1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
|
package feed
import (
"bufio"
"encoding/gob"
"errors"
"fmt"
"os"
"path/filepath"
"time"
"github.com/nightlyone/lockfile"
"github.com/Necoro/feed2imap-go/pkg/log"
)
type Version byte
const (
currentVersion Version = 1
)
type CacheImpl interface {
findItem(*Feed) CachedFeed
Version() Version
Info() string
SpecificInfo(interface{}) string
transformToCurrent() (CacheImpl, error)
}
type Cache struct {
CacheImpl
lock lockfile.Lockfile
locked bool
}
type CachedFeed interface {
Checked(withFailure bool)
Failures() int
Last() time.Time
ID() string
filterItems(items []item, ignoreHash bool, alwaysNew bool) []item
Commit()
}
func cacheForVersion(version Version) (CacheImpl, error) {
switch version {
case v1Version:
return newV1Cache(), nil
default:
return nil, fmt.Errorf("unknown cache version '%d'", version)
}
}
func lockName(fileName string) (string, error) {
return filepath.Abs(fileName + ".lck")
}
func lock(fileName string) (lock lockfile.Lockfile, err error) {
var lockFile string
if lockFile, err = lockName(fileName); err != nil {
return
}
log.Debugf("Handling lock file '%s'", lockFile)
if lock, err = lockfile.New(lockFile); err != nil {
err = fmt.Errorf("Creating lock file: %w", err)
return
}
if err = lock.TryLock(); err != nil {
err = fmt.Errorf("Locking cache: %w", err)
return
}
return
}
func (cache *Cache) store(fileName string) error {
if cache.CacheImpl == nil {
return fmt.Errorf("trying to store nil cache")
}
if cache.Version() != currentVersion {
return fmt.Errorf("trying to store cache with unsupported version '%d' (current: '%d')", cache.Version(), currentVersion)
}
f, err := os.Create(fileName)
if err != nil {
return fmt.Errorf("trying to store cache to '%s': %w", fileName, err)
}
defer f.Close()
writer := bufio.NewWriter(f)
if err = writer.WriteByte(byte(currentVersion)); err != nil {
return fmt.Errorf("writing to '%s': %w", fileName, err)
}
encoder := gob.NewEncoder(writer)
if err = encoder.Encode(cache.CacheImpl); err != nil {
return fmt.Errorf("encoding cache: %w", err)
}
writer.Flush()
log.Printf("Stored cache to '%s'.", fileName)
return cache.Unlock()
}
func (cache *Cache) Unlock() error {
if cache.locked {
if err := cache.lock.Unlock(); err != nil {
return fmt.Errorf("Unlocking cache: %w", err)
}
}
cache.locked = false
return nil
}
func newCache() (Cache, error) {
cache, err := cacheForVersion(currentVersion)
if err != nil {
return Cache{}, err
}
return Cache{
CacheImpl: cache,
locked: false,
}, nil
}
func LoadCache(fileName string) (Cache, error) {
f, err := os.Open(fileName)
if err != nil {
if errors.Is(err, os.ErrNotExist) {
// no cache there yet -- make new
return newCache()
}
return Cache{}, fmt.Errorf("opening cache at '%s': %w", fileName, err)
}
defer f.Close()
lock, err := lock(fileName)
if err != nil {
return Cache{}, err
}
log.Printf("Loading cache from '%s'", fileName)
reader := bufio.NewReader(f)
version, err := reader.ReadByte()
if err != nil {
return Cache{}, fmt.Errorf("reading from '%s': %w", fileName, err)
}
cache, err := cacheForVersion(Version(version))
if err != nil {
return Cache{}, err
}
decoder := gob.NewDecoder(reader)
if err = decoder.Decode(cache); err != nil {
return Cache{}, fmt.Errorf("decoding for version '%d' from '%s': %w", version, fileName, err)
}
if cache, err = cache.transformToCurrent(); err != nil {
return Cache{}, fmt.Errorf("cannot transform from version %d to %d: %w", version, currentVersion, err)
}
log.Printf("Loaded cache (version %d), transformed to version %d.", version, currentVersion)
return Cache{cache, lock, true}, nil
}
|
