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
  22 /*
  23  * Macros to extract possibly-unaligned big-endian integral values.
  24  */
  25 #ifdef LBL_ALIGN
  26 /*
  27  * The processor doesn't natively handle unaligned loads.
  28  */
  29 #ifdef HAVE___ATTRIBUTE__
  30 /*
  31  * We have __attribute__; we assume that means we have __attribute__((packed)).
  32  * Declare packed structures containing a u_int16_t and a u_int32_t,
  33  * cast the pointer to point to one of those, and fetch through it;
  34  * the GCC manual doesn't appear to explicitly say that
  35  * __attribute__((packed)) causes the compiler to generate unaligned-safe
  36  * code, but it apppears to do so.
  37  *
  38  * We do this in case the compiler can generate, for this instruction set,
  39  * better code to do an unaligned load and pass stuff to "ntohs()" or
  40  * "ntohl()" than the code to fetch the bytes one at a time and
  41  * assemble them.  (That might not be the case on a little-endian platform,
  42  * where "ntohs()" and "ntohl()" might not be done inline.)
  43  */
  44 typedef struct {
  45         u_int16_t       val;
  46 } __attribute__((packed)) unaligned_u_int16_t;
  47
  48 typedef struct {
  49         u_int32_t       val;
  50 } __attribute__((packed)) unaligned_u_int32_t;
  51
  52 static inline u_int16_t
  53 EXTRACT_16BITS(const void *p)
  54 {
  55         return ((u_int16_t)ntohs(((const unaligned_u_int16_t *)(p))->val));
  56 }
  57
  58 static inline u_int32_t
  59 EXTRACT_32BITS(const void *p)
  60 {
  61         return ((u_int32_t)ntohl(((const unaligned_u_int32_t *)(p))->val));
  62 }
  63
  64 static inline u_int64_t
  65 EXTRACT_64BITS(const void *p)
  66 {
  67         return ((u_int64_t)(((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 0)->val)) << 32 | \
  68                 ((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 1)->val)) << 0));
  69
  70 }
  71
  72 #else /* HAVE___ATTRIBUTE__ */
  73 /*
  74  * We don't have __attribute__, so do unaligned loads of big-endian
  75  * quantities the hard way - fetch the bytes one at a time and
  76  * assemble them.
  77  */
  78 #define EXTRACT_16BITS(p) \
  79         ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 0) << 8 | \
  80                      (u_int16_t)*((const u_int8_t *)(p) + 1)))
  81 #define EXTRACT_32BITS(p) \
  82         ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 24 | \
  83                      (u_int32_t)*((const u_int8_t *)(p) + 1) << 16 | \
  84                      (u_int32_t)*((const u_int8_t *)(p) + 2) << 8 | \
  85                      (u_int32_t)*((const u_int8_t *)(p) + 3)))
  86 #define EXTRACT_64BITS(p) \
  87         ((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 0) << 56 | \
  88                      (u_int64_t)*((const u_int8_t *)(p) + 1) << 48 | \
  89                      (u_int64_t)*((const u_int8_t *)(p) + 2) << 40 | \
  90                      (u_int64_t)*((const u_int8_t *)(p) + 3) << 32 | \
  91                      (u_int64_t)*((const u_int8_t *)(p) + 4) << 24 | \
  92                      (u_int64_t)*((const u_int8_t *)(p) + 5) << 16 | \
  93                      (u_int64_t)*((const u_int8_t *)(p) + 6) << 8 | \
  94                      (u_int64_t)*((const u_int8_t *)(p) + 7)))
  95 #endif /* HAVE___ATTRIBUTE__ */
  96 #else /* LBL_ALIGN */
  97 /*
  98  * The processor natively handles unaligned loads, so we can just
  99  * cast the pointer and fetch through it.
 100  */
 101 static inline u_int16_t
 102 EXTRACT_16BITS(const void *p)
 103 {
 104         return ((u_int16_t)ntohs(*(const u_int16_t *)(p)));
 105 }
 106
 107 static inline u_int32_t
 108 EXTRACT_32BITS(const void *p)
 109 {
 110         return ((u_int32_t)ntohl(*(const u_int32_t *)(p)));
 111 }
 112
 113 static inline u_int64_t
 114 EXTRACT_64BITS(const void *p)
 115 {
 116         return ((u_int64_t)(((u_int64_t)ntohl(*((const u_int32_t *)(p) + 0))) << 32 | \
 117                 ((u_int64_t)ntohl(*((const u_int32_t *)(p) + 1))) << 0));
 118
 119 }
 120
 121 #endif /* LBL_ALIGN */
 122
 123 #define EXTRACT_24BITS(p) \
 124         ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 16 | \
 125                      (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
 126                      (u_int32_t)*((const u_int8_t *)(p) + 2)))
 127
 128 /*
 129  * Macros to extract possibly-unaligned little-endian integral values.
 130  * XXX - do loads on little-endian machines that support unaligned loads?
 131  */
 132 #define EXTRACT_LE_8BITS(p) (*(p))
 133 #define EXTRACT_LE_16BITS(p) \
 134         ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 1) << 8 | \
 135                      (u_int16_t)*((const u_int8_t *)(p) + 0)))
 136 #define EXTRACT_LE_32BITS(p) \
 137         ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 3) << 24 | \
 138                      (u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \
 139                      (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
 140                      (u_int32_t)*((const u_int8_t *)(p) + 0)))
 141 #define EXTRACT_LE_24BITS(p) \
 142         ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \
 143                      (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
 144                      (u_int32_t)*((const u_int8_t *)(p) + 0)))
 145 #define EXTRACT_LE_64BITS(p) \
 146         ((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 7) << 56 | \
 147                      (u_int64_t)*((const u_int8_t *)(p) + 6) << 48 | \
 148                      (u_int64_t)*((const u_int8_t *)(p) + 5) << 40 | \
 149                      (u_int64_t)*((const u_int8_t *)(p) + 4) << 32 | \
 150                      (u_int64_t)*((const u_int8_t *)(p) + 3) << 24 | \
 151                      (u_int64_t)*((const u_int8_t *)(p) + 2) << 16 | \
 152                      (u_int64_t)*((const u_int8_t *)(p) + 1) << 8 | \
 153                      (u_int64_t)*((const u_int8_t *)(p) + 0)))