contrib/libpcap/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 #ifndef _WIN32
  23 #include <arpa/inet.h>
  24 #endif
  25
  26 #include <pcap/pcap-inttypes.h>
  27 #include <pcap/compiler-tests.h>
  28
  29 /*
  30  * Macros to extract possibly-unaligned big-endian integral values.
  31  */
  32 #ifdef LBL_ALIGN
  33 /*
  34  * The processor doesn't natively handle unaligned loads.
  35  */
  36 #if PCAP_IS_AT_LEAST_GNUC_VERSION(2,0) && \
  37     (defined(__alpha) || defined(__alpha__) || \
  38      defined(__mips) || defined(__mips__))
  39 /*
  40  * This is MIPS or Alpha, which don't natively handle unaligned loads,
  41  * but which have instructions that can help when doing unaligned
  42  * loads, and this is GCC 2.0 or later or a compiler that claims to
  43  * be GCC 2.0 or later, which we assume that mean we have
  44  * __attribute__((packed)), which we can use to convince the compiler
  45  * to generate those instructions.
  46  *
  47  * Declare packed structures containing a uint16_t and a uint32_t,
  48  * cast the pointer to point to one of those, and fetch through it;
  49  * the GCC manual doesn't appear to explicitly say that
  50  * __attribute__((packed)) causes the compiler to generate unaligned-safe
  51  * code, but it apppears to do so.
  52  *
  53  * We do this in case the compiler can generate code using those
  54  * instructions to do an unaligned load and pass stuff to "ntohs()" or
  55  * "ntohl()", which might be better than than the code to fetch the
  56  * bytes one at a time and assemble them.  (That might not be the
  57  * case on a little-endian platform, such as DEC's MIPS machines and
  58  * Alpha machines, where "ntohs()" and "ntohl()" might not be done
  59  * inline.)
  60  *
  61  * We do this only for specific architectures because, for example,
  62  * at least some versions of GCC, when compiling for 64-bit SPARC,
  63  * generate code that assumes alignment if we do this.
  64  *
  65  * XXX - add other architectures and compilers as possible and
  66  * appropriate.
  67  *
  68  * HP's C compiler, indicated by __HP_cc being defined, supports
  69  * "#pragma unaligned N" in version A.05.50 and later, where "N"
  70  * specifies a number of bytes at which the typedef on the next
  71  * line is aligned, e.g.
  72  *
  73  *      #pragma unalign 1
  74  *      typedef uint16_t unaligned_uint16_t;
  75  *
  76  * to define unaligned_uint16_t as a 16-bit unaligned data type.
  77  * This could be presumably used, in sufficiently recent versions of
  78  * the compiler, with macros similar to those below.  This would be
  79  * useful only if that compiler could generate better code for PA-RISC
  80  * or Itanium than would be generated by a bunch of shifts-and-ORs.
  81  *
  82  * DEC C, indicated by __DECC being defined, has, at least on Alpha,
  83  * an __unaligned qualifier that can be applied to pointers to get the
  84  * compiler to generate code that does unaligned loads and stores when
  85  * dereferencing the pointer in question.
  86  *
  87  * XXX - what if the native C compiler doesn't support
  88  * __attribute__((packed))?  How can we get it to generate unaligned
  89  * accesses for *specific* items?
  90  */
  91 typedef struct {
  92         uint16_t        val;
  93 } __attribute__((packed)) unaligned_uint16_t;
  94
  95 typedef struct {
  96         uint32_t        val;
  97 } __attribute__((packed)) unaligned_uint32_t;
  98
  99 static inline uint16_t
 100 EXTRACT_16BITS(const void *p)
 101 {
 102         return ((uint16_t)ntohs(((const unaligned_uint16_t *)(p))->val));
 103 }
 104
 105 static inline uint32_t
 106 EXTRACT_32BITS(const void *p)
 107 {
 108         return ((uint32_t)ntohl(((const unaligned_uint32_t *)(p))->val));
 109 }
 110
 111 static inline uint64_t
 112 EXTRACT_64BITS(const void *p)
 113 {
 114         return ((uint64_t)(((uint64_t)ntohl(((const unaligned_uint32_t *)(p) + 0)->val)) << 32 | \
 115                 ((uint64_t)ntohl(((const unaligned_uint32_t *)(p) + 1)->val)) << 0));
 116 }
 117
 118 #else /* have to do it a byte at a time */
 119 /*
 120  * This isn't a GCC-compatible compiler, we don't have __attribute__,
 121  * or we do but we don't know of any better way with this instruction
 122  * set to do unaligned loads, so do unaligned loads of big-endian
 123  * quantities the hard way - fetch the bytes one at a time and
 124  * assemble them.
