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 /*
  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 #if defined(__GNUC__) && defined(HAVE___ATTRIBUTE__) && \
  34     (defined(__alpha) || defined(__alpha__) || \
  35      defined(__mips) || defined(__mips__))
  36
  37 /*
  38  * This is a GCC-compatible compiler and we have __attribute__, which
  39  * we assume that mean we have __attribute__((packed)), and this is
  40  * MIPS or Alpha, which has instructions that can help when doing
  41  * unaligned loads.
  42  *
  43  * Declare packed structures containing a uint16_t and a uint32_t,
  44  * cast the pointer to point to one of those, and fetch through it;
  45  * the GCC manual doesn't appear to explicitly say that
  46  * __attribute__((packed)) causes the compiler to generate unaligned-safe
  47  * code, but it apppears to do so.
  48  *
  49  * We do this in case the compiler can generate code using those
  50  * instructions to do an unaligned load and pass stuff to "ntohs()" or
  51  * "ntohl()", which might be better than than the code to fetch the
  52  * bytes one at a time and assemble them.  (That might not be the
  53  * case on a little-endian platform, such as DEC's MIPS machines and
  54  * Alpha machines, where "ntohs()" and "ntohl()" might not be done
  55  * inline.)
  56  *
  57  * We do this only for specific architectures because, for example,
  58  * at least some versions of GCC, when compiling for 64-bit SPARC,
  59  * generate code that assumes alignment if we do this.
  60  *
  61  * XXX - add other architectures and compilers as possible and
  62  * appropriate.
  63  *
  64  * HP's C compiler, indicated by __HP_cc being defined, supports
  65  * "#pragma unaligned N" in version A.05.50 and later, where "N"
  66  * specifies a number of bytes at which the typedef on the next
  67  * line is aligned, e.g.
  68  *
  69  *      #pragma unalign 1
  70  *      typedef uint16_t unaligned_uint16_t;
  71  *
  72  * to define unaligned_uint16_t as a 16-bit unaligned data type.
  73  * This could be presumably used, in sufficiently recent versions of
  74  * the compiler, with macros similar to those below.  This would be
  75  * useful only if that compiler could generate better code for PA-RISC
  76  * or Itanium than would be generated by a bunch of shifts-and-ORs.
  77  *
  78  * DEC C, indicated by __DECC being defined, has, at least on Alpha,
  79  * an __unaligned qualifier that can be applied to pointers to get the
  80  * compiler to generate code that does unaligned loads and stores when
  81  * dereferencing the pointer in question.
  82  *
  83  * XXX - what if the native C compiler doesn't support
  84  * __attribute__((packed))?  How can we get it to generate unaligned
  85  * accesses for *specific* items?
  86  */
  87 typedef struct {
  88         uint16_t        val;
  89 } __attribute__((packed)) unaligned_uint16_t;
  90
  91 typedef struct {
  92         uint32_t        val;
  93 } __attribute__((packed)) unaligned_uint32_t;
  94
  95 static inline uint16_t
  96 EXTRACT_16BITS(const void *p)
  97 {
  98         return ((uint16_t)ntohs(((const unaligned_uint16_t *)(p))->val));
  99 }
 100
 101 static inline uint32_t
 102 EXTRACT_32BITS(const void *p)
 103 {
 104         return ((uint32_t)ntohl(((const unaligned_uint32_t *)(p))->val));
 105 }
 106
 107 static inline uint64_t
 108 EXTRACT_64BITS(const void *p)
 109 {
 110         return ((uint64_t)(((uint64_t)ntohl(((const unaligned_uint32_t *)(p) + 0)->val)) << 32 | \
 111                 ((uint64_t)ntohl(((const unaligned_uint32_t *)(p) + 1)->val)) << 0));
 112 }
 113
 114 #else /* have to do it a byte at a time */
 115 /*
 116  * This isn't a GCC-compatible compiler, we don't have __attribute__,
 117  * or we do but we don't know of any better way with this instruction
 118  * set to do unaligned loads, so do unaligned loads of big-endian
 119  * quantities the hard way - fetch the bytes one at a time and
 120  * assemble them.
