nes-proj/core/lib/me.c

117 lines
3.8 KiB
C

/*
* Copyright (c) 2005, Swedish Institute of Computer Science
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. Neither the name of the Institute 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 INSTITUTE 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 INSTITUTE 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.
*
* This file is part of the Contiki operating system.
*
*/
/** \addtogroup me
* @{ */
/**
* \file
* Implementation of the table-driven Manchester encoding and decoding.
* \author
* Adam Dunkels <adam@sics.se>
*/
#include "me_tabs.h"
/*---------------------------------------------------------------------------*/
/**
* Manchester encode an 8-bit byte.
*
* This function Manchester encodes an 8-bit byte into a 16-bit
* word. The function me_decode() does the inverse operation.
*
* \param c The byte to be encoded
*
* \retval The encoded word.
*/
/*---------------------------------------------------------------------------*/
unsigned short
me_encode(unsigned char c)
{
return me_encode_tab[c];
}
/*---------------------------------------------------------------------------*/
/**
* Decode a Manchester encoded 16-bit word.
*
* This function decodes a Manchester encoded 16-bit word into a 8-bit
* byte. The function does not check for parity errors in the encoded
* byte.
*
* \param m The 16-bit Manchester encoded word
* \return The decoded 8-bit byte
*/
/*---------------------------------------------------------------------------*/
unsigned char
me_decode16(unsigned short m)
{
unsigned char m1, m2, c;
m1 = m >> 8;
m2 = m & 0xff;
c = (me_decode_tab[m1] << 4) |
me_decode_tab[m2];
return c;
}
/*---------------------------------------------------------------------------*/
/**
* Decode a Manchester encoded 8-bit byte.
*
* This function decodes a Manchester encoded 8-bit byte into 4
* decoded bits.. The function does not check for parity errors in the
* encoded byte.
*
* \param m The 8-bit Manchester encoded byte
* \return The decoded 4 bits
*/
/*---------------------------------------------------------------------------*/
unsigned char
me_decode8(unsigned char m)
{
return me_decode_tab[m];
}
/*---------------------------------------------------------------------------*/
/**
* Check if an encoded byte is valid.
*/
/*---------------------------------------------------------------------------*/
unsigned char
me_valid(unsigned char m)
{
return me_valid_tab[m];
}
/*---------------------------------------------------------------------------*/
/** @} */