glibc/sysdeps/generic/pagecopy.h
Andreas Jaeger 41bdb6e20c Update to LGPL v2.1.
2001-07-06  Paul Eggert  <eggert@twinsun.com>

	* manual/argp.texi: Remove ignored LGPL copyright notice; it's
	not appropriate for documentation anyway.
	* manual/libc-texinfo.sh: "Library General Public License" ->
	"Lesser General Public License".

2001-07-06  Andreas Jaeger  <aj@suse.de>

	* All files under GPL/LGPL version 2: Place under LGPL version
	2.1.
2001-07-06 04:58:11 +00:00

76 lines
2.7 KiB
C

/* Macros for copying by pages; used in memcpy, memmove. Generic macros.
Copyright (C) 1995, 1997 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 Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 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