112 lines
2.2 KiB
C
112 lines
2.2 KiB
C
/*
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FUNCTION
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<<memset>>---set an area of memory
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INDEX
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memset
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ANSI_SYNOPSIS
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#include <string.h>
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void *memset(const void *<[dst]>, int <[c]>, size_t <[length]>);
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TRAD_SYNOPSIS
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#include <string.h>
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void *memset(<[dst]>, <[c]>, <[length]>)
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void *<[dst]>;
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int <[c]>;
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size_t <[length]>;
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DESCRIPTION
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This function converts the argument <[c]> into an unsigned
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char and fills the first <[length]> characters of the array
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pointed to by <[dst]> to the value.
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RETURNS
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<<memset>> returns the value of <[m]>.
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PORTABILITY
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<<memset>> is ANSI C.
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<<memset>> requires no supporting OS subroutines.
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QUICKREF
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memset ansi pure
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*/
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#include <string.h>
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#define LBLOCKSIZE (sizeof(long))
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#define UNALIGNED(X) ((long)X & (LBLOCKSIZE - 1))
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#define TOO_SMALL(LEN) ((LEN) < LBLOCKSIZE)
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_PTR
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_DEFUN (memset, (m, c, n),
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_PTR m _AND
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int c _AND
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size_t n)
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{
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#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
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char *s = (char *) m;
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while (n-- != 0)
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{
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*s++ = (char) c;
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}
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return m;
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#else
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char *s = (char *) m;
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int i;
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unsigned long buffer;
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unsigned long *aligned_addr;
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unsigned int d = c & 0xff;
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if (!TOO_SMALL (n) && !UNALIGNED (m))
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{
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/* If we get this far, we know that n is large and m is word-aligned. */
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/* To avoid sign extention, copy C to an unsigned variable. */
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aligned_addr = (unsigned long*)m;
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/* Store D into each char sized location in BUFFER so that
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we can set large blocks quickly. */
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if (LBLOCKSIZE == 4)
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{
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buffer = (d << 8) | d;
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buffer |= (buffer << 16);
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}
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else
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{
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buffer = 0;
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for (i = 0; i < LBLOCKSIZE; i++)
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buffer = (buffer << 8) | d;
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}
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while (n >= LBLOCKSIZE*4)
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{
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*aligned_addr++ = buffer;
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*aligned_addr++ = buffer;
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*aligned_addr++ = buffer;
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*aligned_addr++ = buffer;
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n -= 4*LBLOCKSIZE;
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}
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while (n >= LBLOCKSIZE)
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{
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*aligned_addr++ = buffer;
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n -= LBLOCKSIZE;
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}
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/* Pick up the remainder with a bytewise loop. */
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s = (char*)aligned_addr;
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}
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while (n--)
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{
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*s++ = (char)d;
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}
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return m;
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#endif /* not PREFER_SIZE_OVER_SPEED */
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}
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