diff options
Diffstat (limited to 'contrib/tcpdump/extract.h')
| -rw-r--r-- | contrib/tcpdump/extract.h | 77 |
1 files changed, 59 insertions, 18 deletions
diff --git a/contrib/tcpdump/extract.h b/contrib/tcpdump/extract.h index 861f06f..25980e4 100644 --- a/contrib/tcpdump/extract.h +++ b/contrib/tcpdump/extract.h @@ -18,40 +18,81 @@ * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. * - * @(#) $Header: /tcpdump/master/tcpdump/extract.h,v 1.17 2001/09/17 21:57:52 fenner Exp $ (LBL) + * @(#) $Header: /tcpdump/master/tcpdump/extract.h,v 1.19 2002/12/11 07:13:51 guy Exp $ (LBL) */ /* Network to host order macros */ #ifdef LBL_ALIGN +/* + * The processor doesn't natively handle unaligned loads. + */ +#ifdef HAVE___ATTRIBUTE__ +/* + * We have __attribute__; we assume that means we have __attribute__((packed)). + * Declare packed structures containing a u_int16_t and a u_int32_t, + * cast the pointer to point to one of those, and fetch through it; + * the GCC manual doesn't appear to explicitly say that + * __attribute__((packed)) causes the compiler to generate unaligned-safe + * code, but it apppears to do so. + * + * We do this in case the compiler can generate, for this instruction set, + * better code to do an unaligned load and pass stuff to "ntohs()" or + * "ntohl()" than the code to fetch the bytes one at a time and + * assemble them. (That might not be the case on a little-endian platform, + * where "ntohs()" and "ntohl()" might not be done inline.) + */ +typedef struct { + u_int16_t val; +} __attribute__((packed)) unaligned_u_int16_t; + +typedef struct { + u_int32_t val; +} __attribute__((packed)) unaligned_u_int32_t; + #define EXTRACT_16BITS(p) \ - ((u_int16_t)*((const u_int8_t *)(p) + 0) << 8 | \ - (u_int16_t)*((const u_int8_t *)(p) + 1)) + ((u_int16_t)ntohs(((const unaligned_u_int16_t *)(p))->val)) #define EXTRACT_32BITS(p) \ - ((u_int32_t)*((const u_int8_t *)(p) + 0) << 24 | \ - (u_int32_t)*((const u_int8_t *)(p) + 1) << 16 | \ - (u_int32_t)*((const u_int8_t *)(p) + 2) << 8 | \ - (u_int32_t)*((const u_int8_t *)(p) + 3)) -#else + ((u_int32_t)ntohl(((const unaligned_u_int32_t *)(p))->val)) +#else /* HAVE___ATTRIBUTE__ */ +/* + * We don't have __attribute__, so do unaligned loads of big-endian + * quantities the hard way - fetch the bytes one at a time and + * assemble them. + */ +#define EXTRACT_16BITS(p) \ + ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 0) << 8 | \ + (u_int16_t)*((const u_int8_t *)(p) + 1))) +#define EXTRACT_32BITS(p) \ + ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 24 | \ + (u_int32_t)*((const u_int8_t *)(p) + 1) << 16 | \ + (u_int32_t)*((const u_int8_t *)(p) + 2) << 8 | \ + (u_int32_t)*((const u_int8_t *)(p) + 3))) +#endif /* HAVE___ATTRIBUTE__ */ +#else /* LBL_ALIGN */ +/* + * The processor natively handles unaligned loads, so we can just + * cast the pointer and fetch through it. + */ #define EXTRACT_16BITS(p) \ ((u_int16_t)ntohs(*(const u_int16_t *)(p))) #define EXTRACT_32BITS(p) \ ((u_int32_t)ntohl(*(const u_int32_t *)(p))) -#endif +#endif /* LBL_ALIGN */ #define EXTRACT_24BITS(p) \ - ((u_int32_t)*((const u_int8_t *)(p) + 0) << 16 | \ - (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \ - (u_int32_t)*((const u_int8_t *)(p) + 2)) + ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 16 | \ + (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \ + (u_int32_t)*((const u_int8_t *)(p) + 2))) /* Little endian protocol host order macros */ #define EXTRACT_LE_8BITS(p) (*(p)) #define EXTRACT_LE_16BITS(p) \ - ((u_int16_t)*((const u_int8_t *)(p) + 1) << 8 | \ - (u_int16_t)*((const u_int8_t *)(p) + 0)) + ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 1) << 8 | \ + (u_int16_t)*((const u_int8_t *)(p) + 0))) #define EXTRACT_LE_32BITS(p) \ - ((u_int32_t)*((const u_int8_t *)(p) + 3) << 24 | \ - (u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \ - (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \ - (u_int32_t)*((const u_int8_t *)(p) + 0)) + ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 3) << 24 | \ + (u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \ + (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \ + (u_int32_t)*((const u_int8_t *)(p) + 0))) |
