extract.h revision 127668
1126353Smlaier/* 2126353Smlaier * Copyright (c) 1992, 1993, 1994, 1995, 1996 3126353Smlaier * The Regents of the University of California. All rights reserved. 4126353Smlaier * 5126353Smlaier * Redistribution and use in source and binary forms, with or without 6126353Smlaier * modification, are permitted provided that: (1) source code distributions 7126353Smlaier * retain the above copyright notice and this paragraph in its entirety, (2) 8126353Smlaier * distributions including binary code include the above copyright notice and 9126353Smlaier * this paragraph in its entirety in the documentation or other materials 10126353Smlaier * provided with the distribution, and (3) all advertising materials mentioning 11126353Smlaier * features or use of this software display the following acknowledgement: 12126353Smlaier * ``This product includes software developed by the University of California, 13126353Smlaier * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of 14126353Smlaier * the University nor the names of its contributors may be used to endorse 15126353Smlaier * or promote products derived from this software without specific prior 16126353Smlaier * written permission. 17126353Smlaier * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED 18126353Smlaier * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF 19126353Smlaier * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 20126353Smlaier * 21126353Smlaier * @(#) $Header: /tcpdump/master/tcpdump/extract.h,v 1.19 2002/12/11 07:13:51 guy Exp $ (LBL) 22126353Smlaier */ 23126353Smlaier 24126353Smlaier/* Network to host order macros */ 25126353Smlaier 26126353Smlaier#ifdef LBL_ALIGN 27126353Smlaier/* 28126353Smlaier * The processor doesn't natively handle unaligned loads. 29126353Smlaier */ 30126353Smlaier#ifdef HAVE___ATTRIBUTE__ 31126353Smlaier/* 32126353Smlaier * We have __attribute__; we assume that means we have __attribute__((packed)). 33126353Smlaier * Declare packed structures containing a u_int16_t and a u_int32_t, 34126353Smlaier * cast the pointer to point to one of those, and fetch through it; 35126353Smlaier * the GCC manual doesn't appear to explicitly say that 36126353Smlaier * __attribute__((packed)) causes the compiler to generate unaligned-safe 37126353Smlaier * code, but it apppears to do so. 38126353Smlaier * 39126353Smlaier * We do this in case the compiler can generate, for this instruction set, 40126353Smlaier * better code to do an unaligned load and pass stuff to "ntohs()" or 41126353Smlaier * "ntohl()" than the code to fetch the bytes one at a time and 42126353Smlaier * assemble them. (That might not be the case on a little-endian platform, 43126353Smlaier * where "ntohs()" and "ntohl()" might not be done inline.) 44126353Smlaier */ 45126353Smlaiertypedef struct { 46126353Smlaier u_int16_t val; 47126353Smlaier} __attribute__((packed)) unaligned_u_int16_t; 48126353Smlaier 49126353Smlaiertypedef struct { 50126353Smlaier u_int32_t val; 51126353Smlaier} __attribute__((packed)) unaligned_u_int32_t; 52126353Smlaier 53126353Smlaier#define EXTRACT_16BITS(p) \ 54126353Smlaier ((u_int16_t)ntohs(((const unaligned_u_int16_t *)(p))->val)) 55126353Smlaier#define EXTRACT_32BITS(p) \ 56126353Smlaier ((u_int32_t)ntohl(((const unaligned_u_int32_t *)(p))->val)) 57126353Smlaier#else /* HAVE___ATTRIBUTE__ */ 58126353Smlaier/* 59126353Smlaier * We don't have __attribute__, so do unaligned loads of big-endian 60126353Smlaier * quantities the hard way - fetch the bytes one at a time and 61126353Smlaier * assemble them. 62126353Smlaier */ 63126353Smlaier#define EXTRACT_16BITS(p) \ 64126353Smlaier ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 0) << 8 | \ 65126353Smlaier (u_int16_t)*((const u_int8_t *)(p) + 1))) 66126353Smlaier#define EXTRACT_32BITS(p) \ 67126353Smlaier ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 24 | \ 68126353Smlaier (u_int32_t)*((const u_int8_t *)(p) + 1) << 16 | \ 69126353Smlaier (u_int32_t)*((const u_int8_t *)(p) + 2) << 8 | \ 70126353Smlaier (u_int32_t)*((const u_int8_t *)(p) + 3))) 71126353Smlaier#endif /* HAVE___ATTRIBUTE__ */ 72126353Smlaier#else /* LBL_ALIGN */ 73126353Smlaier/* 74126353Smlaier * The processor natively handles unaligned loads, so we can just 75126353Smlaier * cast the pointer and fetch through it. 76126353Smlaier */ 77126353Smlaier#define EXTRACT_16BITS(p) \ 78126353Smlaier ((u_int16_t)ntohs(*(const u_int16_t *)(p))) 79126353Smlaier#define EXTRACT_32BITS(p) \ 80126353Smlaier ((u_int32_t)ntohl(*(const u_int32_t *)(p))) 81126353Smlaier#endif /* LBL_ALIGN */ 82126353Smlaier 83126353Smlaier#define EXTRACT_24BITS(p) \ 84126353Smlaier ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 16 | \ 85126353Smlaier (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \ 86126353Smlaier (u_int32_t)*((const u_int8_t *)(p) + 2))) 87126353Smlaier 88126353Smlaier/* Little endian protocol host order macros */ 89126353Smlaier 90126353Smlaier#define EXTRACT_LE_8BITS(p) (*(p)) 91126353Smlaier#define EXTRACT_LE_16BITS(p) \ 92126353Smlaier ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 1) << 8 | \ 93126353Smlaier (u_int16_t)*((const u_int8_t *)(p) + 0))) 94126353Smlaier#define EXTRACT_LE_32BITS(p) \ 95126353Smlaier ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 3) << 24 | \ 96126353Smlaier (u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \ 97126353Smlaier (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \ 98126353Smlaier (u_int32_t)*((const u_int8_t *)(p) + 0))) 99126353Smlaier