go-fitz/include/mupdf/pdf/document.h

// Copyright (C) 2004-2023 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_PDF_DOCUMENT_H
#define MUPDF_PDF_DOCUMENT_H

#include "mupdf/fitz/export.h"
#include "mupdf/fitz/document.h"
#include "mupdf/fitz/hash.h"
#include "mupdf/fitz/stream.h"
#include "mupdf/fitz/xml.h"
#include "mupdf/pdf/object.h"

typedef struct pdf_xref pdf_xref;
typedef struct pdf_ocg_descriptor pdf_ocg_descriptor;

typedef struct pdf_page pdf_page;
typedef struct pdf_annot pdf_annot;
typedef struct pdf_js pdf_js;
typedef struct pdf_document pdf_document;

enum
{
	PDF_LEXBUF_SMALL = 256,
	PDF_LEXBUF_LARGE = 65536
};

typedef struct
{
	size_t size;
	size_t base_size;
	size_t len;
	int64_t i;
	float f;
	char *scratch;
	char buffer[PDF_LEXBUF_SMALL];
} pdf_lexbuf;

typedef struct
{
	pdf_lexbuf base;
	char buffer[PDF_LEXBUF_LARGE - PDF_LEXBUF_SMALL];
} pdf_lexbuf_large;

/*
	Document event structures are mostly opaque to the app. Only the type
	is visible to the app.
*/
typedef struct pdf_doc_event pdf_doc_event;

/*
	the type of function via which the app receives
	document events.
*/
typedef void (pdf_doc_event_cb)(fz_context *ctx, pdf_document *doc, pdf_doc_event *evt, void *data);

/*
	the type of function via which the app frees
	the data provided to the event callback pdf_doc_event_cb.
*/
typedef void (pdf_free_doc_event_data_cb)(fz_context *ctx, void *data);

typedef struct pdf_js_console pdf_js_console;

/*
	Callback called when the console is dropped because it
	is being replaced or the javascript is being disabled
	by a call to pdf_disable_js().
*/
typedef void (pdf_js_console_drop_cb)(pdf_js_console *console, void *user);

/*
	Callback signalling that a piece of javascript is asking
	the javascript console to be displayed.
*/
typedef void (pdf_js_console_show_cb)(void *user);

/*
	Callback signalling that a piece of javascript is asking
	the javascript console to be hidden.
*/
typedef void (pdf_js_console_hide_cb)(void *user);

/*
	Callback signalling that a piece of javascript is asking
	the javascript console to remove all its contents.
*/
typedef void (pdf_js_console_clear_cb)(void *user);

/*
	Callback signalling that a piece of javascript is appending
	the given message to the javascript console contents.
*/
typedef void (pdf_js_console_write_cb)(void *user, const char *msg);

/*
	The callback functions relating to a javascript console.
*/
typedef struct pdf_js_console {
	pdf_js_console_drop_cb *drop;
	pdf_js_console_show_cb *show;
	pdf_js_console_hide_cb *hide;
	pdf_js_console_clear_cb *clear;
	pdf_js_console_write_cb *write;
} pdf_js_console;

/*
	Retrieve the currently set javascript console, or NULL
	if none is set.
*/
pdf_js_console *pdf_js_get_console(fz_context *ctx, pdf_document *doc);

/*
	Set a new javascript console.

	console: A set of callback functions informing about
	what pieces of executed js is trying to do
	to the js console. The caller transfers ownership of
	console when calling pdf_js_set_console(). Once it and
	the corresponding user pointer are no longer needed
	console->drop() will be called passing both the console
	and the user pointer.

	user: Opaque data that will be passed unchanged to all
	js console callbacks when called. The caller ensures
	that this is valid until either the js console is
	replaced by calling pdf_js_set_console() again with a
	new console, or pdf_disable_js() is called. In either
	case the caller to ensures that the user data is freed.
*/
void pdf_js_set_console(fz_context *ctx, pdf_document *doc, pdf_js_console *console, void *user);

/*
	Open a PDF document.

	Open a PDF document by reading its cross reference table, so
	MuPDF can locate PDF objects inside the file. Upon an broken
	cross reference table or other parse errors MuPDF will restart
	parsing the file from the beginning to try to rebuild a
	(hopefully correct) cross reference table to allow further
	processing of the file.

