36 lines
949 B
C++
36 lines
949 B
C++
|
/*
|
||
|
|
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||
|
|
*
|
||
|
|
* NASA Jet Propulsion Laboratory
|
||
|
|
* California Institute of Technology
|
||
|
|
* (C) 2004-2005 All Rights Reserved
|
||
|
|
*
|
||
|
|
* <LicenseText>
|
||
|
|
*
|
||
|
|
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include "PowerOfTwo.h"
|
||
|
|
|
||
|
|
bool isaPowerOfTwo(int x)
|
||
|
|
{
|
||
|
|
// Test if an integer is a power of two
|
||
|
|
// x & (x-1) = 0 iff x is a power of 2
|
||
|
|
// !(x&(x-1)) = 1 iff x is a power of 2
|
||
|
|
// !(x&(x-1)) && (x>0) = 1 iff x is a power of 2 and x > 0
|
||
|
|
|
||
|
|
return !(x & (x-1)) && (x>0);
|
||
|
|
}
|
||
|
|
|
||
|
|
int whichPowerOfTwo(unsigned int x)
|
||
|
|
{
|
||
|
|
// Find log2 of an integer, assuming it is a power of 2
|
||
|
|
// If x is not a power of 2, the log will be int-truncated
|
||
|
|
// If the value passed in was negative the log will always
|
||
|
|
// equal sizeof(int)*8-1
|
||
|
|
|
||
|
|
int p = 0;
|
||
|
|
while (x >>= 1){ p++; }
|
||
|
|
return p;
|
||
|
|
}
|