X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fmemrchr.c;h=ae8dabcd09080a07c75fff93da33ccd23fc25c9a;hb=c3edfc411c57b3bd4f12a09674f143651990c1f2;hp=9f29900f85b7fed6926a7c44a40add500cfd4f7a;hpb=4589d52c7c039b9d9c9d7bec075f00c9d57ee6e1;p=gnulib.git diff --git a/lib/memrchr.c b/lib/memrchr.c index 9f29900f8..ae8dabcd0 100644 --- a/lib/memrchr.c +++ b/lib/memrchr.c @@ -1,5 +1,8 @@ /* memrchr -- find the last occurrence of a byte in a memory block - Copyright (C) 1991, 93, 96, 97, 99, 2000 Free Software Foundation, Inc. + + Copyright (C) 1991, 1993, 1996, 1997, 1999, 2000, 2003, 2004, 2005 + Free Software Foundation, Inc. + Based on strlen implementation by Torbjorn Granlund (tege@sics.se), with help from Dan Sahlin (dan@sics.se) and commentary by Jim Blandy (jimb@ai.mit.edu); @@ -24,33 +27,15 @@ # include #endif -#include - -#undef __ptr_t -#if defined (__cplusplus) || (defined (__STDC__) && __STDC__) -# define __ptr_t void * -#else /* Not C++ or ANSI C. */ -# define __ptr_t char * -#endif /* C++ or ANSI C. */ - -#if defined (_LIBC) +#if defined _LIBC # include # include #else +# include "memrchr.h" # define reg_char char #endif -#if defined (HAVE_LIMITS_H) || defined (_LIBC) -# include -#endif - -#define LONG_MAX_32_BITS 2147483647 - -#ifndef LONG_MAX -# define LONG_MAX LONG_MAX_32_BITS -#endif - -#include +#include #undef __memrchr #undef memrchr @@ -60,32 +45,29 @@ #endif /* Search no more than N bytes of S for C. */ -__ptr_t -__memrchr (s, c_in, n) - const __ptr_t s; - int c_in; - size_t n; +void * +__memrchr (void const *s, int c_in, size_t n) { const unsigned char *char_ptr; const unsigned long int *longword_ptr; unsigned long int longword, magic_bits, charmask; unsigned reg_char c; + int i; c = (unsigned char) c_in; /* Handle the last few characters by reading one character at a time. Do this until CHAR_PTR is aligned on a longword boundary. */ for (char_ptr = (const unsigned char *) s + n; - n > 0 && ((unsigned long int) char_ptr - & (sizeof (longword) - 1)) != 0; + n > 0 && (size_t) char_ptr % sizeof longword != 0; --n) if (*--char_ptr == c) - return (__ptr_t) char_ptr; + return (void *) char_ptr; /* All these elucidatory comments refer to 4-byte longwords, - but the theory applies equally well to 8-byte longwords. */ + but the theory applies equally well to any size longwords. */ - longword_ptr = (unsigned long int *) char_ptr; + longword_ptr = (const unsigned long int *) char_ptr; /* Bits 31, 24, 16, and 8 of this number are zero. Call these bits the "holes." Note that there is a hole just to the left of @@ -97,26 +79,28 @@ __memrchr (s, c_in, n) The 1-bits make sure that carries propagate to the next 0-bit. The 0-bits provide holes for carries to fall into. */ - if (sizeof (longword) != 4 && sizeof (longword) != 8) - abort (); - -#if LONG_MAX <= LONG_MAX_32_BITS - magic_bits = 0x7efefeff; -#else - magic_bits = ((unsigned long int) 0x7efefefe << 32) | 0xfefefeff; -#endif + /* Set MAGIC_BITS to be this pattern of 1 and 0 bits. + Set CHARMASK to be a longword, each of whose bytes is C. */ - /* Set up a longword, each of whose bytes is C. */ + magic_bits = 0xfefefefe; charmask = c | (c << 8); charmask |= charmask << 16; -#if LONG_MAX > LONG_MAX_32_BITS +#if 0xffffffffU < ULONG_MAX + magic_bits |= magic_bits << 32; charmask |= charmask << 32; + if (8 < sizeof longword) + for (i = 64; i < sizeof longword * 8; i *= 2) + { + magic_bits |= magic_bits << i; + charmask |= charmask << i; + } #endif + magic_bits = (ULONG_MAX >> 1) & (magic_bits | 1); /* Instead of the traditional loop which tests each character, we will test a longword at a time. The tricky part is testing if *any of the four* bytes in the longword in question are zero. */ - while (n >= sizeof (longword)) + while (n >= sizeof longword) { /* We tentatively exit the loop if adding MAGIC_BITS to LONGWORD fails to change any of the hole bits of LONGWORD. @@ -170,27 +154,29 @@ __memrchr (s, c_in, n) const unsigned char *cp = (const unsigned char *) longword_ptr; -#if LONG_MAX > 2147483647 - if (cp[7] == c) - return (__ptr_t) &cp[7]; - if (cp[6] == c) - return (__ptr_t) &cp[6]; - if (cp[5] == c) - return (__ptr_t) &cp[5]; - if (cp[4] == c) - return (__ptr_t) &cp[4]; -#endif + if (8 < sizeof longword) + for (i = sizeof longword - 1; 8 <= i; i--) + if (cp[i] == c) + return (void *) &cp[i]; + if (7 < sizeof longword && cp[7] == c) + return (void *) &cp[7]; + if (6 < sizeof longword && cp[6] == c) + return (void *) &cp[6]; + if (5 < sizeof longword && cp[5] == c) + return (void *) &cp[5]; + if (4 < sizeof longword && cp[4] == c) + return (void *) &cp[4]; if (cp[3] == c) - return (__ptr_t) &cp[3]; + return (void *) &cp[3]; if (cp[2] == c) - return (__ptr_t) &cp[2]; + return (void *) &cp[2]; if (cp[1] == c) - return (__ptr_t) &cp[1]; + return (void *) &cp[1]; if (cp[0] == c) - return (__ptr_t) cp; + return (void *) cp; } - n -= sizeof (longword); + n -= sizeof longword; } char_ptr = (const unsigned char *) longword_ptr; @@ -198,7 +184,7 @@ __memrchr (s, c_in, n) while (n-- > 0) { if (*--char_ptr == c) - return (__ptr_t) char_ptr; + return (void *) char_ptr; } return 0;