	The returned pdf_document should be used when calling most
	other PDF functions. Note that it wraps the context, so those
	functions implicitly get access to the global state in
	context.

	filename: a path to a file as it would be given to open(2).
*/
pdf_document *pdf_open_document(fz_context *ctx, const char *filename);

/*
	Opens a PDF document.

	Same as pdf_open_document, but takes a stream instead of a
	filename to locate the PDF document to open. Increments the
	reference count of the stream. See fz_open_file,
	fz_open_file_w or fz_open_fd for opening a stream, and
	fz_drop_stream for closing an open stream.
*/
pdf_document *pdf_open_document_with_stream(fz_context *ctx, fz_stream *file);

/*
	Closes and frees an opened PDF document.

	The resource store in the context associated with pdf_document
	is emptied.
*/
void pdf_drop_document(fz_context *ctx, pdf_document *doc);

pdf_document *pdf_keep_document(fz_context *ctx, pdf_document *doc);

/*
	down-cast a fz_document to a pdf_document.
	Returns NULL if underlying document is not PDF
*/
pdf_document *pdf_specifics(fz_context *ctx, fz_document *doc);

/*
	Down-cast generic fitz objects into pdf specific variants.
	Returns NULL if the objects are not from a PDF document.
*/
pdf_document *pdf_document_from_fz_document(fz_context *ctx, fz_document *ptr);
pdf_page *pdf_page_from_fz_page(fz_context *ctx, fz_page *ptr);

int pdf_needs_password(fz_context *ctx, pdf_document *doc);

/*
	Attempt to authenticate a
	password.

	Returns 0 for failure, non-zero for success.

	In the non-zero case:
		bit 0 set => no password required
		bit 1 set => user password authenticated
		bit 2 set => owner password authenticated
*/
int pdf_authenticate_password(fz_context *ctx, pdf_document *doc, const char *pw);

int pdf_has_permission(fz_context *ctx, pdf_document *doc, fz_permission p);
int pdf_lookup_metadata(fz_context *ctx, pdf_document *doc, const char *key, char *ptr, int size);

fz_outline *pdf_load_outline(fz_context *ctx, pdf_document *doc);

fz_outline_iterator *pdf_new_outline_iterator(fz_context *ctx, pdf_document *doc);

void pdf_invalidate_xfa(fz_context *ctx, pdf_document *doc);

/*
	Get the number of layer configurations defined in this document.

	doc: The document in question.
*/
int pdf_count_layer_configs(fz_context *ctx, pdf_document *doc);

/*
	Configure visibility of individual layers in this document.
*/
int pdf_count_layers(fz_context *ctx, pdf_document *doc);
const char *pdf_layer_name(fz_context *ctx, pdf_document *doc, int layer);
int pdf_layer_is_enabled(fz_context *ctx, pdf_document *doc, int layer);
void pdf_enable_layer(fz_context *ctx, pdf_document *doc, int layer, int enabled);

typedef struct
{
	const char *name;
	const char *creator;
} pdf_layer_config;

/*
	Fetch the name (and optionally creator) of the given layer config.

	doc: The document in question.

	config_num: A value in the 0..n-1 range, where n is the
	value returned from pdf_count_layer_configs.

	info: Pointer to structure to fill in. Pointers within
	this structure may be set to NULL if no information is
	available.
*/
void pdf_layer_config_info(fz_context *ctx, pdf_document *doc, int config_num, pdf_layer_config *info);

/*
	Set the current configuration.
	This updates the visibility of the optional content groups
	within the document.

	doc: The document in question.

	config_num: A value in the 0..n-1 range, where n is the
	value returned from pdf_count_layer_configs.
*/
void pdf_select_layer_config(fz_context *ctx, pdf_document *doc, int config_num);

/*
	Returns the number of entries in the 'UI' for this layer configuration.

	doc: The document in question.
*/
int pdf_count_layer_config_ui(fz_context *ctx, pdf_document *doc);

/*
	Select a checkbox/radiobox within the 'UI' for this layer
	configuration.

