static void *
wmem_block_alloc(void *private_data, const size_t size)
{
wmem_block_allocator_t *allocator = (wmem_block_allocator_t*) private_data;
wmem_block_chunk_t *chunk;
if (size > WMEM_BLOCK_MAX_ALLOC_SIZE) {
return wmem_block_alloc_jumbo(allocator, size);
}
if (allocator->recycler_head &&
WMEM_CHUNK_DATA_LEN(allocator->recycler_head) >= size) {
/* If we can serve it from the recycler, do so. */
chunk = allocator->recycler_head;
}
else {
if (allocator->master_head &&
WMEM_CHUNK_DATA_LEN(allocator->master_head) < size) {
/* Recycle the head of the master list if necessary. */
chunk = allocator->master_head;
wmem_block_pop_master(allocator);
wmem_block_add_to_recycler(allocator, chunk);
}
if (!allocator->master_head) {
/* Allocate a new block if necessary. */
wmem_block_new_block(allocator);
}
chunk = allocator->master_head;
}
/* if our chunk is used, something is wrong */
g_assert(! chunk->used);
/* if we still don't have the space at this point, something is wrong */
g_assert(size <= WMEM_CHUNK_DATA_LEN(chunk));
/* Split our chunk into two to preserve any trailing free space */
wmem_block_split_free_chunk(allocator, chunk, size);
/* if our split reduced our size too much, something went wrong */
g_assert(size <= WMEM_CHUNK_DATA_LEN(chunk));
/* the resulting chunk should not be in either free list */
g_assert(chunk != allocator->master_head);
g_assert(chunk != allocator->recycler_head);
/* Now cycle the recycler */
wmem_block_cycle_recycler(allocator);
/* mark it as used */
chunk->used = TRUE;
/* and return the user's pointer */
return WMEM_CHUNK_TO_DATA(chunk);
}
/* Takes a used chunk and a size, and splits it into two chunks if possible.
* The first chunk can hold at least `size` bytes of data, while the second gets
* whatever's left over. The second is marked as unused and is added to the
* recycler. */
static void
wmem_block_split_used_chunk(wmem_block_allocator_t *allocator,
wmem_block_chunk_t *chunk,
const size_t size)
{
wmem_block_chunk_t *extra;
size_t aligned_size, available;
gboolean last;
g_assert(chunk->used);
g_assert(WMEM_CHUNK_DATA_LEN(chunk) >= size);
aligned_size = WMEM_ALIGN_SIZE(size) + WMEM_CHUNK_HEADER_SIZE;
if (aligned_size > WMEM_CHUNK_DATA_LEN(chunk)) {
/* in this case we don't have enough space to really split it, so
* it's basically a no-op */
return;
}
/* otherwise, we have room to split it, though the remaining free chunk
* may still not be usefully large */
/* preserve a few values from chunk that we'll need to manipulate */
last = chunk->last;
available = chunk->len - aligned_size;
/* set new values for chunk */
chunk->len = (guint32) aligned_size;
chunk->last = FALSE;
/* with chunk's values set, we can use the standard macro to calculate
* the location and size of the new free chunk */
extra = WMEM_CHUNK_NEXT(chunk);
/* set the new values for the chunk */
extra->len = (guint32) available;
extra->last = last;
extra->prev = chunk->len;
extra->used = FALSE;
extra->jumbo = FALSE;
/* Correctly update the following chunk's back-pointer */
if (!last) {
WMEM_CHUNK_NEXT(extra)->prev = extra->len;
}
/* Merge it to its right if possible (it can't be merged left, obviously).
