/*
 * Copyright (c) 2003 The Regents of The University of Michigan
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef __INTMATH_H__
#define __INTMATH_H__

// Returns the prime number one less than n.
int PrevPrime(int n);

// Determine if a number is prime
inline bool
IsPrime(int n)
{
  int i;

  if (n == 2 || n == 3)
    return true;

  // Don't try every odd number to prove if it is a prime.
  // Toggle between every 2nd and 4th number.
  // (This is because every 6th odd number is divisible by 3.)
  for (i = 5; i*i <= n; i += 6) {
    if (((n % i) == 0 ) || ((n % (i + 2)) == 0) ) {
      return false;
    }
  }

  return true;
}

inline unsigned
LeastSigBit(unsigned n)
{ return n & ~(n - 1); }

inline bool
IsPowerOf2(unsigned n)
{ return n != 0 && LeastSigBit(n) == n; }

inline int
FloorLog2(unsigned x)
{
  if (x == 0)
    return -1;

  int y = 0;

  if (x & 0xffff0000) { y += 16; x >>= 16; }
  if (x & 0x0000ff00) { y +=  8; x >>=  8; }
  if (x & 0x000000f0) { y +=  4; x >>=  4; }
  if (x & 0x0000000c) { y +=  2; x >>=  2; }
  if (x & 0x00000002) { y +=  1; }

  return y;
}

inline int
CeilLog2(unsigned n)
{ return FloorLog2(n-1)+1; }

inline unsigned
FloorPow2(unsigned n)
{ return 1 << FloorLog2(n); }

inline unsigned
CeilPow2(unsigned n)
{ return 1 << CeilLog2(n); }

inline bool
IsHex(char c)
{ return (c >= '0' && c <= '9' ||
          c >= 'A' && c <= 'F' ||
          c >= 'a' && c <= 'f');
}

inline bool
IsOct(char c)
{ return (c >= '0' && c <= '7'); }

inline bool
IsDec(char c)
{ return (c >= '0' && c <= '9'); }

inline int
Hex2Int(char c)
{
  if (c >= '0' && c <= '9')
    return (c - '0');

  if(c >= 'A' && c <= 'F')
    return (c - 'A') + 10;

  if (c >= 'a' && c <= 'f')
    return (c - 'a') + 10;

  return 0;
}

#endif // __INTMATH_H__