Book a Demo!
CoCalc Logo Icon
StoreFeaturesDocsShareSupportNewsAboutPoliciesSign UpSign In
torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/lib/crypto/mpi/mpi-add.c
29278 views
1
/* mpi-add.c  -  MPI functions

2
 * Copyright (C) 1994, 1996, 1998, 2001, 2002,

3
 *               2003 Free Software Foundation, Inc.

4
 *

5
 * This file is part of Libgcrypt.

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
 */

13


14
#include <linux/export.h>

15


16
#include "mpi-internal.h"

17


18
int mpi_add(MPI w, MPI u, MPI v)

19
{

20
	mpi_ptr_t wp, up, vp;

21
	mpi_size_t usize, vsize, wsize;

22
	int usign, vsign, wsign;

23
	int err;

24


25
	if (u->nlimbs < v->nlimbs) { /* Swap U and V. */

26
		usize = v->nlimbs;

27
		usign = v->sign;

28
		vsize = u->nlimbs;

29
		vsign = u->sign;

30
		wsize = usize + 1;

31
		err = RESIZE_IF_NEEDED(w, wsize);

32
		if (err)

33
			return err;

34
		/* These must be after realloc (u or v may be the same as w).  */

35
		up = v->d;

36
		vp = u->d;

37
	} else {

38
		usize = u->nlimbs;

39
		usign = u->sign;

40
		vsize = v->nlimbs;

41
		vsign = v->sign;

42
		wsize = usize + 1;

43
		err = RESIZE_IF_NEEDED(w, wsize);

44
		if (err)

45
			return err;

46
		/* These must be after realloc (u or v may be the same as w).  */

47
		up = u->d;

48
		vp = v->d;

49
	}

50
	wp = w->d;

51
	wsign = 0;

52


53
	if (!vsize) {  /* simple */

54
		MPN_COPY(wp, up, usize);

55
		wsize = usize;

56
		wsign = usign;

57
	} else if (usign != vsign) { /* different sign */

58
		/* This test is right since USIZE >= VSIZE */

59
		if (usize != vsize) {

60
			mpihelp_sub(wp, up, usize, vp, vsize);

61
			wsize = usize;

62
			MPN_NORMALIZE(wp, wsize);

63
			wsign = usign;

64
		} else if (mpihelp_cmp(up, vp, usize) < 0) {

65
			mpihelp_sub_n(wp, vp, up, usize);

66
			wsize = usize;

67
			MPN_NORMALIZE(wp, wsize);

68
			if (!usign)

69
				wsign = 1;

70
		} else {

71
			mpihelp_sub_n(wp, up, vp, usize);

72
			wsize = usize;

73
			MPN_NORMALIZE(wp, wsize);

74
			if (usign)

75
				wsign = 1;

76
		}

77
	} else { /* U and V have same sign. Add them. */

78
		mpi_limb_t cy = mpihelp_add(wp, up, usize, vp, vsize);

79
		wp[usize] = cy;

80
		wsize = usize + cy;

81
		if (usign)

82
			wsign = 1;

83
	}

84


85
	w->nlimbs = wsize;

86
	w->sign = wsign;

87
	return 0;

88
}

89
EXPORT_SYMBOL_GPL(mpi_add);

90


91
int mpi_sub(MPI w, MPI u, MPI v)

92
{

93
	int err;

94
	MPI vv;

95


96
	vv = mpi_copy(v);

97
	if (!vv)

98
		return -ENOMEM;

99


100
	vv->sign = !vv->sign;

101
	err = mpi_add(w, u, vv);

102
	mpi_free(vv);

103


104
	return err;

105
}

106
EXPORT_SYMBOL_GPL(mpi_sub);

107


108
int mpi_addm(MPI w, MPI u, MPI v, MPI m)

109
{

110
	return mpi_add(w, u, v) ?:

111
	       mpi_mod(w, w, m);

112
}

113
EXPORT_SYMBOL_GPL(mpi_addm);

114


115
int mpi_subm(MPI w, MPI u, MPI v, MPI m)

116
{

117
	return mpi_sub(w, u, v) ?:

118
	       mpi_mod(w, w, m);

119
}

120
EXPORT_SYMBOL_GPL(mpi_subm);

121


122