mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-17 18:40:14 +00:00
76 lines
2.7 KiB
C
76 lines
2.7 KiB
C
/* Macros for copying by pages; used in memcpy, memmove. Generic macros.
|
|
Copyright (C) 1995 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Library General Public License as
|
|
published by the Free Software Foundation; either version 2 of the
|
|
License, or (at your option) any later version.
|
|
|
|
The GNU C Library 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
|
|
Library General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Library General Public
|
|
License along with the GNU C Library; see the file COPYING.LIB. If
|
|
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
|
|
Cambridge, MA 02139, USA. */
|
|
|
|
/* This file defines the macro:
|
|
|
|
PAGE_COPY_FWD_MAYBE (dstp, srcp, nbytes_left, nbytes)
|
|
|
|
which is invoked like WORD_COPY_FWD et al. The pointers should be at
|
|
least word aligned. This will check if virtual copying by pages can and
|
|
should be done and do it if so.
|
|
|
|
System-specific pagecopy.h files should define these macros and then
|
|
#include this file:
|
|
|
|
PAGE_COPY_THRESHOLD
|
|
-- Minimum size for which virtual copying by pages is worthwhile.
|
|
|
|
PAGE_SIZE
|
|
-- Size of a page.
|
|
|
|
PAGE_COPY_FWD (dstp, srcp, nbytes_left, nbytes)
|
|
-- Macro to perform the virtual copy operation.
|
|
The pointers will be aligned to PAGE_SIZE bytes.
|
|
*/
|
|
|
|
|
|
#if PAGE_COPY_THRESHOLD
|
|
|
|
#include <assert.h>
|
|
|
|
#define PAGE_COPY_FWD_MAYBE(dstp, srcp, nbytes_left, nbytes) \
|
|
do \
|
|
{ \
|
|
if ((nbytes) >= PAGE_COPY_THRESHOLD && \
|
|
PAGE_OFFSET ((dstp) - (srcp)) == 0) \
|
|
{ \
|
|
/* The amount to copy is past the threshold for copying \
|
|
pages virtually with kernel VM operations, and the \
|
|
source and destination addresses have the same alignment. */ \
|
|
size_t nbytes_before = PAGE_OFFSET (-(dstp)); \
|
|
if (nbytes_before != 0) \
|
|
{ \
|
|
/* First copy the words before the first page boundary. */ \
|
|
WORD_COPY_FWD (dstp, srcp, nbytes_left, nbytes_before); \
|
|
assert (nbytes_left == 0); \
|
|
nbytes -= nbytes_before; \
|
|
} \
|
|
PAGE_COPY_FWD (dstp, srcp, nbytes_left, nbytes); \
|
|
} \
|
|
} while (0)
|
|
|
|
/* The page size is always a power of two, so we can avoid modulo division. */
|
|
#define PAGE_OFFSET(n) ((n) & (PAGE_SIZE - 1))
|
|
|
|
#else
|
|
|
|
#define PAGE_COPY_FWD_MAYBE(dstp, srcp, nbytes_left, nbytes) /* nada */
|
|
|
|
#endif
|