/* Inserts in order a chunk into the free list. Caller adjusts heap state */
static PmReturn_t
heap_linkToFreelist(pPmHeapDesc_t pchunk)
{
uint16_t size;
pPmHeapDesc_t pscan;
/* Ensure the object is already free */
C_ASSERT(OBJ_GET_FREE(pchunk) != 0);
/* If free list is empty, add to head of list */
if (pmHeap.pfreelist == C_NULL)
{
pmHeap.pfreelist = pchunk;
pchunk->next = C_NULL;
pchunk->prev = C_NULL;
return PM_RET_OK;
}
/* Scan free list for insertion point */
pscan = pmHeap.pfreelist;
size = OBJ_GET_SIZE(pchunk);
while ((OBJ_GET_SIZE(pscan) < size) && (pscan->next != C_NULL))
{
pscan = pscan->next;
}
/*
* Insert chunk after the scan chunk (next is NULL).
* This is a slightly rare case where the last chunk in the free list
* is smaller than the chunk being freed.
*/
if (size > OBJ_GET_SIZE(pscan))
{
pchunk->next = pscan->next;
pscan->next = pchunk;
pchunk->prev = pscan;
}
/* Insert chunk before the scan chunk */
else
{
pchunk->next = pscan;
pchunk->prev = pscan->prev;
/* If chunk will be first item in free list */
if (pscan->prev == C_NULL)
{
pmHeap.pfreelist = pchunk;
}
else
{
pscan->prev->next = pchunk;
}
pscan->prev = pchunk;
}
return PM_RET_OK;
}
static void
heap_gcPrintFreelist(void)
{
pPmHeapDesc_t pchunk = pmHeap.pfreelist;
printf("DEBUG: pmHeap.avail = %d\n", pmHeap.avail);
printf("DEBUG: freelist:\n");
while (pchunk != C_NULL)
{
printf("DEBUG: free chunk (%d bytes) @ 0x%0x\n",
OBJ_GET_SIZE(pchunk), (int)pchunk);
pchunk = pchunk->next;
}
}
/* Releases chunk to the free list */
PmReturn_t
heap_freeChunk(pPmObj_t ptr)
{
PmReturn_t retval;
C_DEBUG_PRINT(VERBOSITY_HIGH, "heap_freeChunk(), id=%p, s=%d\n",
ptr, OBJ_GET_SIZE(ptr));
/* Ensure the chunk falls within the heap */
C_ASSERT(((uint8_t *)ptr >= pmHeap.base)
&& ((uint8_t *)ptr < pmHeap.base + HEAP_SIZE));
/* Insert the chunk into the freelist */
OBJ_SET_FREE(ptr, 1);
/* Clear type so that heap descriptor's size's upper byte is zero */
OBJ_SET_TYPE(ptr, 0);
retval = heap_linkToFreelist((pPmHeapDesc_t)ptr);
PM_RETURN_IF_ERROR(retval);
/* Increase heap available amount */
pmHeap.avail += OBJ_GET_SIZE(ptr);
return retval;
}
/* Removes the given chunk from the free list; leaves list in sorted order */
static PmReturn_t
heap_unlinkFromFreelist(pPmHeapDesc_t pchunk)
{
C_ASSERT(pchunk != C_NULL);
pmHeap.avail -= OBJ_GET_SIZE(pchunk);
if (pchunk->next != C_NULL)
{
pchunk->next->prev = pchunk->prev;
}
/* If pchunk was the first chunk in the free list, update the heap ptr */
if (pchunk->prev == C_NULL)
{
pmHeap.pfreelist = pchunk->next;
}
else
{
pchunk->prev->next = pchunk->next;
}
return PM_RET_OK;
}
/**
* Obtains a chunk of memory from the free list
*
* Performs the Best Fit algorithm.
* Iterates through the freelist to see if a chunk of suitable size exists.
* Shaves a chunk to perfect size iff the remainder is greater than
* the minimum chunk size.
