#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <stdarg.h>
#include "jpc_math.h"
/* Calculate the integer quantity floor(log2(x)), where x is a positive
integer. */
int
jpc_floorlog2(int const arg) {
int y;
int x;
assert(arg > 0);
y = 0;
x = arg;
while (x > 1) {
x >>= 1;
++y;
}
return y;
}
/*
jpc_floorlog2() and jpc_firstone() do the same thing.
The only difference is how input 0 is handled.
n : 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
ceil(log2(n)) : x 0 1 2 2 3 3 3 3 4 4 4 4 4 4 4 4 5 5 5
floor(log2(n)) : x 0 1 1 2 2 2 2 3 3 3 3 3 3 3 3 4 4 4 4
31-__builtin_clz(n): x 0 1 1 2 2 2 2 3 3 3 3 3 3 3 3 4 4 4 4
jpc_floorlog2(n) : x 0 1 1 2 2 2 2 3 3 3 3 3 3 3 3 4 4 4 4
jpc_firstone(n) :-1 0 1 1 2 2 2 2 3 3 3 3 3 3 3 3 4 4 4 4
*/
int
jpc_firstone(int const arg) {
/*----------------------------------------------------------------------------
Calculate the bit position of the first leading one in a nonnegative
integer.
-----------------------------------------------------------------------------*/
int n;
int x;
assert(arg >= 0);
n = -1;
x = arg;
while (x > 0) {
x >>= 1;
++n;
}
return n;
}
/*
* Copyright (c) 1999-2000 Image Power, Inc. and the University of
* British Columbia.
* Copyright (c) 2001-2002 Michael David Adams.
* All rights reserved.
*/
/* __START_OF_JASPER_LICENSE__
*
* JasPer Software License
*
* IMAGE POWER JPEG-2000 PUBLIC LICENSE
* ************************************
*
* GRANT:
*
* Permission is hereby granted, free of charge, to any person (the "User")
* obtaining a copy of this software and associated documentation, to deal
* in the JasPer Software without restriction, including without limitation
* the right to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the JasPer Software (in source and binary forms),
* and to permit persons to whom the JasPer Software is furnished to do so,
* provided further that the License Conditions below are met.
*
* License Conditions
* ******************
*
* A. Redistributions of source code must retain the above copyright notice,
* and this list of conditions, and the following disclaimer.
*
* B. Redistributions in binary form must reproduce the above copyright
* notice, and this list of conditions, and the following disclaimer in
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* (including, but not limited to, the University of British Columbia and
* Michael David Adams) may be used to endorse or promote products derived
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* Inc., the University of British Columbia, Michael David Adams, or any
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*
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* OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, WITHOUT LIMITATION,
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* MICHAEL DAVID ADAMS, ANY OTHER CONTRIBUTOR, OR ANY DISTRIBUTOR OF THE
* JASPER SOFTWARE, OR ANY SUPPLIER OF ANY OF SUCH PARTIES, BE LIABLE TO
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*
* __END_OF_JASPER_LICENSE__
*/