On Wed, Feb 28, 2018 at 1:58 PM, <jordan9...@gmail.com> wrote:
>
> What is the best way to get an unsafe.Pointer to a []byte's underlying
> array?
unsafe.Pointer(&b[0])
> I have added this function to syscall/syscall_linux.go to support some of
> our experiments. One of the new getsockopt calls returns a variable length
> amount of data into the buffer, which has no real set size. As such,
> userspace programs will have to retry with a larger buffer if the previous
> try was not large enough.
>
> func GetsockoptString(fd, level, opt, max_size int) (string, error) {
> var arr []byte = make([]byte, max_size, max_size)
> vallen := _Socklen(max_size)
>
> // This is really gross and bad, but first entry in a slice is a pointer
> into the array
> t := (**byte)(unsafe.Pointer(&arr))
>
> err := getsockopt(fd, level, opt, unsafe.Pointer(*t), &vallen)
>
> return string(arr[:vallen]), err
> }
>
>
> This function works fine, but seems gross to me. Am I safe to always assume
> that the first entry in a slice is always a pointer into the array for all
> of Go1.x on Linux?
No.
Ian
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