* This also adds it to the recycler. */
wmem_block_merge_free(allocator, extra);
}
/* Adds a chunk from the recycler. */
static void
wmem_block_add_to_recycler(wmem_block_allocator_t *allocator,
wmem_block_chunk_t *chunk)
{
wmem_block_free_t *free_chunk;
if (WMEM_CHUNK_DATA_LEN(chunk) < sizeof(wmem_block_free_t)) {
return;
}
free_chunk = WMEM_GET_FREE(chunk);
if (! allocator->recycler_head) {
/* First one */
free_chunk->next = chunk;
free_chunk->prev = chunk;
allocator->recycler_head = chunk;
}
else {
free_chunk->next = allocator->recycler_head;
free_chunk->prev = WMEM_GET_FREE(allocator->recycler_head)->prev;
WMEM_GET_FREE(free_chunk->next)->prev = chunk;
WMEM_GET_FREE(free_chunk->prev)->next = chunk;
if (chunk->len > allocator->recycler_head->len) {
allocator->recycler_head = chunk;
}
}
}
static void *
wmem_block_alloc(void *private_data, const size_t size)
{
wmem_block_allocator_t *allocator = (wmem_block_allocator_t*) private_data;
wmem_block_chunk_t *chunk;
if (size > WMEM_BLOCK_MAX_ALLOC_SIZE) {
return wmem_block_alloc_jumbo(allocator, size);
}
if (allocator->recycler_head &&
WMEM_CHUNK_DATA_LEN(allocator->recycler_head) >= size) {
/* If we can serve it from the recycler, do so. */
chunk = allocator->recycler_head;
}
else {
if (allocator->master_head &&
WMEM_CHUNK_DATA_LEN(allocator->master_head) < size) {
/* Recycle the head of the master list if necessary. */
chunk = allocator->master_head;
wmem_block_pop_master(allocator);
wmem_block_add_to_recycler(allocator, chunk);
}
if (!allocator->master_head) {
/* Allocate a new block if necessary. */
wmem_block_new_block(allocator);
}
chunk = allocator->master_head;
}
/* Split our chunk into two to preserve any trailing free space */
wmem_block_split_free_chunk(allocator, chunk, size);
/* Now cycle the recycler */
wmem_block_cycle_recycler(allocator);
/* mark it as used */
chunk->used = TRUE;
/* and return the user's pointer */
return WMEM_CHUNK_TO_DATA(chunk);
}
/* DEBUG AND TEST */
static int
wmem_block_verify_block(wmem_block_hdr_t *block)
{
int total_free_space = 0;
guint32 total_len;
wmem_block_chunk_t *chunk;
chunk = WMEM_BLOCK_TO_CHUNK(block);
total_len = WMEM_BLOCK_HEADER_SIZE;
if (chunk->jumbo) {
/* We can tell nothing else about jumbo chunks except that they are
* always used. */
return 0;
}
g_assert(chunk->prev == 0);
do {
total_len += chunk->len;
g_assert(chunk->len >= WMEM_CHUNK_HEADER_SIZE);
g_assert(!chunk->jumbo);
if (WMEM_CHUNK_NEXT(chunk)) {
g_assert(chunk->len == WMEM_CHUNK_NEXT(chunk)->prev);
}
if (!chunk->used &&
WMEM_CHUNK_DATA_LEN(chunk) >= sizeof(wmem_block_free_t)) {
total_free_space += chunk->len;
if (!chunk->last) {
g_assert(WMEM_GET_FREE(chunk)->next);
g_assert(WMEM_GET_FREE(chunk)->prev);
}
}
chunk = WMEM_CHUNK_NEXT(chunk);
} while (chunk);
g_assert(total_len == WMEM_BLOCK_SIZE);
return total_free_space;
}
static void *
wmem_block_realloc(void *private_data, void *ptr, const size_t size)
{
wmem_block_allocator_t *allocator = (wmem_block_allocator_t*) private_data;
wmem_block_chunk_t *chunk;
chunk = WMEM_DATA_TO_CHUNK(ptr);
if (chunk->jumbo) {
return wmem_block_realloc_jumbo(allocator, chunk, size);
}
if (size > WMEM_CHUNK_DATA_LEN(chunk)) {
/* grow */
wmem_block_chunk_t *tmp;
tmp = WMEM_CHUNK_NEXT(chunk);
if (tmp && (!tmp->used) &&
(size < WMEM_CHUNK_DATA_LEN(chunk) + tmp->len)) {
/* the next chunk is free and has enough extra, so just grab
* from that */
size_t split_size;
/* we ask for the next chunk to be split, but we don't end up
* using the split chunk header (it just gets merged into this one),
* so we want the split to be of (size - curdatalen - header_size).
