sdcc/device/lib/free.c

   1 /*-------------------------------------------------------------------------
   2    free.c - deallocate memory.
   3
   4    Copyright (C) 2015, Philipp Klaus Krause, pkk@spth.de
   5
   6    This library is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by the
   8    Free Software Foundation; either version 2, or (at your option) any
   9    later version.
  10
  11    This library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this library; see the file COPYING. If not, write to the
  18    Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  19    MA 02110-1301, USA.
  20
  21    As a special exception, if you link this library with other files,
  22    some of which are compiled with SDCC, to produce an executable,
  23    this library does not by itself cause the resulting executable to
  24    be covered by the GNU General Public License. This exception does
  25    not however invalidate any other reasons why the executable file
  26    might be covered by the GNU General Public License.
  27 -------------------------------------------------------------------------*/
  28
  29 #include <stdlib.h>
  30 #include <stddef.h>
  31
  32 #if defined(__SDCC_mcs51) || defined(__SDCC_ds390) || defined(__SDCC_ds400)
  33 #define HEAPSPACE __xdata
  34 #elif defined(__SDCC_pdk13) || defined(__SDCC_pdk14) || defined(__SDCC_pdk15)
  35 #define HEAPSPACE __near
  36 #else
  37 #define HEAPSPACE
  38 #endif
  39
  40 typedef struct header HEAPSPACE header_t;
  41
  42 struct header
  43 {
  44         header_t *next;
  45         header_t *next_free;
  46 };
  47
  48 extern header_t *HEAPSPACE __sdcc_heap_free;
  49
  50 void free(void *ptr)
  51 {
  52         header_t *h, *next_free, *prev_free;
  53         header_t *HEAPSPACE *f;
  54
  55         if(!ptr)
  56                 return;
  57
  58         prev_free = 0;
  59         for(h = __sdcc_heap_free, f = &__sdcc_heap_free; h && h < ptr; prev_free = h, f = &(h->next_free), h = h->next_free); // Find adjacent blocks in free list
  60         next_free = h;
  61
  62         h = (void HEAPSPACE *)((char HEAPSPACE *)(ptr) - offsetof(struct header, next_free));
  63
  64         // Insert into free list.
  65         h->next_free = next_free;
  66         *f = h;
  67
  68         if(next_free == h->next) // Merge with next block
  69         {
  70                 h->next_free = h->next->next_free;
  71                 h->next = h->next->next;
  72         }
  73
  74         if (prev_free && prev_free->next == h) // Merge with previous block
  75         {
  76                 prev_free->next = h->next;
  77                 prev_free->next_free = h->next_free;
  78         }
  79 }
  80