void umm_init_x( size_t size ) {
uint32_t UMM_MALLOC_CFG_HEAP_SIZE = (size / sizeof(size_t)) * sizeof(size_t);
if (UMM_MALLOC_CFG_HEAP_SIZE < (sizeof(umm_block) * 128)) fb_alloc_fail();
if (UMM_MALLOC_CFG_HEAP_SIZE > (sizeof(umm_block) * 32768)) UMM_MALLOC_CFG_HEAP_SIZE = sizeof(umm_block) * 32768;
void *UMM_MALLOC_CFG_HEAP_ADDR = fb_alloc(UMM_MALLOC_CFG_HEAP_SIZE);
/* init heap pointer and size, and memset it to 0 */
umm_heap = (umm_block *)UMM_MALLOC_CFG_HEAP_ADDR;
umm_numblocks = (UMM_MALLOC_CFG_HEAP_SIZE / sizeof(umm_block));
memset(umm_heap, 0x00, UMM_MALLOC_CFG_HEAP_SIZE);
/* setup initial blank heap structure */
{
/* index of the 0th `umm_block` */
const unsigned short int block_0th = 0;
/* index of the 1st `umm_block` */
const unsigned short int block_1th = 1;
/* index of the latest `umm_block` */
const unsigned short int block_last = UMM_NUMBLOCKS - 1;
/* setup the 0th `umm_block`, which just points to the 1st */
UMM_NBLOCK(block_0th) = block_1th;
UMM_NFREE(block_0th) = block_1th;
UMM_PFREE(block_0th) = block_1th;
/*
* Now, we need to set the whole heap space as a huge free block. We should
* not touch the 0th `umm_block`, since it's special: the 0th `umm_block`
* is the head of the free block list. It's a part of the heap invariant.
*
* See the detailed explanation at the beginning of the file.
*/
/*
* 1th `umm_block` has pointers:
*
* - next `umm_block`: the latest one
* - prev `umm_block`: the 0th
*
* Plus, it's a free `umm_block`, so we need to apply `UMM_FREELIST_MASK`
*
* And it's the last free block, so the next free block is 0.
*/
UMM_NBLOCK(block_1th) = block_last | UMM_FREELIST_MASK;
UMM_NFREE(block_1th) = 0;
UMM_PBLOCK(block_1th) = block_0th;
UMM_PFREE(block_1th) = block_0th;
/*
* latest `umm_block` has pointers:
*
* - next `umm_block`: 0 (meaning, there are no more `umm_blocks`)
* - prev `umm_block`: the 1st
*
* It's not a free block, so we don't touch NFREE / PFREE at all.
*/
UMM_NBLOCK(block_last) = 0;
UMM_PBLOCK(block_last) = block_1th;
}
}
// returns null pointer without error if size==0
void *fb_alloc(uint32_t size)
{
if (!size) {
return NULL;
}
size=((size+sizeof(uint32_t)-1)/sizeof(uint32_t))*sizeof(uint32_t);// Round Up
char *result = pointer - size;
char *new_pointer = result - sizeof(uint32_t);
// Check if allocation overwrites the framebuffer pixels
if (new_pointer < (char *) FB_PIXELS()) {
fb_alloc_fail();
}
*((uint32_t *) new_pointer) = size + sizeof(uint32_t); // Save size.
pointer = new_pointer;
return result;
}
