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/*
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FUNCTION
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        <<strlen>>---character string length
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INDEX
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        strlen
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ANSI_SYNOPSIS
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        #include <string.h>
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        size_t strlen(const char *<[str]>);
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TRAD_SYNOPSIS
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        #include <string.h>
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        size_t strlen(<[str]>)
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        char *<[src]>;
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DESCRIPTION
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        The <<strlen>> function works out the length of the string
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        starting at <<*<[str]>>> by counting chararacters until it
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        reaches a <<NULL>> character.
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RETURNS
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        <<strlen>> returns the character count.
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PORTABILITY
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<<strlen>> is ANSI C.
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<<strlen>> requires no supporting OS subroutines.
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QUICKREF
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        strlen ansi pure
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*/
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#include "global.h"
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#include "include/_ansi.h"
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#include "include/string.h"
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#include <limits.h>
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#define LBLOCKSIZE   (sizeof (long))
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#define UNALIGNED(X) ((long)X & (LBLOCKSIZE - 1))
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#if LONG_MAX == 2147483647L
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#define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
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#else
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#if LONG_MAX == 9223372036854775807L
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/* Nonzero if X (a long int) contains a NULL byte. */
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#define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
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#else
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#error long int is not a 32bit or 64bit type.
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#endif
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#endif
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#ifndef DETECTNULL
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#error long int is not a 32bit or 64bit byte
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#endif
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size_t
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_DEFUN (strlen, (str),
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        _CONST char *str) ICODE_ATTR;
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size_t
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_DEFUN (strlen, (str),
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        _CONST char *str)
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{
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#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
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  _CONST char *start = str;
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  while (*str)
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    str++;
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  return str - start;
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#else
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  _CONST char *start = str;
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  unsigned long *aligned_addr;
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  if (!UNALIGNED (str))
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    {
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      /* If the string is word-aligned, we can check for the presence of
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         a null in each word-sized block.  */
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      aligned_addr = (unsigned long*)str;
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      while (!DETECTNULL (*aligned_addr))
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        aligned_addr++;
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      /* Once a null is detected, we check each byte in that block for a
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         precise position of the null.  */
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      str = (char*)aligned_addr;
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    }
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  while (*str)
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    str++;
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  return str - start;
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#endif /* not PREFER_SIZE_OVER_SPEED */
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}