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Diffstat (limited to 'libc/string/generic/memcopy.h')
| -rw-r--r-- | libc/string/generic/memcopy.h | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/libc/string/generic/memcopy.h b/libc/string/generic/memcopy.h new file mode 100644 index 000000000..df1ba9a97 --- /dev/null +++ b/libc/string/generic/memcopy.h @@ -0,0 +1,150 @@ +/* memcopy.h -- definitions for memory copy functions. Generic C version. + Copyright (C) 1991, 1992, 1993, 1997 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Torbjorn Granlund (tege@sics.se). + + 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. */ + +/* The strategy of the memory functions is: + + 1. Copy bytes until the destination pointer is aligned. + + 2. Copy words in unrolled loops. If the source and destination + are not aligned in the same way, use word memory operations, + but shift and merge two read words before writing. + + 3. Copy the few remaining bytes. + + This is fast on processors that have at least 10 registers for + allocation by GCC, and that can access memory at reg+const in one + instruction. + + I made an "exhaustive" test of this memmove when I wrote it, + exhaustive in the sense that I tried all alignment and length + combinations, with and without overlap. */ + +#include <sys/cdefs.h> +#include <endian.h> + +/* The macros defined in this file are: + + BYTE_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy) + + BYTE_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy) + + WORD_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_remaining, nbytes_to_copy) + + WORD_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_remaining, nbytes_to_copy) + + MERGE(old_word, sh_1, new_word, sh_2) + [I fail to understand. I feel stupid. --roland] +*/ + +/* Type to use for aligned memory operations. + This should normally be the biggest type supported by a single load + and store. */ +#define op_t unsigned long int +#define OPSIZ (sizeof(op_t)) + +/* Type to use for unaligned operations. */ +typedef unsigned char byte; + +/* Optimal type for storing bytes in registers. */ +#define reg_char char + +#if __BYTE_ORDER == __LITTLE_ENDIAN +#define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2))) +#endif +#if __BYTE_ORDER == __BIG_ENDIAN +#define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2))) +#endif + +/* Copy exactly NBYTES bytes from SRC_BP to DST_BP, + without any assumptions about alignment of the pointers. */ +#define BYTE_COPY_FWD(dst_bp, src_bp, nbytes) \ + do \ + { \ + size_t __nbytes = (nbytes); \ + while (__nbytes > 0) \ + { \ + byte __x = ((byte *) src_bp)[0]; \ + src_bp += 1; \ + __nbytes -= 1; \ + ((byte *) dst_bp)[0] = __x; \ + dst_bp += 1; \ + } \ + } while (0) + +/* Copy exactly NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR, + beginning at the bytes right before the pointers and continuing towards + smaller addresses. Don't assume anything about alignment of the + pointers. */ +#define BYTE_COPY_BWD(dst_ep, src_ep, nbytes) \ + do \ + { \ + size_t __nbytes = (nbytes); \ + while (__nbytes > 0) \ + { \ + byte __x; \ + src_ep -= 1; \ + __x = ((byte *) src_ep)[0]; \ + dst_ep -= 1; \ + __nbytes -= 1; \ + ((byte *) dst_ep)[0] = __x; \ + } \ + } while (0) + +/* Copy *up to* NBYTES bytes from SRC_BP to DST_BP, with + the assumption that DST_BP is aligned on an OPSIZ multiple. If + not all bytes could be easily copied, store remaining number of bytes + in NBYTES_LEFT, otherwise store 0. */ +/* extern void _wordcopy_fwd_aligned __P ((long int, long int, size_t)); */ +/* extern void _wordcopy_fwd_dest_aligned __P ((long int, long int, size_t)); */ +#define WORD_COPY_FWD(dst_bp, src_bp, nbytes_left, nbytes) \ + do \ + { \ + if (src_bp % OPSIZ == 0) \ + _wordcopy_fwd_aligned (dst_bp, src_bp, (nbytes) / OPSIZ); \ + else \ + _wordcopy_fwd_dest_aligned (dst_bp, src_bp, (nbytes) / OPSIZ); \ + src_bp += (nbytes) & -OPSIZ; \ + dst_bp += (nbytes) & -OPSIZ; \ + (nbytes_left) = (nbytes) % OPSIZ; \ + } while (0) + +/* Copy *up to* NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR, + beginning at the words (of type op_t) right before the pointers and + continuing towards smaller addresses. May take advantage of that + DST_END_PTR is aligned on an OPSIZ multiple. If not all bytes could be + easily copied, store remaining number of bytes in NBYTES_REMAINING, + otherwise store 0. */ +/* extern void _wordcopy_bwd_aligned __P ((long int, long int, size_t)); */ +/* extern void _wordcopy_bwd_dest_aligned __P ((long int, long int, size_t)); */ +#define WORD_COPY_BWD(dst_ep, src_ep, nbytes_left, nbytes) \ + do \ + { \ + if (src_ep % OPSIZ == 0) \ + _wordcopy_bwd_aligned (dst_ep, src_ep, (nbytes) / OPSIZ); \ + else \ + _wordcopy_bwd_dest_aligned (dst_ep, src_ep, (nbytes) / OPSIZ); \ + src_ep -= (nbytes) & -OPSIZ; \ + dst_ep -= (nbytes) & -OPSIZ; \ + (nbytes_left) = (nbytes) % OPSIZ; \ + } while (0) + + +/* Threshold value for when to enter the unrolled loops. */ +#define OP_T_THRES 16 |