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Diffstat (limited to 'gnu/lib/libgmp/mpz_sub.c')
-rw-r--r-- | gnu/lib/libgmp/mpz_sub.c | 117 |
1 files changed, 117 insertions, 0 deletions
diff --git a/gnu/lib/libgmp/mpz_sub.c b/gnu/lib/libgmp/mpz_sub.c new file mode 100644 index 0000000..f75f06c --- /dev/null +++ b/gnu/lib/libgmp/mpz_sub.c @@ -0,0 +1,117 @@ +/* mpz_sub -- Subtract two integers. + +Copyright (C) 1991 Free Software Foundation, Inc. + +This file is part of the GNU MP Library. + +The GNU MP Library is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +The GNU MP Library is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +You should have received a copy of the GNU General Public License +along with the GNU MP Library; see the file COPYING. If not, write to +the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */ + +#include "gmp.h" +#include "gmp-impl.h" + +#ifndef BERKELEY_MP +void +#ifdef __STDC__ +mpz_sub (MP_INT *w, const MP_INT *u, const MP_INT *v) +#else +mpz_sub (w, u, v) + MP_INT *w; + const MP_INT *u; + const MP_INT *v; +#endif +#else /* BERKELEY_MP */ +void +#ifdef __STDC__ +msub (const MP_INT *u, const MP_INT *v, MP_INT *w) +#else +msub (u, v, w) + const MP_INT *u; + const MP_INT *v; + MP_INT *w; +#endif +#endif /* BERKELEY_MP */ +{ + mp_srcptr up, vp; + mp_ptr wp; + mp_size usize, vsize, wsize; + mp_size abs_usize; + mp_size abs_vsize; + + usize = u->size; + vsize = -v->size; /* The "-" makes the difference from mpz_add */ + abs_usize = ABS (usize); + abs_vsize = ABS (vsize); + + if (abs_usize < abs_vsize) + { + /* Swap U and V. */ + {const MP_INT *t = u; u = v; v = t;} + {mp_size t = usize; usize = vsize; vsize = t;} + {mp_size t = abs_usize; abs_usize = abs_vsize; abs_vsize = t;} + } + + /* True: abs(USIZE) >= abs(VSIZE) */ + + /* If not space for sum (and possible carry), increase space. */ + wsize = abs_usize + 1; + if (w->alloc < wsize) + _mpz_realloc (w, wsize); + + /* These must be after realloc (u or v may be the same as w). */ + up = u->d; + vp = v->d; + wp = w->d; + + if (usize >= 0) + { + if (vsize >= 0) + { + wsize = mpn_add (wp, up, abs_usize, vp, abs_vsize); + if (wsize != 0) + wp[abs_usize] = 1; + wsize = wsize + abs_usize; + } + else + { + /* The signs are different. Need exact comparision to determine + which operand to subtract from which. */ + if (abs_usize == abs_vsize && mpn_cmp (up, vp, abs_usize) < 0) + wsize = -(abs_usize + mpn_sub (wp, vp, abs_usize, up, abs_usize)); + else + wsize = abs_usize + mpn_sub (wp, up, abs_usize, vp, abs_vsize); + } + } + else + { + if (vsize >= 0) + { + /* The signs are different. Need exact comparision to determine + which operand to subtract from which. */ + if (abs_usize == abs_vsize && mpn_cmp (up, vp, abs_usize) < 0) + wsize = abs_usize + mpn_sub (wp, vp, abs_usize, up, abs_usize); + else + wsize = -(abs_usize + mpn_sub (wp, up, abs_usize, vp, abs_vsize)); + } + else + { + wsize = mpn_add (wp, up, abs_usize, vp, abs_vsize); + if (wsize != 0) + wp[abs_usize] = 1; + wsize = -(wsize + abs_usize); + } + } + + w->size = wsize; +} |