util.c

大师写的二代小波经典之作

/*
 *  -*- Mode: ANSI C -*-
 *  $Id: util.c,v 1.4 1996/08/16 17:25:54 fernande Exp $
 *  $Source: /sgi.acct/sweldens/cvs/liftpack/Util/util.c,v $
 *  Author: Gabriel Fernandez
 *
 *  This file contains the definition of useful mathematical and
 *  general comparison functions.
 */
/* do not edit anything above this line */

/* System header files */
#include <assert.h>
#include <math.h>
#include <stdio.h>
/* FLWT header files */
#include <constant.h>
#include <flwtdef.h>
#include <memchk.h>
#include <util.h>

/* code */

Flt
min3( Flt a, Flt b, Flt c )
{
    Flt m = MIN( a, b );
    return MIN( m, c );
}

Flt
max3( Flt a, Flt b, Flt c )
{
    Flt m = MAX( a, b );
    return MAX( m, c );
}

Flt
min4( Flt a, Flt b, Flt c, Flt d )
{
    Flt m = MIN( a, b );
    m = MIN( m, c );
    return MIN( m, d );
}

Flt
max4( Flt a, Flt b, Flt c, Flt d )
{
    Flt m = MAX( a, b );
    m = MAX( m, c );
    return MAX( m, d );
}

int
zeroEps( const Flt x, const Flt eps )
{
    return ( -eps < x ) && ( x < eps );
}

int
zero( const Flt x )
{
    const Flt __negeps_f = (Flt)-100 * m_eps_f;
    const Flt __poseps_f = (Flt) 100 * m_eps_f;

    return ( __negeps_f < x ) && ( x < __poseps_f );
}

Flt
logBaseN( const Flt x, const Flt n )
{
    return ( (Flt)((Flt)log((Flt)x)/(Flt)log((Flt)n)) );
}

/* should be called only for positive powers of two */
int 
logbasetwo( int x )
{
    int ret = 0;
  
    /* must be positive */
    assert( x > 0 );
    while( !(x & 1) ){
        x >>= 1;
        ret++;
    }
  
    /* must have been a power of two */
    assert( x == 1 );
    return ret;
}

/* true if x >=0 and x is a power of two */
int 
ispoweroftwo( int x )
{
    if( !x ) return 1;
    assert( x > 0 );
    while( !(x & 1) )
        x >>= 1;
    return x == 1;
}

/* given x, returns 2^ceil(log_2 x) */
int 
nextpoweroftwo( int x )
{
    int ret = 1;

    if( !x ) return 0;
    assert( x > 0 );
  
    while( ret < x )
        ret <<= 1;
    return ret;
}