* However, this can underflow by header_size, so we do a quick
* check here and floor the value to 0. */
split_size = size - WMEM_CHUNK_DATA_LEN(chunk);
if (split_size < WMEM_CHUNK_HEADER_SIZE) {
split_size = 0;
}
else {
split_size -= WMEM_CHUNK_HEADER_SIZE;
}
wmem_block_split_free_chunk(allocator, tmp, split_size);
/* Now do a 'quickie' merge between the current block and the left-
* hand side of the split. Simply calling wmem_block_merge_free
* might confuse things, since we may temporarily have two blocks
* to our right that are both free (and it isn't guaranteed to
* handle that case). Update our 'next' count and last flag, and
* our (new) successor's 'prev' count */
chunk->len += tmp->len;
chunk->last = tmp->last;
tmp = WMEM_CHUNK_NEXT(chunk);
if (tmp) {
tmp->prev = chunk->len;
}
/* Now cycle the recycler */
wmem_block_cycle_recycler(allocator);
/* And return the same old pointer */
return ptr;
}
else {
/* no room to grow, need to alloc, copy, free */
void *newptr;
newptr = wmem_block_alloc(private_data, size);
memcpy(newptr, ptr, WMEM_CHUNK_DATA_LEN(chunk));
wmem_block_free(private_data, ptr);
/* No need to cycle the recycler, alloc and free both did that
* already */
return newptr;
}
}
else if (size < WMEM_CHUNK_DATA_LEN(chunk)) {
/* shrink */
wmem_block_split_used_chunk(allocator, chunk, size);
/* Now cycle the recycler */
wmem_block_cycle_recycler(allocator);
return ptr;
}
/* no-op */
return ptr;
}
/* Takes an unused chunk and a size, and splits it into two chunks if possible.
* The first chunk (at the same address as the input chunk) is guaranteed to
* hold at least `size` bytes of data, and to not be in either the master or
* recycler lists.
*
* The second chunk gets whatever data is left over. It is marked unused and
* replaces the input chunk in whichever list it originally inhabited. */
static void
wmem_block_split_free_chunk(wmem_block_allocator_t *allocator,
wmem_block_chunk_t *chunk,
const size_t size)
{
wmem_block_chunk_t *extra;
wmem_block_free_t *old_blk, *new_blk;
size_t aligned_size, available;
gboolean last;
aligned_size = WMEM_ALIGN_SIZE(size) + WMEM_CHUNK_HEADER_SIZE;
if (WMEM_CHUNK_DATA_LEN(chunk) < aligned_size + sizeof(wmem_block_free_t)) {
/* If the available space is not enought to store all of
* (hdr + requested size + alignment padding + hdr + free-header) then
* just remove the current chunk from the free list and return, since we
* can't usefully split it. */
if (chunk == allocator->master_head) {
wmem_block_pop_master(allocator);
}
else if (WMEM_CHUNK_DATA_LEN(chunk) >= sizeof(wmem_block_free_t)) {
wmem_block_remove_from_recycler(allocator, chunk);
}
return;
}
/* preserve a few values from chunk that we'll need to manipulate */
last = chunk->last;
available = chunk->len - aligned_size;
/* set new values for chunk */
chunk->len = (guint32) aligned_size;
chunk->last = FALSE;
/* with chunk's values set, we can use the standard macro to calculate
* the location and size of the new free chunk */
extra = WMEM_CHUNK_NEXT(chunk);
/* Now we move the free chunk's address without changing its location
* in whichever list it is in.
*
* Note that the new chunk header 'extra' may overlap the old free header,
* so we have to copy the free header before we write anything to extra.
