[erlang-questions] NIF wishes

[Rapsey]

Speaking of binaries and NIF. If you send one to a NIF function, you get a
direct pointer to the binary and can modify it in-place. How dangerous is
this?


Sergej

On Tue, Dec 8, 2009 at 5:50 PM, Hans Nilsson R
<hans.r.nilsson@REDACTED>wrote:

> I have been playing with the NIF facility in R13B03 and I have some
> comments. The implementation is very stable, as usual with experimental code
> from Erlang/OTP!  And very fast....
>
> I have a large binary which I pass into a nif, which processes a part of it
> and returns the result and the unprocessed part of the binary.  The
> unprocessed part is then input to the nif again and so on.
>
> Wish 1:
> Now, in the nif, to make a copy of the unprocessed part and make a new
> binary is time consuming, so some function enif_make_sub_binary(env, bin,
> from, to) would be useful.
>
> Wish 2:
> When the nif shall return a part of the binary as a string or a binary, the
> functions enif_make_atom and enif_make_string  assumes that the part is
> zero-terminated.  It is of course possible to save the character, write a
> zero, call the enif-function and then write back the original character, but
> it is of course dangerous to modify in place in a binary...  The alternative
> of copying the characters to a buffer is slow.
>
> Therefore I'd like to have some  enif_make_string_n(env, char *p, int
> length) as well, analogous to the c-library functions strcpy and strncpy.
>
> /Hans Nilsson
>
>
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