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Diffstat (limited to 'lib/mpi/mpi-add.c')
| -rw-r--r-- | lib/mpi/mpi-add.c | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/lib/mpi/mpi-add.c b/lib/mpi/mpi-add.c new file mode 100644 index 0000000..f56b9ba --- /dev/null +++ b/lib/mpi/mpi-add.c @@ -0,0 +1,234 @@ +/* mpi-add.c - MPI functions + * Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc. + * Copyright (C) 1994, 1996 Free Software Foundation, Inc. + * + * This file is part of GnuPG. + * + * GnuPG 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 of the License, or + * (at your option) any later version. + * + * GnuPG 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 this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA + * + * Note: This code is heavily based on the GNU MP Library. + * Actually it's the same code with only minor changes in the + * way the data is stored; this is to support the abstraction + * of an optional secure memory allocation which may be used + * to avoid revealing of sensitive data due to paging etc. + * The GNU MP Library itself is published under the LGPL; + * however I decided to publish this code under the plain GPL. + */ + +#include "mpi-internal.h" + +/**************** + * Add the unsigned integer V to the mpi-integer U and store the + * result in W. U and V may be the same. + */ +int mpi_add_ui(MPI w, const MPI u, unsigned long v) +{ + mpi_ptr_t wp, up; + mpi_size_t usize, wsize; + int usign, wsign; + + usize = u->nlimbs; + usign = u->sign; + wsign = 0; + + /* If not space for W (and possible carry), increase space. */ + wsize = usize + 1; + if (w->alloced < wsize) + if (mpi_resize(w, wsize) < 0) + return -ENOMEM; + + /* These must be after realloc (U may be the same as W). */ + up = u->d; + wp = w->d; + + if (!usize) { /* simple */ + wp[0] = v; + wsize = v ? 1 : 0; + } else if (!usign) { /* mpi is not negative */ + mpi_limb_t cy; + cy = mpihelp_add_1(wp, up, usize, v); + wp[usize] = cy; + wsize = usize + cy; + } else { /* The signs are different. Need exact comparison to determine + * which operand to subtract from which. */ + if (usize == 1 && up[0] < v) { + wp[0] = v - up[0]; + wsize = 1; + } else { + mpihelp_sub_1(wp, up, usize, v); + /* Size can decrease with at most one limb. */ + wsize = usize - (wp[usize - 1] == 0); + wsign = 1; + } + } + + w->nlimbs = wsize; + w->sign = wsign; + return 0; +} + +int mpi_add(MPI w, MPI u, MPI v) +{ + mpi_ptr_t wp, up, vp; + mpi_size_t usize, vsize, wsize; + int usign, vsign, wsign; + + if (u->nlimbs < v->nlimbs) { /* Swap U and V. */ + usize = v->nlimbs; + usign = v->sign; + vsize = u->nlimbs; + vsign = u->sign; + wsize = usize + 1; + if (RESIZE_IF_NEEDED(w, wsize) < 0) + return -ENOMEM; + /* These must be after realloc (u or v may be the same as w). */ + up = v->d; + vp = u->d; + } else { + usize = u->nlimbs; + usign = u->sign; + vsize = v->nlimbs; + vsign = v->sign; + wsize = usize + 1; + if (RESIZE_IF_NEEDED(w, wsize) < 0) + return -ENOMEM; + /* These must be after realloc (u or v may be the same as w). */ + up = u->d; + vp = v->d; + } + wp = w->d; + wsign = 0; + + if (!vsize) { /* simple */ + MPN_COPY(wp, up, usize); + wsize = usize; + wsign = usign; + } else if (usign != vsign) { /* different sign */ + /* This test is right since USIZE >= VSIZE */ + if (usize != vsize) { + mpihelp_sub(wp, up, usize, vp, vsize); + wsize = usize; + MPN_NORMALIZE(wp, wsize); + wsign = usign; + } else if (mpihelp_cmp(up, vp, usize) < 0) { + mpihelp_sub_n(wp, vp, up, usize); + wsize = usize; + MPN_NORMALIZE(wp, wsize); + if (!usign) + wsign = 1; + } else { + mpihelp_sub_n(wp, up, vp, usize); + wsize = usize; + MPN_NORMALIZE(wp, wsize); + if (usign) + wsign = 1; + } + } else { /* U and V have same sign. Add them. */ + mpi_limb_t cy = mpihelp_add(wp, up, usize, vp, vsize); + wp[usize] = cy; + wsize = usize + cy; + if (usign) + wsign = 1; + } + + w->nlimbs = wsize; + w->sign = wsign; + return 0; +} + +/**************** + * Subtract the unsigned integer V from the mpi-integer U and store the + * result in W. + */ +int mpi_sub_ui(MPI w, MPI u, unsigned long v) +{ + mpi_ptr_t wp, up; + mpi_size_t usize, wsize; + int usign, wsign; + + usize = u->nlimbs; + usign = u->sign; + wsign = 0; + + /* If not space for W (and possible carry), increase space. */ + wsize = usize + 1; + if (w->alloced < wsize) + if (mpi_resize(w, wsize) < 0) + return -ENOMEM; + + /* These must be after realloc (U may be the same as W). */ + up = u->d; + wp = w->d; + + if (!usize) { /* simple */ + wp[0] = v; + wsize = v ? 1 : 0; + wsign = 1; + } else if (usign) { /* mpi and v are negative */ + mpi_limb_t cy; + cy = mpihelp_add_1(wp, up, usize, v); + wp[usize] = cy; + wsize = usize + cy; + } else { /* The signs are different. Need exact comparison to determine + * which operand to subtract from which. */ + if (usize == 1 && up[0] < v) { + wp[0] = v - up[0]; + wsize = 1; + wsign = 1; + } else { + mpihelp_sub_1(wp, up, usize, v); + /* Size can decrease with at most one limb. */ + wsize = usize - (wp[usize - 1] == 0); + } + } + + w->nlimbs = wsize; + w->sign = wsign; + return 0; +} + +int mpi_sub(MPI w, MPI u, MPI v) +{ + int rc; + + if (w == v) { + MPI vv; + if (mpi_copy(&vv, v) < 0) + return -ENOMEM; + vv->sign = !vv->sign; + rc = mpi_add(w, u, vv); + mpi_free(vv); + } else { + /* fixme: this is not thread-save (we temp. modify v) */ + v->sign = !v->sign; + rc = mpi_add(w, u, v); + v->sign = !v->sign; + } + return rc; +} + +int mpi_addm(MPI w, MPI u, MPI v, MPI m) +{ + if (mpi_add(w, u, v) < 0 || mpi_fdiv_r(w, w, m) < 0) + return -ENOMEM; + return 0; +} + +int mpi_subm(MPI w, MPI u, MPI v, MPI m) +{ + if (mpi_sub(w, u, v) < 0 || mpi_fdiv_r(w, w, m) < 0) + return -ENOMEM; + return 0; +} |
