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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libc/] [string/] [memchr.c] - Rev 207
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/* FUNCTION <<memchr>>---find character in memory INDEX memchr ANSI_SYNOPSIS #include <string.h> void *memchr(const void *<[src]>, int <[c]>, size_t <[length]>); TRAD_SYNOPSIS #include <string.h> void *memchr(<[src]>, <[c]>, <[length]>) void *<[src]>; void *<[c]>; size_t <[length]>; DESCRIPTION This function searches memory starting at <<*<[src]>>> for the character <[c]>. The search only ends with the first occurrence of <[c]>, or after <[length]> characters; in particular, <<NUL>> does not terminate the search. RETURNS If the character <[c]> is found within <[length]> characters of <<*<[src]>>>, a pointer to the character is returned. If <[c]> is not found, then <<NULL>> is returned. PORTABILITY <<memchr>> is ANSI C. <<memchr>> requires no supporting OS subroutines. QUICKREF memchr ansi pure */ #include <_ansi.h> #include <string.h> #include <limits.h> /* Nonzero if either X or Y is not aligned on a "long" boundary. */ #define UNALIGNED(X) ((long)X & (sizeof (long) - 1)) /* How many bytes are loaded each iteration of the word copy loop. */ #define LBLOCKSIZE (sizeof (long)) /* Threshhold for punting to the bytewise iterator. */ #define TOO_SMALL(LEN) ((LEN) < LBLOCKSIZE) #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 /* DETECTCHAR returns nonzero if (long)X contains the byte used to fill (long)MASK. */ #define DETECTCHAR(X,MASK) (DETECTNULL(X ^ MASK)) _PTR _DEFUN (memchr, (src_void, c, length), _CONST _PTR src_void _AND int c _AND size_t length) { _CONST unsigned char *src = (_CONST unsigned char *) src_void; unsigned char d = c; #if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__) unsigned long *asrc; unsigned long mask; int i; while (UNALIGNED (src)) { if (!length--) return NULL; if (*src == d) return (void *) src; src++; } if (!TOO_SMALL (length)) { /* If we get this far, we know that length is large and src is word-aligned. */ /* The fast code reads the source one word at a time and only performs the bytewise search on word-sized segments if they contain the search character, which is detected by XORing the word-sized segment with a word-sized block of the search character and then detecting for the presence of NUL in the result. */ asrc = (unsigned long *) src; mask = d << 8 | d; mask = mask << 16 | mask; for (i = 32; i < LBLOCKSIZE * 8; i <<= 1) mask = (mask << i) | mask; while (length >= LBLOCKSIZE) { if (DETECTCHAR (*asrc, mask)) break; length -= LBLOCKSIZE; asrc++; } /* If there are fewer than LBLOCKSIZE characters left, then we resort to the bytewise loop. */ src = (unsigned char *) asrc; } #endif /* not PREFER_SIZE_OVER_SPEED */ while (length--) { if (*src == d) return (void *) src; src++; } return NULL; }