projects / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| cdec9cb5 DK |
1 | /* mpihelp-mul_3.c - MPI helper functions |
| 2 | * Copyright (C) 1994, 1996, 1997, 1998, 2001 Free Software Foundation, Inc. | |
| 3 | * | |
| 4 | * This file is part of GnuPG. | |
| 5 | * | |
| 6 | * GnuPG is free software; you can redistribute it and/or modify | |
| 7 | * it under the terms of the GNU General Public License as published by | |
| 8 | * the Free Software Foundation; either version 2 of the License, or | |
| 9 | * (at your option) any later version. | |
| 10 | * | |
| 11 | * GnuPG is distributed in the hope that it will be useful, | |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 14 | * GNU General Public License for more details. | |
| 15 | * | |
| 16 | * You should have received a copy of the GNU General Public License | |
| 17 | * along with this program; if not, write to the Free Software | |
| 18 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA | |
| 19 | * | |
| 20 | * Note: This code is heavily based on the GNU MP Library. | |
| 21 | * Actually it's the same code with only minor changes in the | |
| 22 | * way the data is stored; this is to support the abstraction | |
| 23 | * of an optional secure memory allocation which may be used | |
| 24 | * to avoid revealing of sensitive data due to paging etc. | |
| 25 | * The GNU MP Library itself is published under the LGPL; | |
| 26 | * however I decided to publish this code under the plain GPL. | |
| 27 | */ | |
| 28 | ||
| 29 | #include "mpi-internal.h" | |
| 30 | #include "longlong.h" | |
| 31 | ||
| 32 | mpi_limb_t | |
| 33 | mpihelp_submul_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, | |
| 34 | mpi_size_t s1_size, mpi_limb_t s2_limb) | |
| 35 | { | |
| 36 | mpi_limb_t cy_limb; | |
| 37 | mpi_size_t j; | |
| 38 | mpi_limb_t prod_high, prod_low; | |
| 39 | mpi_limb_t x; | |
| 40 | ||
| 41 | /* The loop counter and index J goes from -SIZE to -1. This way | |
| 42 | * the loop becomes faster. */ | |
| 43 | j = -s1_size; | |
| 44 | res_ptr -= j; | |
| 45 | s1_ptr -= j; | |
| 46 | ||
| 47 | cy_limb = 0; | |
| 48 | do { | |
| 49 | umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb); | |
| 50 | ||
| 51 | prod_low += cy_limb; | |
| 52 | cy_limb = (prod_low < cy_limb ? 1 : 0) + prod_high; | |
| 53 | ||
| 54 | x = res_ptr[j]; | |
| 55 | prod_low = x - prod_low; | |
| 56 | cy_limb += prod_low > x ? 1 : 0; | |
| 57 | res_ptr[j] = prod_low; | |
| 58 | } while (++j); | |
| 59 | ||
| 60 | return cy_limb; | |
| 61 | } |