nsprpub/pr/src/misc/prlong.c@6474c204b198
nsprpub/pr/src/misc/prlong.c
Wed, 31 Dec 2014 06:09:35 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 06:09:35 +0100
- changeset 0
- 6474c204b198
- permissions
- -rw-r--r--
Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.
1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6 #include "prlong.h"
8 static PRInt64 ll_zero = LL_INIT( 0x00000000,0x00000000 );
9 static PRInt64 ll_maxint = LL_INIT( 0x7fffffff, 0xffffffff );
10 static PRInt64 ll_minint = LL_INIT( 0x80000000, 0x00000000 );
11 static PRUint64 ll_maxuint = LL_INIT( 0xffffffff, 0xffffffff );
13 PR_IMPLEMENT(PRInt64) LL_Zero(void) { return ll_zero; }
14 PR_IMPLEMENT(PRInt64) LL_MaxInt(void) { return ll_maxint; }
15 PR_IMPLEMENT(PRInt64) LL_MinInt(void) { return ll_minint; }
16 PR_IMPLEMENT(PRUint64) LL_MaxUint(void) { return ll_maxuint; }
18 #ifndef HAVE_LONG_LONG
19 /*
20 ** Divide 64-bit a by 32-bit b, which must be normalized so its high bit is 1.
21 */
22 static void norm_udivmod32(PRUint32 *qp, PRUint32 *rp, PRUint64 a, PRUint32 b)
23 {
24 PRUint32 d1, d0, q1, q0;
25 PRUint32 r1, r0, m;
27 d1 = _hi16(b);
28 d0 = _lo16(b);
29 r1 = a.hi % d1;
30 q1 = a.hi / d1;
31 m = q1 * d0;
32 r1 = (r1 << 16) | _hi16(a.lo);
33 if (r1 < m) {
34 q1--, r1 += b;
35 if (r1 >= b /* i.e., we didn't get a carry when adding to r1 */
36 && r1 < m) {
37 q1--, r1 += b;
38 }
39 }
40 r1 -= m;
41 r0 = r1 % d1;
42 q0 = r1 / d1;
43 m = q0 * d0;
44 r0 = (r0 << 16) | _lo16(a.lo);
45 if (r0 < m) {
46 q0--, r0 += b;
47 if (r0 >= b
48 && r0 < m) {
49 q0--, r0 += b;
50 }
51 }
52 *qp = (q1 << 16) | q0;
53 *rp = r0 - m;
54 }
56 static PRUint32 CountLeadingZeros(PRUint32 a)
57 {
58 PRUint32 t;
59 PRUint32 r = 32;
61 if ((t = a >> 16) != 0)
62 r -= 16, a = t;
63 if ((t = a >> 8) != 0)
64 r -= 8, a = t;
65 if ((t = a >> 4) != 0)
66 r -= 4, a = t;
67 if ((t = a >> 2) != 0)
68 r -= 2, a = t;
69 if ((t = a >> 1) != 0)
70 r -= 1, a = t;
71 if (a & 1)
72 r--;
73 return r;
74 }
76 PR_IMPLEMENT(void) ll_udivmod(PRUint64 *qp, PRUint64 *rp, PRUint64 a, PRUint64 b)
77 {
78 PRUint32 n0, n1, n2;
79 PRUint32 q0, q1;
80 PRUint32 rsh, lsh;
82 n0 = a.lo;
83 n1 = a.hi;
85 if (b.hi == 0) {
86 if (b.lo > n1) {
87 /* (0 q0) = (n1 n0) / (0 D0) */
89 lsh = CountLeadingZeros(b.lo);
91 if (lsh) {
92 /*
93 * Normalize, i.e. make the most significant bit of the
94 * denominator be set.
