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package afero
import (
"io"
"os"
"path/filepath"
"syscall"
)
// The UnionFile implements the afero.File interface and will be returned
// when reading a directory present at least in the overlay or opening a file
// for writing.
//
// The calls to
// Readdir() and Readdirnames() merge the file os.FileInfo / names from the
// base and the overlay - for files present in both layers, only those
// from the overlay will be used.
//
// When opening files for writing (Create() / OpenFile() with the right flags)
// the operations will be done in both layers, starting with the overlay. A
// successful read in the overlay will move the cursor position in the base layer
// by the number of bytes read.
type UnionFile struct {
base File
layer File
off int
files []os.FileInfo
}
func (f *UnionFile) Close() error {
// first close base, so we have a newer timestamp in the overlay. If we'd close
// the overlay first, we'd get a cacheStale the next time we access this file
// -> cache would be useless ;-)
if f.base != nil {
f.base.Close()
}
if f.layer != nil {
return f.layer.Close()
}
return BADFD
}
func (f *UnionFile) Read(s []byte) (int, error) {
if f.layer != nil {
n, err := f.layer.Read(s)
if (err == nil || err == io.EOF) && f.base != nil {
// advance the file position also in the base file, the next
// call may be a write at this position (or a seek with SEEK_CUR)
if _, seekErr := f.base.Seek(int64(n), os.SEEK_CUR); seekErr != nil {
// only overwrite err in case the seek fails: we need to
// report an eventual io.EOF to the caller
err = seekErr
}
}
return n, err
}
if f.base != nil {
return f.base.Read(s)
}
return 0, BADFD
}
func (f *UnionFile) ReadAt(s []byte, o int64) (int, error) {
if f.layer != nil {
n, err := f.layer.ReadAt(s, o)
if (err == nil || err == io.EOF) && f.base != nil {
_, err = f.base.Seek(o+int64(n), os.SEEK_SET)
}
return n, err
}
if f.base != nil {
return f.base.ReadAt(s, o)
}
return 0, BADFD
}
func (f *UnionFile) Seek(o int64, w int) (pos int64, err error) {
if f.layer != nil {
pos, err = f.layer.Seek(o, w)
if (err == nil || err == io.EOF) && f.base != nil {
_, err = f.base.Seek(o, w)
}
return pos, err
}
if f.base != nil {
return f.base.Seek(o, w)
}
return 0, BADFD
}
func (f *UnionFile) Write(s []byte) (n int, err error) {
if f.layer != nil {
n, err = f.layer.Write(s)
if err == nil && f.base != nil { // hmm, do we have fixed size files where a write may hit the EOF mark?
_, err = f.base.Write(s)
}
return n, err
}
if f.base != nil {
return f.base.Write(s)
}
return 0, BADFD
}
func (f *UnionFile) WriteAt(s []byte, o int64) (n int, err error) {
if f.layer != nil {
n, err = f.layer.WriteAt(s, o)
if err == nil && f.base != nil {
_, err = f.base.WriteAt(s, o)
}
return n, err
}
if f.base != nil {
return f.base.WriteAt(s, o)
}
return 0, BADFD
}
func (f *UnionFile) Name() string {
if f.layer != nil {
return f.layer.Name()
}
return f.base.Name()
}
// Readdir will weave the two directories together and
// return a single view of the overlayed directories
func (f *UnionFile) Readdir(c int) (ofi []os.FileInfo, err error) {
if f.off == 0 {
var files = make(map[string]os.FileInfo)
var rfi []os.FileInfo
if f.layer != nil {
rfi, err = f.layer.Readdir(-1)
if err != nil {
return nil, err
}
for _, fi := range rfi {
files[fi.Name()] = fi
}
}
if f.base != nil {
rfi, err = f.base.Readdir(-1)
if err != nil {
return nil, err
}
for _, fi := range rfi {
if _, exists := files[fi.Name()]; !exists {
files[fi.Name()] = fi
}
}
}
for _, fi := range files {
f.files = append(f.files, fi)
}
}
if c == -1 {
return f.files[f.off:], nil
}
defer func() { f.off += c }()
return f.files[f.off:c], nil
}
func (f *UnionFile) Readdirnames(c int) ([]string, error) {
rfi, err := f.Readdir(c)
if err != nil {
return nil, err
}
var names []string
for _, fi := range rfi {
names = append(names, fi.Name())
}
return names, nil
}
func (f *UnionFile) Stat() (os.FileInfo, error) {
if f.layer != nil {
return f.layer.Stat()
}
if f.base != nil {
return f.base.Stat()
}
return nil, BADFD
}
func (f *UnionFile) Sync() (err error) {
if f.layer != nil {
err = f.layer.Sync()
if err == nil && f.base != nil {
err = f.base.Sync()
}
return err
}
if f.base != nil {
return f.base.Sync()
}
return BADFD
}
func (f *UnionFile) Truncate(s int64) (err error) {
if f.layer != nil {
err = f.layer.Truncate(s)
if err == nil && f.base != nil {
err = f.base.Truncate(s)
}
return err
}
if f.base != nil {
return f.base.Truncate(s)
}
return BADFD
}
func (f *UnionFile) WriteString(s string) (n int, err error) {
if f.layer != nil {
n, err = f.layer.WriteString(s)
if err == nil && f.base != nil {
_, err = f.base.WriteString(s)
}
return n, err
}
if f.base != nil {
return f.base.WriteString(s)
}
return 0, BADFD
}
func copyToLayer(base Fs, layer Fs, name string) error {
bfh, err := base.Open(name)
if err != nil {
return err
}
defer bfh.Close()
// First make sure the directory exists
exists, err := Exists(layer, filepath.Dir(name))
if err != nil {
return err
}
if !exists {
err = layer.MkdirAll(filepath.Dir(name), 0777) // FIXME?
if err != nil {
return err
}
}
// Create the file on the overlay
lfh, err := layer.Create(name)
if err != nil {
return err
}
n, err := io.Copy(lfh, bfh)
if err != nil {
// If anything fails, clean up the file
layer.Remove(name)
lfh.Close()
return err
}
bfi, err := bfh.Stat()
if err != nil || bfi.Size() != n {
layer.Remove(name)
lfh.Close()
return syscall.EIO
}
err = lfh.Close()
if err != nil {
layer.Remove(name)
lfh.Close()
return err
}
return layer.Chtimes(name, bfi.ModTime(), bfi.ModTime())
}
|
