1/* memcopy.h -- definitions for memory copy functions. Generic C version. 2 Copyright (C) 1991, 1992, 1993, 1997, 2004 Free Software Foundation, Inc. 3 This file is part of the GNU C Library. 4 Contributed by Torbjorn Granlund (tege@sics.se). 5 6 The GNU C Library is free software; you can redistribute it and/or 7 modify it under the terms of the GNU Lesser General Public 8 License as published by the Free Software Foundation; either 9 version 2.1 of the License, or (at your option) any later version. 10 11 The GNU C Library is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 Lesser General Public License for more details. 15 16 You should have received a copy of the GNU Lesser General Public 17 License along with the GNU C Library; if not, write to the Free 18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 19 02111-1307 USA. */ 20 21/* The strategy of the memory functions is: 22 23 1. Copy bytes until the destination pointer is aligned. 24 25 2. Copy words in unrolled loops. If the source and destination 26 are not aligned in the same way, use word memory operations, 27 but shift and merge two read words before writing. 28 29 3. Copy the few remaining bytes. 30 31 This is fast on processors that have at least 10 registers for 32 allocation by GCC, and that can access memory at reg+const in one 33 instruction. 34 35 I made an "exhaustive" test of this memmove when I wrote it, 36 exhaustive in the sense that I tried all alignment and length 37 combinations, with and without overlap. */ 38 39#include <sys/cdefs.h> 40#include <endian.h> 41 42/* The macros defined in this file are: 43 44 BYTE_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy) 45 46 BYTE_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy) 47 48 WORD_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_remaining, nbytes_to_copy) 49 50 WORD_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_remaining, nbytes_to_copy) 51 52 MERGE(old_word, sh_1, new_word, sh_2) 53 [I fail to understand. I feel stupid. --roland] 54*/ 55 56/* Type to use for aligned memory operations. 57 This should normally be the biggest type supported by a single load 58 and store. */ 59#define op_t unsigned long int 60#define OPSIZ (sizeof(op_t)) 61 62/* Type to use for unaligned operations. */ 63typedef unsigned char byte; 64 65/* Optimal type for storing bytes in registers. */ 66#define reg_char char 67 68#if __BYTE_ORDER == __LITTLE_ENDIAN 69#define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2))) 70#endif 71#if __BYTE_ORDER == __BIG_ENDIAN 72#define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2))) 73#endif 74 75/* Copy exactly NBYTES bytes from SRC_BP to DST_BP, 76 without any assumptions about alignment of the pointers. */ 77#define BYTE_COPY_FWD(dst_bp, src_bp, nbytes) \ 78 do \ 79 { \ 80 size_t __nbytes = (nbytes); \ 81 while (__nbytes > 0) \ 82 { \ 83 byte __x = ((byte *) src_bp)[0]; \ 84 src_bp += 1; \ 85 __nbytes -= 1; \ 86 ((byte *) dst_bp)[0] = __x; \ 87 dst_bp += 1; \ 88 } \ 89 } while (0) 90 91/* Copy exactly NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR, 92 beginning at the bytes right before the pointers and continuing towards 93 smaller addresses. Don't assume anything about alignment of the 94 pointers. */ 95#define BYTE_COPY_BWD(dst_ep, src_ep, nbytes) \ 96 do \ 97 { \ 98 size_t __nbytes = (nbytes); \ 99 while (__nbytes > 0) \ 100 { \ 101 byte __x; \ 102 src_ep -= 1; \ 103 __x = ((byte *) src_ep)[0]; \ 104 dst_ep -= 1; \ 105 __nbytes -= 1; \ 106 ((byte *) dst_ep)[0] = __x; \ 107 } \ 108 } while (0) 109 110/* Copy *up to* NBYTES bytes from SRC_BP to DST_BP, with 111 the assumption that DST_BP is aligned on an OPSIZ multiple. If 112 not all bytes could be easily copied, store remaining number of bytes 113 in NBYTES_LEFT, otherwise store 0. */ 114extern void _wordcopy_fwd_aligned (long int, long int, size_t) __THROW; 115extern void _wordcopy_fwd_dest_aligned (long int, long int, size_t) __THROW; 116#define WORD_COPY_FWD(dst_bp, src_bp, nbytes_left, nbytes) \ 117 do \ 118 { \ 119 if (src_bp % OPSIZ == 0) \ 120 _wordcopy_fwd_aligned (dst_bp, src_bp, (nbytes) / OPSIZ); \ 121 else \ 122 _wordcopy_fwd_dest_aligned (dst_bp, src_bp, (nbytes) / OPSIZ); \ 123 src_bp += (nbytes) & -OPSIZ; \ 124 dst_bp += (nbytes) & -OPSIZ; \ 125 (nbytes_left) = (nbytes) % OPSIZ; \ 126 } while (0) 127 128/* Copy *up to* NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR, 129 beginning at the words (of type op_t) right before the pointers and 130 continuing towards smaller addresses. May take advantage of that 131 DST_END_PTR is aligned on an OPSIZ multiple. If not all bytes could be 132 easily copied, store remaining number of bytes in NBYTES_REMAINING, 133 otherwise store 0. */ 134extern void _wordcopy_bwd_aligned (long int, long int, size_t) __THROW; 135extern void _wordcopy_bwd_dest_aligned (long int, long int, size_t) __THROW; 136#define WORD_COPY_BWD(dst_ep, src_ep, nbytes_left, nbytes) \ 137 do \ 138 { \ 139 if (src_ep % OPSIZ == 0) \ 140 _wordcopy_bwd_aligned (dst_ep, src_ep, (nbytes) / OPSIZ); \ 141 else \ 142 _wordcopy_bwd_dest_aligned (dst_ep, src_ep, (nbytes) / OPSIZ); \ 143 src_ep -= (nbytes) & -OPSIZ; \ 144 dst_ep -= (nbytes) & -OPSIZ; \ 145 (nbytes_left) = (nbytes) % OPSIZ; \ 146 } while (0) 147 148 149/* Threshold value for when to enter the unrolled loops. */ 150#define OP_T_THRES 16 151