The Tcpdump Group git mirrors - tcpdump/blob - 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 1.25 2006-01-30 16:20:07 hannes 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 static inline u_int16_t
  55 EXTRACT_16BITS(const void *p)
  56 {
  57         return ((u_int16_t)ntohs(((const unaligned_u_int16_t *)(p))->val));
  58 }
  59
  60 static inline u_int32_t
  61 EXTRACT_32BITS(const void *p)
  62 {
  63         return ((u_int32_t)ntohl(((const unaligned_u_int32_t *)(p))->val));
  64 }
  65
  66 static inline u_int64_t
  67 EXTRACT_64BITS(const void *p)
  68 {
  69         return ((u_int64_t)(((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 0)->val)) << 32 | \
  70                 ((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 1)->val)) << 0));
  71
  72 }
  73
  74 #else /* HAVE___ATTRIBUTE__ */
  75 /*
  76  * We don't have __attribute__, so do unaligned loads of big-endian
  77  * quantities the hard way - fetch the bytes one at a time and
  78  * assemble them.
  79  */
  80 #define EXTRACT_16BITS(p) \
  81         ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 0) << 8 | \
  82                      (u_int16_t)*((const u_int8_t *)(p) + 1)))
  83 #define EXTRACT_32BITS(p) \
  84         ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 24 | \
  85                      (u_int32_t)*((const u_int8_t *)(p) + 1) << 16 | \
  86                      (u_int32_t)*((const u_int8_t *)(p) + 2) << 8 | \
  87                      (u_int32_t)*((const u_int8_t *)(p) + 3)))
  88 #define EXTRACT_64BITS(p) \
  89         ((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 0) << 56 | \
  90                      (u_int64_t)*((const u_int8_t *)(p) + 1) << 48 | \
  91                      (u_int64_t)*((const u_int8_t *)(p) + 2) << 40 | \
  92                      (u_int64_t)*((const u_int8_t *)(p) + 3) << 32 | \
  93                      (u_int64_t)*((const u_int8_t *)(p) + 4) << 24 | \
  94                      (u_int64_t)*((const u_int8_t *)(p) + 5) << 16 | \
  95                      (u_int64_t)*((const u_int8_t *)(p) + 6) << 8 | \
  96                      (u_int64_t)*((const u_int8_t *)(p) + 7)))
  97 #endif /* HAVE___ATTRIBUTE__ */
  98 #else /* LBL_ALIGN */
  99 /*
 100  * The processor natively handles unaligned loads, so we can just
 101  * cast the pointer and fetch through it.
 102  */
 103 static inline u_int16_t
 104 EXTRACT_16BITS(const void *p)
 105 {
 106         return ((u_int16_t)ntohs(*(const u_int16_t *)(p)));
 107 }
 108
 109 static inline u_int32_t
 110 EXTRACT_32BITS(const void *p)
 111 {
 112         return ((u_int32_t)ntohl(*(const u_int32_t *)(p)));
 113 }
 114
 115 static inline u_int64_t
 116 EXTRACT_64BITS(const void *p)
 117 {
 118         return ((u_int64_t)(((u_int64_t)ntohl(*((const u_int32_t *)(p) + 0))) << 32 | \
 119                 ((u_int64_t)ntohl(*((const u_int32_t *)(p) + 1))) << 0));
 120
 121 }
 122
 123 #endif /* LBL_ALIGN */
 124
 125 #define EXTRACT_24BITS(p) \
 126         ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 16 | \
 127                      (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
 128                      (u_int32_t)*((const u_int8_t *)(p) + 2)))
 129
 130 /*
 131  * Macros to extract possibly-unaligned little-endian integral values.
 132  * XXX - do loads on little-endian machines that support unaligned loads?
 133  */
 134 #define EXTRACT_LE_8BITS(p) (*(p))
 135 #define EXTRACT_LE_16BITS(p) \
 136         ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 1) << 8 | \
 137                      (u_int16_t)*((const u_int8_t *)(p) + 0)))
 138 #define EXTRACT_LE_32BITS(p) \
 139         ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 3) << 24 | \
 140                      (u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \
 141                      (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
 142                      (u_int32_t)*((const u_int8_t *)(p) + 0)))
 143 #define EXTRACT_LE_24BITS(p) \
 144         ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \
 145                      (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
 146                      (u_int32_t)*((const u_int8_t *)(p) + 0)))
 147 #define EXTRACT_LE_64BITS(p) \
 148         ((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 7) << 56 | \
 149                      (u_int64_t)*((const u_int8_t *)(p) + 6) << 48 | \
 150                      (u_int64_t)*((const u_int8_t *)(p) + 5) << 40 | \
 151                      (u_int64_t)*((const u_int8_t *)(p) + 4) << 32 | \
 152                      (u_int64_t)*((const u_int8_t *)(p) + 3) << 24 | \
 153                      (u_int64_t)*((const u_int8_t *)(p) + 2) << 16 | \
 154                      (u_int64_t)*((const u_int8_t *)(p) + 1) << 8 | \
 155                      (u_int64_t)*((const u_int8_t *)(p) + 0)))