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113 lines
4.0 KiB
C
113 lines
4.0 KiB
C
/* memcopy.h -- definitions for memory copy functions. Generic C version.
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Copyright (C) 1991, 1992, 1993, 1997, 2004, 2006 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Torbjorn Granlund (tege@sics.se).
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library 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
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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/* The strategy of the memory functions is:
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1. Copy bytes until the destination pointer is aligned.
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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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3. Copy the few remaining bytes.
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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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I made an "exhaustive" test of this memmove when I wrote it,
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exhaustive in the sense that I tried all alignment and length
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combinations, with and without overlap. */
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#include <sysdeps/generic/memcopy.h>
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/* The macros defined in this file are:
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BYTE_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy)
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BYTE_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy)
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WORD_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_remaining, nbytes_to_copy)
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WORD_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_remaining, nbytes_to_copy)
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MERGE(old_word, sh_1, new_word, sh_2)
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[I fail to understand. I feel stupid. --roland]
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*/
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/* Threshold value for when to enter the unrolled loops. */
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#undef OP_T_THRES
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#define OP_T_THRES 16
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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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#undef 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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{ \
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size_t __nbytes = (nbytes); \
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if (__nbytes & 1) \
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{ \
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((byte *) dst_bp)[0] = ((byte *) src_bp)[0]; \
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src_bp += 1; \
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dst_bp += 1; \
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__nbytes -= 1; \
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} \
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while (__nbytes > 0) \
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{ \
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byte __x = ((byte *) src_bp)[0]; \
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byte __y = ((byte *) src_bp)[1]; \
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src_bp += 2; \
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__nbytes -= 2; \
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((byte *) dst_bp)[0] = __x; \
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((byte *) dst_bp)[1] = __y; \
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dst_bp += 2; \
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} \
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} while (0)
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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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#undef 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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{ \
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size_t __nbytes = (nbytes); \
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if (__nbytes & 1) \
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{ \
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src_ep -= 1; \
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dst_ep -= 1; \
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((byte *) dst_ep)[0] = ((byte *) src_ep)[0]; \
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__nbytes -= 1; \
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} \
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while (__nbytes > 0) \
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{ \
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byte __x, __y; \
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src_ep -= 2; \
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__y = ((byte *) src_ep)[1]; \
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__x = ((byte *) src_ep)[0]; \
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dst_ep -= 2; \
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__nbytes -= 2; \
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((byte *) dst_ep)[1] = __y; \
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((byte *) dst_ep)[0] = __x; \
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} \
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} while (0)
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