store.h

#ifndef MUPDF_FITZ_STORE_H
#define MUPDF_FITZ_STORE_H

#include "mupdf/fitz/system.h"
#include "mupdf/fitz/context.h"

/*
	Resource store

	MuPDF stores decoded "objects" into a store for potential reuse.
	If the size of the store gets too big, objects stored within it can
	be evicted and freed to recover space. When MuPDF comes to decode
	such an object, it will check to see if a version of this object is
	already in the store - if it is, it will simply reuse it. If not, it
	will decode it and place it into the store.

	All objects that can be placed into the store are derived from the
	fz_storable type (i.e. this should be the first component of the
	objects structure). This allows for consistent (thread safe)
	reference counting, and includes a function that will be called to
	free the object as soon as the reference count reaches zero.

	Most objects offer fz_keep_XXXX/fz_drop_XXXX functions derived
	from fz_keep_storable/fz_drop_storable. Creation of such objects
	includes a call to FZ_INIT_STORABLE to set up the fz_storable header.
 */

typedef struct fz_storable_s fz_storable;

typedef void (fz_store_drop_fn)(fz_context *, fz_storable *);

struct fz_storable_s {
	int refs;
	fz_store_drop_fn *drop;
};

#define FZ_INIT_STORABLE(S_,RC,DROP) \
	do { fz_storable *S = &(S_)->storable; S->refs = (RC); \
	S->drop = (DROP); \
	} while (0)

void *fz_keep_storable(fz_context *, fz_storable *);
void fz_drop_storable(fz_context *, fz_storable *);

/*
	The store can be seen as a dictionary that maps keys to fz_storable
	values. In order to allow keys of different types to be stored, we
	have a structure full of functions for each key 'type'; this
	fz_store_type pointer is stored with each key, and tells the store
	how to perform certain operations (like taking/dropping a reference,
	comparing two keys, outputting details for debugging etc).

	The store uses a hash table internally for speed where possible. In
	order for this to work, we need a mechanism for turning a generic
	'key' into 'a hashable string'. For this purpose the type structure
	contains a make_hash_key function pointer that maps from a void *
	to an fz_store_hash structure. If make_hash_key function returns 0,
	then the key is determined not to be hashable, and the value is
	not stored in the hash table.
*/
typedef struct fz_store_hash_s fz_store_hash;

struct fz_store_hash_s
{
	fz_store_drop_fn *drop;
	union
	{
		struct
		{
			int i0;
			int i1;
			void *ptr;
		} i;
		struct
		{
			void *ptr;
			int i;
		} pi;
		struct
		{
			int id;
			float m[4];
		} im;
	} u;
};

typedef struct fz_store_type_s fz_store_type;

struct fz_store_type_s
{
	int (*make_hash_key)(fz_context *ctx, fz_store_hash *, void *);
	void *(*keep_key)(fz_context *,void *);
	void (*drop_key)(fz_context *,void *);
	int (*cmp_key)(fz_context *ctx, void *, void *);
#ifndef NDEBUG
	void (*debug)(fz_context *ctx, FILE *, void *);
#endif
};

/*
	fz_store_new_context: Create a new store inside the context

	max: The maximum size (in bytes) that the store is allowed to grow
	to. FZ_STORE_UNLIMITED means no limit.
*/
void fz_new_store_context(fz_context *ctx, unsigned int max);

/*
	fz_drop_store_context: Drop a reference to the store.
*/
void fz_drop_store_context(fz_context *ctx);

/*
	fz_keep_store_context: Take a reference to the store.
*/
fz_store *fz_keep_store_context(fz_context *ctx);

/*
	fz_store_item: Add an item to the store.

	Add an item into the store, returning NULL for success. If an item
	with the same key is found in the store, then our item will not be
	inserted, and the function will return a pointer to that value
	instead. This function takes its own reference to val, as required
	(i.e. the caller maintains ownership of its own reference).

	key: The key to use to index the item.

	val: The value to store.

	itemsize: The size in bytes of the value (as counted towards the
	store size).

	type: Functions used to manipulate the key.
*/
void *fz_store_item(fz_context *ctx, void *key, void *val, unsigned int itemsize, fz_store_type *type);

/*
	fz_find_item: Find an item within the store.

	drop: The function used to free the value (to ensure we get a value
	of the correct type).

	key: The key to use to index the item.

	type: Functions used to manipulate the key.

	Returns NULL for not found, otherwise returns a pointer to the value
	indexed by key to which a reference has been taken.
*/
void *fz_find_item(fz_context *ctx, fz_store_drop_fn *drop, void *key, fz_store_type *type);

/*
	fz_remove_item: Remove an item from the store.

	If an item indexed by the given key exists in the store, remove it.

	drop: The function used to free the value (to ensure we get a value
	of the correct type).

	key: The key to use to find the item to remove.

	type: Functions used to manipulate the key.
*/
void fz_remove_item(fz_context *ctx, fz_store_drop_fn *drop, void *key, fz_store_type *type);

/*
	fz_empty_store: Evict everything from the store.
*/
void fz_empty_store(fz_context *ctx);

/*
	fz_store_scavenge: Internal function used as part of the scavenging
	allocator; when we fail to allocate memory, before returning a
	failure to the caller, we try to scavenge space within the store by
	evicting at least 'size' bytes. The allocator then retries.

	size: The number of bytes we are trying to have free.

	phase: What phase of the scavenge we are in. Updated on exit.

	Returns non zero if we managed to free any memory.
*/
int fz_store_scavenge(fz_context *ctx, unsigned int size, int *phase);

/*
	fz_shrink_store: Evict items from the store until the total size of
	the objects in the store is reduced to a given percentage of its
	current size.

	percent: %age of current size to reduce the store to.

	Returns non zero if we managed to free enough memory, zero otherwise.
*/
int fz_shrink_store(fz_context *ctx, unsigned int percent);

/*
	fz_print_store: Dump the contents of the store for debugging.
*/
#ifndef NDEBUG
void fz_print_store(fz_context *ctx, FILE *out);
void fz_print_store_locked(fz_context *ctx, FILE *out);
#endif

#endif