src/core/ebuffer.c

   1 /*
   2  * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 /**
  20  * @file
  21  *
  22  * Automatically expanding buffers
  23  *
  24  */
  25
  26 #include <errno.h>
  27 #include <gpxe/buffer.h>
  28 #include <gpxe/umalloc.h>
  29 #include <gpxe/ebuffer.h>
  30
  31 /**
  32  * Expand expandable buffer
  33  *
  34  * @v buffer            Buffer descriptor
  35  * @v new_len           Required new size
  36  * @ret rc              Return status code
  37  */
  38 static int ebuffer_expand ( struct buffer *buffer, size_t new_len ) {
  39         size_t actual_len = 1;
  40         userptr_t new_addr;
  41
  42         /* Round new_len up to the nearest power of two, to reduce
  43          * total number of reallocations required.  Don't do this for
  44          * the first expansion; this allows for protocols that do
  45          * actually know the exact length in advance.
  46          */
  47         if ( buffer->len ) {
  48                 while ( actual_len < new_len )
  49                         actual_len <<= 1;
  50         } else {
  51                 actual_len = new_len;
  52         }
  53
  54         /* Reallocate buffer */
  55 #warning "urealloc() has issues with length zero"
  56         new_addr = urealloc ( buffer->addr, // actual_len );
  57                               actual_len ? actual_len : 1 );
  58         if ( ! new_addr )
  59                 return -ENOMEM;
  60
  61         buffer->addr = new_addr;
  62         buffer->len = actual_len;
  63         return 0;
  64 }
  65
  66 /**
  67  * Allocate expandable buffer
  68  *
  69  * @v buffer            Buffer descriptor
  70  * @v len               Initial length (may be zero)
  71  * @ret rc              Return status code
  72  *
  73  * Allocates space for the buffer and stores it in @c buffer->addr.
  74  * The space must eventually be freed by calling ufree(buffer->addr).
  75  */
  76 int ebuffer_alloc ( struct buffer *buffer, size_t len ) {
  77         memset ( buffer, 0, sizeof ( *buffer ) );
  78         buffer->expand = ebuffer_expand;
  79         return ebuffer_expand ( buffer, len );
  80 }