/*
* The olsr.org Optimized Link-State Routing daemon(olsrd)
* Copyright (c) 2004, Andreas Tønnesen(andreto@olsr.org)
* 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 olsr.org, olsrd 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.
*
* Visit http://www.olsr.org for more information.
*
* If you find this software useful feel free to make a donation
* to the project. For more information see the website or contact
* the copyright holders.
*
* $Id: mantissa.c,v 1.7 2005/02/20 18:52:18 kattemat Exp $
*/
#include "mantissa.h"
#include "math.h"
#include "olsr_protocol.h"
/**
*Function that converts a double to a mantissa/exponent
*product as described in RFC3626:
*
* value = C*(1+a/16)*2^b [in seconds]
*
* where a is the integer represented by the four highest bits of the
* field and b the integer represented by the four lowest bits of the
* field.
*
*@param interval the time interval to process
*
*@return a 8-bit mantissa/exponent product
*/
olsr_u8_t
double_to_me(double interval)
{
int a, b;
b = 0;
while(interval / VTIME_SCALE_FACTOR >= pow((double)2, (double)b))
b++;
b--;
if(b < 0)
{
a = 1;
b = 0;
}
else
if (b > 15)
{
a = 15;
b = 15;
}
else
{
a = (int)(16*((double)interval/(VTIME_SCALE_FACTOR*(double)pow(2,b))-1));
while(a >= 16)
{
a -= 16;
b++;
}
}
//printf("Generated mantissa/exponent(%d/%d): %d from %f\n", a, b, (olsr_u8_t) (a*16+b), interval);
//printf("Resolves back to: %f\n", me_to_double((olsr_u8_t) (a*16+b)));
return (olsr_u8_t) (a*16+b);
}
/**
*Function that converts a mantissa/exponent 8bit value back
*to double as described in RFC3626:
*
* value = C*(1+a/16)*2^b [in seconds]
*
* where a is the integer represented by the four highest bits of the
* field and b the integer represented by the four lowest bits of the
* field.
*
*@param me the 8 bit mantissa/exponen value
*
*@return a double value
*/
double
me_to_double(olsr_u8_t me)
{
int a, b;
a = me>>4;
b = me - a*16;
return (double)(VTIME_SCALE_FACTOR*(1+(double)a/16)*(double)pow(2,b));
}