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[/] [openrisc/] [trunk/] [gnu-old/] [gdb-7.1/] [gdb/] [gnulib/] [memchr.c] - Diff between revs 227 and 816

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/* Copyright (C) 1991, 1993, 1996, 1997, 1999, 2000, 2003, 2004, 2006, 2009,
/* Copyright (C) 1991, 1993, 1996, 1997, 1999, 2000, 2003, 2004, 2006, 2009,
2010 Free Software Foundation, Inc.
2010 Free Software Foundation, Inc.
 
 
   Based on strlen implementation by Torbjorn Granlund (tege@sics.se),
   Based on strlen implementation by Torbjorn Granlund (tege@sics.se),
   with help from Dan Sahlin (dan@sics.se) and
   with help from Dan Sahlin (dan@sics.se) and
   commentary by Jim Blandy (jimb@ai.mit.edu);
   commentary by Jim Blandy (jimb@ai.mit.edu);
   adaptation to memchr suggested by Dick Karpinski (dick@cca.ucsf.edu),
   adaptation to memchr suggested by Dick Karpinski (dick@cca.ucsf.edu),
   and implemented by Roland McGrath (roland@ai.mit.edu).
   and implemented by Roland McGrath (roland@ai.mit.edu).
 
 
NOTE: The canonical source of this file is maintained with the GNU C Library.
NOTE: The canonical source of this file is maintained with the GNU C Library.
Bugs can be reported to bug-glibc@prep.ai.mit.edu.
Bugs can be reported to bug-glibc@prep.ai.mit.edu.
 
 
This program is free software: you can redistribute it and/or modify it
This program is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 3 of the License, or any
Free Software Foundation; either version 3 of the License, or any
later version.
later version.
 
 
This program is distributed in the hope that it will be useful,
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
GNU General Public License for more details.
 
 
You should have received a copy of the GNU General Public License
You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 
#ifndef _LIBC
#ifndef _LIBC
# include <config.h>
# include <config.h>
#endif
#endif
 
 
#include <string.h>
#include <string.h>
 
 
#include <stddef.h>
#include <stddef.h>
 
 
#if defined _LIBC
#if defined _LIBC
# include <memcopy.h>
# include <memcopy.h>
#else
#else
# define reg_char char
# define reg_char char
#endif
#endif
 
 
#include <limits.h>
#include <limits.h>
 
 
#if HAVE_BP_SYM_H || defined _LIBC
#if HAVE_BP_SYM_H || defined _LIBC
# include <bp-sym.h>
# include <bp-sym.h>
#else
#else
# define BP_SYM(sym) sym
# define BP_SYM(sym) sym
#endif
#endif
 
 
#undef memchr
#undef memchr
#undef __memchr
#undef __memchr
 
 
/* Search no more than N bytes of S for C.  */
/* Search no more than N bytes of S for C.  */
void *
void *
__memchr (void const *s, int c_in, size_t n)
__memchr (void const *s, int c_in, size_t n)
{
{
  const unsigned char *char_ptr;
  const unsigned char *char_ptr;
  const unsigned long int *longword_ptr;
  const unsigned long int *longword_ptr;
  unsigned long int longword, magic_bits, charmask;
  unsigned long int longword, magic_bits, charmask;
  unsigned reg_char c;
  unsigned reg_char c;
  int i;
  int i;
 
 
  c = (unsigned char) c_in;
  c = (unsigned char) c_in;
 
 
  /* Handle the first few characters by reading one character at a time.
  /* Handle the first few characters by reading one character at a time.
     Do this until CHAR_PTR is aligned on a longword boundary.  */
     Do this until CHAR_PTR is aligned on a longword boundary.  */
  for (char_ptr = (const unsigned char *) s;
  for (char_ptr = (const unsigned char *) s;
       n > 0 && (size_t) char_ptr % sizeof longword != 0;
       n > 0 && (size_t) char_ptr % sizeof longword != 0;
       --n, ++char_ptr)
       --n, ++char_ptr)
    if (*char_ptr == c)
    if (*char_ptr == c)
      return (void *) char_ptr;
      return (void *) char_ptr;
 
