338 lines
6.7 KiB
Go
338 lines
6.7 KiB
Go
// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package flushfs
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import (
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"context"
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"fmt"
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"os"
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"sync"
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"github.com/jacobsa/fuse"
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"github.com/jacobsa/fuse/fuseops"
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"github.com/jacobsa/fuse/fuseutil"
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)
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// Create a file system whose sole contents are a file named "foo" and a
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// directory named "bar".
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//
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// The file may be opened for reading and/or writing. Its initial contents are
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// empty. Whenever a flush or fsync is received, the supplied function will be
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// called with the current contents of the file and its status returned.
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//
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// The directory cannot be modified.
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func NewFileSystem(
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reportFlush func(string) error,
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reportFsync func(string) error) (server fuse.Server, err error) {
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fs := &flushFS{
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reportFlush: reportFlush,
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reportFsync: reportFsync,
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}
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server = fuseutil.NewFileSystemServer(fs)
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return
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}
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const (
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fooID = fuseops.RootInodeID + 1 + iota
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barID
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)
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type flushFS struct {
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fuseutil.NotImplementedFileSystem
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reportFlush func(string) error
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reportFsync func(string) error
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mu sync.Mutex
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fooContents []byte // GUARDED_BY(mu)
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}
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////////////////////////////////////////////////////////////////////////
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// Helpers
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////////////////////////////////////////////////////////////////////////
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// LOCKS_REQUIRED(fs.mu)
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func (fs *flushFS) rootAttributes() fuseops.InodeAttributes {
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return fuseops.InodeAttributes{
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Nlink: 1,
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Mode: 0777 | os.ModeDir,
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}
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}
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// LOCKS_REQUIRED(fs.mu)
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func (fs *flushFS) fooAttributes() fuseops.InodeAttributes {
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return fuseops.InodeAttributes{
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Nlink: 1,
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Mode: 0777,
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Size: uint64(len(fs.fooContents)),
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}
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}
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// LOCKS_REQUIRED(fs.mu)
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func (fs *flushFS) barAttributes() fuseops.InodeAttributes {
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return fuseops.InodeAttributes{
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Nlink: 1,
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Mode: 0777 | os.ModeDir,
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}
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}
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// LOCKS_REQUIRED(fs.mu)
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func (fs *flushFS) getAttributes(id fuseops.InodeID) (
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attrs fuseops.InodeAttributes,
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err error) {
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switch id {
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case fuseops.RootInodeID:
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attrs = fs.rootAttributes()
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return
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case fooID:
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attrs = fs.fooAttributes()
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return
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case barID:
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attrs = fs.barAttributes()
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return
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default:
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err = fuse.ENOENT
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return
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}
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}
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////////////////////////////////////////////////////////////////////////
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// FileSystem methods
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////////////////////////////////////////////////////////////////////////
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func (fs *flushFS) StatFS(
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ctx context.Context,
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op *fuseops.StatFSOp) (err error) {
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return
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}
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func (fs *flushFS) LookUpInode(
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ctx context.Context,
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op *fuseops.LookUpInodeOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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// Sanity check.
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if op.Parent != fuseops.RootInodeID {
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err = fuse.ENOENT
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return
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}
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// Set up the entry.
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switch op.Name {
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case "foo":
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op.Entry = fuseops.ChildInodeEntry{
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Child: fooID,
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Attributes: fs.fooAttributes(),
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}
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case "bar":
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op.Entry = fuseops.ChildInodeEntry{
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Child: barID,
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Attributes: fs.barAttributes(),
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}
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default:
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err = fuse.ENOENT
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return
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}
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return
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}
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func (fs *flushFS) GetInodeAttributes(
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ctx context.Context,
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op *fuseops.GetInodeAttributesOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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op.Attributes, err = fs.getAttributes(op.Inode)
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return
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}
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func (fs *flushFS) SetInodeAttributes(
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ctx context.Context,
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op *fuseops.SetInodeAttributesOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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// Ignore any changes and simply return existing attributes.
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op.Attributes, err = fs.getAttributes(op.Inode)
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return
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}
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func (fs *flushFS) OpenFile(
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ctx context.Context,
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op *fuseops.OpenFileOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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// Sanity check.
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if op.Inode != fooID {
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err = fuse.ENOSYS
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return
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}
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return
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}
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func (fs *flushFS) ReadFile(
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ctx context.Context,
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op *fuseops.ReadFileOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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// Ensure the offset is in range.
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if op.Offset > int64(len(fs.fooContents)) {
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return
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}
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// Read what we can.
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op.BytesRead = copy(op.Dst, fs.fooContents[op.Offset:])
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return
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}
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func (fs *flushFS) WriteFile(
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ctx context.Context,
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op *fuseops.WriteFileOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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// Ensure that the contents slice is long enough.
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newLen := int(op.Offset) + len(op.Data)
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if len(fs.fooContents) < newLen {
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padding := make([]byte, newLen-len(fs.fooContents))
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fs.fooContents = append(fs.fooContents, padding...)
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}
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// Copy in the data.
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n := copy(fs.fooContents[op.Offset:], op.Data)
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// Sanity check.
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if n != len(op.Data) {
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panic(fmt.Sprintf("Unexpected short copy: %v", n))
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}
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return
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}
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func (fs *flushFS) SyncFile(
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ctx context.Context,
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op *fuseops.SyncFileOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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err = fs.reportFsync(string(fs.fooContents))
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return
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}
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func (fs *flushFS) FlushFile(
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ctx context.Context,
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op *fuseops.FlushFileOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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err = fs.reportFlush(string(fs.fooContents))
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return
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}
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func (fs *flushFS) OpenDir(
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ctx context.Context,
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op *fuseops.OpenDirOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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// Sanity check.
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switch op.Inode {
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case fuseops.RootInodeID:
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case barID:
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default:
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err = fuse.ENOENT
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return
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}
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return
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}
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func (fs *flushFS) ReadDir(
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ctx context.Context,
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op *fuseops.ReadDirOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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// Create the appropriate listing.
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var dirents []fuseutil.Dirent
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switch op.Inode {
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case fuseops.RootInodeID:
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dirents = []fuseutil.Dirent{
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fuseutil.Dirent{
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Offset: 1,
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Inode: fooID,
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Name: "foo",
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Type: fuseutil.DT_File,
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},
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fuseutil.Dirent{
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Offset: 2,
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Inode: barID,
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Name: "bar",
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Type: fuseutil.DT_Directory,
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},
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}
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case barID:
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default:
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err = fmt.Errorf("Unexpected inode: %v", op.Inode)
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return
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}
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// If the offset is for the end of the listing, we're done. Otherwise we
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// expect it to be for the start.
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switch op.Offset {
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case fuseops.DirOffset(len(dirents)):
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return
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case 0:
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default:
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err = fmt.Errorf("Unexpected offset: %v", op.Offset)
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return
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}
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// Fill in the listing.
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for _, de := range dirents {
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n := fuseutil.WriteDirent(op.Dst[op.BytesRead:], de)
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// We don't support doing this in anything more than one shot.
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if n == 0 {
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err = fmt.Errorf("Couldn't fit listing in %v bytes", len(op.Dst))
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return
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}
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op.BytesRead += n
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}
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return
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}
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