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32 * @(#)bcopy.c 8.1 (Berkeley) 6/4/93
33 * $FreeBSD: src/lib/libc/string/bcopy.c,v 1.7 2007/01/09 00:28:11 imp Exp $
34 * $DragonFly: src/lib/libc/string/bcopy.c,v 1.4 2005/09/18 16:32:34 asmodai Exp $
37 #include <sys/types.h>
40 * sizeof(word) MUST BE A POWER OF TWO
41 * SO THAT wmask BELOW IS ALL ONES
43 typedef int word; /* "word" used for optimal copy speed */
45 #define wsize sizeof(word)
46 #define wmask (wsize - 1)
49 * Copy a block of memory, handling overlap.
50 * This is the routine that actually implements
51 * (the portable versions of) bcopy, memcpy, and memmove.
53 #if defined(MEMCOPY) || defined(MEMMOVE)
62 (void *dst0, const void *src0, size_t length)
67 bcopy(const void *src0, void *dst0, size_t length)
71 const char *src = src0;
74 if (length == 0 || dst == src) /* nothing to do */
78 * Macros: loop-t-times; and loop-t-times, t>0
80 #define TLOOP(s) if (t) TLOOP1(s)
81 #define TLOOP1(s) do { s; } while (--t)
83 if ((unsigned long)dst < (unsigned long)src) {
87 t = (uintptr_t)src; /* only need low bits */
88 if ((t | (uintptr_t)dst) & wmask) {
90 * Try to align operands. This cannot be done
91 * unless the low bits match.
93 if ((t ^ (uintptr_t)dst) & wmask || length < wsize)
96 t = wsize - (t & wmask);
98 TLOOP1(*dst++ = *src++);
101 * Copy whole words, then mop up any trailing bytes.
104 TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
106 TLOOP(*dst++ = *src++);
109 * Copy backwards. Otherwise essentially the same.
110 * Alignment works as before, except that it takes
111 * (t&wmask) bytes to align, not wsize-(t&wmask).
116 if ((t | (uintptr_t)dst) & wmask) {
117 if ((t ^ (uintptr_t)dst) & wmask || length <= wsize)
122 TLOOP1(*--dst = *--src);
125 TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
127 TLOOP(*--dst = *--src);
130 #if defined(MEMCOPY) || defined(MEMMOVE)