1// Package diskcache provides an implementation of httpcache.Cache that uses the diskv package
2// to supplement an in-memory map with persistent storage
3//
4package diskcache
5
6import (
7	"bytes"
8	"crypto/md5"
9	"encoding/hex"
10	"github.com/peterbourgon/diskv"
11	"io"
12)
13
14// Cache is an implementation of httpcache.Cache that supplements the in-memory map with persistent storage
15type Cache struct {
16	d *diskv.Diskv
17}
18
19// Get returns the response corresponding to key if present
20func (c *Cache) Get(key string) (resp []byte, ok bool) {
21	key = keyToFilename(key)
22	resp, err := c.d.Read(key)
23	if err != nil {
24		return []byte{}, false
25	}
26	return resp, true
27}
28
29// Set saves a response to the cache as key
30func (c *Cache) Set(key string, resp []byte) {
31	key = keyToFilename(key)
32	c.d.WriteStream(key, bytes.NewReader(resp), true)
33}
34
35// Delete removes the response with key from the cache
36func (c *Cache) Delete(key string) {
37	key = keyToFilename(key)
38	c.d.Erase(key)
39}
40
41func keyToFilename(key string) string {
42	h := md5.New()
43	io.WriteString(h, key)
44	return hex.EncodeToString(h.Sum(nil))
45}
46
47// New returns a new Cache that will store files in basePath
48func New(basePath string) *Cache {
49	return &Cache{
50		d: diskv.New(diskv.Options{
51			BasePath:     basePath,
52			CacheSizeMax: 100 * 1024 * 1024, // 100MB
53		}),
54	}
55}
56
57// NewWithDiskv returns a new Cache using the provided Diskv as underlying
58// storage.
59func NewWithDiskv(d *diskv.Diskv) *Cache {
60	return &Cache{d}
61}
62