1  /* Copyright (C) 1991-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <libc-pointer-arith.h>
      19  #include <string-fzb.h>
      20  #include <string-fzc.h>
      21  #include <string-fzi.h>
      22  #include <string-shift.h>
      23  #include <string.h>
      24  
      25  #ifdef STRLEN
      26  # define __strlen STRLEN
      27  #endif
      28  
      29  /* Return the length of the null-terminated string STR.  Scan for
      30     the null terminator quickly by testing four bytes at a time.  */
      31  size_t
      32  __strlen (const char *str)
      33  {
      34    /* Align pointer to sizeof op_t.  */
      35    const uintptr_t s_int = (uintptr_t) str;
      36    const op_t *word_ptr = (const op_t*) PTR_ALIGN_DOWN (str, sizeof (op_t));
      37  
      38    op_t word = *word_ptr;
      39    find_t mask = shift_find (find_zero_all (word), s_int);
      40    if (mask != 0)
      41      return index_first (mask);
      42  
      43    do
      44      word = *++word_ptr;
      45    while (! has_zero (word));
      46  
      47    return ((const char *) word_ptr) + index_first_zero (word) - str;
      48  }
      49  #ifndef STRLEN
      50  weak_alias (__strlen, strlen)
      51  libc_hidden_builtin_def (strlen)
      52  #endif