 125  */
 126 #define EXTRACT_16BITS(p) \
 127         ((uint16_t)(((uint16_t)(*((const uint8_t *)(p) + 0)) << 8) | \
 128                     ((uint16_t)(*((const uint8_t *)(p) + 1)) << 0)))
 129 #define EXTRACT_32BITS(p) \
 130         ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 0)) << 24) | \
 131                     ((uint32_t)(*((const uint8_t *)(p) + 1)) << 16) | \
 132                     ((uint32_t)(*((const uint8_t *)(p) + 2)) << 8) | \
 133                     ((uint32_t)(*((const uint8_t *)(p) + 3)) << 0)))
 134 #define EXTRACT_64BITS(p) \
 135         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 56) | \
 136                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 48) | \
 137                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 40) | \
 138                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 32) | \
 139                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 24) | \
 140                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 16) | \
 141                     ((uint64_t)(*((const uint8_t *)(p) + 6)) << 8) | \
 142                     ((uint64_t)(*((const uint8_t *)(p) + 7)) << 0)))
 143 #endif /* must special-case unaligned accesses */
 144 #else /* LBL_ALIGN */
 145 /*
 146  * The processor natively handles unaligned loads, so we can just
 147  * cast the pointer and fetch through it.
 148  */
 149 static inline uint16_t
 150 EXTRACT_16BITS(const void *p)
 151 {
 152         return ((uint16_t)ntohs(*(const uint16_t *)(p)));
 153 }
 154
 155 static inline uint32_t
 156 EXTRACT_32BITS(const void *p)
 157 {
 158         return ((uint32_t)ntohl(*(const uint32_t *)(p)));
 159 }
 160
 161 static inline uint64_t
 162 EXTRACT_64BITS(const void *p)
 163 {
 164         return ((uint64_t)(((uint64_t)ntohl(*((const uint32_t *)(p) + 0))) << 32 | \
 165                 ((uint64_t)ntohl(*((const uint32_t *)(p) + 1))) << 0));
 166
 167 }
 168
 169 #endif /* LBL_ALIGN */
 170
 171 #define EXTRACT_24BITS(p) \
 172         ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 0)) << 16) | \
 173                     ((uint32_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 174                     ((uint32_t)(*((const uint8_t *)(p) + 2)) << 0)))
 175
 176 #define EXTRACT_40BITS(p) \
 177         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 32) | \
 178                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 24) | \
 179                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 16) | \
 180                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 8) | \
 181                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 0)))
 182
 183 #define EXTRACT_48BITS(p) \
 184         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 40) | \
 185                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 32) | \
 186                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 24) | \
 187                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 16) | \
 188                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 8) | \
 189                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 0)))
 190
 191 #define EXTRACT_56BITS(p) \
 192         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 48) | \
 193                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 40) | \
 194                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 32) | \
 195                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 24) | \
 196                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 16) | \
 197                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 8) | \
 198                     ((uint64_t)(*((const uint8_t *)(p) + 6)) << 0)))
 199
 200 /*
 201  * Macros to extract possibly-unaligned little-endian integral values.
 202  * XXX - do loads on little-endian machines that support unaligned loads?
 203  */
 204 #define EXTRACT_LE_8BITS(p) (*(p))
 205 #define EXTRACT_LE_16BITS(p) \
 206         ((uint16_t)(((uint16_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 207                     ((uint16_t)(*((const uint8_t *)(p) + 0)) << 0)))
 208 #define EXTRACT_LE_32BITS(p) \
 209         ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 3)) << 24) | \
 210                     ((uint32_t)(*((const uint8_t *)(p) + 2)) << 16) | \
 211                     ((uint32_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 212                     ((uint32_t)(*((const uint8_t *)(p) + 0)) << 0)))
 213 #define EXTRACT_LE_24BITS(p) \
 214         ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 2)) << 16) | \
 215                     ((uint32_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 216                     ((uint32_t)(*((const uint8_t *)(p) + 0)) << 0)))
 217 #define EXTRACT_LE_64BITS(p) \
 218         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 7)) << 56) | \
 219                     ((uint64_t)(*((const uint8_t *)(p) + 6)) << 48) | \
 220                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 40) | \
 221                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 32) | \
 222                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 24) | \
 223                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 16) | \
 224                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 225                     ((uint64_t)(*((const uint8_t *)(p) + 0)) << 0)))