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// Copyright 2018 The Hugo Authors. 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 filecache
import (
"bytes"
"errors"
"io"
"io/ioutil"
"os"
"path/filepath"
"strings"
"sync"
"time"
"github.com/gohugoio/hugo/common/hugio"
"github.com/gohugoio/hugo/helpers"
"github.com/BurntSushi/locker"
"github.com/spf13/afero"
)
// ErrFatal can be used to signal an unrecoverable error.
var ErrFatal = errors.New("fatal filecache error")
const (
filecacheRootDirname = "filecache"
)
// Cache caches a set of files in a directory. This is usually a file on
// disk, but since this is backed by an Afero file system, it can be anything.
type Cache struct {
Fs afero.Fs
// Max age for items in this cache. Negative duration means forever,
// 0 is effectively turning this cache off.
maxAge time.Duration
// When set, we just remove this entire root directory on expiration.
pruneAllRootDir string
nlocker *lockTracker
}
type lockTracker struct {
seenMu sync.RWMutex
seen map[string]struct{}
*locker.Locker
}
// Lock tracks the ids in use. We use this information to do garbage collection
// after a Hugo build.
func (l *lockTracker) Lock(id string) {
l.seenMu.RLock()
if _, seen := l.seen[id]; !seen {
l.seenMu.RUnlock()
l.seenMu.Lock()
l.seen[id] = struct{}{}
l.seenMu.Unlock()
} else {
l.seenMu.RUnlock()
}
l.Locker.Lock(id)
}
// ItemInfo contains info about a cached file.
type ItemInfo struct {
// This is the file's name relative to the cache's filesystem.
Name string
}
// NewCache creates a new file cache with the given filesystem and max age.
func NewCache(fs afero.Fs, maxAge time.Duration, pruneAllRootDir string) *Cache {
return &Cache{
Fs: fs,
nlocker: &lockTracker{Locker: locker.NewLocker(), seen: make(map[string]struct{})},
maxAge: maxAge,
pruneAllRootDir: pruneAllRootDir,
}
}
// lockedFile is a file with a lock that is released on Close.
type lockedFile struct {
afero.File
unlock func()
}
func (l *lockedFile) Close() error {
defer l.unlock()
return l.File.Close()
}
// WriteCloser returns a transactional writer into the cache.
// It's important that it's closed when done.
func (c *Cache) WriteCloser(id string) (ItemInfo, io.WriteCloser, error) {
id = cleanID(id)
c.nlocker.Lock(id)
info := ItemInfo{Name: id}
f, err := helpers.OpenFileForWriting(c.Fs, id)
if err != nil {
c.nlocker.Unlock(id)
return info, nil, err
}
return info, &lockedFile{
File: f,
unlock: func() { c.nlocker.Unlock(id) },
}, nil
}
// ReadOrCreate tries to lookup the file in cache.
// If found, it is passed to read and then closed.
// If not found a new file is created and passed to create, which should close
// it when done.
func (c *Cache) ReadOrCreate(id string,
read func(info ItemInfo, r io.ReadSeeker) error,
create func(info ItemInfo, w io.WriteCloser) error) (info ItemInfo, err error) {
id = cleanID(id)
c.nlocker.Lock(id)
defer c.nlocker.Unlock(id)
info = ItemInfo{Name: id}
if r := c.getOrRemove(id); r != nil {
err = read(info, r)
defer r.Close()
if err == nil || err == ErrFatal {
// See https://github.com/gohugoio/hugo/issues/6401
// To recover from file corruption we handle read errors
// as the cache item was not found.
// Any file permission issue will also fail in the next step.
return
}
}
f, err := helpers.OpenFileForWriting(c.Fs, id)
if err != nil {
return
}
err = create(info, f)
return
}
// GetOrCreate tries to get the file with the given id from cache. If not found or expired, create will
// be invoked and the result cached.
// This method is protected by a named lock using the given id as identifier.
func (c *Cache) GetOrCreate(id string, create func() (io.ReadCloser, error)) (ItemInfo, io.ReadCloser, error) {
id = cleanID(id)
c.nlocker.Lock(id)
defer c.nlocker.Unlock(id)
info := ItemInfo{Name: id}
if r := c.getOrRemove(id); r != nil {
return info, r, nil
}
var (
r io.ReadCloser
err error
)
r, err = create()
if err != nil {
return info, nil, err
}
if c.maxAge == 0 {
// No caching.
return info, hugio.ToReadCloser(r), nil
}
var buff bytes.Buffer
return info,
hugio.ToReadCloser(&buff),
afero.WriteReader(c.Fs, id, io.TeeReader(r, &buff))
}
// GetOrCreateBytes is the same as GetOrCreate, but produces a byte slice.
func (c *Cache) GetOrCreateBytes(id string, create func() ([]byte, error)) (ItemInfo, []byte, error) {
id = cleanID(id)
c.nlocker.Lock(id)
defer c.nlocker.Unlock(id)
info := ItemInfo{Name: id}
if r := c.getOrRemove(id); r != nil {
defer r.Close()
b, err := ioutil.ReadAll(r)
return info, b, err
}
var (
b []byte
err error
)
b, err = create()
if err != nil {
return info, nil, err
}<
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