X-Git-Url: https://git.tcpdump.org/tcpdump/blobdiff_plain/edb0e92cdcaf06168a38e632847b8fd2c0a62a2d..refs/pull/433/head:/extract.h?ds=sidebyside diff --git a/extract.h b/extract.h index 5e72d2e5..cb62ebdd 100644 --- a/extract.h +++ b/extract.h @@ -17,41 +17,201 @@ * 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. + */ + +/* + * 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. * - * @(#) $Header: /tcpdump/master/tcpdump/extract.h,v 1.18 2002-09-05 00:00:09 guy Exp $ (LBL) + * Declare packed structures containing a uint16_t and a uint32_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 uint16_t unaligned_uint16_t; + * + * to define unaligned_uint16_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 { + uint16_t val; +} __attribute__((packed)) unaligned_uint16_t; -/* Network to host order macros */ +typedef struct { + uint32_t val; +} __attribute__((packed)) unaligned_uint32_t; -#ifdef LBL_ALIGN -#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))) -#else +static inline uint16_t +EXTRACT_16BITS(const void *p) +{ + return ((uint16_t)ntohs(((const unaligned_uint16_t *)(p))->val)); +} + +static inline uint32_t +EXTRACT_32BITS(const void *p) +{ + return ((uint32_t)ntohl(((const unaligned_uint32_t *)(p))->val)); +} + +static inline uint64_t +EXTRACT_64BITS(const void *p) +{ + return ((uint64_t)(((uint64_t)ntohl(((const unaligned_uint32_t *)(p) + 0)->val)) << 32 | \ + ((uint64_t)ntohl(((const unaligned_uint32_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)ntohs(*(const u_int16_t *)(p))) + ((uint16_t)(((uint16_t)(*((const uint8_t *)(p) + 0)) << 8) | \ + ((uint16_t)(*((const uint8_t *)(p) + 1)) << 0))) #define EXTRACT_32BITS(p) \ - ((u_int32_t)ntohl(*(const u_int32_t *)(p))) -#endif + ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 0)) << 24) | \ + ((uint32_t)(*((const uint8_t *)(p) + 1)) << 16) | \ + ((uint32_t)(*((const uint8_t *)(p) + 2)) << 8) | \ + ((uint32_t)(*((const uint8_t *)(p) + 3)) << 0))) +#define EXTRACT_64BITS(p) \ + ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 56) | \ + ((uint64_t)(*((const uint8_t *)(p) + 1)) << 48) | \ + ((uint64_t)(*((const uint8_t *)(p) + 2)) << 40) | \ + ((uint64_t)(*((const uint8_t *)(p) + 3)) << 32) | \ + ((uint64_t)(*((const uint8_t *)(p) + 4)) << 24) | \ + ((uint64_t)(*((const uint8_t *)(p) + 5)) << 16) | \ + ((uint64_t)(*((const uint8_t *)(p) + 6)) << 8) | \ + ((uint64_t)(*((const uint8_t *)(p) + 7)) << 0))) +#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 uint16_t +EXTRACT_16BITS(const void *p) +{ + return ((uint16_t)ntohs(*(const uint16_t *)(p))); +} + +static inline uint32_t +EXTRACT_32BITS(const void *p) +{ + return ((uint32_t)ntohl(*(const uint32_t *)(p))); +} + +static inline uint64_t +EXTRACT_64BITS(const void *p) +{ + return ((uint64_t)(((uint64_t)ntohl(*((const uint32_t *)(p) + 0))) << 32 | \ + ((uint64_t)ntohl(*((const uint32_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))) + ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 0)) << 16) | \ + ((uint32_t)(*((const uint8_t *)(p) + 1)) << 8) | \ + ((uint32_t)(*((const uint8_t *)(p) + 2)) << 0))) -/* Little endian protocol host order macros */ +#define EXTRACT_40BITS(p) \ + ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 32) | \ + ((uint64_t)(*((const uint8_t *)(p) + 1)) << 24) | \ + ((uint64_t)(*((const uint8_t *)(p) + 2)) << 16) | \ + ((uint64_t)(*((const uint8_t *)(p) + 3)) << 8) | \ + ((uint64_t)(*((const uint8_t *)(p) + 4)) << 0))) +#define EXTRACT_48BITS(p) \ + ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 40) | \ + ((uint64_t)(*((const uint8_t *)(p) + 1)) << 32) | \ + ((uint64_t)(*((const uint8_t *)(p) + 2)) << 24) | \ + ((uint64_t)(*((const uint8_t *)(p) + 3)) << 16) | \ + ((uint64_t)(*((const uint8_t *)(p) + 4)) << 8) | \ + ((uint64_t)(*((const uint8_t *)(p) + 5)) << 0))) + +#define EXTRACT_56BITS(p) \ + ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 48) | \ + ((uint64_t)(*((const uint8_t *)(p) + 1)) << 40) | \ + ((uint64_t)(*((const uint8_t *)(p) + 2)) << 32) | \ + ((uint64_t)(*((const uint8_t *)(p) + 3)) << 24) | \ + ((uint64_t)(*((const uint8_t *)(p) + 4)) << 16) | \ + ((uint64_t)(*((const uint8_t *)(p) + 5)) << 8) | \ + ((uint64_t)(*((const uint8_t *)(p) + 6)) << 0))) + +/* + * 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))) + ((uint16_t)(((uint16_t)(*((const uint8_t *)(p) + 1)) << 8) | \ + ((uint16_t)(*((const uint8_t *)(p) + 0)) << 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))) + ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 3)) << 24) | \ + ((uint32_t)(*((const uint8_t *)(p) + 2)) << 16) | \ + ((uint32_t)(*((const uint8_t *)(p) + 1)) << 8) | \ + ((uint32_t)(*((const uint8_t *)(p) + 0)) << 0))) +#define EXTRACT_LE_24BITS(p) \ + ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 2)) << 16) | \ + ((uint32_t)(*((const uint8_t *)(p) + 1)) << 8) | \ + ((uint32_t)(*((const uint8_t *)(p) + 0)) << 0))) +#define EXTRACT_LE_64BITS(p) \ + ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 7)) << 56) | \ + ((uint64_t)(*((const uint8_t *)(p) + 6)) << 48) | \ + ((uint64_t)(*((const uint8_t *)(p) + 5)) << 40) | \ + ((uint64_t)(*((const uint8_t *)(p) + 4)) << 32) | \ + ((uint64_t)(*((const uint8_t *)(p) + 3)) << 24) | \ + ((uint64_t)(*((const uint8_t *)(p) + 2)) << 16) | \ + ((uint64_t)(*((const uint8_t *)(p) + 1)) << 8) | \ + ((uint64_t)(*((const uint8_t *)(p) + 0)) << 0)))