英文:
Modifying a C void* byte array from Go code
问题
基本上，我正在尝试用Go函数替换C程序中的pread。我已经完成了大部分结构，但是我无法弄清楚如何用所需的字节填充缓冲区参数（buf unsafe.Pointer）。
daemon.c的一部分：
static int preadShim(int fd, void *buf, size_t count, off_t offset) {
//return pread(fd, buf, count, offset);
return ReadOver(fd, buf, count, offset);
}
在一个Golang文件中：
package main
import "C"
import "fmt"
import "unsafe"
//export ReadOver
func ReadOver(fd C.int, buf unsafe.Pointer, count C.int, offset C.int) C.int{
fmt.Println("ReadOver被调用了")
newBuf := []byte("注入的字节")
//TODO: 将newBuf复制到buf中
return count
}
另一个Golang文件：
package main
// #include "daemon.c"
import "C"
import "fmt"
func main() {
//启动C程序
C.start()
}
有什么建议吗？我什么都没尝试过，也没有任何想法。
英文:
Basically, I'm trying to replace pread in a C program with a Go function. I've got most of the structure working, but I can't figure out how to populate the buffer argument (buf unsafe.Pointer) with the desired bytes.
Part of daemon.c:
static int preadShim(int fd, void *buf, size_t count, off_t offset) {
//return pread(fd, buf, count, offset);
return ReadOver(fd, buf, count, offset);
}
In a Golang file:
package main
import "C"
import "fmt"
import "unsafe"
//export ReadOver
func ReadOver(fd C.int, buf unsafe.Pointer, count C.int, offset C.int) C.int{
fmt.Println("ReadOver got called")
newBuf := []byte("injected bytes")
//TODO: copy newBuf over buf
return count
}
Another Golang file:
package main
// #include "daemon.c"
import "C"
import "fmt"
func main() {
//Start C program
C.start()
}
Any suggestions? I've tried nothing and I'm all out of ideas.
答案1
得分: 2
你只需要从中创建自己的切片，例如：
func ReadOver(fd C.int, buf unsafe.Pointer, count C.int, offset C.int) C.int {
fmt.Println("ReadOver被调用了")
newBuf := []byte("注入的字节")
slice := &reflect.SliceHeader{Data: uintptr(buf), Len: int(count), Cap: int(count)}
rbuf := *(*[]byte)(unsafe.Pointer(slice))
return C.int(copy(rbuf, newBuf))
}
这段代码是一个示例，它将创建一个新的切片并将其注入到给定的缓冲区中。函数的作用是将newBuf中的字节复制到rbuf中，并返回复制的字节数。
英文:
You just have to create your own slice from it, for example:
func ReadOver(fd C.int, buf unsafe.Pointer, count C.int, offset C.int) C.int {
fmt.Println("ReadOver got called")
newBuf := []byte("injected bytes")
slice := &reflect.SliceHeader{Data: uintptr(buf), Len: int(count), Cap: int(count)}
rbuf := *(*[]byte)(unsafe.Pointer(slice))
return C.int(copy(rbuf, newBuf))
}
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