1/* SPDX-License-Identifier: GPL-2.0-or-later */
  2/* mpi-inline.h  -  Internal to the Multi Precision Integers
  3 *	Copyright (C) 1994, 1996, 1998, 1999 Free Software Foundation, Inc.
  4 *
  5 * This file is part of GnuPG.
  6 *
  7 * Note: This code is heavily based on the GNU MP Library.
  8 *	 Actually it's the same code with only minor changes in the
  9 *	 way the data is stored; this is to support the abstraction
 10 *	 of an optional secure memory allocation which may be used
 11 *	 to avoid revealing of sensitive data due to paging etc.
 12 *	 The GNU MP Library itself is published under the LGPL;
 13 *	 however I decided to publish this code under the plain GPL.
 14 */
 15
 16#ifndef G10_MPI_INLINE_H
 17#define G10_MPI_INLINE_H
 18
 19#ifndef G10_MPI_INLINE_DECL
 20#define G10_MPI_INLINE_DECL  static inline
 21#endif
 22
 23G10_MPI_INLINE_DECL mpi_limb_t
 24mpihelp_add_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
 25	      mpi_size_t s1_size, mpi_limb_t s2_limb)
 26{
 27	mpi_limb_t x;
 28
 29	x = *s1_ptr++;
 30	s2_limb += x;
 31	*res_ptr++ = s2_limb;
 32	if (s2_limb < x) {	/* sum is less than the left operand: handle carry */
 33		while (--s1_size) {
 34			x = *s1_ptr++ + 1;	/* add carry */
 35			*res_ptr++ = x;	/* and store */
 36			if (x)	/* not 0 (no overflow): we can stop */
 37				goto leave;
 38		}
 39		return 1;	/* return carry (size of s1 to small) */
 40	}
 41
 42leave:
 43	if (res_ptr != s1_ptr) {	/* not the same variable */
 44		mpi_size_t i;	/* copy the rest */
 45		for (i = 0; i < s1_size - 1; i++)
 46			res_ptr[i] = s1_ptr[i];
 47	}
 48	return 0;		/* no carry */
 49}
 50
 51G10_MPI_INLINE_DECL mpi_limb_t
 52mpihelp_add(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
 53	    mpi_ptr_t s2_ptr, mpi_size_t s2_size)
 54{
 55	mpi_limb_t cy = 0;
 56
 57	if (s2_size)
 58		cy = mpihelp_add_n(res_ptr, s1_ptr, s2_ptr, s2_size);
 59
 60	if (s1_size - s2_size)
 61		cy = mpihelp_add_1(res_ptr + s2_size, s1_ptr + s2_size,
 62				   s1_size - s2_size, cy);
 63	return cy;
 64}
 65
 66G10_MPI_INLINE_DECL mpi_limb_t
 67mpihelp_sub_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
 68	      mpi_size_t s1_size, mpi_limb_t s2_limb)
 69{
 70	mpi_limb_t x;
 71
 72	x = *s1_ptr++;
 73	s2_limb = x - s2_limb;
 74	*res_ptr++ = s2_limb;
 75	if (s2_limb > x) {
 76		while (--s1_size) {
 77			x = *s1_ptr++;
 78			*res_ptr++ = x - 1;
 79			if (x)
 80				goto leave;
 81		}
 82		return 1;
 83	}
 84
 85leave:
 86	if (res_ptr != s1_ptr) {
 87		mpi_size_t i;
 88		for (i = 0; i < s1_size - 1; i++)
 89			res_ptr[i] = s1_ptr[i];
 90	}
 91	return 0;
 92}
 93
 94G10_MPI_INLINE_DECL mpi_limb_t
 95mpihelp_sub(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
 96	    mpi_ptr_t s2_ptr, mpi_size_t s2_size)
 97{
 98	mpi_limb_t cy = 0;
 99
100	if (s2_size)
101		cy = mpihelp_sub_n(res_ptr, s1_ptr, s2_ptr, s2_size);
102
103	if (s1_size - s2_size)
104		cy = mpihelp_sub_1(res_ptr + s2_size, s1_ptr + s2_size,
105				   s1_size - s2_size, cy);
106	return cy;
107}
108
109#endif /*G10_MPI_INLINE_H */