227 lines
7.0 KiB
C
227 lines
7.0 KiB
C
/*
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* memcopy.h -- definitions for memory copy functions. Generic C version.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
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* Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* The code is derived from the GNU C Library.
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* Copyright (C) 1991, 1992, 1993, 1997, 2004 Free Software Foundation, Inc.
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*/
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#ifndef _LINUX_MEMCOPY_H_
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#define _LINUX_MEMCOPY_H_
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/*
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* The strategy of the memory functions is:
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*
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* 1. Copy bytes until the destination pointer is aligned.
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*
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* 2. Copy words in unrolled loops. If the source and destination
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* are not aligned in the same way, use word memory operations,
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* but shift and merge two read words before writing.
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*
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* 3. Copy the few remaining bytes.
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*
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* This is fast on processors that have at least 10 registers for
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* allocation by GCC, and that can access memory at reg+const in one
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* instruction.
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*/
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#include <linux/types.h>
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#include <linux/compiler.h>
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#include <asm/byteorder.h>
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/*
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* The macros defined in this file are:
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*
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* BYTE_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy)
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*
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* BYTE_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy)
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*
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* WORD_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_remaining, nbytes_to_copy)
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*
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* WORD_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_remaining, nbytes_to_copy)
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*
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* MERGE(old_word, sh_1, new_word, sh_2)
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*
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* MEM_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy)
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*
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* MEM_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy)
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*/
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#define OP_T_THRESHOLD 16
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/*
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* Type to use for aligned memory operations.
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* This should normally be the biggest type supported by a single load
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* and store.
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*/
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#define op_t unsigned long int
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#define OPSIZ (sizeof(op_t))
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/* Type to use for unaligned operations. */
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typedef unsigned char byte;
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#ifndef MERGE
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# ifdef __LITTLE_ENDIAN
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# define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2)))
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# elif defined(__BIG_ENDIAN)
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# define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2)))
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# else
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# error "Macro MERGE() hasn't defined!"
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# endif
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#endif
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/*
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* Copy exactly NBYTES bytes from SRC_BP to DST_BP,
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* without any assumptions about alignment of the pointers.
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*/
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#ifndef BYTE_COPY_FWD
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#define BYTE_COPY_FWD(dst_bp, src_bp, nbytes) \
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do { \
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size_t __nbytes = (nbytes); \
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while (__nbytes > 0) { \
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byte __x = ((byte *) src_bp)[0]; \
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src_bp += 1; \
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__nbytes -= 1; \
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((byte *) dst_bp)[0] = __x; \
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dst_bp += 1; \
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} \
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} while (0)
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#endif
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/*
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* Copy exactly NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR,
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* beginning at the bytes right before the pointers and continuing towards
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* smaller addresses. Don't assume anything about alignment of the
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* pointers.
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*/
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#ifndef BYTE_COPY_BWD
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#define BYTE_COPY_BWD(dst_ep, src_ep, nbytes) \
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do { \
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size_t __nbytes = (nbytes); \
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while (__nbytes > 0) { \
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byte __x; \
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src_ep -= 1; \
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__x = ((byte *) src_ep)[0]; \
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dst_ep -= 1; \
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__nbytes -= 1; \
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((byte *) dst_ep)[0] = __x; \
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} \
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} while (0)
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#endif
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/*
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* Copy *up to* NBYTES bytes from SRC_BP to DST_BP, with
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* the assumption that DST_BP is aligned on an OPSIZ multiple. If
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* not all bytes could be easily copied, store remaining number of bytes
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* in NBYTES_LEFT, otherwise store 0.
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*/
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extern void _wordcopy_fwd_aligned(long int, long int, size_t);
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extern void _wordcopy_fwd_dest_aligned(long int, long int, size_t);
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#ifndef WORD_COPY_FWD
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#define WORD_COPY_FWD(dst_bp, src_bp, nbytes_left, nbytes) \
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do { \
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if (src_bp % OPSIZ == 0) \
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_wordcopy_fwd_aligned (dst_bp, src_bp, (nbytes) / OPSIZ); \
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else \
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_wordcopy_fwd_dest_aligned (dst_bp, src_bp, (nbytes) / OPSIZ);\
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\
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src_bp += (nbytes) & -OPSIZ; \
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dst_bp += (nbytes) & -OPSIZ; \
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(nbytes_left) = (nbytes) % OPSIZ; \
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} while (0)
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#endif
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/*
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* Copy *up to* NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR,
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* beginning at the words (of type op_t) right before the pointers and
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* continuing towards smaller addresses. May take advantage of that
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* DST_END_PTR is aligned on an OPSIZ multiple. If not all bytes could be
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* easily copied, store remaining number of bytes in NBYTES_REMAINING,
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* otherwise store 0.
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*/
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extern void _wordcopy_bwd_aligned(long int, long int, size_t);
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extern void _wordcopy_bwd_dest_aligned(long int, long int, size_t);
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#ifndef WORD_COPY_BWD
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#define WORD_COPY_BWD(dst_ep, src_ep, nbytes_left, nbytes) \
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do { \
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if (src_ep % OPSIZ == 0) \
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_wordcopy_bwd_aligned (dst_ep, src_ep, (nbytes) / OPSIZ); \
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else \
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_wordcopy_bwd_dest_aligned (dst_ep, src_ep, (nbytes) / OPSIZ);\
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\
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src_ep -= (nbytes) & -OPSIZ; \
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dst_ep -= (nbytes) & -OPSIZ; \
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(nbytes_left) = (nbytes) % OPSIZ; \
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} while (0)
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#endif
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/* Copy memory from the beginning to the end */
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#ifndef MEM_COPY_FWD
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static __always_inline void mem_copy_fwd(unsigned long dstp,
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unsigned long srcp,
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size_t count)
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{
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/* If there not too few bytes to copy, use word copy. */
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if (count >= OP_T_THRESHOLD) {
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/* Copy just a few bytes to make dstp aligned. */
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count -= (-dstp) % OPSIZ;
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BYTE_COPY_FWD(dstp, srcp, (-dstp) % OPSIZ);
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/*
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* Copy from srcp to dstp taking advantage of the known
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* alignment of dstp. Number if bytes remaining is put in
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* the third argument.
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*/
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WORD_COPY_FWD(dstp, srcp, count, count);
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/* Fall out and copy the tail. */
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}
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/* There are just a few bytes to copy. Use byte memory operations. */
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BYTE_COPY_FWD(dstp, srcp, count);
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}
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#endif
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/* Copy memory from the end to the beginning. */
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#ifndef MEM_COPY_BWD
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static __always_inline void mem_copy_bwd(unsigned long dstp,
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unsigned long srcp,
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size_t count)
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{
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srcp += count;
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dstp += count;
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/* If there not too few bytes to copy, use word copy. */
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if (count >= OP_T_THRESHOLD) {
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/* Copy just a few bytes to make dstp aligned. */
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count -= dstp % OPSIZ;
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BYTE_COPY_BWD(dstp, srcp, dstp % OPSIZ);
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/*
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* Copy from srcp to dstp taking advantage of the known
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* alignment of dstp. Number if bytes remaining is put in
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* the third argument.
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*/
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WORD_COPY_BWD(dstp, srcp, count, count);
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/* Fall out and copy the tail. */
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}
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/* There are just a few bytes to copy. Use byte memory operations. */
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BYTE_COPY_BWD (dstp, srcp, count);
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}
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#endif
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#endif
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