intmath.hh revision 50 
11039SN/A/*
21762SN/A * Copyright (c) 2003 The Regents of The University of Michigan
31039SN/A * All rights reserved.
41039SN/A *
51039SN/A * Redistribution and use in source and binary forms, with or without
61039SN/A * modification, are permitted provided that the following conditions are
71039SN/A * met: redistributions of source code must retain the above copyright
81039SN/A * notice, this list of conditions and the following disclaimer;
91039SN/A * redistributions in binary form must reproduce the above copyright
101039SN/A * notice, this list of conditions and the following disclaimer in the
111039SN/A * documentation and/or other materials provided with the distribution;
121039SN/A * neither the name of the copyright holders nor the names of its
131039SN/A * contributors may be used to endorse or promote products derived from
141039SN/A * this software without specific prior written permission.
151039SN/A *
161039SN/A * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
171039SN/A * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
181039SN/A * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
191039SN/A * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
201039SN/A * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
211039SN/A * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
221039SN/A * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
231039SN/A * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
241039SN/A * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
251039SN/A * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
261039SN/A * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
272665Ssaidi@eecs.umich.edu */
282760Sbinkertn@umich.edu
292760Sbinkertn@umich.edu#ifndef __INTMATH_HH__
301039SN/A#define __INTMATH_HH__
311039SN/A
321039SN/A// Returns the prime number one less than n.
331039SN/Aint PrevPrime(int n);
341039SN/A
352521SN/A// Determine if a number is prime
361039SN/Atemplate <class T>
372521SN/Ainline bool
381039SN/AIsPrime(T n)
391039SN/A{
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
110inline bool
111IsHex(char c)
112{
113    return c >= '0' && c <= '9' ||
114        c >= 'A' && c <= 'F' ||
115        c >= 'a' && c <= 'f';
116}
117
118inline bool
119IsOct(char c)
120{
121    return c >= '0' && c <= '7';
122}
123
124inline bool
125IsDec(char c)
126{
127    return c >= '0' && c <= '9';
128}
129
130inline int
131Hex2Int(char c)
132{
133  if (c >= '0' && c <= '9')
134    return (c - '0');
135
136  if(c >= 'A' && c <= 'F')
137    return (c - 'A') + 10;
138
139  if (c >= 'a' && c <= 'f')
140    return (c - 'a') + 10;
141
142  return 0;
143}
144
145#endif // __INTMATH_HH__
146