order to not break "touch somefile" if it exists already
default:
fs.Errorf(f.o, "File.applyPendingModTime error: %v", err)
return err
}
return nil
}
// Update the size while writing
func (f *File) setSize(n int64) {
atomic.StoreInt64(&f.size, n)
}
// Update the object when written
func (f *File) setObject(o fs.Object) {
f.mu.Lock()
defer f.mu.Unlock()
f.o = o
_ = f.applyPendingModTime()
f.d.addObject(o, f)
}
// Wait for f.o to become non nil for a short time returning it or an
// error
//
// Call without the mutex held
func (f *File) waitForValidObject() (o fs.Object, err error) {
for i := 0; i < 50; i++ {
f.mu.Lock()
o = f.o
writers := f.writers
f.mu.Unlock()
if o != nil {
return o, nil
}
if writers == 0 {
return nil, errors.New("can't open file - writer failed")
}
time.Sleep(100 * time.Millisecond)
}
return nil, ENOENT
}
// OpenRead open the file for read
func (f *File) OpenRead() (fh *ReadFileHandle, err error) {
// if o is nil it isn't valid yet
o, err := f.waitForValidObject()
if err != nil {
return nil, err
}
// fs.Debugf(o, "File.OpenRead")
fh, err = newReadFileHandle(f, o)
err = errors.Wrap(err, "open for read")
if err != nil {
fs.Errorf(o, "File.OpenRead failed: %v", err)
return nil, err
}
return fh, nil
}
// OpenWrite open the file for write
func (f *File) OpenWrite() (fh *WriteFileHandle, err error) {
if f.d.fsys.readOnly {
return nil, EROFS
}
// if o is nil it isn't valid yet
o, err := f.waitForValidObject()
if err != nil {
return nil, err
}
// fs.Debugf(o, "File.OpenWrite")
src := newCreateInfo(f.d.f, o.Remote())
fh, err = newWriteFileHandle(f.d, f, src)
err = errors.Wrap(err, "open for write")
if err != nil {
fs.Errorf(o, "File.OpenWrite failed: %v", err)
return nil, err
}
return fh, nil
}
// Fsync the file
//
// Note that we don't do anything except return OK
func (f *File) Fsync() error {
return nil
}