英文:
Wrapping FUSE from Go
问题
我正在尝试使用Go来封装FUSE。然而，我在处理struct fuse_operations时遇到了困难。我似乎无法通过声明type Operations C.struct_fuse_operations来公开operations结构体，因为成员是小写的，而且我的纯Go源代码必须使用C-hackery来设置成员。在这种情况下，我的第一个错误是“无法设置getattr”，这看起来是Go中默认复制构造函数的等效物。我的下一个尝试是公开一个接口，该接口期望GetAttr，ReadLink等，并生成C.struct_fuse_operations，并将函数指针绑定到调用给定接口的闭包。
这是我的代码（代码后面有解释）：
package fuse
// #include <fuse.h>
// #include <stdlib.h>
import "C"
import (
"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))
}
这会产生以下错误：
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
我不确定应该传递什么给C.struct_fuse_operations的这些成员，我在几个地方看到提到从C代码调用回Go代码是不可能的。
如果可能的话，我该怎么做？我如何为接口函数提供“默认”值，使其表现得好像对应的C.struct_fuse_operations成员设置为NULL？
英文:
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:
<pre>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</pre>
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?
答案1
得分: 1
http://cheesesun.blogspot.com/2010/04/callbacks-in-cgo.html描述了一种通用的技术，尽管有些复杂。http://groups.google.com/group/golang-nuts/browse_thread/thread/abd0e30dafdbf297?tvc=2&pli=1描述了这个问题。
我怀疑如果你想处理函数指针而不是uintptrs，你将不得不对cgo进行修改。
英文:
http://cheesesun.blogspot.com/2010/04/callbacks-in-cgo.html describes a general - if somewhat convoluted - technique. http://groups.google.com/group/golang-nuts/browse_thread/thread/abd0e30dafdbf297?tvc=2&pli=1 describes the problem.
I suspect that if you want to handle the function pointers as anything other than uintptrs, you'll have to hack on cgo.
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