annotate model/units.c @ 0:5242703e91d3 tip

Initial checkin for AIM92 aimR8.2 (last updated May 1997).

/*
    Copyright (c) Applied Psychology Unit, Medical Research Council. 1988, 1989
    ===========================================================================

    Permission to use, copy, modify, and distribute this software without fee 
    is hereby granted for research purposes, provided that this copyright 
    notice appears in all copies and in all supporting documentation, and that 
    the software is not redistributed for any fee (except for a nominal shipping 
    charge). Anyone wanting to incorporate all or part of this software in a
    commercial product must obtain a license from the Medical Research Council.

    The MRC makes no representations about the suitability of this 
    software for any purpose.  It is provided "as is" without express or implied 
    warranty.
 
*/

/*
    units.c
    =======


    Unit conversion routines for APU model.



    Copyright (c), 1989  The Medical Research Council, Applied Psychology Unit.


    Author  : John Holdsworth
    Written : 22th March, 1989.

    Edited  : Mike Allerhand, 1990.

*/

#ifndef  lint
static char *sccs_id = "@(#)units.c	1.3 John Holdsworth, Mike Allerhand (MRC-APU) 6/6/91" ;
#endif



/*********************** Unit conversion routines ***************************
*  Values are stored as strings.
*  Units are specified by the final char:
*    p          sample points.
*    s          seconds.
*    b or B     decibels.
*    Hz         Hertz.
*  Unit multipliers are specified by the optional penultimate char:
*    k  kilo  (scale by one thousand).
*    d  deci  (scale by one tenth).
*    c  centi (scale by one hundreth).
*    m  milli (scale by one thousandth).
*    u        (scale by one millionth).
*
*  Examples:    "10p"     time period of 10 sample points
*               "10ms"    time period of 10 milliseconds
*               "10kHz"   frequency of 10 kiloHertz
*
*  Conversion routines:
* units( ch )          Multiplier for unit, (k,d,c,m,u).
* Freq( str )          String to value (eg: 10, 10Hz, 10kHz).
* Samples( str )       String to value (num samples) (eg: 10p, 10s, 10ms).
* Scalar( str )        String to value (scalar number), also converts dB's.
*
*  Examples:   Freq("10000")    returns 10000
*              Freq("10kHz")    returns 10000
*              Samples("3p")    returns 3
*              Samples("3ms")   return 30  (when the sample rate is 10kHz).
*              Samples("3")     like "3ms" (milliseconds is default unit).
*              Scalar("10.")    returns 10
*              Scalar( "20dB" ) returns 10
*
* See also stitch.h for conversion routines:
*   ToPoints(type,bytes)  Count in bytes to number of points of given type.
*   ToBytes(type,points ) Number of points of given type to count in bytes.
*
* Cycles( str, cfreq )  This is like Samples( str ), except that it also
*                       allows `c' (cycles) units. A given number of cycles
*                       of a particular channel are converted to samples.
*                       This requires the centre frequency of the channel,
*                       cfreq = frequencies[chan].
****************************************************************************/

#include <math.h>

#if defined(THINK_C) || defined(NeXT)
#include <stdlib.h>
#endif

#include "units.h"
#include "formulae.h"

extern char *samplestr ;

static double units( ch )
char ch ;
{
    switch( ch ) {
	case 'k' :
	    return ( 1000.    ) ;
	case 'd' :
	    return ( 0.1      ) ;
	case 'c' :
	    return ( 0.01     ) ;
	case 'm' :
	    return ( 0.001    ) ;
	case 'u' :
	    return ( 0.000001 ) ;

	default :
	    return ( 1.       ) ;
    }
}

double Freq( str )
char *str ;
{
    char *eptr = str + strlen( str ) ;
    double f ;

    --eptr ;

    if( *eptr == 'e' )
	return ( FofErbScale( atof( str ) ) * units( *--eptr ) ) ;

    if( *eptr == 'z' )
	--eptr ;

    if( *eptr == 'H' || *eptr == 'h' )
	return ( atof( str ) * units( *--eptr ) ) ;

    return ( atof( str ) * units( *eptr ) ) ;
}

double Samples( str, samplerate )
char *str ;
double samplerate ;
{
    char *eptr = str + strlen( str ) ;

    switch( *--eptr ) {
	case 's' : /* seconds */
	    return ( atof( str ) * samplerate * units( *--eptr ) ) ;
	case 'p' : /* points  */
	    return ( atof( str )              * units( *--eptr ) ) ;

	default: /* default to milliseconds for specification of sample parameters */
	    return ( atof( str ) * samplerate * units( 'm' ) ) ;
    }
}

double Scalar( str )
char *str ;
{
    char *eptr = str + strlen( str ) ;

    if( *--eptr == 'B' || *eptr == 'b' )
	return ( pow( 10., atof( str ) * units( *--eptr ) / 2. ) ) ;
    else
	return ( atof( str ) * units( *eptr ) ) ;
}

double Cycles( str, cfreq, samplerate )
char   *str ;
double  cfreq, samplerate ;  /* centre frequency of a particular channel */
{
    char *eptr = str + strlen( str ) ;

    /* Look at last char in the string */
    switch( *--eptr ) {
	case 's' : /* seconds */
	    return ( atof( str ) * samplerate * units( *--eptr ) ) ;
	case 'p' : /* points  */
	    return ( atof( str )              * units( *--eptr ) ) ;
	case 'c' : /* cycles  */
	    return ( atof( str ) * samplerate / cfreq ) ;

	default:   /* default to milliseconds, 'ms' */
	    return ( atof( str ) * samplerate * units( 'm' ) ) ;

    }
}