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79 lines
2.2 KiB
C++
79 lines
2.2 KiB
C++
/* Taken from newlib... */
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#include <cstring>
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#include <cstddef>
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#include <climits>
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/* Nonzero if either X or Y is not aligned on a "long" boundary. */
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#define UNALIGNED(X, Y) \
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(((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
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/* How many bytes are copied each iteration of the 4X unrolled loop. */
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#define BIGBLOCKSIZE (sizeof (long) << 2)
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/* How many bytes are copied each iteration of the word copy loop. */
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#define LITTLEBLOCKSIZE (sizeof (long))
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/* Threshhold for punting to the byte copier. */
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#define TOO_SMALL(LEN) ((LEN) < BIGBLOCKSIZE)
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extern "C"
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void *memmove (void *dst_void, const void *src_void, size_t length)
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{
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char *dst = reinterpret_cast<char *>(dst_void);
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const char *src = reinterpret_cast<const char *>(src_void);
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long *aligned_dst;
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const long *aligned_src;
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if (src < dst && dst < src + length)
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{
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/* Destructive overlap...have to copy backwards */
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src += length;
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dst += length;
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while (length--)
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{
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*--dst = *--src;
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}
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}
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else
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{
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/* Use optimizing algorithm for a non-destructive copy to closely
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match memcpy. If the size is small or either SRC or DST is unaligned,
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then punt into the byte copy loop. This should be rare. */
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if (!TOO_SMALL(length) && !UNALIGNED (src, dst))
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{
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aligned_dst = (long*)dst;
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aligned_src = (long*)src;
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/* Copy 4X long words at a time if possible. */
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while (length >= BIGBLOCKSIZE)
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{
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*aligned_dst++ = *aligned_src++;
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*aligned_dst++ = *aligned_src++;
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*aligned_dst++ = *aligned_src++;
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*aligned_dst++ = *aligned_src++;
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length -= BIGBLOCKSIZE;
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}
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/* Copy one long word at a time if possible. */
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while (length >= LITTLEBLOCKSIZE)
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{
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*aligned_dst++ = *aligned_src++;
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length -= LITTLEBLOCKSIZE;
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}
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/* Pick up any residual with a byte copier. */
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dst = (char*)aligned_dst;
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src = (char*)aligned_src;
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}
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while (length--)
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{
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*dst++ = *src++;
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}
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}
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return dst_void;
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}
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