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#include "fitz.h"
#include "mupdf.h"
struct fz_item_s
{
fz_obj *key;
fz_storable *val;
unsigned int size;
fz_item *next;
fz_item *prev;
fz_store *store;
};
struct refkey
{
fz_store_free_fn *free;
int num;
int gen;
};
struct fz_store_s
{
int refs;
/* Every item in the store is kept in a doubly linked list, ordered
* by usage (so LRU entries are at the end). */
fz_item *head;
fz_item *tail;
/* We have a hash table that allows to quickly find a subset of the
* entries (those whose keys are indirect objects). */
fz_hash_table *hash;
/* We keep track of the size of the store, and keep it below max. */
unsigned int max;
unsigned int size;
};
void
fz_new_store_context(fz_context *ctx, unsigned int max)
{
fz_store *store;
store = fz_malloc_struct(ctx, fz_store);
fz_try(ctx)
{
store->hash = fz_new_hash_table(ctx, 4096, sizeof(struct refkey));
}
fz_catch(ctx)
{
fz_free(ctx, store);
fz_rethrow(ctx);
}
store->refs = 1;
store->head = NULL;
store->tail = NULL;
store->size = 0;
store->max = max;
ctx->store = store;
}
void *
fz_keep_storable(fz_context *ctx, fz_storable *s)
{
if (s == NULL)
return NULL;
fz_lock(ctx, FZ_LOCK_ALLOC);
if (s->refs > 0)
s->refs++;
fz_unlock(ctx, FZ_LOCK_ALLOC);
return s;
}
void
fz_drop_storable(fz_context *ctx, fz_storable *s)
{
int do_free = 0;
if (s == NULL)
return;
fz_lock(ctx, FZ_LOCK_ALLOC);
if (s->refs < 0)
{
/* It's a static object. Dropping does nothing. */
}
else if (--s->refs == 0)
{
/* If we are dropping the last reference to an object, then
* it cannot possibly be in the store (as the store always
* keeps a ref to everything in it, and doesn't drop via
* this method. So we can simply drop the storable object
* itself without any operations on the fz_store. */
do_free = 1;
}
fz_unlock(ctx, FZ_LOCK_ALLOC);
if (do_free)
s->free(ctx, s);
}
static void
evict(fz_context *ctx, fz_item *item)
{
fz_store *store = ctx->store;
int drop;
store->size -= item->size;
/* Unlink from the linked list */
if (item->next)
item->next->prev = item->prev;
else
store->tail = item->prev;
if (item->prev)
item->prev->next = item->next;
else
store->head = item->next;
/* Drop a reference to the value (freeing if required) */
drop = (item->val->refs > 0 && --item->val->refs == 0);
fz_unlock(ctx, FZ_LOCK_ALLOC);
/* Remove from the hash table */
if (fz_is_indirect(item->key))
{
struct refkey refkey;
refkey.free = item->val->free;
refkey.num = fz_to_num(item->key);
refkey.gen = fz_to_gen(item->key);
fz_hash_remove(ctx, store->hash, &refkey);
}
if (drop)
item->val->free(ctx, item->val);
/* Always drops the key and free the item */
fz_drop_obj(item->key);
fz_free(ctx, item);
fz_lock(ctx, FZ_LOCK_ALLOC);
}
static int
ensure_space(fz_context *ctx, unsigned int tofree)
{
fz_item *item, *prev;
unsigned int count;
fz_store *store = ctx->store;
fz_assert_lock_held(ctx, FZ_LOCK_ALLOC);
/* First check that we *can* free tofree; if not, we'd rather not
* cache this. */
count = 0;
for (item = store->tail; item; item = item->prev)
{
if (item->val->refs == 1)
{
count += item->size;
if (count >= tofree)
break;
}
}
/* If we ran out of items to search, then we can never free enough */
if (item == NULL)
{
return 0;
}
/* Actually free the items */
count = 0;
for (item = store->tail; item; item = prev)
{
prev = item->prev;
if (item->val->refs == 1)
{
/* Free this item. Evict has to drop the lock to
* manage that, which could cause prev to be removed
* in the meantime. To avoid that we bump its reference
* count here. This may cause another simultaneous
* evict process to fail to make enough space as prev is
* pinned - but that will only happen if we're near to
* the limit anyway, and it will only cause something to
* not be cached. */
count += item->size;
if (prev)
prev->val->refs++;
evict(ctx, item); /* Drops then retakes lock */
/* So the store has 1 reference to prev, as do we, so
* no other evict process can have thrown prev away in
* the meantime. So we are safe to just decrement its
* reference count here. */
if (prev)
--prev->val->refs;
if (count >= tofree)
return count;
}
}
return count;
}
void
fz_store_item(fz_context *ctx, fz_obj *key, void *val_, unsigned int itemsize)
{
fz_item *item = NULL;
unsigned int size;
fz_storable *val = (fz_storable *)val_;
fz_store *store = ctx->store;
int indirect;
struct refkey refkey;
if (!store)
return;
fz_var(item);
/* Form the key before we take the lock */
indirect = fz_is_indirect(key);
if (indirect)
{
refkey.free = val->free;
refkey.num = fz_to_num(key);
refkey.gen = fz_to_gen(key);
}
/* If we fail for any reason, we swallow the exception and continue.
