218 lines
8.5 KiB
C
218 lines
8.5 KiB
C
/*
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* Copyright (c) 1992, 1993, 1994, 1995, 1996
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that: (1) source code distributions
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* retain the above copyright notice and this paragraph in its entirety, (2)
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* distributions including binary code include the above copyright notice and
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* this paragraph in its entirety in the documentation or other materials
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* provided with the distribution, and (3) all advertising materials mentioning
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* features or use of this software display the following acknowledgement:
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* ``This product includes software developed by the University of California,
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* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
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* the University nor the names of its contributors may be used to endorse
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* or promote products derived from this software without specific prior
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* written permission.
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*/
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/*
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* Macros to extract possibly-unaligned big-endian integral values.
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*/
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#ifdef LBL_ALIGN
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/*
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* The processor doesn't natively handle unaligned loads.
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*/
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#if defined(__GNUC__) && defined(HAVE___ATTRIBUTE__) && \
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(defined(__alpha) || defined(__alpha__) || \
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defined(__mips) || defined(__mips__))
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/*
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* This is a GCC-compatible compiler and we have __attribute__, which
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* we assume that mean we have __attribute__((packed)), and this is
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* MIPS or Alpha, which has instructions that can help when doing
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* unaligned loads.
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*
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* Declare packed structures containing a uint16_t and a uint32_t,
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* cast the pointer to point to one of those, and fetch through it;
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* the GCC manual doesn't appear to explicitly say that
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* __attribute__((packed)) causes the compiler to generate unaligned-safe
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* code, but it apppears to do so.
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*
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* We do this in case the compiler can generate code using those
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* instructions to do an unaligned load and pass stuff to "ntohs()" or
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* "ntohl()", which might be better than than the code to fetch the
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* bytes one at a time and assemble them. (That might not be the
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* case on a little-endian platform, such as DEC's MIPS machines and
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* Alpha machines, where "ntohs()" and "ntohl()" might not be done
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* inline.)
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*
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* We do this only for specific architectures because, for example,
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* at least some versions of GCC, when compiling for 64-bit SPARC,
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* generate code that assumes alignment if we do this.
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*
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* XXX - add other architectures and compilers as possible and
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* appropriate.
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*
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* HP's C compiler, indicated by __HP_cc being defined, supports
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* "#pragma unaligned N" in version A.05.50 and later, where "N"
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* specifies a number of bytes at which the typedef on the next
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* line is aligned, e.g.
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*
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* #pragma unalign 1
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* typedef uint16_t unaligned_uint16_t;
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*
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* to define unaligned_uint16_t as a 16-bit unaligned data type.
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* This could be presumably used, in sufficiently recent versions of
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* the compiler, with macros similar to those below. This would be
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* useful only if that compiler could generate better code for PA-RISC
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* or Itanium than would be generated by a bunch of shifts-and-ORs.
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*
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* DEC C, indicated by __DECC being defined, has, at least on Alpha,
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* an __unaligned qualifier that can be applied to pointers to get the
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* compiler to generate code that does unaligned loads and stores when
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* dereferencing the pointer in question.
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*
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* XXX - what if the native C compiler doesn't support
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* __attribute__((packed))? How can we get it to generate unaligned
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* accesses for *specific* items?
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*/
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typedef struct {
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uint16_t val;
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} __attribute__((packed)) unaligned_uint16_t;
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typedef struct {
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uint32_t val;
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} __attribute__((packed)) unaligned_uint32_t;
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static inline uint16_t
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EXTRACT_16BITS(const void *p)
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{
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return ((uint16_t)ntohs(((const unaligned_uint16_t *)(p))->val));
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}
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static inline uint32_t
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EXTRACT_32BITS(const void *p)
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{
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return ((uint32_t)ntohl(((const unaligned_uint32_t *)(p))->val));
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}
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static inline uint64_t
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EXTRACT_64BITS(const void *p)
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{
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return ((uint64_t)(((uint64_t)ntohl(((const unaligned_uint32_t *)(p) + 0)->val)) << 32 | \
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((uint64_t)ntohl(((const unaligned_uint32_t *)(p) + 1)->val)) << 0));
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}
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#else /* have to do it a byte at a time */
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/*
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* This isn't a GCC-compatible compiler, we don't have __attribute__,
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* or we do but we don't know of any better way with this instruction
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* set to do unaligned loads, so do unaligned loads of big-endian
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* quantities the hard way - fetch the bytes one at a time and
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* assemble them.