*
* @param size Requested chunk size
* @param r_pchunk Return ptr to chunk
* @return Return status
*/
static PmReturn_t
heap_getChunkImpl(uint16_t size, uint8_t **r_pchunk)
{
PmReturn_t retval;
pPmHeapDesc_t pchunk;
pPmHeapDesc_t premainderChunk;
C_ASSERT(r_pchunk != C_NULL);
/* Skip to the first chunk that can hold the requested size */
pchunk = pmHeap.pfreelist;
while ((pchunk != C_NULL) && (OBJ_GET_SIZE(pchunk) < size))
{
pchunk = pchunk->next;
}
/* No chunk of appropriate size was found, raise OutOfMemory exception */
if (pchunk == C_NULL)
{
*r_pchunk = C_NULL;
PM_RAISE(retval, PM_RET_EX_MEM);
return retval;
}
/* Remove the chunk from the free list */
retval = heap_unlinkFromFreelist(pchunk);
PM_RETURN_IF_ERROR(retval);
/* Check if a chunk should be carved from what is available */
if (OBJ_GET_SIZE(pchunk) - size >= HEAP_MIN_CHUNK_SIZE)
{
/* Create the heap descriptor for the remainder chunk */
premainderChunk = (pPmHeapDesc_t)((uint8_t *)pchunk + size);
OBJ_SET_FREE(premainderChunk, 1);
OBJ_SET_SIZE(premainderChunk, OBJ_GET_SIZE(pchunk) - size);
/* Put the remainder chunk back in the free list */
retval = heap_linkToFreelist(premainderChunk);
PM_RETURN_IF_ERROR(retval);
/* Convert the chunk from a heap descriptor to an object descriptor */
OBJ_SET_SIZE(pchunk, 0);
OBJ_SET_FREE(pchunk, 0);
OBJ_SET_SIZE(pchunk, size);
C_DEBUG_PRINT(VERBOSITY_HIGH,
"heap_getChunkImpl()carved, id=%p, s=%d\n", pchunk,
size);
}
else
{
/* Set chunk's type to none (overwrites size field's high byte) */
OBJ_SET_TYPE((pPmObj_t)pchunk, OBJ_TYPE_NON);
OBJ_SET_FREE(pchunk, 0);
C_DEBUG_PRINT(VERBOSITY_HIGH,
"heap_getChunkImpl()exact, id=%p, s=%d\n", pchunk,
OBJ_GET_SIZE(pchunk));
}
/*
* Set the chunk's GC mark so it will be collected during the next GC cycle
* if it is not reachable
*/
OBJ_SET_GCVAL(pchunk, pmHeap.gcval);
/* Return the chunk */
*r_pchunk = (uint8_t *)pchunk;
return retval;
}
/*
* Reclaims any object that does not have a current mark.
* Puts it in the free list. Coalesces all contiguous free chunks.
*/
static PmReturn_t
heap_gcSweep(void)
{
PmReturn_t retval;
pPmObj_t pobj;
pPmHeapDesc_t pchunk;
uint16_t totalchunksize;
#if USE_STRING_CACHE
retval = heap_purgeStringCache(pmHeap.gcval);
#endif
/* Start at the base of the heap */
pobj = (pPmObj_t)pmHeap.base;
while ((uint8_t *)pobj < &pmHeap.base[PM_HEAP_SIZE])
{
/* Skip to the next unmarked or free chunk within the heap */
while (!OBJ_GET_FREE(pobj)
&& (OBJ_GET_GCVAL(pobj) == pmHeap.gcval)
&& ((uint8_t *)pobj < &pmHeap.base[PM_HEAP_SIZE]))
{
pobj = (pPmObj_t)((uint8_t *)pobj + OBJ_GET_SIZE(pobj));
}
/* Stop if reached the end of the heap */
if ((uint8_t *)pobj >= &pmHeap.base[PM_HEAP_SIZE])
{
break;
}
/* Accumulate the sizes of all consecutive unmarked or free chunks */
totalchunksize = 0;
/* Coalesce all contiguous free chunks */
pchunk = (pPmHeapDesc_t)pobj;
while (OBJ_GET_FREE(pchunk)
|| (!OBJ_GET_FREE(pchunk)
&& (OBJ_GET_GCVAL(pchunk) != pmHeap.gcval)))
{
if ((totalchunksize + OBJ_GET_SIZE(pchunk))
> HEAP_MAX_FREE_CHUNK_SIZE)
{
break;
}
totalchunksize = totalchunksize + OBJ_GET_SIZE(pchunk);
/*
* If the chunk is already free, unlink it because its size
* is about to change
*/
if (OBJ_GET_FREE(pchunk))
{
retval = heap_unlinkFromFreelist(pchunk);
PM_RETURN_IF_ERROR(retval);
}
/* Otherwise free and reclaim the unmarked chunk */
else
{
OBJ_SET_TYPE(pchunk, 0);
OBJ_SET_FREE(pchunk, 1);
}
C_DEBUG_PRINT(VERBOSITY_HIGH, "heap_gcSweep(), id=%p, s=%d\n",
pchunk, OBJ_GET_SIZE(pchunk));
/* Proceed to the next chunk */
pchunk = (pPmHeapDesc_t)
((uint8_t *)pchunk + OBJ_GET_SIZE(pchunk));
/* Stop if it's past the end of the heap */
if ((uint8_t *)pchunk >= &pmHeap.base[PM_HEAP_SIZE])
{
break;
}
}
/* Set the heap descriptor data */
OBJ_SET_FREE(pobj, 1);
OBJ_SET_SIZE(pobj, totalchunksize);
/* Insert chunk into free list */
retval = heap_linkToFreelist((pPmHeapDesc_t)pobj);
PM_RETURN_IF_ERROR(retval);
/* Continue to the next chunk */
pobj = (pPmObj_t)pchunk;
}
return PM_RET_OK;
}
/*
* Reclaims any object that doesn't have a current mark.
