diff --git a/main.c b/main.c index eaddc08..b15c67f 100644 --- a/main.c +++ b/main.c @@ -1,15 +1,110 @@ #include +#include +#include -void* malloc(unsigned long size) +#define ALIGN4(s) (((((s)-1)>>2)<<2)+4) +#define BLOCK_SIZE sizeof(struct block) + +struct block { - return NULL; + size_t size; + struct block* next; + int free; +}; + +struct block* freeList = NULL; + +struct block* extend_heap(struct block* last, size_t s) +{ + struct block* b = sbrk(0); + + if (sbrk(BLOCK_SIZE + s) == (void*)-1) + return NULL; + + b->size = s; + b->next = NULL; + b->free = 0; + + if (last) + last->next = b; + + return b; +} + +struct block* find_first(size_t s) +{ + struct block* current = freeList; + while (current && (!current->free || current->size < s)) + current = current->next; + + return current; +} + +struct block* find_last() +{ + struct block* current = freeList; + while (current && current->next) + current = freeList->next; + + return current; +} + +void* malloc(size_t size) +{ + struct block* b; + + size_t alignedSize = ALIGN4(size); + + if (freeList) + { + b = find_first(alignedSize); + if (!b) + b = extend_heap(find_last(), alignedSize); + } + else + { + b = extend_heap(NULL, alignedSize); + if (!b) + return NULL; + + freeList = b; + } + + return (char*)b + BLOCK_SIZE; } void free(void* ptr) { + if (!ptr) + return; + + struct block* b = (struct block*)((char*)ptr - BLOCK_SIZE); + b->free = 1; + + struct block* link = b->next; + while (b->next && b->next->free) + { + b->size += BLOCK_SIZE + b->next->size; + b->next = link->next; + } + + if (!b->next) + brk(b); } -int main(void) +int main() { + int* a = (int*)malloc(sizeof(int)); + int* b = (int*)malloc(sizeof(int)); + + *a = 5; + *b = 12; + + printf("Test 1: %i\n", *a); + printf("Test 2: %i", *b); + + free(b); + free(a); + return 0; } \ No newline at end of file