text: /*
   * Copyright (c) 2001-2004 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. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission. 
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 lwIP TCP/IP stack.
   * 
   * Author: Adam Dunkels <adam@sics.se>
   *
   */
  #ifndef __LWIP_DEF_H__
  #define __LWIP_DEF_H__
  
  /* arch.h might define NULL already */
  #include "lwip/arch.h"
  #include "lwip/opt.h"
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  #define LWIP_MAX(x , y)  (((x) > (y)) ? (x) : (y))
  #define LWIP_MIN(x , y)  (((x) < (y)) ? (x) : (y))
  
  #ifndef NULL
  #define NULL ((void *)0)
  #endif
  
  /** Get the absolute difference between 2 u32_t values (correcting overflows)
   * 'a' is expected to be 'higher' (without overflow) than 'b'. */
  #define LWIP_U32_DIFF(a, b) (((a) >= (b)) ? ((a) - (b)) : (((a) + ((b) ^ 0xFFFFFFFF) + 1))) 
  
  /* Endianess-optimized shifting of two u8_t to create one u16_t */
  #if BYTE_ORDER == LITTLE_ENDIAN
  #define LWIP_MAKE_U16(a, b) ((a << 8) | b)
  #else
  #define LWIP_MAKE_U16(a, b) ((b << 8) | a)
  #endif 
  
  #ifndef LWIP_PLATFORM_BYTESWAP
  #define LWIP_PLATFORM_BYTESWAP 0
  #endif
  
  #ifndef LWIP_PREFIX_BYTEORDER_FUNCS
  /* workaround for naming collisions on some platforms */
  
  #ifdef htons
  #undef htons
  #endif /* htons */
  #ifdef htonl
  #undef htonl
  #endif /* htonl */
  #ifdef ntohs
  #undef ntohs
  #endif /* ntohs */
  #ifdef ntohl
  #undef ntohl
  #endif /* ntohl */
  
  #define htons(x) lwip_htons(x)
  #define ntohs(x) lwip_ntohs(x)
  #define htonl(x) lwip_htonl(x)
  #define ntohl(x) lwip_ntohl(x)
  #endif /* LWIP_PREFIX_BYTEORDER_FUNCS */
  
  #if BYTE_ORDER == BIG_ENDIAN
  #define lwip_htons(x) (x)
  #define lwip_ntohs(x) (x)
  #define lwip_htonl(x) (x)
  #define lwip_ntohl(x) (x)
  #define PP_HTONS(x) (x)
  #define PP_NTOHS(x) (x)
  #define PP_HTONL(x) (x)
  #define PP_NTOHL(x) (x)
  #else /* BYTE_ORDER != BIG_ENDIAN */
  #if LWIP_PLATFORM_BYTESWAP
  #define lwip_htons(x) LWIP_PLATFORM_HTONS(x)
  #define lwip_ntohs(x) LWIP_PLATFORM_HTONS(x)
  #define lwip_htonl(x) LWIP_PLATFORM_HTONL(x)
  #define lwip_ntohl(x) LWIP_PLATFORM_HTONL(x)
  #else /* LWIP_PLATFORM_BYTESWAP */
  u16_t lwip_htons(u16_t x);
  u16_t lwip_ntohs(u16_t x);
  u32_t lwip_htonl(u32_t x);
  u32_t lwip_ntohl(u32_t x);
  #endif /* LWIP_PLATFORM_BYTESWAP */
  
  /* These macros should be calculated by the preprocessor and are used
     with compile-time constants only (so that there is no little-endian
     overhead at runtime). */
  #define PP_HTONS(x) ((((x) & 0xff) << 8) | (((x) & 0xff00) >> 8))
  #define PP_NTOHS(x) PP_HTONS(x)
  #define PP_HTONL(x) ((((x) & 0xff) << 24) | \
                       (((x) & 0xff00) << 8) | \
                       (((x) & 0xff0000UL) >> 8) | \
                       (((x) & 0xff000000UL) >> 24))
  #define PP_NTOHL(x) PP_HTONL(x)
  
  #endif /* BYTE_ORDER == BIG_ENDIAN */
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* __LWIP_DEF_H__ */
  
  