mpi-inline.h

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/* mpi-inline.h  -  Internal to the Multi Precision Integers
 *  Copyright (C) 1994, 1996, 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
 *
 * 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.
 */

#ifndef G10_MPI_INLINE_H
#define G10_MPI_INLINE_H

#ifndef G10_MPI_INLINE_DECL
#define G10_MPI_INLINE_DECL  extern inline
#endif

G10_MPI_INLINE_DECL mpi_limb_t
mpihelp_add_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
          mpi_size_t s1_size, mpi_limb_t s2_limb)
{
    mpi_limb_t x;

    x = *s1_ptr++;
    s2_limb += x;
    *res_ptr++ = s2_limb;
    if (s2_limb < x) {  /* sum is less than the left operand: handle carry */
        while (--s1_size) {
            x = *s1_ptr++ + 1;  /* add carry */
            *res_ptr++ = x; /* and store */
            if (x)  /* not 0 (no overflow): we can stop */
                goto leave;
        }
        return 1;   /* return carry (size of s1 to small) */
    }

leave:
    if (res_ptr != s1_ptr) {    /* not the same variable */
        mpi_size_t i;   /* copy the rest */
        for (i = 0; i < s1_size - 1; i++)
            res_ptr[i] = s1_ptr[i];
    }
    return 0;       /* no carry */
}

G10_MPI_INLINE_DECL mpi_limb_t
mpihelp_add(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
        mpi_ptr_t s2_ptr, mpi_size_t s2_size)
{
    mpi_limb_t cy = 0;

    if (s2_size)
        cy = mpihelp_add_n(res_ptr, s1_ptr, s2_ptr, s2_size);

    if (s1_size - s2_size)
        cy = mpihelp_add_1(res_ptr + s2_size, s1_ptr + s2_size,
                   s1_size - s2_size, cy);
    return cy;
}

G10_MPI_INLINE_DECL mpi_limb_t
mpihelp_sub_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
          mpi_size_t s1_size, mpi_limb_t s2_limb)
{
    mpi_limb_t x;

    x = *s1_ptr++;
    s2_limb = x - s2_limb;
    *res_ptr++ = s2_limb;
    if (s2_limb > x) {
        while (--s1_size) {
            x = *s1_ptr++;
            *res_ptr++ = x - 1;
            if (x)
                goto leave;
        }
        return 1;
    }

leave:
    if (res_ptr != s1_ptr) {
        mpi_size_t i;
        for (i = 0; i < s1_size - 1; i++)
            res_ptr[i] = s1_ptr[i];
    }
    return 0;
}

G10_MPI_INLINE_DECL mpi_limb_t
mpihelp_sub(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
        mpi_ptr_t s2_ptr, mpi_size_t s2_size)
{
    mpi_limb_t cy = 0;

    if (s2_size)
        cy = mpihelp_sub_n(res_ptr, s1_ptr, s2_ptr, s2_size);

    if (s1_size - s2_size)
        cy = mpihelp_sub_1(res_ptr + s2_size, s1_ptr + s2_size,
                   s1_size - s2_size, cy);
    return cy;
}

#endif /*G10_MPI_INLINE_H */