| 0,0 → 1,88 |
|---|
| /* |
| 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; |
| } |