kc3-lang/gnulib/lib/areadlinkat.c

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• Hash : b2e2010c
  Author :
  Date : 2010-01-01T10:31:12
  

  update nearly all FSF copyright year lists to include 2010
  
  Use the same procedure as for 2009, outlined in
  http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/20081
  

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• lib/areadlinkat.c

• /* areadlinkat.c -- readlinkat wrapper to return malloc'd link name
     Unlike xreadlinkat, only call exit on failure to change directory.
  
     Copyright (C) 2001, 2003-2007, 2009-2010 Free Software Foundation, Inc.
  
     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 Free Software Foundation; either version 3 of the License, or
     (at your option) any later version.
  
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
  
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  
  /* Written by Jim Meyering <jim@meyering.net>,
     and Bruno Haible <bruno@clisp.org>,
     and Eric Blake <ebb9@byu.net>.  */
  
  #include <config.h>
  
  /* Specification.  */
  #include "areadlink.h"
  
  #include <errno.h>
  #include <limits.h>
  #include <stdint.h>
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
  
  #ifndef SSIZE_MAX
  # define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2))
  #endif
  
  #if HAVE_READLINKAT
  
  /* The initial buffer size for the link value.  A power of 2
     detects arithmetic overflow earlier, but is not required.  */
  enum {
    INITIAL_BUF_SIZE = 1024
  };
  
  /* Call readlinkat to get the symbolic link value of FILENAME relative to FD.
     Return a pointer to that NUL-terminated string in malloc'd storage.
     If readlinkat fails, return NULL and set errno (although failure to
     change directory will issue a diagnostic and exit).
     If realloc fails, or if the link value is longer than SIZE_MAX :-),
     return NULL and set errno to ENOMEM.  */
  
  char *
  areadlinkat (int fd, char const *filename)
  {
    /* Allocate the initial buffer on the stack.  This way, in the common
       case of a symlink of small size, we get away with a single small malloc()
       instead of a big malloc() followed by a shrinking realloc().  */
    char initial_buf[INITIAL_BUF_SIZE];
  
    char *buffer = initial_buf;
    size_t buf_size = sizeof initial_buf;
  
    while (1)
      {
        /* Attempt to read the link into the current buffer.  */
         ssize_t link_length = readlinkat (fd, filename, buffer, buf_size);
  
        /* On AIX 5L v5.3 and HP-UX 11i v2 04/09, readlink returns -1
           with errno == ERANGE if the buffer is too small.  */
        if (link_length < 0 && errno != ERANGE)
          {
            if (buffer != initial_buf)
              {
                int saved_errno = errno;
                free (buffer);
                errno = saved_errno;
              }
            return NULL;
          }
  
        if ((size_t) link_length < buf_size)
          {
            buffer[link_length++] = '\0';
  
            /* Return it in a chunk of memory as small as possible.  */
            if (buffer == initial_buf)
              {
                buffer = (char *) malloc (link_length);
                if (buffer == NULL)
                  /* errno is ENOMEM.  */
                  return NULL;
                memcpy (buffer, initial_buf, link_length);
              }
            else
              {
                /* Shrink buffer before returning it.  */
                if ((size_t) link_length < buf_size)
                  {
                    char *smaller_buffer = (char *) realloc (buffer, link_length);
  
                    if (smaller_buffer != NULL)
                      buffer = smaller_buffer;
                  }
              }
            return buffer;
          }
  
        if (buffer != initial_buf)
          free (buffer);
        buf_size *= 2;
        if (SSIZE_MAX < buf_size || (SIZE_MAX / 2 < SSIZE_MAX && buf_size == 0))
          {
            errno = ENOMEM;
            return NULL;
          }
        buffer = (char *) malloc (buf_size);
        if (buffer == NULL)
          /* errno is ENOMEM.  */
          return NULL;
      }
  }
  
  #else /* !HAVE_READLINKAT */
  
  /* It is more efficient to change directories only once and call
     areadlink, rather than repeatedly call the replacement
     readlinkat.  */
  
  # define AT_FUNC_NAME areadlinkat
  # define AT_FUNC_F1 areadlink
  # define AT_FUNC_POST_FILE_PARAM_DECLS /* empty */
  # define AT_FUNC_POST_FILE_ARGS        /* empty */
  # define AT_FUNC_RESULT char *
  # define AT_FUNC_FAIL NULL
  # include "at-func.c"
  # undef AT_FUNC_NAME
  # undef AT_FUNC_F1
  # undef AT_FUNC_POST_FILE_PARAM_DECLS
  # undef AT_FUNC_POST_FILE_ARGS
  # undef AT_FUNC_RESULT
  # undef AT_FUNC_FAIL
  
  #endif /* !HAVE_READLINKAT */
  

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