 121  */
 122 #define EXTRACT_16BITS(p) \
 123         ((uint16_t)(((uint16_t)(*((const uint8_t *)(p) + 0)) << 8) | \
 124                     ((uint16_t)(*((const uint8_t *)(p) + 1)) << 0)))
 125 #define EXTRACT_32BITS(p) \
 126         ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 0)) << 24) | \
 127                     ((uint32_t)(*((const uint8_t *)(p) + 1)) << 16) | \
 128                     ((uint32_t)(*((const uint8_t *)(p) + 2)) << 8) | \
 129                     ((uint32_t)(*((const uint8_t *)(p) + 3)) << 0)))
 130 #define EXTRACT_64BITS(p) \
 131         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 56) | \
 132                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 48) | \
 133                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 40) | \
 134                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 32) | \
 135                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 24) | \
 136                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 16) | \
 137                     ((uint64_t)(*((const uint8_t *)(p) + 6)) << 8) | \
 138                     ((uint64_t)(*((const uint8_t *)(p) + 7)) << 0)))
 139 #endif /* must special-case unaligned accesses */
 140 #else /* LBL_ALIGN */
 141 /*
 142  * The processor natively handles unaligned loads, so we can just
 143  * cast the pointer and fetch through it.
 144  */
 145 static inline uint16_t
 146 EXTRACT_16BITS(const void *p)
 147 {
 148         return ((uint16_t)ntohs(*(const uint16_t *)(p)));
 149 }
 150
 151 static inline uint32_t
 152 EXTRACT_32BITS(const void *p)
 153 {
 154         return ((uint32_t)ntohl(*(const uint32_t *)(p)));
 155 }
 156
 157 static inline uint64_t
 158 EXTRACT_64BITS(const void *p)
 159 {
 160         return ((uint64_t)(((uint64_t)ntohl(*((const uint32_t *)(p) + 0))) << 32 | \
 161                 ((uint64_t)ntohl(*((const uint32_t *)(p) + 1))) << 0));
 162
 163 }
 164
 165 #endif /* LBL_ALIGN */
 166
 167 #define EXTRACT_24BITS(p) \
 168         ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 0)) << 16) | \
 169                     ((uint32_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 170                     ((uint32_t)(*((const uint8_t *)(p) + 2)) << 0)))
 171
 172 #define EXTRACT_40BITS(p) \
 173         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 32) | \
 174                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 24) | \
 175                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 16) | \
 176                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 8) | \
 177                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 0)))
 178
 179 #define EXTRACT_48BITS(p) \
 180         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 40) | \
 181                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 32) | \
 182                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 24) | \
 183                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 16) | \
 184                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 8) | \
 185                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 0)))
 186
 187 #define EXTRACT_56BITS(p) \
 188         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 48) | \
 189                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 40) | \
 190                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 32) | \
 191                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 24) | \
 192                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 16) | \
 193                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 8) | \
 194                     ((uint64_t)(*((const uint8_t *)(p) + 6)) << 0)))
 195
 196 /*
 197  * Macros to extract possibly-unaligned little-endian integral values.
 198  * XXX - do loads on little-endian machines that support unaligned loads?
 199  */
 200 #define EXTRACT_LE_8BITS(p) (*(p))
 201 #define EXTRACT_LE_16BITS(p) \
 202         ((uint16_t)(((uint16_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 203                     ((uint16_t)(*((const uint8_t *)(p) + 0)) << 0)))
 204 #define EXTRACT_LE_32BITS(p) \
 205         ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 3)) << 24) | \
 206                     ((uint32_t)(*((const uint8_t *)(p) + 2)) << 16) | \
 207                     ((uint32_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 208                     ((uint32_t)(*((const uint8_t *)(p) + 0)) << 0)))
 209 #define EXTRACT_LE_24BITS(p) \
 210         ((uint32_t)(((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_64BITS(p) \
 214         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 7)) << 56) | \
 215                     ((uint64_t)(*((const uint8_t *)(p) + 6)) << 48) | \
 216                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 40) | \
 217                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 32) | \
 218                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 24) | \
 219                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 16) | \
 220                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 221                     ((uint64_t)(*((const uint8_t *)(p) + 0)) << 0)))