alloc.c

#include "alloc.h"

static meta p_meta = NULL;

void *origin=NULL;

void *m_malloc(size_t size){

	if(p_meta == NULL || sbrk(0) == origin){
		origin = sbrk(0);
		p_meta = sbrk(size + sizeof(struct meta_struct));
		p_meta->prev = NULL;
		p_meta->next = NULL;
		p_meta->size = size;
		p_meta->free = 0;
		
		return (void *)(p_meta+sizeof(struct meta_struct));
	}
	
	meta new = p_meta;
	meta pre = p_meta;
	
	if(fit == 'F'){
		while(new){
			if( (new->free == 1) && (size <= new->size) ){
				break;
			}
			pre = new;
			new = new->next;
		}
	}
	if(fit == 'B'){
		meta tmp = NULL;
		int chk=0;
		while(new){
			if( (new->free == 1) && (size <= new->size) ){
				if(tmp == NULL)
					tmp = new;
				if(new->size <= tmp->size){
					tmp = new;
					chk = 1;
				}
			}
			pre = new;
			new = new->next;
		}
		if(chk == 1)
			new = tmp;
	}
	if(fit == 'W'){
		meta tmp = NULL;
		int chk=0;
		while(new){
			if( (new->free == 1) && (size <= new->size) ){
				if(tmp == NULL)
					tmp = new;
				if(new->size >= tmp->size){
					tmp = new;
					chk = 1;
				}
			}
			pre = new;
			new = new->next;
		}
		if(chk == 1)
			new = tmp;
	}
	
	if(new == NULL){
		new = sbrk(0);
		sbrk(size + sizeof(struct meta_struct));
		new->prev = pre;
		new->next = NULL;
		new->size = size;
		new->free = 0;
			
		pre->next = new;
		
		return (void *)(new+sizeof(struct meta_struct));
	}
	else{
		pre = new;
		new = (void *)(pre + size + sizeof(struct meta_struct));
		new->prev = pre;
		new->next = pre->next;
		new->size = pre->size - size;
		new->free = 1;
		if(new->next != NULL)
			new->next->prev = new;
			
		if(new->size == 0){
			if(new->next != NULL)
				new->next->prev = new->prev;
			new = new->next;
		}
		pre->next = new;
		pre->size = size;
		pre->free = 0;
		return (void *)(pre + sizeof(struct meta_struct));
	}
}

void *m_free(void *ptr){

		meta cur = ptr;
		cur = (void *)(cur-sizeof(struct meta_struct));
		cur->free = 1;
	
	if(cur->prev == NULL && cur->next == NULL){
		brk(origin);
	}
	else if(cur->next == NULL){
		cur->prev->next = NULL;
		brk(cur);
	}
	
	if(cur->next != NULL && cur->next->free == 1){
		cur->size = cur->size + cur->next->size;
		if(cur->next->next != NULL)
			cur->next->next->prev = cur;
		cur->next = cur->next->next;
	}
	if(cur->prev != NULL && cur->prev->free == 1){
		cur->prev->size = cur->size + cur->prev->size;
		if(cur->prev->prev != NULL)
			cur->prev->prev->next = cur->prev;
		cur->next->prev = cur->prev;
		cur->prev->next = cur->next;
	}
	
	
}

void *m_realloc(void *ptr,size_t size){	
	meta new = ptr;
	new = (void *)(new-sizeof(struct meta_struct));
	
	if(size > new->size){
		if(new->next == NULL){
			sbrk(size - new->size);
			new->size = size;
			
			return (void *)(new+sizeof(struct meta_struct));
		}
		else if(new->next != NULL && new->next->free == 1){
			if( (new->size + new->next->size) > size){
				new->next = (void *)new + sizeof(struct meta_struct) + size;
				new->next->size = (new->size + new->next->size) - size;
				new->next->prev = new;
				new->next->free = 1;
				
				return (void *)(new+sizeof(struct meta_struct));
			}
			else if((new->size + new->next->size) == size){
				new->next = new->next->next;
				new->next->next->prev = new;
				new->size = size;
				
				return (void *)(new+sizeof(struct meta_struct));
			}
			else{
				meta tmp = m_malloc(size);
				memcpy(tmp,new,size);
				m_free(ptr);
				
				return (void *)(tmp+sizeof(struct meta_struct));
			}
		}
		else{
			meta tmp = m_malloc(size);
			tmp = (void *)(tmp-sizeof(struct meta_struct));
			
			memcpy((void *)(tmp+sizeof(struct meta_struct)),
							(void *)(new+sizeof(struct meta_struct)),
														(size+sizeof(struct meta_struct)));
			m_free(ptr);
			
			return (void *)(tmp+sizeof(struct meta_struct));
		}
	}
	else{ // size < ptr->size
		meta tmp = (void *)new + sizeof(struct meta_struct) + size;
		tmp->prev = new;
		tmp->next = new->next;
		tmp->next->prev = tmp;
		tmp->size = new->size  - size;
		tmp->free = 1;
		
		new->next = tmp;
		new->size = size;
		memcpy(new,ptr,(size+sizeof(struct meta_struct)));
				
		return (void *)(new+sizeof(struct meta_struct));
	}
}