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Claims  |
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WHAT IS CLAIMED AS NEW AND DESIRED TO BE SECURED BY LETTERS PATENT OF THE
UNITED STATES IS:
1. An apparatus for control of the-presentation of a document by a
presentation device, comprising:
input means for accepting an input document data stream defining said
document, said data stream composed of a picture or a pageset with a
hierarchically ordered structure;
said picture comprising zero or more prologue and zero or more picture
body, and said pageset comprising zero or more prologue and zero or more
pageset body;
said picture body comprising zero or more tokensequences and zero or more
pictures;
said pageset body comprising zero or more pictures and zero or more
pagesets;
structure processing means coupled to said input means to determine pageset
definitions or picture definitions to detect a begin and an associated end
of each pageset definition or picture definition, for processing each
prologue in the determined pageset or picture definitions, for ordering
body portions between each detected begin and associated detected end in
an ordered hierarchy, and for generating and outputting output document
instructions for controlling said presentation device; and
output means coupled to said structure processing means for applying said
output document instructions to said presentation device.
2. An apparatus for control of a presentation of a document by a
presentation device, comprising:
input means for accepting an input document data stream defining said
document, said data stream composed of a hierarchically ordered set of one
or more prologues each having zero or more associated content portions;
structure processing means coupled to said input means for processing each
prologue to determine pageset definitions and picture elements of said
document data stream, for processing the determined pageset definitions to
detect a begin and an associated end of each pageset definition, for
ordering content portions between each detected begin and associated
detected end in an ordered hierarchy, and for generating and outputting
output document instructions for controlling said presentation device; and
output means coupled to said structure processing means for applying said
output document instructions to said presentation device.
3. The apparatus as in claim 2, further comprising:
means for controlling a scope in said ordered hierarchy of a given pageset
and picture.
4. The apparatus as in claim 2, wherein said means for controlling
comprises:
a stack memory means.
5. An apparatus as in claim 2, further comprising:
storing means coupled to said structure processing means for storing said
zero or more associated content portions defined by a processed prologue.
6. An apparatus as in claim 5, further comprising:
syntactic analysis section means for checking syntactic correctness of each
detected begin and its associated end of each pageset definition.
7. An apparatus as in claim 5, wherein said structure processing means
comprises:
stack memory means for controlling a hierarchical ordering of said zero or
more content portions stored by said storing means.
8. An apparatus as in claim 7, wherein said stack memory means employs a
pointer structure to maintain identification of said stored items.
9. An apparatus as in claim 7, wherein said stack memory means comprises:
a stack memory which stores a linked list of pointers identifying the
ordered hierarchy and thereby providing a search path defined by said
linked list of stored pointers.
10. An apparatus as in claim 7, further comprising:
means for releasing for reuse stored pointers in the ordered hierarchy
corresponding the content portions of the document data stream that are at
a lower level of said hierarchy relative to the content portions of the
presented page in the ordered hierarchy after presentation of a page
defined by said pageset definition and the presentation of all pages in
the document data stream which are at a lower level in the ordered
hierarchy.
11. The apparatus as in claim 2, further comprising:
means for storing and presenting a page number.
12. The apparatus as in claim 2, further comprising:
means for selectively presenting pages from said inputted document data
system.
13. An apparatus for controlling a presentation of a document by means of a
presentation device, comprising:
input means for accepting an input document data stream defining said
document, said data stream comprising at least one prologue and zero or
more associated content portions;
CPU means coupled to said input means for processing said data stream and
producing output document instructions based on the processed data stream,
comprising,
means for ordering addressing of said at least one prologue and associated
content portions in an ordered hierarchy, and
means for processing at least one prologue and associated content portions
in said ordered hierarchy to produce said output document instructions;
and
output means coupled to said CPU means for applying said output document
instructions to said presentation device for the presentation of the
document represented by said output document instructions.
