intmath.hh revision 52 
1/*
2 * Copyright (c) 2003 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#ifndef __INTMATH_HH__
30#define __INTMATH_HH__
31
32// Returns the prime number one less than n.
33int PrevPrime(int n);
34
35// Determine if a number is prime
36template <class T>
37inline bool
38IsPrime(T n)
39{
40    T i;
41
42    if (n == 2 || n == 3)
43        return true;
44
45    // Don't try every odd number to prove if it is a prime.
46    // Toggle between every 2nd and 4th number.
47    // (This is because every 6th odd number is divisible by 3.)
48    for (i = 5; i*i <= n; i += 6) {
49        if (((n % i) == 0 ) || ((n % (i + 2)) == 0) ) {
50            return false;
51        }
52    }
53
54    return true;
55}
56
57template <class T>
58inline T
59LeastSigBit(T n)
60{
61    return n & ~(n - 1);
62}
63
64template <class T>
65inline bool
66IsPowerOf2(T n)
67{
68    return n != 0 && LeastSigBit(n) == n;
69}
70
71template <class T>
72inline int
73FloorLog2(T x)
74{
75    if (x == 0)
76        return -1;
77
78    int y = 0;
79
80    if (x & 0xffff0000) { y += 16; x >>= 16; }
81    if (x & 0x0000ff00) { y +=  8; x >>=  8; }
82    if (x & 0x000000f0) { y +=  4; x >>=  4; }
83    if (x & 0x0000000c) { y +=  2; x >>=  2; }
84    if (x & 0x00000002) { y +=  1; }
85
86    return y;
87}
88
89template <class T>
90inline int
91CeilLog2(T n)
92{
93    return FloorLog2(n - 1) + 1;
94}
95
96template <class T>
97inline T
98FloorPow2(T n)
99{
100    return (T)1 << FloorLog2(n);
101}
102
103template <class T>
104inline T
105CeilPow2(T n)
106{
107    return (T)1 << CeilLog2(n);
108}
109
110template <class T>
111inline T
112DivCeil(T a, T b)
113{
114    return (a + b - 1) / b;
115}
116
117template <class T>
118inline T
119RoundUp(T val, T align)
120{
121    T mask = align - 1;
122    return (val + mask) & ~mask;
123}
124
125template <class T>
126inline T
127RoundDown(T val, T align)
128{
129    T mask = align - 1;
130    return val & ~mask;
131}
132
133inline bool
134IsHex(char c)
135{
136    return c >= '0' && c <= '9' ||
137        c >= 'A' && c <= 'F' ||
138        c >= 'a' && c <= 'f';
139}
140
141inline bool
142IsOct(char c)
143{
144    return c >= '0' && c <= '7';
145}
146
147inline bool
148IsDec(char c)
149{
150    return c >= '0' && c <= '9';
151}
152
153inline int
154Hex2Int(char c)
155{
156  if (c >= '0' && c <= '9')
157    return (c - '0');
158
159  if(c >= 'A' && c <= 'F')
160    return (c - 'A') + 10;
161
162  if (c >= 'a' && c <= 'f')
163    return (c - 'a') + 10;
164
165  return 0;
166}
167
168#endif // __INTMATH_HH__
169