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// Copyright 2021 Google LLC All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package cache
import (
"errors"
"fmt"
"io"
"os"
"path/filepath"
"runtime"
v1 "github.com/google/go-containerregistry/pkg/v1"
"github.com/google/go-containerregistry/pkg/v1/tarball"
)
type fscache struct {
path string
}
// NewFilesystemCache returns a Cache implementation backed by files.
func NewFilesystemCache(path string) Cache {
return &fscache{path}
}
func (fs *fscache) Put(l v1.Layer) (v1.Layer, error) {
digest, err := l.Digest()
if err != nil {
return nil, err
}
diffID, err := l.DiffID()
if err != nil {
return nil, err
}
return &layer{
Layer: l,
path: fs.path,
digest: digest,
diffID: diffID,
}, nil
}
type layer struct {
v1.Layer
path string
digest, diffID v1.Hash
}
func (l *layer) create(h v1.Hash) (io.WriteCloser, error) {
if err := os.MkdirAll(l.path, 0700); err != nil {
return nil, err
}
return os.Create(cachepath(l.path, h))
}
func (l *layer) Compressed() (io.ReadCloser, error) {
f, err := l.create(l.digest)
if err != nil {
return nil, err
}
rc, err := l.Layer.Compressed()
if err != nil {
return nil, err
}
return &readcloser{
t: io.TeeReader(rc, f),
closes: []func() error{rc.Close, f.Close},
}, nil
}
func (l *layer) Uncompressed() (io.ReadCloser, error) {
f, err := l.create(l.diffID)
if err != nil {
return nil, err
}
rc, err := l.Layer.Uncompressed()
if err != nil {
return nil, err
}
return &readcloser{
t: io.TeeReader(rc, f),
closes: []func() error{rc.Close, f.Close},
}, nil
}
type readcloser struct {
t io.Reader
closes []func() error
}
func (rc *readcloser) Read(b []byte) (int, error) {
return rc.t.Read(b)
}
func (rc *readcloser) Close() error {
// Call all Close methods, even if any returned an error. Return the
// first returned error.
var err error
for _, c := range rc.closes {
lastErr := c()
if err == nil {
err = lastErr
}
}
return err
}
func (fs *fscache) Get(h v1.Hash) (v1.Layer, error) {
l, err := tarball.LayerFromFile(cachepath(fs.path, h))
if os.IsNotExist(err) {
return nil, ErrNotFound
}
if errors.Is(err, io.ErrUnexpectedEOF) {
// Delete and return ErrNotFound because the layer was incomplete.
if err := fs.Delete(h); err != nil {
return nil, err
}
return nil, ErrNotFound
}
return l, err
}
func (fs *fscache) Delete(h v1.Hash) error {
err := os.Remove(cachepath(fs.path, h))
if os.IsNotExist(err) {
return ErrNotFound
}
return err
}
func cachepath(path string, h v1.Hash) string {
var file string
if runtime.GOOS == "windows" {
file = fmt.Sprintf("%s-%s", h.Algorithm, h.Hex)
} else {
file = h.String()
}
return filepath.Join(path, file)
}
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