contrib/tcpdump-3.9/extract.h

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