| /* |
| * 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) |
| */ |
| |
| /* |
| * Macros to extract possibly-unaligned big-endian integral values. |
| */ |
| #ifdef LBL_ALIGN |
| /* |
| * The processor doesn't natively handle unaligned loads. |
| */ |
| #if defined(__GNUC__) && defined(HAVE___ATTRIBUTE__) && \ |
| (defined(__alpha) || defined(__alpha__) || \ |
| defined(__mips) || defined(__mips__)) |
| |
| /* |
| * This is a GCC-compatible compiler and we have __attribute__, which |
| * we assume that mean we have __attribute__((packed)), and this is |
| * MIPS or Alpha, which has instructions that can help when doing |
| * unaligned loads. |
| * |
| * 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 code using those |
| * instructions to do an unaligned load and pass stuff to "ntohs()" or |
| * "ntohl()", which might be better than 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, such as DEC's MIPS machines and |
| * Alpha machines, where "ntohs()" and "ntohl()" might not be done |
| * inline.) |
| * |
| * We do this only for specific architectures because, for example, |
| * at least some versions of GCC, when compiling for 64-bit SPARC, |
| * generate code that assumes alignment if we do this. |
| * |
| * XXX - add other architectures and compilers as possible and |
| * appropriate. |
| * |
| * HP's C compiler, indicated by __HP_cc being defined, supports |
| * "#pragma unaligned N" in version A.05.50 and later, where "N" |
| * specifies a number of bytes at which the typedef on the next |
| * line is aligned, e.g. |
| * |
| * #pragma unalign 1 |
| * typedef u_int16_t unaligned_u_int16_t; |
| * |
| * to define unaligned_u_int16_t as a 16-bit unaligned data type. |
| * This could be presumably used, in sufficiently recent versions of |
| * the compiler, with macros similar to those below. This would be |
| * useful only if that compiler could generate better code for PA-RISC |
| * or Itanium than would be generated by a bunch of shifts-and-ORs. |
| * |
| * DEC C, indicated by __DECC being defined, has, at least on Alpha, |
| * an __unaligned qualifier that can be applied to pointers to get the |
| * compiler to generate code that does unaligned loads and stores when |
| * dereferencing the pointer in question. |
| * |
| * XXX - what if the native C compiler doesn't support |
| * __attribute__((packed))? How can we get it to generate unaligned |
| * accesses for *specific* items? |
| */ |
| 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 to do it a byte at a time */ |
| /* |
| * This isn't a GCC-compatible compiler, we don't have __attribute__, |
| * or we do but we don't know of any better way with this instruction |
| * set to do unaligned loads, 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 /* must special-case unaligned accesses */ |
| #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))) |