swarm/api: FUSE read-write support (#13872)

- Moved fuse related code in a new package, swarm/fuse
- Added write support
  - Create new files
  - Delete existing files
  - Append to files (with limitations)
- More test coverage

swarm/fuse/fuse_file.go

@@ -0,0 +1,144 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// +build linux darwin freebsd
+
+package fuse
+
+import (
+	"bazil.org/fuse"
+	"bazil.org/fuse/fs"
+	"errors"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/swarm/storage"
+	"golang.org/x/net/context"
+	"io"
+	"os"
+	"sync"
+)
+
+const (
+	MaxAppendFileSize = 10485760 // 10Mb
+)
+
+var (
+	errInvalidOffset           = errors.New("Invalid offset during write")
+	errFileSizeMaxLimixReached = errors.New("File size exceeded max limit")
+)
+
+var (
+	_ fs.Node         = (*SwarmFile)(nil)
+	_ fs.HandleReader = (*SwarmFile)(nil)
+	_ fs.HandleWriter = (*SwarmFile)(nil)
+)
+
+type SwarmFile struct {
+	inode    uint64
+	name     string
+	path     string
+	key      storage.Key
+	fileSize int64
+	reader   storage.LazySectionReader
+
+	mountInfo *MountInfo
+	lock      *sync.RWMutex
+}
+
+func NewSwarmFile(path, fname string, minfo *MountInfo) *SwarmFile {
+	newFile := &SwarmFile{
+		inode:    NewInode(),
+		name:     fname,
+		path:     path,
+		key:      nil,
+		fileSize: -1, // -1 means , file already exists in swarm and you need to just get the size from swarm
+		reader:   nil,
+
+		mountInfo: minfo,
+		lock:      &sync.RWMutex{},
+	}
+	return newFile
+}
+
+func (file *SwarmFile) Attr(ctx context.Context, a *fuse.Attr) error {
+
+	a.Inode = file.inode
+	//TODO: need to get permission as argument
+	a.Mode = 0700
+	a.Uid = uint32(os.Getuid())
+	a.Gid = uint32(os.Getegid())
+
+	if file.fileSize == -1 {
+		reader := file.mountInfo.swarmApi.Retrieve(file.key)
+		quitC := make(chan bool)
+		size, err := reader.Size(quitC)
+		if err != nil {
+			log.Warn("Couldnt get size of file %s : %v", file.path, err)
+		}
+		file.fileSize = int64(size)
+	}
+	a.Size = uint64(file.fileSize)
+	return nil
+}
+
+func (sf *SwarmFile) Read(ctx context.Context, req *fuse.ReadRequest, resp *fuse.ReadResponse) error {
+
+	sf.lock.RLock()
+	defer sf.lock.RUnlock()
+	if sf.reader == nil {
+		sf.reader = sf.mountInfo.swarmApi.Retrieve(sf.key)
+	}
+	buf := make([]byte, req.Size)
+	n, err := sf.reader.ReadAt(buf, req.Offset)
+	if err == io.ErrUnexpectedEOF || err == io.EOF {
+		err = nil
+	}
+	resp.Data = buf[:n]
+	sf.reader = nil
+	return err
+
+}
+
+func (sf *SwarmFile) Write(ctx context.Context, req *fuse.WriteRequest, resp *fuse.WriteResponse) error {
+
+	if sf.fileSize == 0 && req.Offset == 0 {
+
+		// A new file is created
+		err := addFileToSwarm(sf, req.Data, len(req.Data))
+		if err != nil {
+			return err
+		}
+		resp.Size = len(req.Data)
+
+	} else if req.Offset <= sf.fileSize {
+
+		totalSize := sf.fileSize + int64(len(req.Data))
+		if totalSize > MaxAppendFileSize {
+			log.Warn("Append file size reached (%v) : (%v)", sf.fileSize, len(req.Data))
+			return errFileSizeMaxLimixReached
+		}
+
+		err := appendToExistingFileInSwarm(sf, req.Data, req.Offset, int64(len(req.Data)))
+		if err != nil {
+			return err
+		}
+		resp.Size = int(sf.fileSize)
+	} else {
+		log.Warn("Invalid write request size(%v) : off(%v)", sf.fileSize, req.Offset)
+		return errInvalidOffset
+	}
+
+	return nil
+}