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memcopy.h
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memcopy.h
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/*
* memcopy.h -- definitions for memory copy functions. Generic C version.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2.1 of the License, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
* Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*
* The code is derived from the GNU C Library.
* Copyright (C) 1991, 1992, 1993, 1997, 2004 Free Software Foundation, Inc.
*/
#ifndef _LINUX_MEMCOPY_H_
#define _LINUX_MEMCOPY_H_
/*
* The strategy of the memory functions is:
*
* 1. Copy bytes until the destination pointer is aligned.
*
* 2. Copy words in unrolled loops. If the source and destination
* are not aligned in the same way, use word memory operations,
* but shift and merge two read words before writing.
*
* 3. Copy the few remaining bytes.
*
* This is fast on processors that have at least 10 registers for
* allocation by GCC, and that can access memory at reg+const in one
* instruction.
*/
#include <linux/types.h>
#include <linux/compiler.h>
#include <asm/byteorder.h>
/*
* The macros defined in this file are:
*
* BYTE_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy)
*
* BYTE_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy)
*
* WORD_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_remaining, nbytes_to_copy)
*
* WORD_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_remaining, nbytes_to_copy)
*
* MERGE(old_word, sh_1, new_word, sh_2)
*
* MEM_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy)
*
* MEM_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy)
*/
#define OP_T_THRESHOLD 16
/*
* Type to use for aligned memory operations.
* This should normally be the biggest type supported by a single load
* and store.
*/
#define op_t unsigned long int
#define OPSIZ (sizeof(op_t))
/* Type to use for unaligned operations. */
typedef unsigned char byte;
#ifndef MERGE
# ifdef __LITTLE_ENDIAN
# define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2)))
# elif defined(__BIG_ENDIAN)
# define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2)))
# else
# error "Macro MERGE() hasn't defined!"
# endif
#endif
/*
* Copy exactly NBYTES bytes from SRC_BP to DST_BP,
* without any assumptions about alignment of the pointers.
*/
#ifndef BYTE_COPY_FWD
#define BYTE_COPY_FWD(dst_bp, src_bp, nbytes) \
do { \
size_t __nbytes = (nbytes); \
while (__nbytes > 0) { \
byte __x = ((byte *) src_bp)[0]; \
src_bp += 1; \
__nbytes -= 1; \
((byte *) dst_bp)[0] = __x; \
dst_bp += 1; \
} \
} while (0)
#endif
/*
* Copy exactly NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR,
* beginning at the bytes right before the pointers and continuing towards
* smaller addresses. Don't assume anything about alignment of the
* pointers.
*/
#ifndef BYTE_COPY_BWD
#define BYTE_COPY_BWD(dst_ep, src_ep, nbytes) \
do { \
size_t __nbytes = (nbytes); \
while (__nbytes > 0) { \
byte __x; \
src_ep -= 1; \
__x = ((byte *) src_ep)[0]; \
dst_ep -= 1; \
__nbytes -= 1; \
((byte *) dst_ep)[0] = __x; \
} \
} while (0)
#endif
/*
* Copy *up to* NBYTES bytes from SRC_BP to DST_BP, with
* the assumption that DST_BP is aligned on an OPSIZ multiple. If
* not all bytes could be easily copied, store remaining number of bytes
* in NBYTES_LEFT, otherwise store 0.
*/
extern void _wordcopy_fwd_aligned(long int, long int, size_t);
extern void _wordcopy_fwd_dest_aligned(long int, long int, size_t);
#ifndef WORD_COPY_FWD
#define WORD_COPY_FWD(dst_bp, src_bp, nbytes_left, nbytes) \
do { \
if (src_bp % OPSIZ == 0) \
_wordcopy_fwd_aligned (dst_bp, src_bp, (nbytes) / OPSIZ); \
else \
_wordcopy_fwd_dest_aligned (dst_bp, src_bp, (nbytes) / OPSIZ);\
\
src_bp += (nbytes) & -OPSIZ; \
dst_bp += (nbytes) & -OPSIZ; \
(nbytes_left) = (nbytes) % OPSIZ; \
} while (0)
#endif
/*
* Copy *up to* NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR,
* beginning at the words (of type op_t) right before the pointers and
* continuing towards smaller addresses. May take advantage of that
* DST_END_PTR is aligned on an OPSIZ multiple. If not all bytes could be
* easily copied, store remaining number of bytes in NBYTES_REMAINING,
* otherwise store 0.
*/
extern void _wordcopy_bwd_aligned(long int, long int, size_t);
extern void _wordcopy_bwd_dest_aligned(long int, long int, size_t);
#ifndef WORD_COPY_BWD
#define WORD_COPY_BWD(dst_ep, src_ep, nbytes_left, nbytes) \
do { \
if (src_ep % OPSIZ == 0) \
_wordcopy_bwd_aligned (dst_ep, src_ep, (nbytes) / OPSIZ); \
else \
_wordcopy_bwd_dest_aligned (dst_ep, src_ep, (nbytes) / OPSIZ);\
\
src_ep -= (nbytes) & -OPSIZ; \
dst_ep -= (nbytes) & -OPSIZ; \
(nbytes_left) = (nbytes) % OPSIZ; \
} while (0)
#endif
/* Copy memory from the beginning to the end */
#ifndef MEM_COPY_FWD
static __always_inline void mem_copy_fwd(unsigned long dstp,
unsigned long srcp,
size_t count)
{
/* If there not too few bytes to copy, use word copy. */
if (count >= OP_T_THRESHOLD) {
/* Copy just a few bytes to make dstp aligned. */
count -= (-dstp) % OPSIZ;
BYTE_COPY_FWD(dstp, srcp, (-dstp) % OPSIZ);
/*
* Copy from srcp to dstp taking advantage of the known
* alignment of dstp. Number if bytes remaining is put in
* the third argument.
*/
WORD_COPY_FWD(dstp, srcp, count, count);
/* Fall out and copy the tail. */
}
/* There are just a few bytes to copy. Use byte memory operations. */
BYTE_COPY_FWD(dstp, srcp, count);
}
#endif
/* Copy memory from the end to the beginning. */
#ifndef MEM_COPY_BWD
static __always_inline void mem_copy_bwd(unsigned long dstp,
unsigned long srcp,
size_t count)
{
srcp += count;
dstp += count;
/* If there not too few bytes to copy, use word copy. */
if (count >= OP_T_THRESHOLD) {
/* Copy just a few bytes to make dstp aligned. */
count -= dstp % OPSIZ;
BYTE_COPY_BWD(dstp, srcp, dstp % OPSIZ);
/*
* Copy from srcp to dstp taking advantage of the known
* alignment of dstp. Number if bytes remaining is put in
* the third argument.
*/
WORD_COPY_BWD(dstp, srcp, count, count);
/* Fall out and copy the tail. */
}
/* There are just a few bytes to copy. Use byte memory operations. */
BYTE_COPY_BWD (dstp, srcp, count);
}
#endif
#endif