Contiki 2.6

uip-ipchksum.c

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00001 /*
00002  * Copyright (c) 2007, Swedish Institute of Computer Science.
00003  * All rights reserved.
00004  *
00005  * Redistribution and use in source and binary forms, with or without
00006  * modification, are permitted provided that the following conditions
00007  * are met:
00008  * 1. Redistributions of source code must retain the above copyright
00009  *    notice, this list of conditions and the following disclaimer.
00010  * 2. Redistributions in binary form must reproduce the above copyright
00011  *    notice, this list of conditions and the following disclaimer in the
00012  *    documentation and/or other materials provided with the distribution.
00013  * 3. Neither the name of the Institute nor the names of its contributors
00014  *    may be used to endorse or promote products derived from this software
00015  *    without specific prior written permission.
00016  *
00017  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
00018  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
00019  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
00020  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
00021  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
00022  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
00023  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
00024  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00025  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
00026  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00027  * SUCH DAMAGE.
00028  *
00029  * This file is part of the Contiki operating system.
00030  *
00031  * $Id: uip-ipchksum.c,v 1.4 2007/04/04 11:53:07 bg- Exp $
00032  */
00033 
00034 /**
00035  * \file
00036  *         uIP checksum calculation for MSP430
00037  */
00038 
00039 #include "net/uip.h"
00040 
00041 #define asmv(arg) __asm__ __volatile__(arg)
00042 /*---------------------------------------------------------------------------*/
00043 #ifdef UIP_ARCH_IPCHKSUM
00044 #ifdef __IAR_SYSTEMS_ICC__
00045 uint16_t
00046 uip_ipchksum(void)
00047 {
00048   return 0;
00049 }
00050 #else
00051 uint16_t
00052 uip_ipchksum(void)
00053 {
00054   /* Assumes proper alignement of uip_buf. */
00055   uint16_t *p = (uint16_t *)&uip_buf[UIP_LLH_LEN];
00056   register uint16_t sum;
00057 
00058   sum = p[0];
00059   asmv("add  %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[1]));
00060   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[2]));
00061   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[3]));
00062   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[4]));
00063   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[5]));
00064   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[6]));
00065   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[7]));
00066   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[8]));
00067   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[9]));
00068 
00069   /* Finally, add the remaining carry bit. */
00070   asmv("addc #0, %[sum]": [sum] "+r" (sum));
00071 
00072   /* Return sum in network byte order. */
00073   return (sum == 0) ? 0xffff : sum;
00074 }
00075 #endif
00076 #endif
00077 /*---------------------------------------------------------------------------*/