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 <string.h>
      26  
      27  bool
      28  __libc_scratch_buffer_grow_preserve (struct scratch_buffer *buffer)
      29  {
      30    size_t new_length = 2 * buffer->length;
      31    void *new_ptr;
      32  
      33    if (buffer->data == buffer->__space.__c)
      34      {
      35        /* Move buffer to the heap.  No overflow is possible because
      36  	 buffer->length describes a small buffer on the stack.  */
      37        new_ptr = malloc (new_length);
      38        if (new_ptr == NULL)
      39  	return false;
      40        memcpy (new_ptr, buffer->__space.__c, buffer->length);
      41      }
      42    else
      43      {
      44        /* Buffer was already on the heap.  Check for overflow.  */
      45        if (__glibc_likely (new_length >= buffer->length))
      46  	new_ptr = realloc (buffer->data, new_length);
      47        else
      48  	{
      49  	  __set_errno (ENOMEM);
      50  	  new_ptr = NULL;
      51  	}
      52  
      53        if (__glibc_unlikely (new_ptr == NULL))
      54  	{
      55  	  /* Deallocate, but buffer must remain valid to free.  */
      56  	  free (buffer->data);
      57  	  scratch_buffer_init (buffer);
      58  	  return false;
      59  	}
      60      }
      61  
      62    /* Install new heap-based buffer.  */
      63    buffer->data = new_ptr;
      64    buffer->length = new_length;
      65    return true;
      66  }
      67  libc_hidden_def (__libc_scratch_buffer_grow_preserve)