	Selecting a UI entry that is a radiobox may disable
	other UI entries.

	doc: The document in question.

	ui: A value in the 0..m-1 range, where m is the value
	returned by pdf_count_layer_config_ui.
*/
void pdf_select_layer_config_ui(fz_context *ctx, pdf_document *doc, int ui);

/*
	Select a checkbox/radiobox within the 'UI' for this layer configuration.

	doc: The document in question.

	ui: A value in the 0..m-1 range, where m is the value
	returned by pdf_count_layer_config_ui.
*/
void pdf_deselect_layer_config_ui(fz_context *ctx, pdf_document *doc, int ui);

/*
	Toggle a checkbox/radiobox within the 'UI' for this layer configuration.

	Toggling a UI entry that is a radiobox may disable
	other UI entries.

	doc: The document in question.

	ui: A value in the 0..m-1 range, where m is the value
	returned by pdf_count_layer_config_ui.
*/
void pdf_toggle_layer_config_ui(fz_context *ctx, pdf_document *doc, int ui);

typedef enum
{
	PDF_LAYER_UI_LABEL = 0,
	PDF_LAYER_UI_CHECKBOX = 1,
	PDF_LAYER_UI_RADIOBOX = 2
} pdf_layer_config_ui_type;

typedef struct
{
	const char *text;
	int depth;
	pdf_layer_config_ui_type type;
	int selected;
	int locked;
} pdf_layer_config_ui;

/*
	Get the info for a given entry in the layer config ui.

	doc: The document in question.

	ui: A value in the 0..m-1 range, where m is the value
	returned by pdf_count_layer_config_ui.

	info: Pointer to a structure to fill in with information
	about the requested ui entry.
*/
void pdf_layer_config_ui_info(fz_context *ctx, pdf_document *doc, int ui, pdf_layer_config_ui *info);

/*
	Write the current layer config back into the document as the default state.
*/
void pdf_set_layer_config_as_default(fz_context *ctx, pdf_document *doc);

/*
	Determine whether changes have been made since the
	document was opened or last saved.
*/
int pdf_has_unsaved_changes(fz_context *ctx, pdf_document *doc);

/*
	Determine if this PDF has been repaired since opening.
*/
int pdf_was_repaired(fz_context *ctx, pdf_document *doc);

/* Object that can perform the cryptographic operation necessary for document signing */
typedef struct pdf_pkcs7_signer pdf_pkcs7_signer;

/* Unsaved signature fields */
typedef struct pdf_unsaved_sig
{
	pdf_obj *field;
	size_t byte_range_start;
	size_t byte_range_end;
	size_t contents_start;
	size_t contents_end;
	pdf_pkcs7_signer *signer;
	struct pdf_unsaved_sig *next;
} pdf_unsaved_sig;

typedef struct
{
	int page;
	int object;
} pdf_rev_page_map;

typedef struct
{
	int number; /* Page object number */
	int64_t offset; /* Offset of page object */
	int64_t index; /* Index into shared hint_shared_ref */
} pdf_hint_page;

typedef struct
{
	int number; /* Object number of first object */
	int64_t offset; /* Offset of first object */
} pdf_hint_shared;

struct pdf_document
{
	fz_document super;

	fz_stream *file;

	int version;
	int64_t startxref;
	int64_t file_size;
	pdf_crypt *crypt;
	pdf_ocg_descriptor *ocg;
	fz_colorspace *oi;

	int max_xref_len;
	int num_xref_sections;
	int saved_num_xref_sections;
	int num_incremental_sections;
	int xref_base;
	int disallow_new_increments;

	/* The local_xref is only active, if local_xref_nesting >= 0 */
	pdf_xref *local_xref;
	int local_xref_nesting;

	pdf_xref *xref_sections;
	pdf_xref *saved_xref_sections;
	int *xref_index;
	int save_in_progress;
	int last_xref_was_old_style;
	int has_linearization_object;

	int map_page_count;
	pdf_rev_page_map *rev_page_map;
	pdf_obj **fwd_page_map;
	int page_tree_broken;

	int repair_attempted;
	int repair_in_progress;
	int non_structural_change; /* True if we are modifying the document in a way that does not change the (page) structure */

