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Diffstat (limited to '')
| -rw-r--r-- | lib/mpi/mpi-add.c | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/lib/mpi/mpi-add.c b/lib/mpi/mpi-add.c new file mode 100644 index 000000000..2cdae54c1 --- /dev/null +++ b/lib/mpi/mpi-add.c @@ -0,0 +1,155 @@ +/* mpi-add.c - MPI functions + * Copyright (C) 1994, 1996, 1998, 2001, 2002, + * 2003 Free Software Foundation, Inc. + * + * This file is part of Libgcrypt. + * + * 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. + */ + +#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. + */ +void mpi_add_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) + mpi_resize(w, wsize); + + /* 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; +} + + +void 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; + RESIZE_IF_NEEDED(w, wsize); + /* 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; + RESIZE_IF_NEEDED(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; + 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; +} +EXPORT_SYMBOL_GPL(mpi_add); + +void mpi_sub(MPI w, MPI u, MPI v) +{ + MPI vv = mpi_copy(v); + vv->sign = !vv->sign; + mpi_add(w, u, vv); + mpi_free(vv); +} + + +void mpi_addm(MPI w, MPI u, MPI v, MPI m) +{ + mpi_add(w, u, v); + mpi_mod(w, w, m); +} +EXPORT_SYMBOL_GPL(mpi_addm); + +void mpi_subm(MPI w, MPI u, MPI v, MPI m) +{ + mpi_sub(w, u, v); + mpi_mod(w, w, m); +} +EXPORT_SYMBOL_GPL(mpi_subm); |