Wrapping FUSE from Go
- by Matt Joiner
I'm playing around with wrapping FUSE with Go. However I've come stuck with how to deal with struct fuse_operations. I can't seem to expose the operations struct by declaring type Operations C.struct_fuse_operations as the members are lower case, and my pure-Go sources would have to use C-hackery to set the members anyway. My first error in this case is "can't set getattr" in what looks to be the Go equivalent of a default copy constructor. My next attempt is to expose an interface that expects GetAttr, ReadLink etc, and then generate C.struct_fuse_operations and bind the function pointers to closures that call the given interface.
This is what I've got (explanation continues after code):
package fuse
// #include <fuse.h>
// #include <stdlib.h>
import "C"
import (
//"fmt"
"os"
"unsafe"
)
type Operations interface {
GetAttr(string, *os.FileInfo) int
}
func Main(args []string, ops Operations) int {
argv := make([]*C.char, len(args) + 1)
for i, s := range args {
p := C.CString(s)
defer C.free(unsafe.Pointer(p))
argv[i] = p
}
cop := new(C.struct_fuse_operations)
cop.getattr = func(*C.char, *C.struct_stat) int {}
argc := C.int(len(args))
return int(C.fuse_main_real(argc, &argv[0], cop, C.size_t(unsafe.Sizeof(cop)), nil))
}
package main
import (
"fmt"
"fuse"
"os"
)
type CpfsOps struct {
a int
}
func (me *CpfsOps) GetAttr(string, *os.FileInfo) int {
return -1;
}
func main() {
fmt.Println(os.Args)
ops := &CpfsOps{}
fmt.Println("fuse main returned", fuse.Main(os.Args, ops))
}
This gives the following error:
fuse.go:21[fuse.cgo1.go:23]: cannot use func literal (type func(*_Ctype_char, *_Ctype_struct_stat) int) as type *[0]uint8 in assignment
I'm not sure what to pass to these members of C.struct_fuse_operations, and I've seen mention in a few places it's not possible to call from C back into Go code.
If it is possible, what should I do? How can I provide the "default" values for interface functions that acts as though the corresponding C.struct_fuse_operations member is set to NULL?
