Hi!
22-Мар-2004 14:23 [EMAIL PROTECTED] (Bart Oldeman) wrote to
[EMAIL PROTECTED]:
BO> add_far is only used at a few select places where we want to have the
BO> offset part as low as possible. Nothing to do with structures but
BO> everything to do with potentially large file reads, with "read chunk,
BO> update pointer" loops.
BO> Quite possibly Arkady's approach minimizing normalizations has merit but
BO> then each add_far caller needs to be checked if it needs to manually
BO> normalize the pointer afterwards.
Then rename "add_far" into "normalize_ptr" and remove misleading. Also,
I may offer next code to always perform normalization: (BTW, is "protection"
from wrapping HMA pointer into IVT by replacing wrapping into start of HMA
worth of code?)
void FAR *normalize_ptr (void FAR *fp, unsigned add)
{
unsigned ofs = add + FP_OFF (fp);
seg/*_t*/ s = FP_SEG (fp);
if (ofs < FP_OFF (fp)) /* arithmetic overflow? */
s += 0x1000; /* add carry */
return MK_FP ((ofs >> 4) + s, 0xF & ofs);
}
BO> But for now, because it's not called very often, the time it takes is very
BO> small in comparison with the BIOS calls following, and normalization doesn't
BO> hurt, I haven't changed it.
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