1PDF::API2::Basic::PDF::UFsielre(C3o)ntributed Perl DocumPeDnFt:a:tAiPoIn2::Basic::PDF::File(3)
2
6 PDF::API2::Basic::PDF::File - Low-level PDF file access
7
9 $p = PDF::API2::Basic::PDF::File->open("filename.pdf", 1);
10 $p->new_obj($obj_ref);
11 $p->free_obj($obj_ref);
12 $p->append_file;
13 $p->close_file;
14 $p->release; # IMPORTANT!
15
17 This class keeps track of the directory aspects of a PDF file. There
18 are two parts to the directory: the main directory object which is the
19 parent to all other objects and a chain of cross-reference tables and
20 corresponding trailer dictionaries starting with the main directory
21 object.
22
24 Within this class hierarchy, rather than making everything visible via
25 methods, which would be a lot of work, there are various instance
26 variables which are accessible via associative array referencing. To
27 distinguish instance variables from content variables (which may come
28 from the PDF content itself), each such variable will start with a
29 space.
30 Variables which do not start with a space directly reflect elements in
32 a PDF dictionary. In the case of a PDF::API2::Basic::PDF::File, the
33 elements reflect those in the trailer dictionary.
34 Since some variables are not designed for class users to access,
36 variables are marked in the documentation with (R) to indicate that
37 such an entry should only be used as read-only information. (P)
38 indicates that the information is private and not designed for user use
39 at all, but is included in the documentation for completeness and to
40 ensure that nobody else tries to use it.
41 newroot
43 This variable allows the user to create a new root entry to occur
44 in the trailer dictionary which is output when the file is written
45 or appended. If you wish to over-ride the root element in the
46 dictionary you have, use this entry to indicate that without losing
47 the current Root entry. Notice that newroot should point to a PDF
48 level object and not just to a dictionary which does not have
49 object status.
50 INFILE (R)
52 Contains the filehandle used to read this information into this PDF
53 directory. Is an IO object.
54 fname (R)
56 This is the filename which is reflected by INFILE, or the original
57 IO object passed in.
58 update (R)
60 This indicates that the read file has been opened for update and
61 that at some point, $p->appendfile() can be called to update the
62 file with the changes that have been made to the memory
63 representation.
64 maxobj (R)
66 Contains the first usable object number above any that have already
67 appeared in the file so far.
68 outlist (P)
70 This is a list of Objind which are to be output when the next
71 appendfile or outfile occurs.
72 firstfree (P)
74 Contains the first free object in the free object list. Free
75 objects are removed from the front of the list and added to the
76 end.
77 lastfree (P)
79 Contains the last free object in the free list. It may be the same
80 as the firstfree if there is only one free object.
81 objcache (P)
83 All objects are held in the cache to ensure that a system only has
84 one occurrence of each object. In effect, the objind class acts as
85 a container type class to hold the PDF object structure and it
86 would be unfortunate if there were two identical place-holders
87 floating around a system.
88 epos (P)
90 The end location of the read-file.
91 Each trailer dictionary contains a number of private instance variables
93 which hold the chain together.
94 loc (P)
96 Contains the location of the start of the cross-reference table
97 preceding the trailer.
98 xref (P)
100 Contains an anonymous array of each cross-reference table entry.
101 prev (P)
103 A reference to the previous table. Note this differs from the Prev
104 entry which is in PDF which contains the location of the previous
105 cross-reference table.
106
108 PDF::API2::Basic::PDF::File->new
109 Creates a new, empty file object which can act as the host to other PDF
110 objects. Since there is no file associated with this object, it is
111 assumed that the object is created in readiness for creating a new PDF
112 file.
113 $p = PDF::API2::Basic::PDF::File->open($filename, $update)
115 Opens the file and reads all the trailers and cross reference tables to
116 build a complete directory of objects.
117 $update specifies whether this file is being opened for updating and
119 editing, or simply to be read.
120 $filename may be an IO object
122 $p->version($version)
124 Gets/sets the PDF version (e.g. 1.4)
125 $version = $p->header_version($version)
127 Gets/sets the PDF version stored in the file header.
128 $version = $p->trailer_version($version)
130 Gets/sets the PDF version stored in the document catalog.
131 $prev_version = $p->require_version($version)
133 Ensures that the PDF version is at least $version.
134 $p->release()
136 Releases ALL of the memory used by the PDF document and all of its
137 component objects. After calling this method, do NOT expect to have
138 anything left in the "PDF::API2::Basic::PDF::File" object (so if you
139 need to save, be sure to do it before calling this method).
