gbdk-2020 | GameBoy Development Kit |
| download: https://git.y1.nz/archives/gbdk.tar.gz | |
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gbdk-lib/libc/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
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