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 23 G10_MPI_INLINE_DECL mpi_limb_t 24 mpihelp_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 42 leave: 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 51 G10_MPI_INLINE_DECL mpi_limb_t 52 mpihelp_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 66 G10_MPI_INLINE_DECL mpi_limb_t 67 mpihelp_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 85 leave: 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 94 G10_MPI_INLINE_DECL mpi_limb_t 95 mpihelp_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 */ 110