	/* State indicating which file parsing method we are using */
	int file_reading_linearly;
	int64_t file_length;

	int linear_page_count;
	pdf_obj *linear_obj; /* Linearized object (if used) */
	pdf_obj **linear_page_refs; /* Page objects for linear loading */
	int linear_page1_obj_num;

	/* The state for the pdf_progressive_advance parser */
	int64_t linear_pos;
	int linear_page_num;

	int hint_object_offset;
	int hint_object_length;
	int hints_loaded; /* Set to 1 after the hints loading has completed,
			   * whether successful or not! */
	/* Page n references shared object references:
	 *   hint_shared_ref[i]
	 * where
	 *      i = s to e-1
	 *	s = hint_page[n]->index
	 *	e = hint_page[n+1]->index
	 * Shared object reference r accesses objects:
	 *   rs to re-1
	 * where
	 *   rs = hint_shared[r]->number
	 *   re = hint_shared[r]->count + rs
	 * These are guaranteed to lie within the region starting at
	 * hint_shared[r]->offset of length hint_shared[r]->length
	 */
	pdf_hint_page *hint_page;
	int *hint_shared_ref;
	pdf_hint_shared *hint_shared;
	int hint_obj_offsets_max;
	int64_t *hint_obj_offsets;

	int resources_localised;

	pdf_lexbuf_large lexbuf;

	pdf_js *js;

	int recalculate;
	int redacted;
	int resynth_required;

	pdf_doc_event_cb *event_cb;
	pdf_free_doc_event_data_cb *free_event_data_cb;
	void *event_cb_data;

	int num_type3_fonts;
	int max_type3_fonts;
	fz_font **type3_fonts;

	struct {
		fz_hash_table *fonts;
	} resources;

	int orphans_max;
	int orphans_count;
	pdf_obj **orphans;

	fz_xml_doc *xfa;

	pdf_journal *journal;
};

pdf_document *pdf_create_document(fz_context *ctx);

typedef struct pdf_graft_map pdf_graft_map;

/*
	Return a deep copied object equivalent to the
	supplied object, suitable for use within the given document.

	dst: The document in which the returned object is to be used.

	obj: The object deep copy.

	Note: If grafting multiple objects, you should use a pdf_graft_map
	to avoid potential duplication of target objects.
*/
pdf_obj *pdf_graft_object(fz_context *ctx, pdf_document *dst, pdf_obj *obj);

/*
	Prepare a graft map object to allow objects
	to be deep copied from one document to the given one, avoiding
	problems with duplicated child objects.

	dst: The document to copy objects to.

	Note: all the source objects must come from the same document.
*/
pdf_graft_map *pdf_new_graft_map(fz_context *ctx, pdf_document *dst);

pdf_graft_map *pdf_keep_graft_map(fz_context *ctx, pdf_graft_map *map);
void pdf_drop_graft_map(fz_context *ctx, pdf_graft_map *map);

/*
	Return a deep copied object equivalent
	to the supplied object, suitable for use within the target
	document of the map.

	map: A map targeted at the document in which the returned
	object is to be used.

	obj: The object to be copied.

	Note: Copying multiple objects via the same graft map ensures
	that any shared children are not copied more than once.
*/
pdf_obj *pdf_graft_mapped_object(fz_context *ctx, pdf_graft_map *map, pdf_obj *obj);

/*
	Graft a page (and its resources) from the src document to the
	destination document of the graft. This involves a deep copy
	of the objects in question.

	map: A map targetted at the document into which the page should
	be inserted.

	page_to: The position within the destination document at which
	the page should be inserted (pages numbered from 0, with -1
	meaning "at the end").

	src: The document from which the page should be copied.

	page_from: The page number which should be copied from the src
	document (pages numbered from 0, with -1 meaning "at the end").
*/
void pdf_graft_page(fz_context *ctx, pdf_document *dst, int page_to, pdf_document *src, int page_from);
void pdf_graft_mapped_page(fz_context *ctx, pdf_graft_map *map, int page_to, pdf_document *src, int page_from);

/*
	Create a device that will record the
	graphical operations given to it into a sequence of
	pdf operations, together with a set of resources. This
	sequence/set pair can then be used as the basis for
	adding a page to the document (see pdf_add_page).
	Returns a kept reference.

	doc: The document for which these are intended.

	mediabox: The bbox for the created page.

	presources: Pointer to a place to put the created
	resources dictionary.

	pcontents: Pointer to a place to put the created
	contents buffer.
*/
fz_device *pdf_page_write(fz_context *ctx, pdf_document *doc, fz_rect mediabox, pdf_obj **presources, fz_buffer **pcontents);

/*
	Create a pdf device. Rendering to the device creates
	new pdf content. WARNING: this device is work in progress. It doesn't
	currently support all rendering cases.

