1/* mpz_xor -- Logical xor.
2
3Copyright 1991, 1993, 1994, 1996, 1997, 2000, 2001, 2005, 2012,
42015-2018 Free Software Foundation, Inc.
5
6This file is part of the GNU MP Library.
7
8The GNU MP Library is free software; you can redistribute it and/or modify
9it under the terms of either:
10
11  * the GNU Lesser General Public License as published by the Free
12    Software Foundation; either version 3 of the License, or (at your
13    option) any later version.
14
15or
16
17  * the GNU General Public License as published by the Free Software
18    Foundation; either version 2 of the License, or (at your option) any
19    later version.
20
21or both in parallel, as here.
22
23The GNU MP Library is distributed in the hope that it will be useful, but
24WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
25or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
26for more details.
27
28You should have received copies of the GNU General Public License and the
29GNU Lesser General Public License along with the GNU MP Library.  If not,
30see https://www.gnu.org/licenses/.  */
31
32#include "gmp-impl.h"
33
34void
35mpz_xor (mpz_ptr res, mpz_srcptr op1, mpz_srcptr op2)
36{
37  mp_srcptr op1_ptr, op2_ptr;
38  mp_size_t op1_size, op2_size;
39  mp_ptr res_ptr;
40  mp_size_t res_size;
41
42  op1_size = SIZ(op1);
43  op2_size = SIZ(op2);
44
45  if (op1_size < op2_size)
46    {
47      MPZ_SRCPTR_SWAP (op1, op2);
48      MP_SIZE_T_SWAP (op1_size, op2_size);
49    }
50
51  op1_ptr = PTR(op1);
52  res_ptr = PTR(res);
53
54  if (op2_size >= 0)
55    {
56      if (res_ptr != op1_ptr)
57	{
58	  res_ptr = MPZ_REALLOC (res, op1_size);
59	  MPN_COPY (res_ptr + op2_size, op1_ptr + op2_size,
60		    op1_size - op2_size);
61	}
62      if (LIKELY (op2_size != 0))
63	mpn_xor_n (res_ptr, op1_ptr, PTR(op2), op2_size);
64      res_size = op1_size;
65
66      MPN_NORMALIZE (res_ptr, res_size);
67      SIZ(res) = res_size;
68    }
69  else
70    {
71      mp_ptr opx;
72      TMP_DECL;
73
74      op2_size = -op2_size;
75      TMP_MARK;
76      if (op1_size < 0)
77	{
78	  mp_ptr opy;
79
80	  /* Both operands are negative, the result will be positive.
81	      (-OP1) ^ (-OP2) =
82	     = ~(OP1 - 1) ^ ~(OP2 - 1) =
83	     = (OP1 - 1) ^ (OP2 - 1)  */
84
85	  op1_size = -op1_size;
86
87	  /* Possible optimization: Decrease mpn_sub precision,
88	     as we won't use the entire res of both.  */
89	  TMP_ALLOC_LIMBS_2 (opx, op1_size, opy, op2_size);
90	  mpn_sub_1 (opx, op1_ptr, op1_size, (mp_limb_t) 1);
91	  op1_ptr = opx;
92
93	  mpn_sub_1 (opy, PTR(op2), op2_size, (mp_limb_t) 1);
94	  op2_ptr = opy;
95
96	  res_ptr = MPZ_NEWALLOC (res, op2_size);
97	  /* Don't re-read OP1_PTR and OP2_PTR.  They point to temporary
98	     space--never to the space PTR(res) used to point to before
99	     reallocation.  */
100
101	  MPN_COPY (res_ptr + op1_size, op2_ptr + op1_size,
102		    op2_size - op1_size);
103	  mpn_xor_n (res_ptr, op1_ptr, op2_ptr, op1_size);
104	  TMP_FREE;
105	  res_size = op2_size;
106
107	  MPN_NORMALIZE (res_ptr, res_size);
108	  SIZ(res) = res_size;
109	}
110      else
111	{
112	  /* Operand 2 negative, so will be the result.
113	     -(OP1 ^ (-OP2)) = -(OP1 ^ ~(OP2 - 1)) =
114	     = ~(OP1 ^ ~(OP2 - 1)) + 1 =
115	     = (OP1 ^ (OP2 - 1)) + 1      */
116
117	  res_size = MAX (op1_size, op2_size);
118	  res_ptr = MPZ_REALLOC (res, res_size + 1);
119	  op1_ptr = PTR(op1);
120
121	  opx = TMP_ALLOC_LIMBS (op2_size);
122	  mpn_sub_1 (opx, PTR(op2), op2_size, (mp_limb_t) 1);
123	  op2_ptr = opx;
124
125	  if (res_size == op1_size)
126	    {
127	      MPN_COPY (res_ptr + op2_size, op1_ptr + op2_size, op1_size - op2_size);
128	      mpn_xor_n (res_ptr, op1_ptr, op2_ptr, op2_size);
129	    }
130	  else
131	    {
132	      MPN_COPY (res_ptr + op1_size, op2_ptr + op1_size, op2_size - op1_size);
133	      if (LIKELY (op1_size != 0))
134		mpn_xor_n (res_ptr, op1_ptr, op2_ptr, op1_size);
135	    }
136	  TMP_FREE;
137
138	  res_ptr[res_size] = 0;
139	  MPN_INCR_U (res_ptr, res_size + 1, (mp_limb_t) 1);
140	  res_size += res_ptr[res_size];
141
142	  MPN_NORMALIZE_NOT_ZERO (res_ptr, res_size);
143	  SIZ(res) = -res_size;
144	}
145    }
146}
147