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Diffstat (limited to 'lib/mpi/mpi-bit.c')
| -rw-r--r-- | lib/mpi/mpi-bit.c | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/lib/mpi/mpi-bit.c b/lib/mpi/mpi-bit.c new file mode 100644 index 000000000000..2f526627e4f5 --- /dev/null +++ b/lib/mpi/mpi-bit.c @@ -0,0 +1,217 @@ +/* mpi-bit.c - MPI bit level fucntions + * Copyright (C) 1998, 1999 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 + */ + +#include "mpi-internal.h" +#include "longlong.h" + +#define A_LIMB_1 ((mpi_limb_t) 1) + +/**************** + * Sometimes we have MSL (most significant limbs) which are 0; + * this is for some reasons not good, so this function removes them. + */ +void mpi_normalize(MPI a) +{ + for (; a->nlimbs && !a->d[a->nlimbs - 1]; a->nlimbs--) + ; +} + +/**************** + * Return the number of bits in A. + */ +unsigned mpi_get_nbits(MPI a) +{ + unsigned n; + + mpi_normalize(a); + + if (a->nlimbs) { + mpi_limb_t alimb = a->d[a->nlimbs - 1]; + if (alimb) + count_leading_zeros(n, alimb); + else + n = BITS_PER_MPI_LIMB; + n = BITS_PER_MPI_LIMB - n + (a->nlimbs - 1) * BITS_PER_MPI_LIMB; + } else + n = 0; + return n; +} +EXPORT_SYMBOL_GPL(mpi_get_nbits); + +/**************** + * Test whether bit N is set. + */ +int mpi_test_bit(MPI a, unsigned n) +{ + unsigned limbno, bitno; + mpi_limb_t limb; + + limbno = n / BITS_PER_MPI_LIMB; + bitno = n % BITS_PER_MPI_LIMB; + + if (limbno >= a->nlimbs) + return 0; /* too far left: this is a 0 */ + limb = a->d[limbno]; + return (limb & (A_LIMB_1 << bitno)) ? 1 : 0; +} + +/**************** + * Set bit N of A. + */ +int mpi_set_bit(MPI a, unsigned n) +{ + unsigned limbno, bitno; + + limbno = n / BITS_PER_MPI_LIMB; + bitno = n % BITS_PER_MPI_LIMB; + + if (limbno >= a->nlimbs) { /* resize */ + if (a->alloced >= limbno) + if (mpi_resize(a, limbno + 1) < 0) + return -ENOMEM; + a->nlimbs = limbno + 1; + } + a->d[limbno] |= (A_LIMB_1 << bitno); + return 0; +} + +/**************** + * Set bit N of A. and clear all bits above + */ +int mpi_set_highbit(MPI a, unsigned n) +{ + unsigned limbno, bitno; + + limbno = n / BITS_PER_MPI_LIMB; + bitno = n % BITS_PER_MPI_LIMB; + + if (limbno >= a->nlimbs) { /* resize */ + if (a->alloced >= limbno) + if (mpi_resize(a, limbno + 1) < 0) + return -ENOMEM; + a->nlimbs = limbno + 1; + } + a->d[limbno] |= (A_LIMB_1 << bitno); + for (bitno++; bitno < BITS_PER_MPI_LIMB; bitno++) + a->d[limbno] &= ~(A_LIMB_1 << bitno); + a->nlimbs = limbno + 1; + return 0; +} + +/**************** + * clear bit N of A and all bits above + */ +void mpi_clear_highbit(MPI a, unsigned n) +{ + unsigned limbno, bitno; + + limbno = n / BITS_PER_MPI_LIMB; + bitno = n % BITS_PER_MPI_LIMB; + + if (limbno >= a->nlimbs) + return; /* not allocated, so need to clear bits :-) */ + + for (; bitno < BITS_PER_MPI_LIMB; bitno++) + a->d[limbno] &= ~(A_LIMB_1 << bitno); + a->nlimbs = limbno + 1; +} + +/**************** + * Clear bit N of A. + */ +void mpi_clear_bit(MPI a, unsigned n) +{ + unsigned limbno, bitno; + + limbno = n / BITS_PER_MPI_LIMB; + bitno = n % BITS_PER_MPI_LIMB; + + if (limbno >= a->nlimbs) + return; /* don't need to clear this bit, it's to far to left */ + a->d[limbno] &= ~(A_LIMB_1 << bitno); +} + +/**************** + * Shift A by N bits to the right + * FIXME: should use alloc_limb if X and A are same. + */ +int mpi_rshift(MPI x, MPI a, unsigned n) +{ + mpi_ptr_t xp; + mpi_size_t xsize; + + xsize = a->nlimbs; + x->sign = a->sign; + if (RESIZE_IF_NEEDED(x, (size_t) xsize) < 0) + return -ENOMEM; + xp = x->d; + + if (xsize) { + mpihelp_rshift(xp, a->d, xsize, n); + MPN_NORMALIZE(xp, xsize); + } + x->nlimbs = xsize; + return 0; +} + +/**************** + * Shift A by COUNT limbs to the left + * This is used only within the MPI library + */ +int mpi_lshift_limbs(MPI a, unsigned int count) +{ + mpi_ptr_t ap = a->d; + int n = a->nlimbs; + int i; + + if (!count || !n) + return 0; + + if (RESIZE_IF_NEEDED(a, n + count) < 0) + return -ENOMEM; + + for (i = n - 1; i >= 0; i--) + ap[i + count] = ap[i]; + for (i = 0; i < count; i++) + ap[i] = 0; + a->nlimbs += count; + return 0; +} + +/**************** + * Shift A by COUNT limbs to the right + * This is used only within the MPI library + */ +void mpi_rshift_limbs(MPI a, unsigned int count) +{ + mpi_ptr_t ap = a->d; + mpi_size_t n = a->nlimbs; + unsigned int i; + + if (count >= n) { + a->nlimbs = 0; + return; + } + + for (i = 0; i < n - count; i++) + ap[i] = ap[i + count]; + ap[i] = 0; + a->nlimbs -= count; +} |