Parsing null terminated strings in a binary.

[Per Gustafsson]

I tested some different versions of the z_split program and the fastest
one I found was this:


z_split(B) when is_binary(B) ->
  z_split3(B, 0, size(B)).

z_split3(B, N, X) ->
  case B of
    <<_:N/binary,0,_/binary>> ->
      <<B1:N/binary,0,B2/binary>> = B,
      {B1,B2};
    _ when X > N  ->
    z_split3(B, N+1, X);
    _ ->
      B
  end.

This moves the call to size outside the loop and it also avoids creating a
subbinary unless an actual zero has been found.

If you hipe compile the code however this is the fastest version:

z_splita(B) when is_binary(B) ->
  z_splita2(B, 0).
z_splita2(B,N) ->
  case B of
    <<_:N/binary,0,_/binary>> ->
      <<B1:N/binary,0,B2/binary>> = B,
      {B1,B2};
    <<_:N/binary>> ->
      B;
    _ ->
      z_splita2(B, N+1)
  end.

About 3.5 times faster than the non hipe compiled version

Per

On Thu, 13 Jan 2005, Mats Cronqvist wrote:

>    sorry to keep harping on this...
>    ...but would it be (noticably) faster to move the call to size/1 outside the loop?
>    or equivalently, how fast is size/1 (compared to the binary match)?
>    i would guess plenty fast but i'm too lazy to try it.
>
>    mats
>
> Raimo Niskanen wrote:
> > You are missing nothing. The code just evolved in my head to
> > what it became - some cruft was left. This might be even clearer
> > (untested):
> >
> > z_split(B, N) when is_binary(B), is_integer(N) ->
> >      case B of
> > 	<<B1:N/binary,0,B2/binary>> ->
> >             {B1,B2};
> >         _ when size(B) > N
> >             z_split(B, N+1);
> >         _ ->
> >             B
> >      end.
> >
> >
>