--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/include/mupdf/fitz/store.h	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,465 @@
+// Copyright (C) 2004-2021 Artifex Software, Inc.
+//
+// This file is part of MuPDF.
+//
+// MuPDF is free software: you can redistribute it and/or modify it under the
+// terms of the GNU Affero General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// MuPDF is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+// FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+// details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with MuPDF. If not, see <https://www.gnu.org/licenses/agpl-3.0.en.html>
+//
+// Alternative licensing terms are available from the licensor.
+// For commercial licensing, see <https://www.artifex.com/> or contact
+// Artifex Software, Inc., 39 Mesa Street, Suite 108A, San Francisco,
+// CA 94129, USA, for further information.
+
+#ifndef MUPDF_FITZ_STORE_H
+#define MUPDF_FITZ_STORE_H
+
+#include "mupdf/fitz/system.h"
+#include "mupdf/fitz/context.h"
+#include "mupdf/fitz/output.h"
+#include "mupdf/fitz/log.h"
+#include "mupdf/fitz/types.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 fz_storable;
+
+/**
+	Function type for a function to drop a storable object.
+
+	Objects within the store are identified by type by comparing
+	their drop_fn pointers.
+*/
+typedef void (fz_store_drop_fn)(fz_context *, fz_storable *);
+
+/**
+	Function type for a function to check whether a storable
+	object can be dropped at the moment.
+
+	Return 0 for 'cannot be dropped', 1 otherwise.
+*/
+typedef int (fz_store_droppable_fn)(fz_context *, fz_storable *);
+
+/**
+	Any storable object should include an fz_storable structure
+	at the start (by convention at least) of their structure.
+	(Unless it starts with an fz_key_storable, see below).
+*/
+struct fz_storable {
+	int refs;
+	fz_store_drop_fn *drop;
+	fz_store_droppable_fn *droppable;
+};
+
+/**
+	Any storable object that can appear in the key of another
+	storable object should include an fz_key_storable structure
+	at the start (by convention at least) of their structure.
+*/
+typedef struct
+{
+	fz_storable storable;
+	short store_key_refs;
+} fz_key_storable;
+
+/**
+	Macros to initialise a storable object.
+*/
+#define FZ_INIT_STORABLE(S_,RC,DROP) \
+	do { fz_storable *S = &(S_)->storable; S->refs = (RC); \
+	S->drop = (DROP); S->droppable = NULL; \
+	} while (0)
+
+#define FZ_INIT_AWKWARD_STORABLE(S_,RC,DROP,DROPPABLE) \
+	do { fz_storable *S = &(S_)->storable; S->refs = (RC); \
+	S->drop = (DROP); S->droppable = (DROPPABLE); \
+	} while (0)
+
+/**
+	Macro to initialise a key storable object.
+*/
+#define FZ_INIT_KEY_STORABLE(KS_,RC,DROP) \
+	do { fz_key_storable *KS = &(KS_)->key_storable; KS->store_key_refs = 0;\
+	FZ_INIT_STORABLE(KS,RC,DROP); \
+	} while (0)
+
+/**
+	Increment the reference count for a storable object.
+	Returns the same pointer.
+
+	Never throws exceptions.
+*/
+void *fz_keep_storable(fz_context *, const fz_storable *);
+
+/**
+	Decrement the reference count for a storable object. When the
+	reference count hits zero, the drop function for that object
+	is called to free the object.
+
+	Never throws exceptions.
+*/
+void fz_drop_storable(fz_context *, const fz_storable *);
+
+/**
+	Increment the (normal) reference count for a key storable
+	object. Returns the same pointer.
+
+	Never throws exceptions.
+*/
+void *fz_keep_key_storable(fz_context *, const fz_key_storable *);
+
+/**
+	Decrement the (normal) reference count for a storable object.
+	When the total reference count hits zero, the drop function for
+	that object is called to free the object.
+
+	Never throws exceptions.
+*/
+void fz_drop_key_storable(fz_context *, const fz_key_storable *);
+
+/**
+	Increment the (key) reference count for a key storable
+	object. Returns the same pointer.
+
+	Never throws exceptions.
+*/
+void *fz_keep_key_storable_key(fz_context *, const fz_key_storable *);
+
+/**
+	Decrement the (key) reference count for a storable object.
+	When the total reference count hits zero, the drop function for
+	that object is called to free the object.
+
+	Never throws exceptions.
+*/
+void fz_drop_key_storable_key(fz_context *, const fz_key_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 a 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.
+
+	Some objects can be used both as values within the store, and as
+	a component of keys within the store. We refer to these objects
+	as "key storable" objects. In this case, we need to take
+	additional care to ensure that we do not end up keeping an item
+	within the store, purely because its value is referred to by
+	another key in the store.
+
+	An example of this are fz_images in PDF files. Each fz_image is
+	placed into the	store to enable it to be easily reused. When the
+	image is rendered, a pixmap is generated from the image, and the
+	pixmap is placed into the store so it can be reused on
+	subsequent renders. The image forms part of the key for the
+	pixmap.
+
+	When we close the pdf document (and any associated pages/display
+	lists etc), we drop the images from the store. This may leave us
+	in the position of the images having non-zero reference counts
+	purely because they are used as part of the keys for the
+	pixmaps.
+
+	We therefore use special reference counting functions to keep
+	track of these "key storable" items, and hence store the number
+	of references to these items that are used in keys.
