131 lines
5.7 KiB
C
131 lines
5.7 KiB
C
/*
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* Copyright (c) 1992, 1993, 1994, 1995, 1996
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that: (1) source code distributions
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* retain the above copyright notice and this paragraph in its entirety, (2)
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* distributions including binary code include the above copyright notice and
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* this paragraph in its entirety in the documentation or other materials
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* provided with the distribution, and (3) all advertising materials mentioning
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* features or use of this software display the following acknowledgement:
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* ``This product includes software developed by the University of California,
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* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
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* the University nor the names of its contributors may be used to endorse
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* or promote products derived from this software without specific prior
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* written permission.
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*
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* @(#) $Header: /tcpdump/master/tcpdump/extract.h,v 1.25 2006-01-30 16:20:07 hannes Exp $ (LBL)
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*/
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/*
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* Macros to extract possibly-unaligned big-endian integral values.
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*/
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#ifdef LBL_ALIGN
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/*
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* The processor doesn't natively handle unaligned loads.
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*/
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#ifdef HAVE___ATTRIBUTE__
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/*
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* We have __attribute__; we assume that means we have __attribute__((packed)).
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* Declare packed structures containing a u_int16_t and a u_int32_t,
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* cast the pointer to point to one of those, and fetch through it;
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* the GCC manual doesn't appear to explicitly say that
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* __attribute__((packed)) causes the compiler to generate unaligned-safe
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* code, but it apppears to do so.
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*
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* We do this in case the compiler can generate, for this instruction set,
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* better code to do an unaligned load and pass stuff to "ntohs()" or
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* "ntohl()" than the code to fetch the bytes one at a time and
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* assemble them. (That might not be the case on a little-endian platform,
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* where "ntohs()" and "ntohl()" might not be done inline.)
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*/
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typedef struct {
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u_int16_t val;
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} __attribute__((packed)) unaligned_u_int16_t;
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typedef struct {
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u_int32_t val;
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} __attribute__((packed)) unaligned_u_int32_t;
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#define EXTRACT_16BITS(p) \
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((u_int16_t)ntohs(((const unaligned_u_int16_t *)(p))->val))
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#define EXTRACT_32BITS(p) \
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((u_int32_t)ntohl(((const unaligned_u_int32_t *)(p))->val))
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#define EXTRACT_64BITS(p) \
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((u_int64_t)(((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 0)->val)) << 32 | \
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((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 1)->val)) << 0))
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#else /* HAVE___ATTRIBUTE__ */
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/*
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* We don't have __attribute__, so do unaligned loads of big-endian
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* quantities the hard way - fetch the bytes one at a time and
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* assemble them.
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*/
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#define EXTRACT_16BITS(p) \
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((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 0) << 8 | \
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(u_int16_t)*((const u_int8_t *)(p) + 1)))
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#define EXTRACT_32BITS(p) \
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((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 24 | \
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(u_int32_t)*((const u_int8_t *)(p) + 1) << 16 | \
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(u_int32_t)*((const u_int8_t *)(p) + 2) << 8 | \
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(u_int32_t)*((const u_int8_t *)(p) + 3)))
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#define EXTRACT_64BITS(p) \
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((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 0) << 56 | \
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(u_int64_t)*((const u_int8_t *)(p) + 1) << 48 | \
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(u_int64_t)*((const u_int8_t *)(p) + 2) << 40 | \
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(u_int64_t)*((const u_int8_t *)(p) + 3) << 32 | \
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(u_int64_t)*((const u_int8_t *)(p) + 4) << 24 | \
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(u_int64_t)*((const u_int8_t *)(p) + 5) << 16 | \
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(u_int64_t)*((const u_int8_t *)(p) + 6) << 8 | \
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(u_int64_t)*((const u_int8_t *)(p) + 7)))
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#endif /* HAVE___ATTRIBUTE__ */
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#else /* LBL_ALIGN */
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/*
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* The processor natively handles unaligned loads, so we can just
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* cast the pointer and fetch through it.
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*/
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#define EXTRACT_16BITS(p) \
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((u_int16_t)ntohs(*(const u_int16_t *)(p)))
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#define EXTRACT_32BITS(p) \
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((u_int32_t)ntohl(*(const u_int32_t *)(p)))
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#define EXTRACT_64BITS(p) \
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((u_int64_t)(((u_int64_t)ntohl(*((const u_int32_t *)(p) + 0))) << 32 | \
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((u_int64_t)ntohl(*((const u_int32_t *)(p) + 1))) << 0))
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#endif /* LBL_ALIGN */
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#define EXTRACT_24BITS(p) \
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((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 16 | \
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(u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
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(u_int32_t)*((const u_int8_t *)(p) + 2)))
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/*
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* Macros to extract possibly-unaligned little-endian integral values.
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* XXX - do loads on little-endian machines that support unaligned loads?
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*/
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#define EXTRACT_LE_8BITS(p) (*(p))
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#define EXTRACT_LE_16BITS(p) \
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((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 1) << 8 | \
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(u_int16_t)*((const u_int8_t *)(p) + 0)))
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#define EXTRACT_LE_32BITS(p) \
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((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 3) << 24 | \
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(u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \
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(u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
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(u_int32_t)*((const u_int8_t *)(p) + 0)))
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#define EXTRACT_LE_24BITS(p) \
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((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \
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(u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
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(u_int32_t)*((const u_int8_t *)(p) + 0)))
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#define EXTRACT_LE_64BITS(p) \
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((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 7) << 56 | \
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(u_int64_t)*((const u_int8_t *)(p) + 6) << 48 | \
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(u_int64_t)*((const u_int8_t *)(p) + 5) << 40 | \
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(u_int64_t)*((const u_int8_t *)(p) + 4) << 32 | \
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(u_int64_t)*((const u_int8_t *)(p) + 3) << 24 | \
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(u_int64_t)*((const u_int8_t *)(p) + 2) << 16 | \
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(u_int64_t)*((const u_int8_t *)(p) + 1) << 8 | \
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(u_int64_t)*((const u_int8_t *)(p) + 0)))
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