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*/
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#define EXTRACT_16BITS(p) \
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((uint16_t)((uint16_t)*((const uint8_t *)(p) + 0) << 8 | \
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(uint16_t)*((const uint8_t *)(p) + 1)))
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#define EXTRACT_32BITS(p) \
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((uint32_t)((uint32_t)*((const uint8_t *)(p) + 0) << 24 | \
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(uint32_t)*((const uint8_t *)(p) + 1) << 16 | \
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(uint32_t)*((const uint8_t *)(p) + 2) << 8 | \
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(uint32_t)*((const uint8_t *)(p) + 3)))
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#define EXTRACT_64BITS(p) \
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((uint64_t)((uint64_t)*((const uint8_t *)(p) + 0) << 56 | \
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(uint64_t)*((const uint8_t *)(p) + 1) << 48 | \
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(uint64_t)*((const uint8_t *)(p) + 2) << 40 | \
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(uint64_t)*((const uint8_t *)(p) + 3) << 32 | \
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(uint64_t)*((const uint8_t *)(p) + 4) << 24 | \
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(uint64_t)*((const uint8_t *)(p) + 5) << 16 | \
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(uint64_t)*((const uint8_t *)(p) + 6) << 8 | \
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(uint64_t)*((const uint8_t *)(p) + 7)))
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#endif /* must special-case unaligned accesses */
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#else /* LBL_ALIGN */
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/*
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* The processor natively handles unaligned loads, so we can just
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* cast the pointer and fetch through it.
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*/
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static inline uint16_t
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EXTRACT_16BITS(const void *p)
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{
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return ((uint16_t)ntohs(*(const uint16_t *)(p)));
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}
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static inline uint32_t
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EXTRACT_32BITS(const void *p)
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{
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return ((uint32_t)ntohl(*(const uint32_t *)(p)));
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}
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static inline uint64_t
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EXTRACT_64BITS(const void *p)
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{
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return ((uint64_t)(((uint64_t)ntohl(*((const uint32_t *)(p) + 0))) << 32 | \
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((uint64_t)ntohl(*((const uint32_t *)(p) + 1))) << 0));
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}
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#endif /* LBL_ALIGN */
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#define EXTRACT_24BITS(p) \
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((uint32_t)((uint32_t)*((const uint8_t *)(p) + 0) << 16 | \
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(uint32_t)*((const uint8_t *)(p) + 1) << 8 | \
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(uint32_t)*((const uint8_t *)(p) + 2)))
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#define EXTRACT_40BITS(p) \
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((uint64_t)((uint64_t)*((const uint8_t *)(p) + 0) << 32 | \
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(uint64_t)*((const uint8_t *)(p) + 1) << 24 | \
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(uint64_t)*((const uint8_t *)(p) + 2) << 16 | \
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(uint64_t)*((const uint8_t *)(p) + 3) << 8 | \
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(uint64_t)*((const uint8_t *)(p) + 4)))
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#define EXTRACT_48BITS(p) \
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((uint64_t)((uint64_t)*((const uint8_t *)(p) + 0) << 40 | \
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(uint64_t)*((const uint8_t *)(p) + 1) << 32 | \
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(uint64_t)*((const uint8_t *)(p) + 2) << 24 | \
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(uint64_t)*((const uint8_t *)(p) + 3) << 16 | \
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(uint64_t)*((const uint8_t *)(p) + 4) << 8 | \
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(uint64_t)*((const uint8_t *)(p) + 5)))
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#define EXTRACT_56BITS(p) \
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((uint64_t)((uint64_t)*((const uint8_t *)(p) + 0) << 48 | \
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(uint64_t)*((const uint8_t *)(p) + 1) << 40 | \
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(uint64_t)*((const uint8_t *)(p) + 2) << 32 | \
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(uint64_t)*((const uint8_t *)(p) + 3) << 24 | \
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(uint64_t)*((const uint8_t *)(p) + 4) << 16 | \
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(uint64_t)*((const uint8_t *)(p) + 5) << 8 | \
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(uint64_t)*((const uint8_t *)(p) + 6)))
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/*
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* Macros to extract possibly-unaligned little-endian integral values.
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* XXX - do loads on little-endian machines that support unaligned loads?
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*/
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#define EXTRACT_LE_8BITS(p) (*(p))
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#define EXTRACT_LE_16BITS(p) \
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((uint16_t)((uint16_t)*((const uint8_t *)(p) + 1) << 8 | \
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(uint16_t)*((const uint8_t *)(p) + 0)))
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#define EXTRACT_LE_32BITS(p) \
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((uint32_t)((uint32_t)*((const uint8_t *)(p) + 3) << 24 | \
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(uint32_t)*((const uint8_t *)(p) + 2) << 16 | \
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(uint32_t)*((const uint8_t *)(p) + 1) << 8 | \
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(uint32_t)*((const uint8_t *)(p) + 0)))
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#define EXTRACT_LE_24BITS(p) \
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((uint32_t)((uint32_t)*((const uint8_t *)(p) + 2) << 16 | \
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(uint32_t)*((const uint8_t *)(p) + 1) << 8 | \
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(uint32_t)*((const uint8_t *)(p) + 0)))
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#define EXTRACT_LE_64BITS(p) \
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((uint64_t)((uint64_t)*((const uint8_t *)(p) + 7) << 56 | \
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(uint64_t)*((const uint8_t *)(p) + 6) << 48 | \
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(uint64_t)*((const uint8_t *)(p) + 5) << 40 | \
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(uint64_t)*((const uint8_t *)(p) + 4) << 32 | \
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(uint64_t)*((const uint8_t *)(p) + 3) << 24 | \
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(uint64_t)*((const uint8_t *)(p) + 2) << 16 | \
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(uint64_t)*((const uint8_t *)(p) + 1) << 8 | \
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(uint64_t)*((const uint8_t *)(p) + 0)))
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