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      1 /**
      2  * @file
      3  * Common functions used throughout the stack.
      4  *
      5  */
      6 
      7 /*
      8  * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
      9  * All rights reserved.
     10  *
     11  * Redistribution and use in source and binary forms, with or without modification,
     12  * are permitted provided that the following conditions are met:
     13  *
     14  * 1. Redistributions of source code must retain the above copyright notice,
     15  *    this list of conditions and the following disclaimer.
     16  * 2. Redistributions in binary form must reproduce the above copyright notice,
     17  *    this list of conditions and the following disclaimer in the documentation
     18  *    and/or other materials provided with the distribution.
     19  * 3. The name of the author may not be used to endorse or promote products
     20  *    derived from this software without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
     23  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     24  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
     25  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     26  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
     27  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     28  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     29  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
     30  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
     31  * OF SUCH DAMAGE.
     32  *
     33  * This file is part of the lwIP TCP/IP stack.
     34  *
     35  * Author: Simon Goldschmidt
     36  *
     37  */
     38 
     39 #include "lwip/opt.h"
     40 #include "lwip/def.h"
     41 
     42 /**
     43  * These are reference implementations of the byte swapping functions.
     44  * Again with the aim of being simple, correct and fully portable.
     45  * Byte swapping is the second thing you would want to optimize. You will
     46  * need to port it to your architecture and in your cc.h:
     47  *
     48  * #define LWIP_PLATFORM_BYTESWAP 1
     49  * #define LWIP_PLATFORM_HTONS(x) <your_htons>
     50  * #define LWIP_PLATFORM_HTONL(x) <your_htonl>
     51  *
     52  * Note ntohs() and ntohl() are merely references to the htonx counterparts.
     53  */
     54 
     55 #if (LWIP_PLATFORM_BYTESWAP == 0) && (BYTE_ORDER == LITTLE_ENDIAN)
     56 
     57 /**
     58  * Convert an u16_t from host- to network byte order.
     59  *
     60  * @param n u16_t in host byte order
     61  * @return n in network byte order
     62  */
     63 u16_t
     64 lwip_htons(u16_t n)
     65 {
     66   return ((n & 0xff) << 8) | ((n & 0xff00) >> 8);
     67 }
     68 
     69 /**
     70  * Convert an u16_t from network- to host byte order.
     71  *
     72  * @param n u16_t in network byte order
     73  * @return n in host byte order
     74  */
     75 u16_t
     76 lwip_ntohs(u16_t n)
     77 {
     78   return lwip_htons(n);
     79 }
     80 
     81 /**
     82  * Convert an u32_t from host- to network byte order.
     83  *
     84  * @param n u32_t in host byte order
     85  * @return n in network byte order
     86  */
     87 u32_t
     88 lwip_htonl(u32_t n)
     89 {
     90   return ((n & 0xff) << 24) |
     91     ((n & 0xff00) << 8) |
     92     ((n & 0xff0000UL) >> 8) |
     93     ((n & 0xff000000UL) >> 24);
     94 }
     95 
     96 /**
     97  * Convert an u32_t from network- to host byte order.
     98  *
     99  * @param n u32_t in network byte order
    100  * @return n in host byte order
    101  */
    102 u32_t
    103 lwip_ntohl(u32_t n)
    104 {
    105   return lwip_htonl(n);
    106 }
    107 
    108 #endif /* (LWIP_PLATFORM_BYTESWAP == 0) && (BYTE_ORDER == LITTLE_ENDIAN) */
    109