On 2012-04-08 18:30:49 +0000, Andrei Alexandrescu
<seewebsiteforem...@erdani.org> said:
On 4/8/12 1:26 PM, Andrei Alexandrescu wrote:
On 4/8/12 1:16 PM, Michel Fortin wrote:
Also, if the variable is a temporary copy such as a by-value function
parameter, only the representation of that temporary copy will be
affected. Every time you call a function which calls .ptr a new copy
will be allocated on the heap. If such a function call is part of a
loop, it'll degrade performance noticeably.
I think there's a bit of a confusion. Could you please clarify with an
example?
I think I understand:
string s;
foreach (lots)
fun(s);
void fun(string s)
{
... s.ptr ...
}
Exactly.
I agree in this case there would be one allocation per call.
Basically, it's the same problem as receiving a const(char)[] as a
function parameter and .idup-ing it in the function. The recommendation
is for such functions to accept only immutable(char)[] and let the
caller find a way to send an immutable string. That way, if the caller
is repeatedly using the same string, it can reuse the efficient
representation.
The same principles apply here: if your function needs to use .ptr, it
should request a type on which you can call .ptr efficiently and let
the caller find a way to pass think kind of string. To me, your small
buffer optimization proposal looks like an argument in favor of
creating a separate string type free from the constrains of offering at
all time bare access to the bytes. If only that type could be the
default...
--
Michel Fortin
michel.for...@michelf.com
http://michelf.com/
