Wrote much of package statfs.

samples/statfs/statfs.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 statfs
+
+import (
+	"os"
+	"sync"
+
+	"golang.org/x/net/context"
+
+	"github.com/jacobsa/fuse"
+	"github.com/jacobsa/fuse/fuseops"
+	"github.com/jacobsa/fuse/fuseutil"
+)
+
+// A file system that allows orchestrating canned responses to statfs ops, for
+// testng out OS-specific statfs behavior.
+//
+// The file system allows opening and writing to any name that is a child of
+// the root inode, and keeps track of the most recent write size delivered by
+// the kernel (in order to test statfs response block size effects on write
+// size, if any).
+//
+// Safe for concurrent access.
+type FS interface {
+	fuseutil.FileSystem
+
+	// Set the canned response to be used for future statfs ops.
+	SetStatFSResponse(r fuseops.StatFSOp)
+
+	// Return the size of the most recent write delivered by the kernel, or -1 if
+	// none.
+	MostRecentWriteSize() int
+}
+
+func New() (fs FS) {
+	fs = &statFS{
+		mostRecentWriteSize: -1,
+	}
+
+	return
+}
+
+const childInodeID = fuseops.RootInodeID + 1
+
+type statFS struct {
+	fuseutil.NotImplementedFileSystem
+
+	mu                  sync.Mutex
+	cannedResponse      fuseops.StatFSOp // GUARDED_BY(mu)
+	mostRecentWriteSize int              // GUARDED_BY(mu)
+}
+
+////////////////////////////////////////////////////////////////////////
+// Helpers
+////////////////////////////////////////////////////////////////////////
+
+func dirAttrs() fuseops.InodeAttributes {
+	return fuseops.InodeAttributes{
+		Mode: os.ModeDir | 0777,
+	}
+}
+
+func fileAttrs() fuseops.InodeAttributes {
+	return fuseops.InodeAttributes{
+		Mode: 0666,
+	}
+}
+
+////////////////////////////////////////////////////////////////////////
+// Public interface
+////////////////////////////////////////////////////////////////////////
+
+// LOCKS_EXCLUDED(fs.mu)
+func (fs *statFS) SetStatFSResponse(r fuseops.StatFSOp) {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+
+	fs.cannedResponse = r
+}
+
+// LOCKS_EXCLUDED(fs.mu)
+func (fs *statFS) MostRecentWriteSize() int {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+
+	return fs.mostRecentWriteSize
+}
+
+////////////////////////////////////////////////////////////////////////
+// FileSystem methods
+////////////////////////////////////////////////////////////////////////
+
+func (fs *statFS) LookUpInode(
+	ctx context.Context,
+	op *fuseops.LookUpInodeOp) (err error) {
+	// Pretend that every name exists as a child of the root inode, and is a
+	// file.
+	if op.Parent != fuseops.RootInodeID {
+		err = fuse.ENOENT
+		return
+	}
+
+	op.Entry.Child = childInodeID
+	op.Entry.Attributes = fileAttrs()
+
+	return
+}
+
+func (fs *statFS) GetInodeAttributes(
+	ctx context.Context,
+	op *fuseops.GetInodeAttributesOp) (err error) {
+	switch op.Inode {
+	case fuseops.RootInodeID:
+		op.Attributes = dirAttrs()
+
+	case childInodeID:
+		op.Attributes = fileAttrs()
+
+	default:
+		err = fuse.ENOENT
+	}
+
+	return
+}
+
+func (fs *statFS) OpenFile(
+	ctx context.Context,
+	op *fuseops.OpenFileOp) (err error) {
+	return
+}
+
+// LOCKS_EXCLUDED(fs.mu)
+func (fs *statFS) WriteFile(
+	ctx context.Context,
+	op *fuseops.WriteFileOp) (err error) {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+
+	fs.mostRecentWriteSize = len(op.Data)
+	return
+}