Array length & allocation question

[Derek Parnell]

On Tue, 13 Jun 2006 09:24:34 +0200, Oskar Linde wrote:

> What is even more interesting is that the above "buggy" behavior
> seems intentional. The following patch removes the forced
> reallocation when changing length of a 0-length array:

Hmmm... I just rewrote that function as below and it seems to test out
quite well too. I incorporated your change plus I removed the check for a
zero new length. Seems to work without any problems.

-----------------
extern (C)
byte[] _d_arraysetlength(size_t newlength, size_t sizeelem, Array *p)
in
{
    assert(sizeelem);
    assert(!p.length || p.data);
}
body
{
    byte* newdata;
    newdata = p.data;
    if (newlength > p.length)
    {
        version (D_InlineAsm_X86)
        {
            size_t newsize = void;
            asm
            {
            mov EAX,newlength   ;
            mul EAX,sizeelem    ;
            mov newsize,EAX ;
            jc  Loverflow   ;
            }
        }
        else
        {
            size_t newsize = sizeelem * newlength;
            if (newsize / newlength != sizeelem)
            goto Loverflow;
        }
        size_t size = p.length * sizeelem;
        size_t cap = _gc.capacity(p.data);
        if (cap <= newsize)
        {
            newdata = cast(byte *)_gc.malloc(newsize + 1);
            newdata[0 .. size] = p.data[0 .. size];
        }
        newdata[size .. newsize] = 0;
    }
    p.data = newdata;
    p.length = newlength;
    return newdata[0 .. newlength];
Loverflow:
    _d_OutOfMemory();
}
---------------

-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocrity!"
13/06/2006 5:54:57 PM