* Puts it in the free list. Coalesces all contiguous free chunks.
*/
static PmReturn_t
heap_gcSweep(void)
{
PmReturn_t retval;
pPmObj_t pobj;
pPmHeapDesc_t pchunk;
uint16_t totalchunksize;
uint16_t additionalheapsize;
/* Start at the base of the heap */
pobj = (pPmObj_t)pmHeap.base;
while ((uint8_t *)pobj < &pmHeap.base[HEAP_SIZE])
{
/* Skip to the next unmarked or free chunk within the heap */
while (!OBJ_GET_FREE(pobj)
&& (OBJ_GET_GCVAL(pobj) == pmHeap.gcval)
&& ((uint8_t *)pobj < &pmHeap.base[HEAP_SIZE]))
{
pobj = (pPmObj_t)((uint8_t *)pobj + OBJ_GET_SIZE(pobj));
/*printf("Object is at addr <%x>\n",(uint32_t)pobj);*/
#if 0
printf("pobj=");obj_print(pobj,0);printf("; type=%x; size=%x\n",OBJ_GET_TYPE(pobj),OBJ_GET_SIZE(pobj));
#endif
}
/* Stop if reached the end of the heap */
if ((uint8_t *)pobj >= &pmHeap.base[HEAP_SIZE])
{
break;
}
/* Accumulate the sizes of all consecutive unmarked or free chunks */
totalchunksize = 0;
additionalheapsize = 0;
/* Coalesce all contiguous free chunks */
pchunk = (pPmHeapDesc_t)pobj;
while (OBJ_GET_FREE(pchunk)
|| (!OBJ_GET_FREE(pchunk)
&& (OBJ_GET_GCVAL(pchunk) != pmHeap.gcval)))
{
totalchunksize += OBJ_GET_SIZE(pchunk);
/*
* If the chunk is already free, unlink it because its size
* is about to change
*/
if (OBJ_GET_FREE(pchunk))
{
retval = heap_unlinkFromFreelist(pchunk);
PM_RETURN_IF_ERROR(retval);
}
/* Otherwise free and reclaim the unmarked chunk */
else
{
OBJ_SET_TYPE(pchunk, 0);
OBJ_SET_FREE(pchunk, 1);
additionalheapsize += OBJ_GET_SIZE(pchunk);
}
C_DEBUG_PRINT(VERBOSITY_HIGH, "heap_gcSweep(), id=%p, s=%d\n",
pchunk, OBJ_GET_SIZE(pchunk));
#if 0
/* It's possible for 0-sized chunks to exist (which makes no sense) TODO:solve */
/* They result in infinite loops, so we must curtail them */
if (OBJ_GET_SIZE(pchunk) == 0)
{
break;
}
#endif
/* Proceed to the next chunk */
pchunk = (pPmHeapDesc_t)
((uint8_t *)pchunk + OBJ_GET_SIZE(pchunk));
/* Stop if it's past the end of the heap */
if ((uint8_t *)pchunk >= &pmHeap.base[HEAP_SIZE])
{
break;
}
}
/* Adjust the heap stats */
pmHeap.avail += additionalheapsize;
/* Set the heap descriptor data */
OBJ_SET_FREE(pobj, 1);
OBJ_SET_SIZE(pobj, totalchunksize);
#if 0
/* avoid loops by breaking on 0-size */
if (totalchunksize == 0)
{
break;
}
#endif
/* Insert chunk into free list */
retval = heap_linkToFreelist((pPmHeapDesc_t)pobj);
PM_RETURN_IF_ERROR(retval);
/* Continue to the next chunk */
pobj = (pPmObj_t)pchunk;
}
return PM_RET_OK;
}
