| /* mpn_sub_n -- Subtract two limb vectors of equal, non-zero length. |

| |

| Copyright (C) 1992, 1993, 1994, 1996 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 Lesser General Public License as published by |

| the Free Software Foundation; either version 2.1 of the License, 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 Lesser General Public |

| License for more details. |

| |

| You should have received a copy of the GNU Lesser General Public License |

| along with the GNU MP Library; see the file COPYING.LIB. If not, write to |

| the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |

| MA 02111-1307, USA. */ |

| |

| #include <config.h> |

| #include "gmp-impl.h" |

| |

| mp_limb_t |

| #if __STDC__ |

| mpn_sub_n (mp_ptr res_ptr, mp_srcptr s1_ptr, mp_srcptr s2_ptr, mp_size_t size) |

| #else |

| mpn_sub_n (res_ptr, s1_ptr, s2_ptr, size) |

| register mp_ptr res_ptr; |

| register mp_srcptr s1_ptr; |

| register mp_srcptr s2_ptr; |

| mp_size_t size; |

| #endif |

| { |

| register mp_limb_t x, y, cy; |

| register mp_size_t j; |

| |

| /* The loop counter and index J goes from -SIZE to -1. This way |

| the loop becomes faster. */ |

| j = -size; |

| |

| /* Offset the base pointers to compensate for the negative indices. */ |

| s1_ptr -= j; |

| s2_ptr -= j; |

| res_ptr -= j; |

| |

| cy = 0; |

| do |

| { |

| y = s2_ptr[j]; |

| x = s1_ptr[j]; |

| y += cy; /* add previous carry to subtrahend */ |

| cy = (y < cy); /* get out carry from that addition */ |

| y = x - y; /* main subtract */ |

| cy = (y > x) + cy; /* get out carry from the subtract, combine */ |

| res_ptr[j] = y; |

| } |

| while (++j != 0); |

| |

| return cy; |

| } |