	Note that contents must be a stream (dictionary) to be updated (or
	a reference to a stream). Callers should take care to ensure that it
	is not an array, and that is it not shared with other objects/pages.
*/
fz_device *pdf_new_pdf_device(fz_context *ctx, pdf_document *doc, fz_matrix topctm, pdf_obj *resources, fz_buffer *contents);

/*
	Create a pdf_obj within a document that
	represents a page, from a previously created resources
	dictionary and page content stream. This should then be
	inserted into the document using pdf_insert_page.

	After this call the page exists within the document
	structure, but is not actually ever displayed as it is
	not linked into the PDF page tree.

	doc: The document to which to add the page.

	mediabox: The mediabox for the page (should be identical
	to that used when creating the resources/contents).

	rotate: 0, 90, 180 or 270. The rotation to use for the
	page.

	resources: The resources dictionary for the new page
	(typically created by pdf_page_write).

	contents: The page contents for the new page (typically
	create by pdf_page_write).
*/
pdf_obj *pdf_add_page(fz_context *ctx, pdf_document *doc, fz_rect mediabox, int rotate, pdf_obj *resources, fz_buffer *contents);

/*
	Insert a page previously created by
	pdf_add_page into the pages tree of the document.

	doc: The document to insert into.

	at: The page number to insert at (pages numbered from 0).
	0 <= n <= page_count inserts before page n. Negative numbers
	or INT_MAX are treated as page count, and insert at the end.
	0 inserts at the start. All existing pages are after the
	insertion point are shuffled up.

	page: The page to insert.
*/
void pdf_insert_page(fz_context *ctx, pdf_document *doc, int at, pdf_obj *page);

/*
	Delete a page from the page tree of
	a document. This does not remove the page contents
	or resources from the file.

	doc: The document to operate on.

	number: The page to remove (numbered from 0)
*/
void pdf_delete_page(fz_context *ctx, pdf_document *doc, int number);

/*
	Delete a range of pages from the
	page tree of a document. This does not remove the page
	contents or resources from the file.

	doc: The document to operate on.

	start, end: The range of pages (numbered from 0)
	(inclusive, exclusive) to remove. If end is negative or
	greater than the number of pages in the document, it
	will be taken to be the end of the document.
*/
void pdf_delete_page_range(fz_context *ctx, pdf_document *doc, int start, int end);

/*
	Get page label (string) from a page number (index).
*/
void pdf_page_label(fz_context *ctx, pdf_document *doc, int page, char *buf, size_t size);
void pdf_page_label_imp(fz_context *ctx, fz_document *doc, int chapter, int page, char *buf, size_t size);

typedef enum {
	PDF_PAGE_LABEL_NONE = 0,
	PDF_PAGE_LABEL_DECIMAL = 'D',
	PDF_PAGE_LABEL_ROMAN_UC = 'R',
	PDF_PAGE_LABEL_ROMAN_LC = 'r',
	PDF_PAGE_LABEL_ALPHA_UC = 'A',
	PDF_PAGE_LABEL_ALPHA_LC = 'a',
} pdf_page_label_style;

void pdf_set_page_labels(fz_context *ctx, pdf_document *doc, int index, pdf_page_label_style style, const char *prefix, int start);
void pdf_delete_page_labels(fz_context *ctx, pdf_document *doc, int index);

fz_text_language pdf_document_language(fz_context *ctx, pdf_document *doc);
void pdf_set_document_language(fz_context *ctx, pdf_document *doc, fz_text_language lang);

