| /* 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 |