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Corrected an off-by-one error (lib/6314 Torbjorn Granlund)

This commit is contained in:
kristerw 1999-03-26 21:04:24 +00:00
parent 6ee909b24f
commit 8dab0300c3
1 changed files with 11 additions and 27 deletions
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38
lib/libc/quad/fixunsdfdi.c
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@ -1,4 +1,4 @@
/* $NetBSD: fixunsdfdi.c,v 1.4 1997/07/13 20:01:45 christos Exp $ */
/* $NetBSD: fixunsdfdi.c,v 1.5 1999/03/26 21:04:24 kristerw Exp $ */
/*-
* Copyright (c) 1992, 1993
@ -42,7 +42,7 @@
#if 0
static char sccsid[] = "@(#)fixunsdfdi.c 8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: fixunsdfdi.c,v 1.4 1997/07/13 20:01:45 christos Exp $");
__RCSID("$NetBSD: fixunsdfdi.c,v 1.5 1999/03/26 21:04:24 kristerw Exp $");
#endif
#endif /* LIBC_SCCS and not lint */
@ -61,8 +61,8 @@ u_quad_t
__fixunsdfdi(x)
double x;
{
double toppart;
union uu t;
unsigned long tmp;
if (x < 0)
return (UQUAD_MAX); /* ??? should be 0? ERANGE??? */
@ -74,30 +74,14 @@ __fixunsdfdi(x)
return (UQUAD_MAX);
#endif
/*
* Get the upper part of the result. Note that the divide
* may round up; we want to avoid this if possible, so we
* subtract `1/2' first.
* Now we know that 0 <= x <= 18446744073709549568. The upper
* limit is one ulp less than 18446744073709551615 tested for above.
* Dividing this by 2^32 will *not* round irrespective of any
* rounding modes (except if the result is an IEEE denorm).
* Furthermore, the quotient will fit into a 32-bit integer.
*/
toppart = (x - ONE_HALF) / ONE;
/*
* Now build a u_quad_t out of the top part. The difference
* between x and this is the bottom part (this may introduce
* a few fuzzy bits, but what the heck). With any luck this
* difference will be nonnegative: x should wind up in the
* range [0..ULONG_MAX]. For paranoia, we assume [LONG_MIN..
* 2*ULONG_MAX] instead.
*/
t.ul[H] = (unsigned long)toppart;
t.ul[L] = 0;
x -= (double)t.uq;
if (x < 0) {
t.ul[H]--;
x += ULONG_MAX;
}
if (x > ULONG_MAX) {
t.ul[H]++;
x -= ULONG_MAX;
}
t.ul[L] = (u_long)x;
tmp = x / ONE;
t.ul[L] = (unsigned long) (x - tmp * ONE);
t.ul[H] = tmp;
return (t.uq);
}