alloc.c

unix环境下实现的cmm语言编译器

/*alloc.c: 对内存进行分配管理*/
#include "cmm.h"
#include "alloc.h"

struct block {
	struct block *next;
	char *limit;
	char *avail;
};

union align {
	int i;
	char *p;
	void (*func)(void);
};

union header{
	struct block b;
	union align a;
};
static struct block first[] = { {NULL}, {NULL},
	{NULL}},*arena[3] = {&first[0], &first[1],&first[2]};
static struct block *freeblock;

void *allocate(unsigned long n, unsigned a)
{
	struct block *ap;
	assert(n > 0);
	assert(a >= 0 && a < NELEMS(arena));

	ap = arena[a];
	n = roundup(n, sizeof(union align));
	while(n > ap->limit - ap->avail) {
		if ( (ap->next = freeblock) != NULL) {
			ap = ap->next;
			freeblock = freeblock->next;	
		}else {
			unsigned long m = n + sizeof(union header) + 10 * 1024;
			ap->next = malloc(m);
			if (ap->next == NULL) {
				error("memory allocate fail");
				exit(1);
			}
			ap = ap->next;
			ap->limit = (char *) ap + m;
		}
		ap->next = NULL;	
		ap->avail = (char *)((union header *)ap + 1);
	}
	arena[a] = ap;
	ap->avail += n;
	return ap->avail - n;
}

void deallocate(unsigned a)
{
	assert(a >= 0 && a < NELEMS(arena));
	arena[a]->next = freeblock;
	freeblock = first[a].next;
	first[a].next = NULL;
	arena[a] = &first[a];
}
void dispose(void)
{
	struct block *b,*next;
	for(b = freeblock; b != NULL; b = next) {
		next = b->next;
		free(b);
	}
	freeblock = NULL;
}
void *newarray(unsigned  m, unsigned n,  unsigned a)
{
	return allocate( m*n, a);
}