libwebsockets/lib/misc/lwsac/lwsac.c

/*
 * libwebsockets - small server side websockets and web server implementation
 *
 * Copyright (C) 2010 - 2020 Andy Green <andy@warmcat.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include "private-lib-core.h"
#include "private-lib-misc-lwsac.h"

void
lws_list_ptr_insert(lws_list_ptr *head, lws_list_ptr *add,
		    lws_list_ptr_sort_func_t sort_func)
{
	while (sort_func && *head) {
		if (sort_func(add, *head) <= 0)
			break;

		head = *head;
	}

	*add = *head;
	*head = add;
}

size_t
lwsac_align(size_t length)
{
	size_t align = sizeof(int *);

	if (length & (align - 1))
		length += align - (length & (align - 1));

	return length;
}

size_t
lwsac_sizeof(int first)
{
	return sizeof(struct lwsac) + (first ? sizeof(struct lwsac_head) : 0);
}

size_t
lwsac_get_tail_pos(struct lwsac *lac)
{
	return lac->ofs;
}

struct lwsac *
lwsac_get_next(struct lwsac *lac)
{
	return lac->next;
}

int
lwsac_extend(struct lwsac *head, int amount)
{
	struct lwsac_head *lachead;
	struct lwsac *bf;

	assert(head);
	lachead = (struct lwsac_head *)&head[1];

	bf = lachead->curr;
	assert(bf);

	if (bf->alloc_size - bf->ofs < lwsac_align(amount))
		return 1;

	/* memset so constant folding never sees uninitialized data */

	memset(((uint8_t *)bf) + bf->ofs, 0, lwsac_align(amount));
	bf->ofs += lwsac_align(amount);

	return 0;
}

static void *
_lwsac_use(struct lwsac **head, size_t ensure, size_t chunk_size, char backfill)
{
	struct lwsac_head *lachead = NULL;
	size_t ofs, alloc, al, hp;
	struct lwsac *bf = *head;

	if (bf)
		lachead = (struct lwsac_head *)&bf[1];

	al = lwsac_align(ensure);

	/* backfill into earlier chunks if that is allowed */

	if (backfill)
		/*
		 * check if anything can take it, from the start
		 */
		while (bf) {
			if (bf->alloc_size - bf->ofs >= ensure)
				goto do_use;

			bf = bf->next;
		}
	else {
		/*
		 * If there's a current chunk, just check if he can take it
		 */
		if (lachead && lachead->curr) {
			bf = lachead->curr;
			if (bf->alloc_size - bf->ofs >= ensure)
				goto do_use;
		}
	}

	/* nothing can currently take it... so we must allocate */

	hp = sizeof(*bf); /* always need the normal header part... */
	if (!*head)
		hp += sizeof(struct lwsac_head);

	if (!chunk_size)
		alloc = LWSAC_CHUNK_SIZE + hp;
	else
		alloc = chunk_size + hp;

	/*
	 * If we get asked for something outside our expectation,
	 * increase the allocation to meet it
	 */

	if (al >= alloc - hp)
		alloc = al + hp;

	lwsl_debug("%s: alloc %d for %d\n", __func__, (int)alloc, (int)ensure);
	bf = malloc(alloc);
	if (!bf) {
		lwsl_err("%s: OOM trying to alloc %llud\n", __func__,
				(unsigned long long)alloc);
		return NULL;
	}

	/*
	 * belabouring the point... ofs is aligned to the platform's
	 * generic struct alignment at the start then
	 */
	bf->ofs = sizeof(*bf);

	if (!*head) {
		/*
		 * We are the first, head, entry...
		 */
		*head = bf;
		/*
		 * ... allocate for the special head block
		 */
		bf->ofs += sizeof(*lachead);
		lachead = (struct lwsac_head *)&bf[1];
		memset(lachead, 0, sizeof(*lachead));
	} else
		if (lachead->curr)
			lachead->curr->next = bf;

	lachead->curr = bf;
	bf->head = *head;
	bf->next = NULL;
	bf->alloc_size = alloc;

	lachead->total_alloc_size += alloc;
	lachead->total_blocks++;

do_use:

	ofs = bf->ofs;