 
  /* All these elucidatory comments refer to 4-byte longwords,
  /* All these elucidatory comments refer to 4-byte longwords,
     but the theory applies equally well to any size longwords.  */
     but the theory applies equally well to any size longwords.  */
 
 
  longword_ptr = (const 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
  /* 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
     the "holes."  Note that there is a hole just to the left of
     each byte, with an extra at the end:
     each byte, with an extra at the end:
 
 
     bits:  01111110 11111110 11111110 11111111
     bits:  01111110 11111110 11111110 11111111
     bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD
     bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD
 
 
     The 1-bits make sure that carries propagate to the next 0-bit.
     The 1-bits make sure that carries propagate to the next 0-bit.
     The 0-bits provide holes for carries to fall into.  */
     The 0-bits provide holes for carries to fall into.  */
 
 
  /* Set MAGIC_BITS to be this pattern of 1 and 0 bits.
  /* 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 CHARMASK to be a longword, each of whose bytes is C.  */
 
 
  magic_bits = 0xfefefefe;
  magic_bits = 0xfefefefe;
  charmask = c | (c << 8);
  charmask = c | (c << 8);
  charmask |= charmask << 16;
  charmask |= charmask << 16;
#if 0xffffffffU < ULONG_MAX
#if 0xffffffffU < ULONG_MAX
  magic_bits |= magic_bits << 32;
  magic_bits |= magic_bits << 32;
  charmask |= charmask << 32;
  charmask |= charmask << 32;
  if (8 < sizeof longword)
  if (8 < sizeof longword)
    for (i = 64; i < sizeof longword * 8; i *= 2)
    for (i = 64; i < sizeof longword * 8; i *= 2)
      {
      {
        magic_bits |= magic_bits << i;
        magic_bits |= magic_bits << i;
        charmask |= charmask << i;
        charmask |= charmask << i;
      }
      }
#endif
#endif
  magic_bits = (ULONG_MAX >> 1) & (magic_bits | 1);
  magic_bits = (ULONG_MAX >> 1) & (magic_bits | 1);
 
 
  /* Instead of the traditional loop which tests each character,
  /* Instead of the traditional loop which tests each character,
     we will test a longword at a time.  The tricky part is testing
     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.  */
     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
      /* We tentatively exit the loop if adding MAGIC_BITS to
         LONGWORD fails to change any of the hole bits of LONGWORD.
         LONGWORD fails to change any of the hole bits of LONGWORD.
 
 
         1) Is this safe?  Will it catch all the zero bytes?
         1) Is this safe?  Will it catch all the zero bytes?
         Suppose there is a byte with all zeros.  Any carry bits
         Suppose there is a byte with all zeros.  Any carry bits
         propagating from its left will fall into the hole at its
         propagating from its left will fall into the hole at its
         least significant bit and stop.  Since there will be no
         least significant bit and stop.  Since there will be no
         carry from its most significant bit, the LSB of the
         carry from its most significant bit, the LSB of the
         byte to the left will be unchanged, and the zero will be
         byte to the left will be unchanged, and the zero will be
         detected.
         detected.
 
 
         2) Is this worthwhile?  Will it ignore everything except
         2) Is this worthwhile?  Will it ignore everything except
         zero bytes?  Suppose every byte of LONGWORD has a bit set
         zero bytes?  Suppose every byte of LONGWORD has a bit set
         somewhere.  There will be a carry into bit 8.  If bit 8
         somewhere.  There will be a carry into bit 8.  If bit 8
         is set, this will carry into bit 16.  If bit 8 is clear,
         is set, this will carry into bit 16.  If bit 8 is clear,
         one of bits 9-15 must be set, so there will be a carry
         one of bits 9-15 must be set, so there will be a carry
         into bit 16.  Similarly, there will be a carry into bit
         into bit 16.  Similarly, there will be a carry into bit
         24.  If one of bits 24-30 is set, there will be a carry
         24.  If one of bits 24-30 is set, there will be a carry
         into bit 31, so all of the hole bits will be changed.
         into bit 31, so all of the hole bits will be changed.
 
 
         The one misfire occurs when bits 24-30 are clear and bit
         The one misfire occurs when bits 24-30 are clear and bit
         31 is set; in this case, the hole at bit 31 is not
         31 is set; in this case, the hole at bit 31 is not
         changed.  If we had access to the processor carry flag,
         changed.  If we had access to the processor carry flag,
         we could close this loophole by putting the fourth hole
         we could close this loophole by putting the fourth hole
         at bit 32!
         at bit 32!
 