140 NOTE, that it is important that you call this method on any
142 "PDF::API2::Basic::PDF::File" object when you wish to destruct it and
143 free up its memory. Internally, PDF files have an enormous number of
144 cross-references and this causes circular references within the
145 internal data structures. Calling 'release()' forces a brute-force
146 cleanup of the data structures, freeing up all of the memory. Once
147 you've called this method, though, don't expect to be able to do
148 anything else with the "PDF::API2::Basic::PDF::File" object; it'll have
149 no internal state whatsoever.
150 $p->append_file()
152 Appends the objects for output to the read file and then appends the
153 appropriate table.
154 $p->out_file($fname)
156 Writes a PDF file to a file of the given filename based on the current
157 list of objects to be output. It creates the trailer dictionary based
158 on information in $self.
159 $fname may be an IO object;
161 $p->create_file($fname)
163 Creates a new output file (no check is made of an existing open file)
164 of the given filename or IO object. Note, make sure that $p->{'
165 version'} is set correctly before calling this function.
166 $p->clone_file($fname)
168 Creates a copy of the input file at the specified filename and sets it
169 as the output file for future writes. A file handle may be passed
170 instead of a filename.
171 $p->close_file
173 Closes up the open file for output by outputting the trailer etc.
174 ($value, $str) = $p->readval($str, %opts)
176 Reads a PDF value from the current position in the file. If $str is too
177 short then read some more from the current location in the file until
178 the whole object is read. This is a recursive call which may slurp in a
179 whole big stream (unprocessed).
180 Returns the recursive data structure read and also the current $str
182 that has been read from the file.
183 $ref = $p->read_obj($objind, %opts)
185 Given an indirect object reference, locate it and read the object
186 returning the read in object.
187 $ref = $p->read_objnum($num, $gen, %opts)
189 Returns a fully read object of given number and generation in this file
190 $objind = $p->new_obj($obj)
192 Creates a new, free object reference based on free space in the cross
193 reference chain. If nothing free then thinks up a new number. If $obj
194 then turns that object into this new object rather than returning a new
195 object.
196 $p->out_obj($objind)
198 Indicates that the given object reference should appear in the output
199 xref table whether with data or freed.
200 $p->free_obj($objind)
202 Marks an object reference for output as being freed.
203 $p->remove_obj($objind)
205 Removes the object from all places where we might remember it
206 $p->ship_out(@objects)
208 Ships the given objects (or all objects for output if @objects is
209 empty) to the currently open output file (assuming there is one). Freed
210 objects are not shipped, and once an object is shipped it is switched
211 such that this file becomes its source and it will not be shipped again
212 unless out_obj is called again. Notice that a shipped out object can be
213 re-output or even freed, but that it will not cause the data already
214 output to be changed.
215 $p->copy($outpdf, \&filter)
217 Iterates over every object in the file reading the object, calling
218 filter with the object and outputting the result. if filter is not
219 defined, then just copies input to output.
220
222 The following methods and functions are considered private to this
223 class. This does not mean you cannot use them if you have a need, just
224 that they aren't really designed for users of this class.
225 $offset = $p->locate_obj($num, $gen)
227 Returns a file offset to the object asked for by following the chain of
228 cross reference tables until it finds the one you want.
229 update($fh, $str, $instream)
231 Keeps reading $fh for more data to ensure that $str has at least a line
232 full for "readval" to work on. At this point we also take the
233 opportunity to ignore comments.
234 $objind = $p->test_obj($num, $gen)
236 Tests the cache to see whether an object reference (which may or may
237 not have been getobj()ed) has been cached. Returns it if it has.
238 $p->add_obj($objind)
240 Adds the given object to the internal object cache.
241 $tdict = $p->readxrtr($xpos)
243 Recursive function which reads each of the cross-reference and trailer
244 tables in turn until there are no more.
245 Returns a dictionary corresponding to the trailer chain. Each trailer
247 also includes the corresponding cross-reference table.
248 The structure of the xref private element in a trailer dictionary is of
250 an anonymous hash of cross reference elements by object number. Each
251 element consists of an array of 3 elements corresponding to the three
252 elements read in [location, generation number, free or used]. See the
253 PDF specification for details.
254 $p->out_trailer($tdict)
256 Outputs the body and trailer for a PDF file by outputting all the
257 objects in the ' outlist' and then outputting a xref table for those
258 objects and any freed ones. It then outputs the trailing dictionary and
259 the trailer code.
260 PDF::API2::Basic::PDF::File->_new
262 Creates a very empty PDF file object (used by new and open)
263
265 Martin Hosken Martin_Hosken@sil.org
266 Copyright Martin Hosken 1999 and onwards
268 No warranty or expression of effectiveness, least of all regarding
270 anyone's safety, is implied in this software or documentation.
271perl v5.36.0 2023-01-20 PDF::API2::Basic::PDF::File(3)