95 */
96 b.lo = b.lo << lsh;
97 n1 = (n1 << lsh) | (n0 >> (32 - lsh));
98 n0 = n0 << lsh;
99 }
101 a.lo = n0, a.hi = n1;
102 norm_udivmod32(&q0, &n0, a, b.lo);
103 q1 = 0;
105 /* remainder is in n0 >> lsh */
106 } else {
107 /* (q1 q0) = (n1 n0) / (0 d0) */
109 if (b.lo == 0) /* user wants to divide by zero! */
110 b.lo = 1 / b.lo; /* so go ahead and crash */
112 lsh = CountLeadingZeros(b.lo);
114 if (lsh == 0) {
115 /*
116 * From (n1 >= b.lo)
117 * && (the most significant bit of b.lo is set),
118 * conclude that
119 * (the most significant bit of n1 is set)
120 * && (the leading quotient digit q1 = 1).
121 *
122 * This special case is necessary, not an optimization
123 * (Shifts counts of 32 are undefined).
124 */
125 n1 -= b.lo;
126 q1 = 1;
127 } else {
128 /*
129 * Normalize.
130 */
131 rsh = 32 - lsh;
133 b.lo = b.lo << lsh;
134 n2 = n1 >> rsh;
135 n1 = (n1 << lsh) | (n0 >> rsh);
136 n0 = n0 << lsh;
138 a.lo = n1, a.hi = n2;
139 norm_udivmod32(&q1, &n1, a, b.lo);
140 }
142 /* n1 != b.lo... */
144 a.lo = n0, a.hi = n1;
145 norm_udivmod32(&q0, &n0, a, b.lo);
147 /* remainder in n0 >> lsh */
148 }
150 if (rp) {
151 rp->lo = n0 >> lsh;
152 rp->hi = 0;
153 }
154 } else {
155 if (b.hi > n1) {
156 /* (0 0) = (n1 n0) / (D1 d0) */
158 q0 = 0;
159 q1 = 0;
161 /* remainder in (n1 n0) */
162 if (rp) {
163 rp->lo = n0;
164 rp->hi = n1;
165 }
166 } else {
167 /* (0 q0) = (n1 n0) / (d1 d0) */
169 lsh = CountLeadingZeros(b.hi);
170 if (lsh == 0) {
171 /*
172 * From (n1 >= b.hi)
173 * && (the most significant bit of b.hi is set),
174 * conclude that
175 * (the most significant bit of n1 is set)
176 * && (the quotient digit q0 = 0 or 1).
177 *
178 * This special case is necessary, not an optimization.
179 */
181 /*
182 * The condition on the next line takes advantage of that
183 * n1 >= b.hi (true due to control flow).
184 */
185 if (n1 > b.hi || n0 >= b.lo) {
186 q0 = 1;
187 a.lo = n0, a.hi = n1;
188 LL_SUB(a, a, b);
189 } else {
190 q0 = 0;
191 }
192 q1 = 0;
194 if (rp) {
195 rp->lo = n0;
196 rp->hi = n1;
197 }
198 } else {
199 PRInt64 m;
201 /*
202 * Normalize.
203 */
204 rsh = 32 - lsh;
206 b.hi = (b.hi << lsh) | (b.lo >> rsh);
207 b.lo = b.lo << lsh;
208 n2 = n1 >> rsh;
209 n1 = (n1 << lsh) | (n0 >> rsh);
210 n0 = n0 << lsh;
212 a.lo = n1, a.hi = n2;
213 norm_udivmod32(&q0, &n1, a, b.hi);
214 LL_MUL32(m, q0, b.lo);
216 if ((m.hi > n1) || ((m.hi == n1) && (m.lo > n0))) {
217 q0--;
218 LL_SUB(m, m, b);
219 }
221 q1 = 0;
223 /* Remainder is ((n1 n0) - (m1 m0)) >> lsh */
224 if (rp) {
225 a.lo = n0, a.hi = n1;
226 LL_SUB(a, a, m);
227 rp->lo = (a.hi << rsh) | (a.lo >> lsh);
228 rp->hi = a.hi >> lsh;
229 }
230 }
231 }
232 }
234 if (qp) {
235 qp->lo = q0;
236 qp->hi = q1;
237 }
238 }
239 #endif /* !HAVE_LONG_LONG */
