1/*
2   Copyright The containerd Authors.
3
4   Licensed under the Apache License, Version 2.0 (the "License");
5   you may not use this file except in compliance with the License.
6   You may obtain a copy of the License at
7
8       http://www.apache.org/licenses/LICENSE-2.0
9
10   Unless required by applicable law or agreed to in writing, software
11   distributed under the License is distributed on an "AS IS" BASIS,
12   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   See the License for the specific language governing permissions and
14   limitations under the License.
15*/
16
17package local
18
19import (
20	"os"
21
22	"github.com/pkg/errors"
23
24	"github.com/containerd/containerd/content"
25	"github.com/containerd/containerd/errdefs"
26)
27
28// readerat implements io.ReaderAt in a completely stateless manner by opening
29// the referenced file for each call to ReadAt.
30type sizeReaderAt struct {
31	size int64
32	fp   *os.File
33}
34
35// OpenReader creates ReaderAt from a file
36func OpenReader(p string) (content.ReaderAt, error) {
37	fi, err := os.Stat(p)
38	if err != nil {
39		if !os.IsNotExist(err) {
40			return nil, err
41		}
42
43		return nil, errors.Wrap(errdefs.ErrNotFound, "blob not found")
44	}
45
46	fp, err := os.Open(p)
47	if err != nil {
48		if !os.IsNotExist(err) {
49			return nil, err
50		}
51
52		return nil, errors.Wrap(errdefs.ErrNotFound, "blob not found")
53	}
54
55	return sizeReaderAt{size: fi.Size(), fp: fp}, nil
56}
57
58func (ra sizeReaderAt) ReadAt(p []byte, offset int64) (int, error) {
59	return ra.fp.ReadAt(p, offset)
60}
61
62func (ra sizeReaderAt) Size() int64 {
63	return ra.size
64}
65
66func (ra sizeReaderAt) Close() error {
67	return ra.fp.Close()
68}
69