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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libc/] [string/] [strlen.c] - Rev 273
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/* FUNCTION <<strlen>>---character string length INDEX strlen ANSI_SYNOPSIS #include <string.h> size_t strlen(const char *<[str]>); TRAD_SYNOPSIS #include <string.h> size_t strlen(<[str]>) char *<[src]>; DESCRIPTION The <<strlen>> function works out the length of the string starting at <<*<[str]>>> by counting chararacters until it reaches a <<NULL>> character. RETURNS <<strlen>> returns the character count. PORTABILITY <<strlen>> is ANSI C. <<strlen>> requires no supporting OS subroutines. QUICKREF strlen ansi pure */ #include <_ansi.h> #include <string.h> #include <limits.h> #define LBLOCKSIZE (sizeof (long)) #define UNALIGNED(X) ((long)X & (LBLOCKSIZE - 1)) #if LONG_MAX == 2147483647L #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080) #else #if LONG_MAX == 9223372036854775807L /* Nonzero if X (a long int) contains a NULL byte. */ #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080) #else #error long int is not a 32bit or 64bit type. #endif #endif #ifndef DETECTNULL #error long int is not a 32bit or 64bit byte #endif size_t _DEFUN (strlen, (str), _CONST char *str) { _CONST char *start = str; #if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__) unsigned long *aligned_addr; /* Align the pointer, so we can search a word at a time. */ while (UNALIGNED (str)) { if (!*str) return str - start; str++; } /* If the string is word-aligned, we can check for the presence of a null in each word-sized block. */ aligned_addr = (unsigned long *)str; while (!DETECTNULL (*aligned_addr)) aligned_addr++; /* Once a null is detected, we check each byte in that block for a precise position of the null. */ str = (char *) aligned_addr; #endif /* not PREFER_SIZE_OVER_SPEED */ while (*str) str++; return str - start; }
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