heap.c


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#include<u.h>
#include<libc.h>
#include<mheap.h>

static void *pool = nil;
static void *ptop;
static ulong psz = 0;
static ulong csz = 0;

static void *stack[128]; // Stack depth is 128 maximum
static void **stop = stack;

int hdebug = 0;

void
hinit(ulong sz)
{
	if(pool)
		free(pool);
	pool = malloc(sz);
	if(pool == nil)
		sysfatal("hinit: %r");
	
	psz = sz;
	csz = 0;
	ptop = pool;
}

void *
halloc(ulong sz)
{
	void *ptr;
	
	/* Check bounds */
	if(sz + csz > psz)
		sysfatal("halloc: heap exhausted");
	
	ptr = ptop;
	ptop = sz + (uchar*)ptop;
	csz += sz;
	
	if(hdebug)
		fprint(2, "halloc: %uld\n", csz);
	
	return ptr;
}

/* Stack management */

ulong
hpush(void)
{
	*stop = ptop;
	return (ulong)*stop++;
}

ulong
hpop(void)
{
	ptop = *--stop;
	csz = ((uchar *)ptop - (uchar*)pool);
	return (ulong)ptop;
}