fusego/samples/cachingfs/caching_fs.go

// Copyright 2015 Google Inc. 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 cachingfs

import (
	"sync"
	"time"

	"github.com/jacobsa/fuse"
	"github.com/jacobsa/fuse/fuseutil"
	"golang.org/x/net/context"
)

// A file system with a fixed structure that looks like this:
//
//     foo
//     dir/
//         bar
//
// The file system is configured with durations that specify how long to allow
// inode entries and attributes to be cached, used when responding to fuse
// requests. It also exposes methods for renumbering inodes and updating mtimes
// that are useful in testing that these durations are honored.
type CachingFS interface {
	fuse.FileSystem

	// Return the current inode ID of the file/directory with the given name.
	FooID() fuse.InodeID
	DirID() fuse.InodeID
	BarID() fuse.InodeID

	// Cause the inode IDs to change to values that have never before been used.
	RenumberInodes()

	// Cause further queries for the attributes of inodes to use the supplied
	// time as the inode's mtime.
	SetMtime(mtime time.Time)
}

// Create a file system that issues cacheable responses according to the
// following rules:
//
//  *  LookUpInodeResponse.Entry.EntryExpiration is set according to
//     lookupEntryTimeout.
//
//  *  GetInodeAttributesResponse.AttributesExpiration is set according to
//     getattrTimeout.
//
//  *  Nothing else is marked cacheable. (In particular, the attributes
//     returned by LookUpInode are not cacheable.)
//
func NewCachingFS(
	lookupEntryTimeout time.Duration,
	getattrTimeout time.Duration) (fs CachingFS, err error) {
	fs = &cachingFS{
		inodeIDBase: fuse.RootInodeID + 1,
		mtime:       time.Now(),
	}

	return
}

type cachingFS struct {
	fuseutil.NotImplementedFileSystem
	mu sync.Mutex

	// GUARDED_BY(mu)
	inodeIDBase fuse.InodeID

	// GUARDED_BY(mu)
	mtime time.Time
}

// LOCKS_EXCLUDED(fs.mu)
func (fs *cachingFS) RenumberInodes(base fuse.InodeID) {
	fs.mu.Lock()
	defer fs.mu.Unlock()

	fs.inodeIDBase = base
}

// LOCKS_EXCLUDED(fs.mu)
func (fs *cachingFS) SetMtime(mtime time.Time) {
	fs.mu.Lock()
	defer fs.mu.Unlock()

	fs.mtime = mtime
}

func (fs *cachingFS) Init(
	ctx context.Context,
	req *fuse.InitRequest) (resp *fuse.InitResponse, err error) {
	resp = &fuse.InitResponse{}
	return
}