*/
old_blk = WMEM_GET_FREE(chunk);
new_blk = WMEM_GET_FREE(extra);
if (allocator->master_head == chunk) {
new_blk->prev = old_blk->prev;
new_blk->next = old_blk->next;
if (old_blk->next) {
WMEM_GET_FREE(old_blk->next)->prev = extra;
}
allocator->master_head = extra;
}
else {
if (old_blk->prev == chunk) {
new_blk->prev = extra;
new_blk->next = extra;
}
else {
new_blk->prev = old_blk->prev;
new_blk->next = old_blk->next;
WMEM_GET_FREE(old_blk->prev)->next = extra;
WMEM_GET_FREE(old_blk->next)->prev = extra;
}
if (allocator->recycler_head == chunk) {
allocator->recycler_head = extra;
}
}
/* Now that we've copied over the free-list stuff (which may have overlapped
* with our new chunk header) we can safely write our new chunk header. */
extra->len = (guint32) available;
extra->last = last;
extra->prev = chunk->len;
extra->used = FALSE;
extra->jumbo = FALSE;
/* Correctly update the following chunk's back-pointer */
if (!last) {
WMEM_CHUNK_NEXT(extra)->prev = extra->len;
}
}
/* Takes a free chunk and checks the chunks to its immediate right and left in
* the block. If they are also free, the contigous free chunks are merged into
* a single free chunk. The resulting chunk ends up in either the master list or
* the recycler, depending on where the merged chunks were originally.
*/
static void
wmem_block_merge_free(wmem_block_allocator_t *allocator,
wmem_block_chunk_t *chunk)
{
wmem_block_chunk_t *tmp;
wmem_block_chunk_t *left_free = NULL;
wmem_block_chunk_t *right_free = NULL;
/* Check the chunk to our right. If it is free, merge it into our current
* chunk. If it is big enough to hold a free-header, save it for later (we
* need to know about the left chunk before we decide what goes where). */
tmp = WMEM_CHUNK_NEXT(chunk);
if (tmp && !tmp->used) {
if (WMEM_CHUNK_DATA_LEN(tmp) >= sizeof(wmem_block_free_t)) {
right_free = tmp;
}
chunk->len += tmp->len;
chunk->last = tmp->last;
}
/* Check the chunk to our left. If it is free, merge our current chunk into
* it (thus chunk = tmp). As before, save it if it has enough space to
* hold a free-header. */
tmp = WMEM_CHUNK_PREV(chunk);
if (tmp && !tmp->used) {
if (WMEM_CHUNK_DATA_LEN(tmp) >= sizeof(wmem_block_free_t)) {
left_free = tmp;
}
tmp->len += chunk->len;
tmp->last = chunk->last;
chunk = tmp;
}
/* The length of our chunk may have changed. If we have a chunk following,
* update its 'prev' count. */
if (!chunk->last) {
WMEM_CHUNK_NEXT(chunk)->prev = chunk->len;
}
/* Now that the chunk headers are merged and consistent, we need to figure
* out what goes where in which free list. */
if (right_free && right_free == allocator->master_head) {
/* If we merged right, and that chunk was the head of the master list,
* then we leave the resulting chunk at the head of the master list. */
wmem_block_free_t *moved;
if (left_free) {
wmem_block_remove_from_recycler(allocator, left_free);
}
moved = WMEM_GET_FREE(chunk);
moved->prev = NULL;
moved->next = WMEM_GET_FREE(right_free)->next;
allocator->master_head = chunk;
if (moved->next) {
WMEM_GET_FREE(moved->next)->prev = chunk;
}
}
else {
/* Otherwise, we remove the right-merged chunk (if there was one) from
* the recycler. Then, if we merged left we have nothing to do, since
* that recycler entry is still valid. If not, we add the chunk. */
if (right_free) {
wmem_block_remove_from_recycler(allocator, right_free);
}
if (!left_free) {
wmem_block_add_to_recycler(allocator, chunk);
}
}
}
