| 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 | * @(#) $Header: /tcpdump/master/tcpdump/extract.h,v 1.24 2005/01/15 02:06:50 guy Exp $ (LBL) |
| 22 | */ |
| 23 | |
| 24 | /* |
| 25 | * Macros to extract possibly-unaligned big-endian integral values. |
| 26 | */ |
| 27 | #ifdef LBL_ALIGN |
| 28 | /* |
| 29 | * The processor doesn't natively handle unaligned loads. |
| 30 | */ |
| 31 | #ifdef HAVE___ATTRIBUTE__ |
| 32 | /* |
| 33 | * We have __attribute__; we assume that means we have __attribute__((packed)). |
| 34 | * Declare packed structures containing a u_int16_t and a u_int32_t, |
| 35 | * cast the pointer to point to one of those, and fetch through it; |
| 36 | * the GCC manual doesn't appear to explicitly say that |
| 37 | * __attribute__((packed)) causes the compiler to generate unaligned-safe |
| 38 | * code, but it apppears to do so. |
| 39 | * |
| 40 | * We do this in case the compiler can generate, for this instruction set, |
| 41 | * better code to do an unaligned load and pass stuff to "ntohs()" or |
| 42 | * "ntohl()" than the code to fetch the bytes one at a time and |
| 43 | * assemble them. (That might not be the case on a little-endian platform, |
| 44 | * where "ntohs()" and "ntohl()" might not be done inline.) |
| 45 | */ |
| 46 | typedef struct { |
| 47 | u_int16_t val; |
| 48 | } __attribute__((packed)) unaligned_u_int16_t; |
| 49 | |
| 50 | typedef struct { |
| 51 | u_int32_t val; |
| 52 | } __attribute__((packed)) unaligned_u_int32_t; |
| 53 | |
| 54 | #define EXTRACT_16BITS(p) \ |
| 55 | ((u_int16_t)ntohs(((const unaligned_u_int16_t *)(p))->val)) |
| 56 | #define EXTRACT_32BITS(p) \ |
| 57 | ((u_int32_t)ntohl(((const unaligned_u_int32_t *)(p))->val)) |
| 58 | #define EXTRACT_64BITS(p) \ |
| 59 | ((u_int64_t)(((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 0)->val)) << 32 | \ |
| 60 | ((u_int64_t)ntohl(((const unaligned_u_int32_t *)(p) + 1)->val)) << 0)) |
| 61 | |
| 62 | #else /* HAVE___ATTRIBUTE__ */ |
| 63 | /* |
| 64 | * We don't have __attribute__, so do unaligned loads of big-endian |
| 65 | * quantities the hard way - fetch the bytes one at a time and |
| 66 | * assemble them. |
| 67 | */ |
| 68 | #define EXTRACT_16BITS(p) \ |
| 69 | ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 0) << 8 | \ |
| 70 | (u_int16_t)*((const u_int8_t *)(p) + 1))) |
| 71 | #define EXTRACT_32BITS(p) \ |
| 72 | ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 24 | \ |
| 73 | (u_int32_t)*((const u_int8_t *)(p) + 1) << 16 | \ |
| 74 | (u_int32_t)*((const u_int8_t *)(p) + 2) << 8 | \ |
| 75 | (u_int32_t)*((const u_int8_t *)(p) + 3))) |
| 76 | #define EXTRACT_64BITS(p) \ |
| 77 | ((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 0) << 56 | \ |
| 78 | (u_int64_t)*((const u_int8_t *)(p) + 1) << 48 | \ |
| 79 | (u_int64_t)*((const u_int8_t *)(p) + 2) << 40 | \ |
| 80 | (u_int64_t)*((const u_int8_t *)(p) + 3) << 32 | \ |
| 81 | (u_int64_t)*((const u_int8_t *)(p) + 4) << 24 | \ |
| 82 | (u_int64_t)*((const u_int8_t *)(p) + 5) << 16 | \ |
| 83 | (u_int64_t)*((const u_int8_t *)(p) + 6) << 8 | \ |
| 84 | (u_int64_t)*((const u_int8_t *)(p) + 7))) |
| 85 | #endif /* HAVE___ATTRIBUTE__ */ |
| 86 | #else /* LBL_ALIGN */ |
| 87 | /* |
| 88 | * The processor natively handles unaligned loads, so we can just |
| 89 | * cast the pointer and fetch through it. |
| 90 | */ |
| 91 | #define EXTRACT_16BITS(p) \ |
| 92 | ((u_int16_t)ntohs(*(const u_int16_t *)(p))) |
| 93 | #define EXTRACT_32BITS(p) \ |
| 94 | ((u_int32_t)ntohl(*(const u_int32_t *)(p))) |
| 95 | #define EXTRACT_64BITS(p) \ |
| 96 | ((u_int64_t)(((u_int64_t)ntohl(*((const u_int32_t *)(p) + 0))) << 32 | \ |
| 97 | ((u_int64_t)ntohl(*((const u_int32_t *)(p) + 1))) << 0)) |
| 98 | #endif /* LBL_ALIGN */ |
| 99 | |
| 100 | #define EXTRACT_24BITS(p) \ |
| 101 | ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 0) << 16 | \ |
| 102 | (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \ |
| 103 | (u_int32_t)*((const u_int8_t *)(p) + 2))) |
| 104 | |
| 105 | /* |
| 106 | * Macros to extract possibly-unaligned little-endian integral values. |
| 107 | * XXX - do loads on little-endian machines that support unaligned loads? |
| 108 | */ |
| 109 | #define EXTRACT_LE_8BITS(p) (*(p)) |
| 110 | #define EXTRACT_LE_16BITS(p) \ |
| 111 | ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 1) << 8 | \ |
| 112 | (u_int16_t)*((const u_int8_t *)(p) + 0))) |
| 113 | #define EXTRACT_LE_32BITS(p) \ |
| 114 | ((u_int32_t)((u_int32_t)*((const u_int8_t *)(p) + 3) << 24 | \ |
| 115 | (u_int32_t)*((const u_int8_t *)(p) + 2) << 16 | \ |
| 116 | (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \ |
| 117 | (u_int32_t)*((const u_int8_t *)(p) + 0))) |
| 118 | #define EXTRACT_LE_64BITS(p) \ |
| 119 | ((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 7) << 56 | \ |
| 120 | (u_int64_t)*((const u_int8_t *)(p) + 6) << 48 | \ |
| 121 | (u_int64_t)*((const u_int8_t *)(p) + 5) << 40 | \ |
| 122 | (u_int64_t)*((const u_int8_t *)(p) + 4) << 32 | \ |
| 123 | (u_int64_t)*((const u_int8_t *)(p) + 3) << 24 | \ |
| 124 | (u_int64_t)*((const u_int8_t *)(p) + 2) << 16 | \ |
| 125 | (u_int64_t)*((const u_int8_t *)(p) + 1) << 8 | \ |
| 126 | (u_int64_t)*((const u_int8_t *)(p) + 0))) |