* All that the above program will see is that we failed to store
* the item. */
fz_try(ctx)
{
item = fz_malloc_struct(ctx, fz_item);
}
fz_catch(ctx)
{
return;
}
fz_lock(ctx, FZ_LOCK_ALLOC);
if (store->max != FZ_STORE_UNLIMITED)
{
size = store->size + itemsize;
while (size > store->max)
{
/* ensure_space may drop, then retake the lock */
if (ensure_space(ctx, size - store->max) == 0)
{
/* Failed to free any space */
fz_unlock(ctx, FZ_LOCK_ALLOC);
fz_free(ctx, item);
return;
}
}
}
store->size += itemsize;
item->key = fz_keep_obj(key);
item->val = val;
item->size = itemsize;
item->next = NULL;
/* If we can index it fast, put it into the hash table */
if (indirect)
{
fz_unlock(ctx, FZ_LOCK_ALLOC);
fz_try(ctx)
{
fz_hash_insert(ctx, store->hash, &refkey, item);
}
fz_catch(ctx)
{
fz_free(ctx, item);
fz_lock(ctx, FZ_LOCK_ALLOC);
store->size -= itemsize;
fz_unlock(ctx, FZ_LOCK_ALLOC);
return;
}
fz_lock(ctx, FZ_LOCK_ALLOC);
}
/* Now we can never fail, bump the ref */
if (val->refs > 0)
val->refs++;
/* Regardless of whether it's indexed, it goes into the linked list */
item->next = store->head;
if (item->next)
item->next->prev = item;
else
store->tail = item;
store->head = item;
item->prev = NULL;
fz_unlock(ctx, FZ_LOCK_ALLOC);
}
void *
fz_find_item(fz_context *ctx, fz_store_free_fn *free, fz_obj *key)
{
struct refkey refkey;
fz_item *item;
fz_store *store = ctx->store;
int indirect;
if (!store)
return NULL;
if (!key)
return NULL;
/* Form the key before we take the lock */
indirect = fz_is_indirect(key);
if (indirect)
{
refkey.free = free;
refkey.num = fz_to_num(key);
refkey.gen = fz_to_gen(key);
}
fz_lock(ctx, FZ_LOCK_ALLOC);
if (indirect)
{
/* We can find objects keyed on indirected objects quickly */
item = fz_hash_find(ctx, store->hash, &refkey);
}
else
{
/* Others we have to hunt for slowly */
for (item = store->head; item; item = item->next)
{
if (item->val->free == free && !fz_objcmp(item->key, key))
break;
}
}
if (item)
{
/* LRU: Move the block to the front */
/* Unlink from present position */
if (item->next)
item->next->prev = item->prev;
else
store->tail = item->prev;
if (item->prev)
item->prev->next = item->next;
else
store->head = item->next;
/* Insert at head */
item->next = store->head;
if (item->next)
item->next->prev = item;
else
store->tail = item;
item->prev = NULL;
store->head = item;
/* And bump the refcount before returning */
if (item->val->refs > 0)
item->val->refs++;
fz_unlock(ctx, FZ_LOCK_ALLOC);
return (void *)item->val;
}
fz_unlock(ctx, FZ_LOCK_ALLOC);
return NULL;
}
void
fz_remove_item(fz_context *ctx, fz_store_free_fn *free, fz_obj *key)
{
struct refkey refkey;
fz_item *item;
fz_store *store = ctx->store;
int drop, indirect;
/* Form the key before we take the lock */
indirect = fz_is_indirect(key);
if (indirect)
{
refkey.free = free;
refkey.num = fz_to_num(key);
refkey.gen = fz_to_gen(key);
}
fz_lock(ctx, FZ_LOCK_ALLOC);
if (indirect)
{
/* We can find objects keyed on indirect objects quickly */
item = fz_hash_find(ctx, store->hash, &refkey);
if (item)
fz_hash_remove(ctx, store->hash, &refkey);
}
else
{
/* Others we have to hunt for slowly */
for (item = store->head; item; item = item->next)
if (item->val->free == free && !fz_objcmp(item->key, key))
break;
}
if (item)
{
if (item->next)
item->next->prev = item->prev;
else
store->tail = item->prev;
if (item->prev)
item->prev->next = item->next;
else
store->head = item->next;
