Note to BDS C Users Who Use the "qsort" Library Function:
(From Leor Zolman, Feb 1982)
The low-level swap function that qsort uses, called "_swp", is pretty
inefficient. A version that works much more quickly is given below, but
note that this method necessarily requires that some upper maximum be set
on the size ("width") of a single object of the class being sorted. The
new _swp function is as follows:
-------------------------------------------------------------------------------
#define MAX_WIDTH 1000 /* largest allowable width */
_swp(width, a, b);
{
char swapbuf[MAX_WIDTH];
movmem(a,swapbuf,width); /* simply swap through the temporary */
movmem(b,a,width); /* buffer allocated on the stack */
movmem(swapbuf,b,width);
}
-------------------------------------------------------------------------------
To install this modification, replace the _swp function in STDLIB1.C with
this version, recompile STDLIB1.C, and use the librarian (CLIB) to delete
the old version of "_swp" in DEFF.CRL and replace it with the new one from
STDLIB1.CRL. And make sure that the MAX_WIDTH define is set so that you're
never likely to want to sort object of larger size. If you DO, remember to
go back and change the define....
-leor
