tcpdump/dist/extract.h

/*
 * Copyright (c) 1992, 1993, 1994, 1995, 1996
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the University of California,
 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
 * the University nor the names of its contributors may be used to endorse
 * or promote products derived from this software without specific prior
 * written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * @(#) Header: /tcpdump/master/tcpdump/extract.h,v 1.25 2006-01-30 16:20:07 hannes Exp  (LBL)
 */

#ifdef __NetBSD__
#include <string.h>

/*
 * Do it the portable way and let the compiler optimize the code
 */
static inline uint16_t EXTRACT_16BITS(const void *p)
{
	uint16_t t;
	memcpy(&t, p, sizeof(t));
	return ntohs(t);
}

static inline uint32_t EXTRACT_24BITS(const void *p)
{
	uint8_t t[3];
	memcpy(t, p, sizeof(t));
	return
	    ((uint32_t)t[0] << 16) |
	    ((uint32_t)t[1] << 8) |
	    t[2];
}

static inline uint32_t EXTRACT_32BITS(const void *p)
{
	uint32_t t;
	memcpy(&t, p, sizeof(t));
	return ntohl(t);
}

static inline uint64_t EXTRACT_64BITS(const void *p)
{
	uint32_t t[2];
	memcpy(&t[0], p, sizeof(t[0]));
	memcpy(&t[1], (const uint8_t *)p + sizeof(t[0]), sizeof(t[1]));
	return ((uint64_t)ntohl(t[0]) << 32) | ntohl(t[1]);
}

static inline uint8_t EXTRACT_LE_8BITS(const void *p)
{
	uint8_t t[1];
	memcpy(t, p, sizeof(t));
	return t[0];
}

static inline uint16_t EXTRACT_LE_16BITS(const void *p)
{
	uint8_t t[2];
	memcpy(t, p, sizeof(t));
	return
	    ((uint16_t)t[1] << 8) |
	    t[0];
}

static inline uint32_t EXTRACT_LE_24BITS(const void *p)
{
	uint8_t t[3];
	memcpy(t, p, sizeof(t));
	return
	    ((uint32_t)t[2] << 16) |
	    ((uint32_t)t[1] << 8) |
	    t[0];
}

static inline uint32_t EXTRACT_LE_32BITS(const void *p)
{
	uint8_t t[4];
	memcpy(t, p, sizeof(t));
	return
	    ((uint32_t)t[3] << 24) |
	    ((uint32_t)t[2] << 16) |
	    ((uint32_t)t[1] << 8) |
	    t[0];
}

static inline uint64_t EXTRACT_LE_64BITS(const void *p)
{
	uint8_t t[8];
	memcpy(&t, p, sizeof(t));
	return
	    ((uint64_t)t[7] << 56) |
	    ((uint64_t)t[6] << 48) |
	    ((uint64_t)t[5] << 40) |
	    ((uint64_t)t[4] << 32) |
	    ((uint64_t)t[3] << 24) |
	    ((uint64_t)t[2] << 16) |
	    ((uint64_t)t[1] << 8) |
	    t[0];
}

#else /* Fast & Loose */
/*
 * Macros to extract possibly-unaligned big-endian integral values.
 */
#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;

static inline u_int16_t
EXTRACT_16BITS(const void *p)
{
	return ((u_int16_t)ntohs(((const unaligned_u_int16_t *)(p))->val));
}

static inline u_int32_t
EXTRACT_32BITS(const void *p)
{
	return ((u_int32_t)ntohl(((const unaligned_u_int32_t *)(p))->val));
}

static inline u_int64_t
EXTRACT_64BITS(const void *p)
{
	return ((u_int64_t)(((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 0)->val)) << 32 | \
		((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 1)->val)) << 0));

}

#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)))
#define EXTRACT_64BITS(p) \
	((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 0) << 56 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 1) << 48 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 2) << 40 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 3) << 32 | \
	             (u_int64_t)*((const u_int8_t *)(p) + 4) << 24 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 5) << 16 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 6) << 8 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 7)))
#endif /* HAVE___ATTRIBUTE__ */
#else /* LBL_ALIGN */
/*
 * The processor natively handles unaligned loads, so we can just
 * cast the pointer and fetch through it.
 */
static inline u_int16_t
EXTRACT_16BITS(const void *p)
{
	return ((u_int16_t)ntohs(*(const u_int16_t *)(p)));
}

static inline u_int32_t
EXTRACT_32BITS(const void *p)
{
	return ((u_int32_t)ntohl(*(const u_int32_t *)(p)));
}

static inline u_int64_t
EXTRACT_64BITS(const void *p)
{
	return ((u_int64_t)(((u_int64_t)ntohl(*((const u_int32_t *)(p) + 0))) << 32 | \
		((u_int64_t)ntohl(*((const u_int32_t *)(p) + 1))) << 0));

}

#endif /* LBL_ALIGN */

#define EXTRACT_24BITS(p) \
	((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)))

/*
 * Macros to extract possibly-unaligned little-endian integral values.
 * XXX - do loads on little-endian machines that support unaligned loads?
 */
#define EXTRACT_LE_8BITS(p) (*(p))
#define EXTRACT_LE_16BITS(p) \
	((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)((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)))
#define EXTRACT_LE_24BITS(p) \
	((u_int32_t)((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)))
#define EXTRACT_LE_64BITS(p) \
	((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 7) << 56 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 6) << 48 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 5) << 40 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 4) << 32 | \
	             (u_int64_t)*((const u_int8_t *)(p) + 3) << 24 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 2) << 16 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 1) << 8 | \
		     (u_int64_t)*((const u_int8_t *)(p) + 0)))
#endif /* __NetBSD__ */