drop = (item->val->refs > 0 && --item->val->refs == 0);
fz_unlock(ctx, FZ_LOCK_ALLOC);
if (drop)
item->val->free(ctx, item->val);
fz_drop_obj(item->key);
fz_free(ctx, item);
}
else
fz_unlock(ctx, FZ_LOCK_ALLOC);
}
void
fz_empty_store(fz_context *ctx)
{
fz_store *store = ctx->store;
if (store == NULL)
return;
fz_lock(ctx, FZ_LOCK_ALLOC);
/* Run through all the items in the store */
while (store->head)
{
evict(ctx, store->head); /* Drops then retakes lock */
}
fz_unlock(ctx, FZ_LOCK_ALLOC);
}
fz_store *
fz_store_keep(fz_context *ctx)
{
if (ctx == NULL || ctx->store == NULL)
return NULL;
fz_lock(ctx, FZ_LOCK_ALLOC);
ctx->store->refs++;
fz_unlock(ctx, FZ_LOCK_ALLOC);
return ctx->store;
}
void
fz_drop_store_context(fz_context *ctx)
{
int refs;
if (ctx == NULL || ctx->store == NULL)
return;
fz_lock(ctx, FZ_LOCK_ALLOC);
refs = --ctx->store->refs;
fz_unlock(ctx, FZ_LOCK_ALLOC);
if (refs != 0)
return;
fz_empty_store(ctx);
fz_free_hash(ctx, ctx->store->hash);
fz_free(ctx, ctx->store);
ctx->store = NULL;
}
void
fz_debug_store(fz_context *ctx)
{
fz_item *item, *next;
fz_store *store = ctx->store;
printf("-- resource store contents --\n");
fz_lock(ctx, FZ_LOCK_ALLOC);
for (item = store->head; item; item = next)
{
next = item->next;
next->val->refs++;
printf("store[*][refs=%d][size=%d] ", item->val->refs, item->size);
fz_unlock(ctx, FZ_LOCK_ALLOC);
if (fz_is_indirect(item->key))
{
printf("(%d %d R) ", fz_to_num(item->key), fz_to_gen(item->key));
} else
fz_debug_obj(item->key);
printf(" = %p\n", item->val);
fz_lock(ctx, FZ_LOCK_ALLOC);
next->val->refs--;
}
fz_unlock(ctx, FZ_LOCK_ALLOC);
}
/* This is now an n^2 algorithm - not ideal, but it'll only be bad if we are
* actually managing to scavenge lots of blocks back. */
static int
scavenge(fz_context *ctx, unsigned int tofree)
{
fz_store *store = ctx->store;
unsigned int count = 0;
fz_item *item, *prev;
/* Free the items */
for (item = store->tail; item; item = prev)
{
prev = item->prev;
if (item->val->refs == 1)
{
/* Free this item */
count += item->size;
evict(ctx, item); /* Drops then retakes lock */
if (count >= tofree)
break;
/* Have to restart search again, as prev may no longer
* be valid due to release of lock in evict. */
prev = store->tail;
}
}
/* Success is managing to evict any blocks */
return count != 0;
}
int fz_store_scavenge(fz_context *ctx, unsigned int size, int *phase)
{
fz_store *store;
unsigned int max;
if (ctx == NULL)
return 0;
store = ctx->store;
if (store == NULL)
return 0;
#ifdef DEBUG_SCAVENGING
printf("Scavenging: store=%d size=%d phase=%d\n", store->size, size, *phase);
fz_debug_store(ctx);
Memento_stats();
#endif
do
{
unsigned int tofree;
/* Calculate 'max' as the maximum size of the store for this phase */
if (*phase >= 16)
max = 0;
else if (store->max != FZ_STORE_UNLIMITED)
max = store->max / 16 * (16 - *phase);
else
max = store->size / (16 - *phase) * (15 - *phase);
(*phase)++;
/* Slightly baroque calculations to avoid overflow */
if (size > UINT_MAX - store->size)
tofree = UINT_MAX - max;
else if (size + store->size > max)
continue;
else
tofree = size + store->size - max;
if (scavenge(ctx, tofree))
{
#ifdef DEBUG_SCAVENGING
printf("scavenged: store=%d\n", store->size);
fz_debug_store(ctx);
Memento_stats();
#endif
return 1;
}
}
while (max > 0);
#ifdef DEBUG_SCAVENGING
printf("scavenging failed\n");
fz_debug_store(ctx);
Memento_listBlocks();
#endif
return 0;
}
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