1  /* Variable-sized buffer with on-stack default allocation.
       2     Copyright (C) 2015-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #ifndef _LIBC
      20  # include <libc-config.h>
      21  #endif
      22  
      23  #include <scratch_buffer.h>
      24  #include <errno.h>
      25  #include <limits.h>
      26  
      27  bool
      28  __libc_scratch_buffer_set_array_size (struct scratch_buffer *buffer,
      29  				      size_t nelem, size_t size)
      30  {
      31    size_t new_length = nelem * size;
      32  
      33    /* Avoid overflow check if both values are small. */
      34    if ((nelem | size) >> (sizeof (size_t) * CHAR_BIT / 2) != 0
      35        && nelem != 0 && size != new_length / nelem)
      36      {
      37        /* Overflow.  Discard the old buffer, but it must remain valid
      38  	 to free.  */
      39        scratch_buffer_free (buffer);
      40        scratch_buffer_init (buffer);
      41        __set_errno (ENOMEM);
      42        return false;
      43      }
      44  
      45    if (new_length <= buffer->length)
      46      return true;
      47  
      48    /* Discard old buffer.  */
      49    scratch_buffer_free (buffer);
      50  
      51    char *new_ptr = malloc (new_length);
      52    if (new_ptr == NULL)
      53      {
      54        /* Buffer must remain valid to free.  */
      55        scratch_buffer_init (buffer);
      56        return false;
      57      }
      58  
      59    /* Install new heap-based buffer.  */
      60    buffer->data = new_ptr;
      61    buffer->length = new_length;
      62    return true;
      63  }
      64  libc_hidden_def (__libc_scratch_buffer_set_array_size)