1 /* mpn_popcount, mpn_hamdist -- mpn bit population count/hamming distance.
2
3 Copyright 1994, 1996, 2000-2002, 2005, 2011, 2012 Free Software Foundation,
4 Inc.
5
6 This file is part of the GNU MP Library.
7
8 The GNU MP Library is free software; you can redistribute it and/or modify
9 it 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
15 or
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
21 or both in parallel, as here.
22
23 The GNU MP Library is distributed in the hope that it will be useful, but
24 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
25 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
26 for more details.
27
28 You should have received copies of the GNU General Public License and the
29 GNU Lesser General Public License along with the GNU MP Library. If not,
30 see https://www.gnu.org/licenses/. */
31
32 #include "gmp.h"
33 #include "gmp-impl.h"
34
35 #if OPERATION_popcount
36 #define FNAME mpn_popcount
37 #define POPHAM(u,v) u
38 #endif
39
40 #if OPERATION_hamdist
41 #define FNAME mpn_hamdist
42 #define POPHAM(u,v) u ^ v
43 #endif
44
45 mp_bitcnt_t
FNAME(mp_srcptr up,mp_srcptr vp,mp_size_t n)46 FNAME (mp_srcptr up,
47 #if OPERATION_hamdist
48 mp_srcptr vp,
49 #endif
50 mp_size_t n) __GMP_NOTHROW
51 {
52 mp_bitcnt_t result = 0;
53 mp_limb_t p0, p1, p2, p3, x, p01, p23;
54 mp_size_t i;
55
56 ASSERT (n >= 1); /* Actually, this code handles any n, but some
57 assembly implementations do not. */
58
59 for (i = n >> 2; i != 0; i--)
60 {
61 p0 = POPHAM (up[0], vp[0]);
62 p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
63 p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5); /* 4 0-4 */
64
65 p1 = POPHAM (up[1], vp[1]);
66 p1 -= (p1 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
67 p1 = ((p1 >> 2) & MP_LIMB_T_MAX/5) + (p1 & MP_LIMB_T_MAX/5); /* 4 0-4 */
68
69 p01 = p0 + p1; /* 8 0-8 */
70 p01 = ((p01 >> 4) & MP_LIMB_T_MAX/17) + (p01 & MP_LIMB_T_MAX/17); /* 8 0-16 */
71
72 p2 = POPHAM (up[2], vp[2]);
73 p2 -= (p2 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
74 p2 = ((p2 >> 2) & MP_LIMB_T_MAX/5) + (p2 & MP_LIMB_T_MAX/5); /* 4 0-4 */
75
76 p3 = POPHAM (up[3], vp[3]);
77 p3 -= (p3 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
78 p3 = ((p3 >> 2) & MP_LIMB_T_MAX/5) + (p3 & MP_LIMB_T_MAX/5); /* 4 0-4 */
79
80 p23 = p2 + p3; /* 8 0-8 */
81 p23 = ((p23 >> 4) & MP_LIMB_T_MAX/17) + (p23 & MP_LIMB_T_MAX/17); /* 8 0-16 */
82
83 x = p01 + p23; /* 8 0-32 */
84 x = (x >> 8) + x; /* 8 0-64 */
85 x = (x >> 16) + x; /* 8 0-128 */
86 #if GMP_LIMB_BITS > 32
87 x = ((x >> 32) & 0xff) + (x & 0xff); /* 8 0-256 */
88 result += x;
89 #else
90 result += x & 0xff;
91 #endif
92 up += 4;
93 #if OPERATION_hamdist
94 vp += 4;
95 #endif
96 }
97
98 n &= 3;
99 if (n != 0)
100 {
101 x = 0;
102 do
103 {
104 p0 = POPHAM (up[0], vp[0]);
105 p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
106 p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5); /* 4 0-4 */
107 p0 = ((p0 >> 4) + p0) & MP_LIMB_T_MAX/17; /* 8 0-8 */
108
109 x += p0;
110 up += 1;
111 #if OPERATION_hamdist
112 vp += 1;
113 #endif
114 }
115 while (--n);
116
117 x = (x >> 8) + x;
118 x = (x >> 16) + x;
119 #if GMP_LIMB_BITS > 32
120 x = (x >> 32) + x;
121 #endif
122 result += x & 0xff;
123 }
124
125 return result;
126 }
127