1 files changed, 384 insertions, 0 deletions
diff --git a/cache/filecache/filecache.go b/cache/filecache/filecache.go
new file mode 100644
index 000000000..63d939ef6
--- /dev/null
+++ b/cache/filecache/filecache.go
@@ -0,0 +1,384 @@
+// 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
+	}
+
+	if c.maxAge == 0 {
+		return info, b, nil
+	}
+
+	if err := afero.WriteReader(c.Fs, id, bytes.NewReader(b)); err != nil {
+		return info, nil, err
+	}
+	return info, b, nil
+}
+
+// GetBytes gets the file content with the given id from the cache, nil if none found.
+func (c *Cache) GetBytes(id string) (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
+	}
+
+	return info, nil, nil
+}
+
+// Get gets the file with the given id from the cahce, nil if none found.
+func (c *Cache) Get(id string) (ItemInfo, io.ReadCloser, error) {
+	id = cleanID(id)
+
+	c.nlocker.Lock(id)
+	defer c.nlocker.Unlock(id)
+
+	info := ItemInfo{Name: id}
+
+	r := c.getOrRemove(id)
+
+	return info, r, nil
+}
+
+// getOrRemove gets the file with the given id. If it's expired, it will
+// be removed.
+func (c *Cache) getOrRemove(id string) hugio.ReadSeekCloser {
+	if c.maxAge == 0 {
+		// No caching.
+		return nil
+	}
+
+	if c.maxAge > 0 {
+		fi, err := c.Fs.Stat(id)
+		if err != nil {
+			return nil
+		}
+
+		if c.isExpired(fi.ModTime()) {
+			c.Fs.Remove(id)
+			return nil
+		}
+	}
+
+	f, err := c.Fs.Open(id)
+	if err != nil {
+		return nil
+	}
+
+	return f
+}
+
+func (c *Cache) isExpired(modTime time.Time) bool {
+	if c.maxAge < 0 {
+		return false
+	}
+
+	// Note the use of time.Since here.
+	// We cannot use Hugo's global Clock for this.
+	return c.maxAge == 0 || time.Since(modTime) > c.maxAge
+}
+
+// For testing
+func (c *Cache) getString(id string) string {
+	id = cleanID(id)
+
+	c.nlocker.Lock(id)
+	defer c.nlocker.Unlock(id)
+
+	f, err := c.Fs.Open(id)
+	if err != nil {
+		return ""
+	}
+	defer f.Close()
+
+	b, _ := ioutil.ReadAll(f)
+	return string(b)
+}
+
+// Caches is a named set of caches.
+type Caches map[string]*Cache
+
+// Get gets a named cache, nil if none found.
+func (f Caches) Get(name string) *Cache {
+	return f[strings.ToLower(name)]
+}
+
+// NewCaches creates a new set of file caches from the given
+// configuration.
+func NewCaches(p *helpers.PathSpec) (Caches, error) {
+	var dcfg Configs
+	if c, ok := p.Cfg.Get("filecacheConfigs").(Configs); ok {
+		dcfg = c
+	} else {
+		var err error
+		dcfg, err = DecodeConfig(p.Fs.Source, p.Cfg)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	fs := p.Fs.Source
+
+	m := make(Caches)
+	for k, v := range dcfg {
+		var cfs afero.Fs
+
+		if v.isResourceDir {
+			cfs = p.BaseFs.ResourcesCache
+		} else {
+			cfs = fs
+		}
+
+		if cfs == nil {
+			// TODO(bep) we still have some places that do not initialize the
+			// full dependencies of a site, e.g. the import Jekyll command.
+			// That command does not need these caches, so let us just continue
+			// for now.
+			continue
+		}
+
+		baseDir := v.Dir
+
+		if err := cfs.MkdirAll(baseDir, 0777); err != nil && !os.IsExist(err) {
+			return nil, err
+		}
+
+		bfs := afero.NewBasePathFs(cfs, baseDir)
+
+		var pruneAllRootDir string
+		if k == cacheKeyModules {
+			pruneAllRootDir = "pkg"
+		}
+
+		m[k] = NewCache(bfs, v.MaxAge, pruneAllRootDir)
+	}
+
+	return m, nil
+}
+
+func cleanID(name string) string {
+	return strings.TrimPrefix(filepath.Clean(name), helpers.FilePathSeparator)
+}