How to convert [1024]C.char to [1024]byte

Question

How do I convert this C (array) type:

char my_buf[BUF_SIZE];

to this Go (array) type:

type buffer [C.BUF_SIZE]byte

? Trying to do an interface conversion gives me this error:

cannot convert (*_Cvar_my_buf) (type [1024]C.char) to type [1024]byte

Answer 1

The easiest and safest way is to copy it to a slice, not specifically to [1024]byte

mySlice := C.GoBytes(unsafe.Pointer(&C.my_buff), C.BUFF_SIZE)

To use the memory directly without a copy, you can "cast" it through an unsafe.Pointer.

mySlice := (*[1 << 30]byte)(unsafe.Pointer(&C.my_buf))[:int(C.BUFF_SIZE):int(C.BUFF_SIZE)]
// or for an array if BUFF_SIZE is a constant
myArray := *(*[C.BUFF_SIZE]byte)(unsafe.Pointer(&C.my_buf))

Answer 2

To create a Go slice with the contents of C.my_buf:

arr := C.GoBytes(unsafe.Pointer(&C.my_buf), C.BUF_SIZE)

To create a Go array...

var arr [C.BUF_SIZE]byte
copy(arr[:], C.GoBytes(unsafe.Pointer(&C.my_buf), C.BUF_SIZE))