1 files changed, 151 insertions, 0 deletions
diff --git a/pkg/v1/cache/fs.go b/pkg/v1/cache/fs.go
new file mode 100644
index 0000000..75b826e
--- /dev/null
+++ b/pkg/v1/cache/fs.go
@@ -0,0 +1,151 @@
+// 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)
+}