cpu/msp430/uip-ipchksum.c

   1 /*
   2  * Copyright (c) 2007, Swedish Institute of Computer Science.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the Institute nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * This file is part of the Contiki operating system.
  30  *
  31  * $Id: uip-ipchksum.c,v 1.4 2007/04/04 11:53:07 bg- Exp $
  32  */
  33
  34 /**
  35  * \file
  36  *         uIP checksum calculation for MSP430
  37  */
  38
  39 #include "net/uip.h"
  40
  41 #define asmv(arg) __asm__ __volatile__(arg)
  42 /*---------------------------------------------------------------------------*/
  43 #ifdef UIP_ARCH_IPCHKSUM
  44 u16_t
  45 uip_ipchksum(void)
  46 {
  47   /* Assumes proper alignement of uip_buf. */
  48   u16_t *p = (u16_t *)&uip_buf[UIP_LLH_LEN];
  49   register u16_t sum;
  50
  51   sum = p[0];
  52   asmv("add  %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[1]));
  53   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[2]));
  54   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[3]));
  55   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[4]));
  56   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[5]));
  57   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[6]));
  58   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[7]));
  59   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[8]));
  60   asmv("addc %[p], %[sum]": [sum] "+r" (sum): [p] "m" (p[9]));
  61
  62   /* Finally, add the remaining carry bit. */
  63   asmv("addc #0, %[sum]": [sum] "+r" (sum));
  64
  65   /* Return sum in network byte order. */
  66   return (sum == 0) ? 0xffff : sum;
  67 }
  68 #endif
  69 /*---------------------------------------------------------------------------*/