1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
|
#include <stddef.h>
#include <stdint.h>
#include "malloc.h"
void * sbrk(ptrdiff_t incr);
typedef struct _heap_t {
void * ptr;
size_t size;
struct _heap_t * prev, * next;
} heap_t;
static void * heap_base = NULL;
static heap_t * head = NULL, * tail = NULL;
static heap_t * find_fit(heap_t * head, size_t size) {
heap_t * prev = head;
uintptr_t prev_top, next_bot;
while (prev) {
if (prev->next) {
prev_top = (uintptr_t) prev->ptr + prev->size;
next_bot = (uintptr_t) prev->next - prev_top;
if (next_bot >= size)
return prev;
}
prev = prev->next;
}
return prev;
}
void * base_malloc(size_t size) {
void * ptr = NULL, * heap_ptr;
heap_t * new, * prev;
size = (size + sizeof(heap_t) + 7) & ~7;
// Nothing's initialized yet ? Let's just initialize the bottom of our heap,
// flag it as allocated.
if (!head) {
if (!heap_base)
heap_base = sbrk(0);
heap_ptr = sbrk(size);
if (!heap_ptr)
return NULL;
ptr = (void *) ((uintptr_t) heap_ptr + sizeof(heap_t));
head = (heap_t *) heap_ptr;
head->ptr = ptr;
head->size = size - sizeof(heap_t);
head->prev = NULL;
head->next = NULL;
tail = head;
return ptr;
}
// We *may* have the bottom of our heap that has shifted, because of a free.
// So let's check first if we have free space there, because I'm nervous
// about having an incomplete data structure.
if (((uintptr_t) heap_base + size) < (uintptr_t) head) {
new = (heap_t *) heap_base;
ptr = (void *) ((uintptr_t) new + sizeof(heap_t));
new->ptr = ptr;
new->size = size - sizeof(heap_t);
new->prev = NULL;
new->next = head;
head->prev = new;
head = new;
return ptr;
}
// No luck at the beginning of the heap, let's walk the heap to find a fit.
prev = find_fit(head, size);
if (prev) {
new = (heap_t *) ((uintptr_t) prev->ptr + prev->size);
ptr = (void *) ((uintptr_t) new + sizeof(heap_t));
new->ptr = ptr;
new->size = size - sizeof(heap_t);
new->prev = prev;
new->next = prev->next;
new->next->prev = new;
prev->next = new;
return ptr;
}
// Time to extend the size of the heap.
heap_ptr = sbrk(size);
if (!heap_ptr)
return NULL;
ptr = (void *) ((uintptr_t) heap_ptr + sizeof(heap_t));
new = (heap_t *) heap_ptr;
new->ptr = ptr;
new->size = size - sizeof(heap_t);
new->prev = tail;
new->next = NULL;
tail->next = new;
tail = new;
return ptr;
}
void * base_realloc(void * ptr, size_t size) {
heap_t * prev;
void * new = NULL;
if (!size && ptr) {
free(ptr);
return NULL;
}
if (!ptr)
return malloc(size);
size = (size + sizeof(heap_t) + 7) & ~7;
prev = (heap_t *) ((uintptr_t) ptr - sizeof(heap_t));
// New memory block shorter ?
if (prev->size >= size) {
prev->size = size;
if (!prev->next)
sbrk(ptr + size - sbrk(0));
return ptr;
}
// New memory block larger
// Is it the last one ?
if (!prev->next) {
new = sbrk(size - prev->size);
if (!new)
return NULL;
prev->size = size;
return ptr;
}
// Do we have free memory after it ?
if ((prev->next->ptr - ptr) > size) {
prev->size = size;
return ptr;
}
// No luck.
new = malloc(size);
if (!new)
return NULL;
memcpy(new, ptr, prev->size);
free(ptr);
return new;
}
void base_free(void * ptr) {
heap_t * cur;
void * top;
size_t size;
if (!ptr || !head)
return;
// First block; bumping head ahead.
if (ptr == head->ptr) {
size = head->size + (size_t) (head->ptr - (void *) head);
head = head->next;
if (head) {
head->prev = NULL;
} else {
tail = NULL;
sbrk(-size);
}
return;
}
// Finding the proper block
cur = head;
for (cur = head; ptr != cur->ptr; cur = cur->next)
if (!cur->next)
return;
if (cur->next) {
// In the middle, just unlink it
cur->next->prev = cur->prev;
} else {
// At the end, shrink heap
tail = cur->prev;
top = sbrk(0);
size = (top - cur->prev->ptr) - cur->prev->size;
sbrk(-size);
}
cur->prev->next = cur->next;
}
__attribute__((weak)) void * __builtin_new(size_t size) { return malloc(size); }
__attribute__((weak)) void __builtin_delete(void * ptr) { free(ptr); }
malloc_t malloc = base_malloc;
free_t free = base_free;
realloc_t realloc = base_realloc;
|
