dist/tcpdump/extract.h

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * Copyright (c) 1992, 1993, 1994, 1995, 1996
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that: (1) source code distributions
   9  * retain the above copyright notice and this paragraph in its entirety, (2)
  10  * distributions including binary code include the above copyright notice and
  11  * this paragraph in its entirety in the documentation or other materials
  12  * provided with the distribution, and (3) all advertising materials mentioning
  13  * features or use of this software display the following acknowledgement:
  14  * ``This product includes software developed by the University of California,
  15  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  16  * the University nor the names of its contributors may be used to endorse
  17  * or promote products derived from this software without specific prior
  18  * written permission.
  19  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  20  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  21  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  22  *
  23  * @(#) Header: /tcpdump/master/tcpdump/extract.h,v 1.24 2005/01/15 02:06:50 guy Exp (LBL)
  24  */
  25
  26 /*
  27  * Macros to extract possibly-unaligned big-endian integral values.
  28  */
  29 #ifdef LBL_ALIGN
  30 /*
  31  * The processor doesn't natively handle unaligned loads.
  32  */
  33 #ifdef HAVE___ATTRIBUTE__
  34 /*
  35  * We have __attribute__; we assume that means we have __attribute__((packed)).
  36  * Declare packed structures containing a u_int16_t and a u_int32_t,
  37  * cast the pointer to point to one of those, and fetch through it;
  38  * the GCC manual doesn't appear to explicitly say that
  39  * __attribute__((packed)) causes the compiler to generate unaligned-safe
  40  * code, but it apppears to do so.
  41  *
  42  * We do this in case the compiler can generate, for this instruction set,
  43  * better code to do an unaligned load and pass stuff to "ntohs()" or
  44  * "ntohl()" than the code to fetch the bytes one at a time and
  45  * assemble them.  (That might not be the case on a little-endian platform,
  46  * where "ntohs()" and "ntohl()" might not be done inline.)
  47  */
  48 typedef struct {
  49         u_int16_t       val;
  50 } __attribute__((packed)) unaligned_u_int16_t;
  51
  52 typedef struct {
  53         u_int32_t       val;
  54 } __attribute__((packed)) unaligned_u_int32_t;
  55
  56 #define EXTRACT_16BITS(p) \
  57         ((u_int16_t)ntohs(((const unaligned_u_int16_t *)(p))->val))
  58 #define EXTRACT_32BITS(p) \
  59         ((u_int32_t)ntohl(((const unaligned_u_int32_t *)(p))->val))
  60 #define EXTRACT_64BITS(p) \
  61         ((u_int64_t)(((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 0)->val)) << 32 | \
  62                      ((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 1)->val)) << 0))
  63
  64 #else /* HAVE___ATTRIBUTE__ */
  65 /*
  66  * We don't have __attribute__, so do unaligned loads of big-endian
  67  * quantities the hard way - fetch the bytes one at a time and
  68  * assemble them.
  69  */
  70 #define EXTRACT_16BITS(p) \
  71         ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 0) << 8 | \
  72                      (u_int16_t)*((const u_int8_t *)(p) + 1)))
  73 #define EXTRACT_32BITS(p) \
  74         ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 24 | \
  75                      (u_int32_t)*((const u_int8_t *)(p) + 1) << 16 | \
  76                      (u_int32_t)*((const u_int8_t *)(p) + 2) << 8 | \
  77                      (u_int32_t)*((const u_int8_t *)(p) + 3)))
  78 #define EXTRACT_64BITS(p) \
  79         ((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 0) << 56 | \
  80                      (u_int64_t)*((const u_int8_t *)(p) + 1) << 48 | \
  81                      (u_int64_t)*((const u_int8_t *)(p) + 2) << 40 | \
  82                      (u_int64_t)*((const u_int8_t *)(p) + 3) << 32 | \
  83                      (u_int64_t)*((const u_int8_t *)(p) + 4) << 24 | \
  84                      (u_int64_t)*((const u_int8_t *)(p) + 5) << 16 | \
  85                      (u_int64_t)*((const u_int8_t *)(p) + 6) << 8 | \
  86                      (u_int64_t)*((const u_int8_t *)(p) + 7)))
  87 #endif /* HAVE___ATTRIBUTE__ */
  88 #else /* LBL_ALIGN */
  89 /*
  90  * The processor natively handles unaligned loads, so we can just
  91  * cast the pointer and fetch through it.
  92  */
  93 #define EXTRACT_16BITS(p) \
  94         ((u_int16_t)ntohs(*(const u_int16_t *)(p)))
  95 #define EXTRACT_32BITS(p) \
  96         ((u_int32_t)ntohl(*(const u_int32_t *)(p)))
  97 #define EXTRACT_64BITS(p) \
  98         ((u_int64_t)(((u_int64_t)ntohl(*((const u_int32_t *)(p) + 0))) << 32 | \
  99                      ((u_int64_t)ntohl(*((const u_int32_t *)(p) + 1))) << 0))
 100 #endif /* LBL_ALIGN */
 101
 102 #define EXTRACT_24BITS(p) \
 103         ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 16 | \
 104                      (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
 105                      (u_int32_t)*((const u_int8_t *)(p) + 2)))
 106
 107 /*
 108  * Macros to extract possibly-unaligned little-endian integral values.
 109  * XXX - do loads on little-endian machines that support unaligned loads?
 110  */
 111 #define EXTRACT_LE_8BITS(p) (*(p))
 112 #define EXTRACT_LE_16BITS(p) \
 113         ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 1) << 8 | \
 114                      (u_int16_t)*((const u_int8_t *)(p) + 0)))
 115 #define EXTRACT_LE_32BITS(p) \
 116         ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 3) << 24 | \
 117                      (u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \
 118                      (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
 119                      (u_int32_t)*((const u_int8_t *)(p) + 0)))
 120 #define EXTRACT_LE_64BITS(p) \
 121         ((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 7) << 56 | \
 122                      (u_int64_t)*((const u_int8_t *)(p) + 6) << 48 | \
 123                      (u_int64_t)*((const u_int8_t *)(p) + 5) << 40 | \
 124                      (u_int64_t)*((const u_int8_t *)(p) + 4) << 32 | \
 125                      (u_int64_t)*((const u_int8_t *)(p) + 3) << 24 | \
 126                      (u_int64_t)*((const u_int8_t *)(p) + 2) << 16 | \
 127                      (u_int64_t)*((const u_int8_t *)(p) + 1) << 8 | \
 128                      (u_int64_t)*((const u_int8_t *)(p) + 0)))