distribution/registry/storage/driver/walk.go
Sargun Dhillon 32ac467992 Introduce Walk Method Per Storage Driver
Move the Walk types into registry/storage/driver, and add a Walk method to each
storage driver. Although this is yet another API to implement, there is a fall
back implementation that relies on List and Stat. For some filesystems this is
very slow.

Also, this WalkDir Method conforms better do a traditional WalkDir (a la filepath).

This change is in preparation for refactoring.

Signed-off-by: Sargun Dhillon <sargun@sargun.me>
2018-01-07 22:45:17 -08:00

52 lines
1.6 KiB
Go

package driver
import (
"context"
"errors"
"sort"
)
// ErrSkipDir is used as a return value from onFileFunc to indicate that
// the directory named in the call is to be skipped. It is not returned
// as an error by any function.
var ErrSkipDir = errors.New("skip this directory")
// WalkFn is called once per file by Walk
type WalkFn func(fileInfo FileInfo) error
// WalkFallback traverses a filesystem defined within driver, starting
// from the given path, calling f on each file. It uses the List method and Stat to drive itself.
// If the returned error from the WalkFn is ErrSkipDir and fileInfo refers
// to a directory, the directory will not be entered and Walk
// will continue the traversal. If fileInfo refers to a normal file, processing stops
func WalkFallback(ctx context.Context, driver StorageDriver, from string, f WalkFn) error {
children, err := driver.List(ctx, from)
if err != nil {
return err
}
sort.Stable(sort.StringSlice(children))
for _, child := range children {
// TODO(stevvooe): Calling driver.Stat for every entry is quite
// expensive when running against backends with a slow Stat
// implementation, such as s3. This is very likely a serious
// performance bottleneck.
fileInfo, err := driver.Stat(ctx, child)
if err != nil {
return err
}
err = f(fileInfo)
if err == nil && fileInfo.IsDir() {
if err := WalkFallback(ctx, driver, child, f); err != nil {
return err
}
} else if err == ErrSkipDir {
// Stop iteration if it's a file, otherwise noop if it's a directory
if !fileInfo.IsDir() {
return nil
}
} else if err != nil {
return err
}
}
return nil
}