/*
	In calls to fz_save_document, the following options structure can be used
	to control aspects of the writing process. This structure may grow
	in the future, and should be zero-filled to allow forwards compatibility.
*/
typedef struct
{
	int do_incremental; /* Write just the changed objects. */
	int do_pretty; /* Pretty-print dictionaries and arrays. */
	int do_ascii; /* ASCII hex encode binary streams. */
	int do_compress; /* Compress streams. */
	int do_compress_images; /* Compress (or leave compressed) image streams. */
	int do_compress_fonts; /* Compress (or leave compressed) font streams. */
	int do_decompress; /* Decompress streams (except when compressing images/fonts). */
	int do_garbage; /* Garbage collect objects before saving; 1=gc, 2=re-number, 3=de-duplicate. */
	int do_linear; /* Write linearised. */
	int do_clean; /* Clean content streams. */
	int do_sanitize; /* Sanitize content streams. */
	int do_appearance; /* (Re)create appearance streams. */
	int do_encrypt; /* Encryption method to use: keep, none, rc4-40, etc. */
	int dont_regenerate_id; /* Don't regenerate ID if set (used for clean) */
	int permissions; /* Document encryption permissions. */
	char opwd_utf8[128]; /* Owner password. */
	char upwd_utf8[128]; /* User password. */
	int do_snapshot; /* Do not use directly. Use the snapshot functions. */
	int do_preserve_metadata; /* When cleaning, preserve metadata unchanged. */
} pdf_write_options;

FZ_DATA extern const pdf_write_options pdf_default_write_options;

/*
	Parse option string into a pdf_write_options struct.
	Matches the command line options to 'mutool clean':
		g: garbage collect
		d, i, f: expand all, fonts, images
		l: linearize
		a: ascii hex encode
		z: deflate
		c: clean content streams
		s: sanitize content streams
*/
pdf_write_options *pdf_parse_write_options(fz_context *ctx, pdf_write_options *opts, const char *args);

/*
	Returns true if there are digital signatures waiting to
	to updated on save.
*/
int pdf_has_unsaved_sigs(fz_context *ctx, pdf_document *doc);

/*
	Write out the document to an output stream with all changes finalised.
*/
void pdf_write_document(fz_context *ctx, pdf_document *doc, fz_output *out, const pdf_write_options *opts);

/*
	Write out the document to a file with all changes finalised.
*/
void pdf_save_document(fz_context *ctx, pdf_document *doc, const char *filename, const pdf_write_options *opts);

/*
	Snapshot the document to a file. This does not cause the
	incremental xref to be finalized, so the document in memory
	remains (essentially) unchanged.
*/
void pdf_save_snapshot(fz_context *ctx, pdf_document *doc, const char *filename);

/*
	Snapshot the document to an output stream. This does not cause
	the incremental xref to be finalized, so the document in memory
	remains (essentially) unchanged.
*/
void pdf_write_snapshot(fz_context *ctx, pdf_document *doc, fz_output *out);

char *pdf_format_write_options(fz_context *ctx, char *buffer, size_t buffer_len, const pdf_write_options *opts);

/*
	Return true if the document can be saved incrementally. Applying
	redactions or having a repaired document make incremental saving
	impossible.
*/
int pdf_can_be_saved_incrementally(fz_context *ctx, pdf_document *doc);

/*
	Write out the journal to an output stream.
*/
void pdf_write_journal(fz_context *ctx, pdf_document *doc, fz_output *out);

/*
	Write out the journal to a file.
*/
void pdf_save_journal(fz_context *ctx, pdf_document *doc, const char *filename);

/*
	Read a journal from a filename. Will do nothing if the journal
	does not match. Will throw on a corrupted journal.
*/
void pdf_load_journal(fz_context *ctx, pdf_document *doc, const char *filename);

/*
	Read a journal from a stream. Will do nothing if the journal
	does not match. Will throw on a corrupted journal.
*/
void pdf_read_journal(fz_context *ctx, pdf_document *doc, fz_stream *stm);

/*
	Minimize the memory used by a document.

	We walk the in memory xref tables, evicting the PDF objects
	therein that aren't in use.

	This reduces the current memory use, but any subsequent use
	of these objects will load them back into memory again.
*/
void pdf_minimize_document(fz_context *ctx, pdf_document *doc);


#endif