	if (al > ensure)
		/* zero down the alignment padding part */
		memset((char *)bf + ofs + ensure, 0, al - ensure);

	bf->ofs += al;
	if (bf->ofs >= bf->alloc_size)
		bf->ofs = bf->alloc_size;

	return (char *)bf + ofs;
}

void *
lwsac_use(struct lwsac **head, size_t ensure, size_t chunk_size)
{
	return _lwsac_use(head, ensure, chunk_size, 0);
}

void *
lwsac_use_backfill(struct lwsac **head, size_t ensure, size_t chunk_size)
{
	return _lwsac_use(head, ensure, chunk_size, 1);
}

uint8_t *
lwsac_scan_extant(struct lwsac *head, uint8_t *find, size_t len, int nul)
{
	while (head) {
		uint8_t *pos = (uint8_t *)&head[1],
			*end = ((uint8_t *)head) + head->ofs - len;

		if (head->ofs - sizeof(*head) >= len)
			while (pos < end) {
				if (*pos == *find && (!nul || !pos[len]) &&
				    pos[len - 1] == find[len - 1] &&
				    !memcmp(pos, find, len))
					/* found the blob */
					return pos;
				pos++;
			}

		head = head->next;
	}

	return NULL;
}

uint64_t
lwsac_total_overhead(struct lwsac *head)
{
	uint64_t overhead = 0;

	while (head) {
		overhead += (head->alloc_size - head->ofs) + sizeof(*head);

		head = head->next;
	}

	return overhead;
}

void *
lwsac_use_zero(struct lwsac **head, size_t ensure, size_t chunk_size)
{
	void *p = lwsac_use(head, ensure, chunk_size);

	if (p)
		memset(p, 0, ensure);

	return p;
}

void
lwsac_free(struct lwsac **head)
{
	struct lwsac *it = *head;

	*head = NULL;
	lwsl_debug("%s: head %p\n", __func__, *head);

	while (it) {
		struct lwsac *tmp = it->next;

		free(it);
		it = tmp;
	}
}

void
lwsac_info(struct lwsac *head)
{
#if _LWS_ENABLED_LOGS & LLL_DEBUG
	struct lwsac_head *lachead;

	if (!head) {
		lwsl_debug("%s: empty\n", __func__);
		return;
	}

	lachead = (struct lwsac_head *)&head[1];

	lwsl_debug("%s: lac %p: %dKiB in %d blocks\n", __func__, head,
		   (int)(lachead->total_alloc_size >> 10), lachead->total_blocks);
#endif
}

uint64_t
lwsac_total_alloc(struct lwsac *head)
{
	struct lwsac_head *lachead;

	if (!head)
		return 0;

	lachead = (struct lwsac_head *)&head[1];
	return lachead->total_alloc_size;
}

void
lwsac_reference(struct lwsac *head)
{
	struct lwsac_head *lachead = (struct lwsac_head *)&head[1];

	lachead->refcount++;
	lwsl_debug("%s: head %p: (det %d) refcount -> %d\n",
		    __func__, head, lachead->detached, lachead->refcount);
}

void
lwsac_unreference(struct lwsac **head)
{
	struct lwsac_head *lachead;

	if (!(*head))
		return;

	lachead = (struct lwsac_head *)&(*head)[1];

	if (!lachead->refcount)
		lwsl_warn("%s: refcount going below zero\n", __func__);

	lachead->refcount--;

	lwsl_debug("%s: head %p: (det %d) refcount -> %d\n",
		    __func__, *head, lachead->detached, lachead->refcount);

	if (lachead->detached && !lachead->refcount) {
		lwsl_debug("%s: head %p: FREED\n", __func__, *head);
		lwsac_free(head);
	}
}

void
lwsac_detach(struct lwsac **head)
{
	struct lwsac_head *lachead;

	if (!(*head))
		return;

	lachead = (struct lwsac_head *)&(*head)[1];

	lachead->detached = 1;
	if (!lachead->refcount) {
		lwsl_debug("%s: head %p: FREED\n", __func__, *head);
		lwsac_free(head);
	} else
		lwsl_debug("%s: head %p: refcount %d: Marked as detached\n",
			    __func__, *head, lachead->refcount);
}