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package staticfs
import (
"context"
"io"
"io/fs"
"os"
"github.com/tonistiigi/fsutil"
"golang.org/x/sync/errgroup"
)
type MergeFS struct {
Lower fsutil.FS
Upper fsutil.FS
}
var _ fsutil.FS = &MergeFS{}
func NewMergeFS(lower, upper fsutil.FS) *MergeFS {
return &MergeFS{
Lower: lower,
Upper: upper,
}
}
type record struct {
path string
entry fs.DirEntry
err error
}
func (r *record) key() string {
if r == nil {
return ""
}
return convertPathToKey(r.path)
}
func (mfs *MergeFS) Walk(ctx context.Context, target string, fn fs.WalkDirFunc) error {
ch1 := make(chan *record, 10)
ch2 := make(chan *record, 10)
eg, ctx := errgroup.WithContext(ctx)
eg.Go(func() error {
defer close(ch1)
return mfs.Lower.Walk(ctx, target, func(path string, entry fs.DirEntry, err error) error {
select {
case ch1 <- &record{path: path, entry: entry, err: err}:
case <-ctx.Done():
}
return context.Cause(ctx)
})
})
eg.Go(func() error {
defer close(ch2)
return mfs.Upper.Walk(ctx, target, func(path string, entry fs.DirEntry, err error) error {
select {
case ch2 <- &record{path: path, entry: entry, err: err}:
case <-ctx.Done():
}
return context.Cause(ctx)
})
})
eg.Go(func() error {
next1, ok1 := <-ch1
key1 := next1.key()
next2, ok2 := <-ch2
key2 := next2.key()
for {
if !ok1 && !ok2 {
break
}
if !ok2 || ok1 && key1 < key2 {
if err := fn(next1.path, next1.entry, next1.err); err != nil {
return err
}
next1, ok1 = <-ch1
key1 = next1.key()
} else if !ok1 || ok2 && key1 >= key2 {
if err := fn(next2.path, next2.entry, next2.err); err != nil {
return err
}
if ok1 && key1 == key2 {
next1, ok1 = <-ch1
key1 = next1.key()
}
next2, ok2 = <-ch2
key2 = next2.key()
}
}
return nil
})
return eg.Wait()
}
func (mfs *MergeFS) Open(p string) (io.ReadCloser, error) {
r, err := mfs.Upper.Open(p)
if err != nil {
if !os.IsNotExist(err) {
return nil, err
}
return mfs.Lower.Open(p)
}
return r, nil
}
|
