malloc.c

开源的BIOS启动软件

#include <bios/malloc.h>
#include <bios/system.h>
#include <bios/debug.h>

#ifndef DEBUG
# define debug_printf(x...)
#endif

/*
 * Make sure we're aligned to this
 */
#define OVERHEAD	16

struct free {
	int		size;
	struct free	*next;
};

static struct free *free_list;
extern int ram_size;

void malloc_init(void)
{
	free_list = (struct free *)(ram_size - 1048576);
	free_list->next = NULL;
	free_list->size = 1048576;
}

void *malloc(int size)
{
	struct free **f;
	void *ptr = NULL;
	flags_t flags;

	/*
	 * We will need to align it, so...
	 */
	size = (size + 15 + OVERHEAD) & ~15;

	debug_printf("malloc(%d)", size);

	flags = save_flags();
	cli();

	for (f = &free_list; *f; f = &(*f)->next) {
		struct free *tf, *nf;

		tf = *f;

		debug_printf(" (chk blk %p sz %d)", tf, tf->size);

		if (tf->size < size)
			continue;

		ptr = (void *)((int)tf + OVERHEAD);

		if (tf->size >= size + sizeof(struct free)) {
			nf = (struct free *)((int)tf + size);
			nf->next = tf->next;
			nf->size = tf->size - size;
			*f = nf;
			debug_printf(" (new blk %p sz %d)", nf, nf->size);
		} else {
			debug_printf(" (exact)");
			*f = tf->next;
		}

		tf->size = size;
		break;
	}

	restore_flags(flags);
	debug_printf(" at %p\n", ptr);
	return ptr;
}

void free(void *ptr)
{
	struct free *tf, **ff;
	flags_t flags;

	if (!ptr)
		return;

	tf = (struct free *)((int)ptr - OVERHEAD);

	debug_printf("free(%p) size %d", ptr, tf->size);

	flags = save_flags();
	cli();

	for (ff = &free_list; *ff; ff = &(*ff)->next) {
		struct free *pf;

		pf = *ff;

		if ((int)pf + pf->size == (int)tf) {
			debug_printf(" (prev %p sz %d)", pf, pf->size);
			pf->size += tf->size;
			tf = pf;
			ptr = NULL;
		}
		if ((int)tf + tf->size == (int)pf) {
			debug_printf(" (next %p sz %d)", pf, pf->size);
			tf->next = pf->next;
			tf->size += pf->size;
			*ff = tf;
			ptr = NULL;
		}
	}

	if (ptr) {
		for (ff = &free_list; *ff && (int)*ff < (int)tf; ff = &(*ff)->next);

		tf->next = *ff;
		*ff = tf;
	}

	restore_flags(flags);
	debug_printf("\n");
}