/* SPDX-License-Identifier: GPL-2.0-or-later */
/* 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.
 *
 * 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  static 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 */