free.c (2504B)
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 40typedef struct header HEAPSPACE header_t; 41 42struct header 43{ 44 header_t *next; 45 header_t *next_free; 46}; 47 48extern header_t *HEAPSPACE __sdcc_heap_free; 49 50void 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