143 lines
3.4 KiB
C
143 lines
3.4 KiB
C
/*
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FUNCTION
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<<memmove>>---move possibly overlapping memory
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INDEX
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memmove
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ANSI_SYNOPSIS
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#include <string.h>
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void *memmove(void *<[dst]>, const void *<[src]>, size_t <[length]>);
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TRAD_SYNOPSIS
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#include <string.h>
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void *memmove(<[dst]>, <[src]>, <[length]>)
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void *<[dst]>;
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void *<[src]>;
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size_t <[length]>;
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DESCRIPTION
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This function moves <[length]> characters from the block of
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memory starting at <<*<[src]>>> to the memory starting at
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<<*<[dst]>>>. <<memmove>> reproduces the characters correctly
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at <<*<[dst]>>> even if the two areas overlap.
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RETURNS
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The function returns <[dst]> as passed.
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PORTABILITY
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<<memmove>> is ANSI C.
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<<memmove>> requires no supporting OS subroutines.
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QUICKREF
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memmove ansi pure
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*/
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#include <string.h>
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#include <_ansi.h>
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#include <stddef.h>
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#include <limits.h>
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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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/*SUPPRESS 20*/
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_PTR
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_DEFUN (memmove, (dst_void, src_void, length),
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_PTR dst_void _AND
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_CONST _PTR src_void _AND
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size_t length)
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{
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#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
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char *dst = dst_void;
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_CONST char *src = src_void;
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if (src < dst && dst < src + length)
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{
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/* 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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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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#else
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char *dst = dst_void;
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_CONST char *src = 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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#endif /* not PREFER_SIZE_OVER_SPEED */
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}
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