+
+	When the number of references to an object == the number of
+	references to an object from keys in the store, we know that we
+	can remove all the items which have that object as part of the
+	key. This is done by running a pass over the store, 'reaping'
+	those items.
+
+	Reap passes are slower than we would like as they touch every
+	item in the store. We therefore provide a way to 'batch' such
+	reap passes together, using fz_defer_reap_start/
+	fz_defer_reap_end to bracket a region in which many may be
+	triggered.
+*/
+typedef struct
+{
+	fz_store_drop_fn *drop;
+	union
+	{
+		struct
+		{
+			const void *ptr;
+			int i;
+		} pi; /* 8 or 12 bytes */
+		struct
+		{
+			const void *ptr;
+			int i;
+			fz_irect r;
+		} pir; /* 24 or 28 bytes */
+		struct
+		{
+			int id;
+			char has_shape;
+			char has_group_alpha;
+			float m[4];
+			void *ptr;
+			int doc_id;
+		} im; /* 32 or 36 bytes */
+		struct
+		{
+			unsigned char src_md5[16];
+			unsigned char dst_md5[16];
+			unsigned int ri:2;
+			unsigned int bp:1;
+			unsigned int format:1;
+			unsigned int proof:1;
+			unsigned int src_extras:5;
+			unsigned int dst_extras:5;
+			unsigned int copy_spots:1;
+			unsigned int bgr:1;
+		} link; /* 36 bytes */
+	} u;
+	/* 0 or 4 bytes padding */
+} fz_store_hash; /* 40 or 48 bytes */
+
+/**
+	Every type of object to be placed into the store defines an
+	fz_store_type. This contains the pointers to functions to
+	make hashes, manipulate keys, and check for needing reaping.
+*/
+typedef struct
+{
+	const char *name;
+	int (*make_hash_key)(fz_context *ctx, fz_store_hash *hash, void *key);
+	void *(*keep_key)(fz_context *ctx, void *key);
+	void (*drop_key)(fz_context *ctx, void *key);
+	int (*cmp_key)(fz_context *ctx, void *a, void *b);
+	void (*format_key)(fz_context *ctx, char *buf, size_t size, void *key);
+	int (*needs_reap)(fz_context *ctx, void *key);
+} fz_store_type;
+
+/**
+	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, size_t max);
+
+/**
+	Increment the reference count for the store context. Returns
+	the same pointer.
+
+	Never throws exceptions.
+*/
+fz_store *fz_keep_store_context(fz_context *ctx);
+
+/**
+	Decrement the reference count for the store context. When the
+	reference count hits zero, the store context is freed.
+
+	Never throws exceptions.
+*/
+void fz_drop_store_context(fz_context *ctx);
+
+/**
+	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 used 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, size_t itemsize, const fz_store_type *type);
+
+/**
+	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 used 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, const fz_store_type *type);
+
+/**
+	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 used 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, const fz_store_type *type);
+
+/**
+	Evict every item from the store.
+*/
+void fz_empty_store(fz_context *ctx);
+
+/**
+	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, size_t size, int *phase);
+
+/**
+	External function for callers to use
+	to scavenge while trying allocations.
+
+	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_external(fz_context *ctx, size_t size, int *phase);
+
+/**
+	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);
+
+/**
+	Callback function called by fz_filter_store on every item within
+	the store.
+
+	Return 1 to drop the item from the store, 0 to retain.
+*/
+typedef int (fz_store_filter_fn)(fz_context *ctx, void *arg, void *key);
+
+/**
+	Filter every element in the store with a matching type with the
+	given function.
+
+	If the function returns 1 for an element, drop the element.
+*/
+void fz_filter_store(fz_context *ctx, fz_store_filter_fn *fn, void *arg, const fz_store_type *type);
+
+/**
+	Filter the store and throw away any stored tiles drawn for a
+	given document.
+*/
+void fz_drop_drawn_tiles_for_document(fz_context *ctx, fz_document *doc);
+
+/**
+	Output debugging information for the current state of the store
+	to the given output channel.
+*/
+void fz_debug_store(fz_context *ctx, fz_output *out);
+
+/**
+	Increment the defer reap count.
+
+	No reap operations will take place (except for those
+	triggered by an immediate failed malloc) until the
+	defer reap count returns to 0.
+
+	Call this at the start of a process during which you
+	potentially might drop many reapable objects.
+
+	It is vital that every fz_defer_reap_start is matched
+	by a fz_defer_reap_end call.
+*/
+void fz_defer_reap_start(fz_context *ctx);
+
+/**
+	Decrement the defer reap count.
+
+	If the defer reap count returns to 0, and the store
+	has reapable objects in, a reap pass will begin.
+
+	Call this at the end of a process during which you
+	potentially might drop many reapable objects.
+
+	It is vital that every fz_defer_reap_start is matched
+	by a fz_defer_reap_end call.
+*/
+void fz_defer_reap_end(fz_context *ctx);
+
+#ifdef ENABLE_STORE_LOGGING
+
+void fz_log_dump_store(fz_context *ctx, const char *fmt, ...);
+
+#define FZ_LOG_STORE(CTX, ...) fz_log_module(CTX, "STORE", __VA_ARGS__)
+#define FZ_LOG_DUMP_STORE(...) fz_log_dump_store(__VA_ARGS__)
+
+#else
+
+#define FZ_LOG_STORE(...) do {} while (0)
+#define FZ_LOG_DUMP_STORE(...) do {} while (0)
+
+#endif
+
+#endif