 
         So it ignores everything except 128's, when they're aligned
         So it ignores everything except 128's, when they're aligned
         properly.
         properly.
 
 
         3) But wait!  Aren't we looking for C, not zero?
         3) But wait!  Aren't we looking for C, not zero?
         Good point.  So what we do is XOR LONGWORD with a longword,
         Good point.  So what we do is XOR LONGWORD with a longword,
         each of whose bytes is C.  This turns each byte that is C
         each of whose bytes is C.  This turns each byte that is C
         into a zero.  */
         into a zero.  */
 
 
      longword = *longword_ptr++ ^ charmask;
      longword = *longword_ptr++ ^ charmask;
 
 
      /* Add MAGIC_BITS to LONGWORD.  */
      /* Add MAGIC_BITS to LONGWORD.  */
      if ((((longword + magic_bits)
      if ((((longword + magic_bits)
 
 
            /* Set those bits that were unchanged by the addition.  */
            /* Set those bits that were unchanged by the addition.  */
            ^ ~longword)
            ^ ~longword)
 
 
           /* Look at only the hole bits.  If any of the hole bits
           /* Look at only the hole bits.  If any of the hole bits
              are unchanged, most likely one of the bytes was a
              are unchanged, most likely one of the bytes was a
              zero.  */
              zero.  */
           & ~magic_bits) != 0)
           & ~magic_bits) != 0)
        {
        {
          /* Which of the bytes was C?  If none of them were, it was
          /* Which of the bytes was C?  If none of them were, it was
             a misfire; continue the search.  */
             a misfire; continue the search.  */
 
 
          const unsigned char *cp = (const unsigned char *) (longword_ptr - 1);
          const unsigned char *cp = (const unsigned char *) (longword_ptr - 1);
 
 
          if (cp[0] == c)
          if (cp[0] == c)
            return (void *) cp;
            return (void *) cp;
          if (cp[1] == c)
          if (cp[1] == c)
            return (void *) &cp[1];
            return (void *) &cp[1];
          if (cp[2] == c)
          if (cp[2] == c)
            return (void *) &cp[2];
            return (void *) &cp[2];
          if (cp[3] == c)
          if (cp[3] == c)
            return (void *) &cp[3];
            return (void *) &cp[3];
          if (4 < sizeof longword && cp[4] == c)
          if (4 < sizeof longword && cp[4] == c)
            return (void *) &cp[4];
            return (void *) &cp[4];
          if (5 < sizeof longword && cp[5] == c)
          if (5 < sizeof longword && cp[5] == c)
            return (void *) &cp[5];
            return (void *) &cp[5];
          if (6 < sizeof longword && cp[6] == c)
          if (6 < sizeof longword && cp[6] == c)
            return (void *) &cp[6];
            return (void *) &cp[6];
          if (7 < sizeof longword && cp[7] == c)
          if (7 < sizeof longword && cp[7] == c)
            return (void *) &cp[7];
            return (void *) &cp[7];
          if (8 < sizeof longword)
          if (8 < sizeof longword)
            for (i = 8; i < sizeof longword; i++)
            for (i = 8; i < sizeof longword; i++)
              if (cp[i] == c)
              if (cp[i] == c)
                return (void *) &cp[i];
                return (void *) &cp[i];
        }
        }
 
 
      n -= sizeof longword;
      n -= sizeof longword;
    }
    }
 
 
  char_ptr = (const unsigned char *) longword_ptr;
  char_ptr = (const unsigned char *) longword_ptr;
 
 
  while (n-- > 0)
  while (n-- > 0)
    {
    {
      if (*char_ptr == c)
      if (*char_ptr == c)
        return (void *) char_ptr;
        return (void *) char_ptr;
      else
      else
        ++char_ptr;
        ++char_ptr;
    }
    }
 
 
  return 0;
  return 0;
}
}
#ifdef weak_alias
#ifdef weak_alias
weak_alias (__memchr, BP_SYM (memchr))
weak_alias (__memchr, BP_SYM (memchr))
#endif
#endif
 
 

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