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155 lines
3.4 KiB
155 lines
3.4 KiB
/* mpi-add.c - MPI functions |
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* Copyright (C) 1994, 1996, 1998, 2001, 2002, |
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* 2003 Free Software Foundation, Inc. |
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* |
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* This file is part of Libgcrypt. |
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* |
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* Note: This code is heavily based on the GNU MP Library. |
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* Actually it's the same code with only minor changes in the |
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* way the data is stored; this is to support the abstraction |
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* of an optional secure memory allocation which may be used |
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* to avoid revealing of sensitive data due to paging etc. |
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*/ |
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#include "mpi-internal.h" |
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/**************** |
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* Add the unsigned integer V to the mpi-integer U and store the |
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* result in W. U and V may be the same. |
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*/ |
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void mpi_add_ui(MPI w, MPI u, unsigned long v) |
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{ |
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mpi_ptr_t wp, up; |
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mpi_size_t usize, wsize; |
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int usign, wsign; |
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usize = u->nlimbs; |
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usign = u->sign; |
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wsign = 0; |
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/* If not space for W (and possible carry), increase space. */ |
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wsize = usize + 1; |
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if (w->alloced < wsize) |
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mpi_resize(w, wsize); |
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/* These must be after realloc (U may be the same as W). */ |
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up = u->d; |
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wp = w->d; |
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if (!usize) { /* simple */ |
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wp[0] = v; |
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wsize = v ? 1:0; |
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} else if (!usign) { /* mpi is not negative */ |
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mpi_limb_t cy; |
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cy = mpihelp_add_1(wp, up, usize, v); |
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wp[usize] = cy; |
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wsize = usize + cy; |
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} else { |
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/* The signs are different. Need exact comparison to determine |
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* which operand to subtract from which. |
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*/ |
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if (usize == 1 && up[0] < v) { |
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wp[0] = v - up[0]; |
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wsize = 1; |
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} else { |
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mpihelp_sub_1(wp, up, usize, v); |
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/* Size can decrease with at most one limb. */ |
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wsize = usize - (wp[usize-1] == 0); |
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wsign = 1; |
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} |
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} |
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w->nlimbs = wsize; |
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w->sign = wsign; |
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} |
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void mpi_add(MPI w, MPI u, MPI v) |
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{ |
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mpi_ptr_t wp, up, vp; |
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mpi_size_t usize, vsize, wsize; |
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int usign, vsign, wsign; |
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if (u->nlimbs < v->nlimbs) { /* Swap U and V. */ |
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usize = v->nlimbs; |
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usign = v->sign; |
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vsize = u->nlimbs; |
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vsign = u->sign; |
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wsize = usize + 1; |
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RESIZE_IF_NEEDED(w, wsize); |
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/* These must be after realloc (u or v may be the same as w). */ |
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up = v->d; |
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vp = u->d; |
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} else { |
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usize = u->nlimbs; |
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usign = u->sign; |
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vsize = v->nlimbs; |
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vsign = v->sign; |
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wsize = usize + 1; |
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RESIZE_IF_NEEDED(w, wsize); |
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/* These must be after realloc (u or v may be the same as w). */ |
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up = u->d; |
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vp = v->d; |
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} |
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wp = w->d; |
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wsign = 0; |
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if (!vsize) { /* simple */ |
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MPN_COPY(wp, up, usize); |
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wsize = usize; |
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wsign = usign; |
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} else if (usign != vsign) { /* different sign */ |
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/* This test is right since USIZE >= VSIZE */ |
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if (usize != vsize) { |
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mpihelp_sub(wp, up, usize, vp, vsize); |
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wsize = usize; |
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MPN_NORMALIZE(wp, wsize); |
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wsign = usign; |
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} else if (mpihelp_cmp(up, vp, usize) < 0) { |
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mpihelp_sub_n(wp, vp, up, usize); |
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wsize = usize; |
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MPN_NORMALIZE(wp, wsize); |
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if (!usign) |
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wsign = 1; |
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} else { |
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mpihelp_sub_n(wp, up, vp, usize); |
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wsize = usize; |
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MPN_NORMALIZE(wp, wsize); |
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if (usign) |
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wsign = 1; |
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} |
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} else { /* U and V have same sign. Add them. */ |
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mpi_limb_t cy = mpihelp_add(wp, up, usize, vp, vsize); |
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wp[usize] = cy; |
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wsize = usize + cy; |
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if (usign) |
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wsign = 1; |
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} |
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w->nlimbs = wsize; |
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w->sign = wsign; |
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} |
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EXPORT_SYMBOL_GPL(mpi_add); |
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void mpi_sub(MPI w, MPI u, MPI v) |
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{ |
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MPI vv = mpi_copy(v); |
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vv->sign = !vv->sign; |
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mpi_add(w, u, vv); |
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mpi_free(vv); |
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} |
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EXPORT_SYMBOL_GPL(mpi_sub); |
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void mpi_addm(MPI w, MPI u, MPI v, MPI m) |
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{ |
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mpi_add(w, u, v); |
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mpi_mod(w, w, m); |
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} |
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EXPORT_SYMBOL_GPL(mpi_addm); |
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void mpi_subm(MPI w, MPI u, MPI v, MPI m) |
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{ |
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mpi_sub(w, u, v); |
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mpi_mod(w, w, m); |
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} |
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EXPORT_SYMBOL_GPL(mpi_subm);
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