cloudfs.go

package main

import (
	"context"
	"fmt"
	"os"
	"strings"

	"github.com/billziss-gh/cgofuse/fuse"
	"gocloud.dev/blob"
	_ "gocloud.dev/blob/azureblob"
	_ "gocloud.dev/blob/gcsblob"
	_ "gocloud.dev/blob/s3blob"
)

const (
	filename = "hello"
	contents = "hello, world\n"
)

type CloudFileSystem struct {
	fuse.FileSystemBase
	bucket *blob.Bucket
}

func (cf *CloudFileSystem) Open(path string, flags int) (errc int, fh uint64) {
	ok, err := cf.bucket.Exists(context.Background(), strings.TrimLeft(path, "/"))
	if err != nil || !ok {
		return -fuse.ENOENT, ^uint64(0)
	}
	return 0, 0
}

func (cf *CloudFileSystem) Getattr(path string, stat *fuse.Stat_t, fh uint64) (errc int) {
	if path == "/" {
		stat.Mode = fuse.S_IFDIR | 0555
		return 0
	}
	ctx := context.Background()
	name := strings.TrimLeft(path, "/")
	a, err := cf.bucket.Attributes(ctx, name)
	if err != nil {
		_, err := cf.bucket.Attributes(ctx, name+"/")
		if err != nil {
			return -fuse.ENOENT
		}
		stat.Mode = fuse.S_IFDIR | 0555
	} else {
		stat.Mode = fuse.S_IFREG | 0444
		stat.Size = a.Size
		stat.Mtim = fuse.NewTimespec(a.ModTime)
		stat.Gid = uint32(os.Getgid())
		stat.Uid = uint32(os.Getuid())
	}
	return 0
}

func (cf *CloudFileSystem) Read(path string, buff []byte, ofst int64, fh uint64) (n int) {
	name := strings.TrimLeft(path, "/")
	reader, err := cf.bucket.NewRangeReader(context.Background(), name, ofst, int64(len(buff)), nil)
	if err != nil {
		return
	}
	defer reader.Close()
	n, _ = reader.Read(buff)
	return
}

func (cf *CloudFileSystem) Readdir(path string, fill func(name string, stat *fuse.Stat_t, ofst int64) bool, ofst int64, fh uint64) (errc int) {
	ctx := context.Background()
	fill(".", nil, 0)
	fill("..", nil, 0)
	prefix := strings.TrimLeft(path, "/")
	if prefix != "" {
		prefix = prefix + "/"
	}
	i := cf.bucket.List(&blob.ListOptions{
		Prefix:    prefix,
		Delimiter: "/",
	})
	for {
		o, err := i.Next(ctx)
		if err != nil {
			break
		}
		key := o.Key[len(prefix):]
		if len(key) == 0 {
			continue
		}
		name := strings.TrimRight(key, "/")
		fill(name, nil, 0)
	}
	return 0
}

func (cf *CloudFileSystem) Releasedir(path string, fh uint64) int {
	return 0
}

func main() {
	ctx := context.Background()
	if len(os.Args) < 3 {
		fmt.Printf("%s [bucket-path] [mount-point] etc...", os.Args[0])
		os.Exit(1)
	}
	b, err := blob.OpenBucket(ctx, os.Args[1])
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	defer b.Close()
	cf := &CloudFileSystem{bucket: b}
	host := fuse.NewFileSystemHost(cf)
	host.Mount(os.Args[2], os.Args[3:])
}