14. The apparatus according to claim 13, wherein said ordering means
comprises:
stack memory means for storing pointers allocating memory locations for
storage of prologues and associated content portions in a retrieving
sequence defined by said pointers.
15. In a method for controlling a presentation of a document defined by a
document data stream, the improvement comprising the steps of:
(a) inputting to a processor unit a document data stream defining a
document to be presented, said document data stream including pageset
definitions, each pageset definition including a begin, zero or more
picture elements and an end, said picture elements comprising zero or more
prologues, each prologue comprising zero or more prologue elements and
content portions, said content portions containing image defining
tokensequence elements;
(b) parsing said inputted document data stream to determine the begin and
end of a prologue within said inputted document data stream to determine
the existence thereof;
(c) allocating memory at a given hierarchical level of memory allocation
ordering and storing in the allocated memory at said given hierarchical
level document data defined between a given detected begin and an
associated detected end of a prologue;
(d) pushing onto a stack a pointer identifying memory allocated at said
given hierarchical level;
(e) allocating memory at a lower hierarchical level below the given
hierarchical level and storing at said lower hierarchical level document
data defined between a further detected begin, which is detected before
the detected end associated with said given detected begin, and a detected
end associated with said further detected begin; and
(f) pushing onto said stack a pointer identifying memory allocated at said
lower hierarchical level.
16. The method according to claim 15, further comprising the step of:
popping from said stack pointers corresponding to content portions of the
document data stream that are at a lower hierarchical level relative to
the content portions of the presented page upon the presentation of a page
defined by said pageset definition and the presentation of all pages in
the document.
17. The method according to claim 15, comprising:
repeating steps (e) and (f) whenever a begin at a lower hierarchical level
is detected before detection of an end associated with a detected begin at
a higher hierarchical level.
18. A processor apparatus for control of presentation of a document defined
by a document data stream, said processor programmed to perform the steps
of:
(a) inputting to a processor unit a document data stream defining a
document to be presented, said document data stream including pageset
definitions, each pageset definition including a begin, zero or more
picture elements and an end, said picture elements comprising zero or more
prologues, each prologue comprising zero or more prologue elements and
content portions, said content portions containing image defining
tokensequence elements;
(b) parsing said inputted document data stream to determine the begin and
end of a prologue within said inputted document data stream to determine
the existence thereof;
(c) allocating memory at a given hierarchical level of memory allocation
ordering and storing in the allocated memory at said given hierarchical
level document data defined between a given detected begin and an
associated detected end of a prologue;
(d) pushing onto a stack a pointer identifying memory allocated at said
given hierarchical level;
(e) allocating memory at a lower hierarchical level below the given
hierarchical level and storing at said lower hierarchical level document
data defined between a further detected begin, which is detected before
the detected end associated with said given detected begin, and a detected
end associated with said further detected begin; and
(f) pushing onto said stack a pointer identifying memory allocated at said
lower hierarchical level.
19. A computer readable medium for storing a program for control of
presentation of a document defined by a document data stream, said program
defining the steps of:
(a) inputting to a processor unit a document data stream defining a
document to be presented, said document data stream including pageset
definitions, each pageset definition including a begin, zero or more
picture elements and an end, said picture elements comprising zero or more
prologues, each prologue comprising zero or more prologue elements and
content portions, said content portions containing image defining
tokensequence elements;
(b) parsing said inputted document data stream to determine the begin and
end of a prologue within said inputted document data stream to determine
the existence thereof;
(c) allocating memory at a given hierarchical level of memory allocation
ordering and storing in the allocated memory at said given hierarchical
level document data defined between a given detected begin and an
associated detected end of a prologue;
(d) pushing onto a stack a pointer identifying memory allocated at said
given hierarchical level;
(e) allocating memory at a lower hierarchical level below the given
hierarchical level and storing at said lower hierarchical level document
data defined between a further detected begin, which is detected before
the detected end associated with said given detected begin, and a detected
end associated with said further detected begin; and
(f) pushing onto said stack a pointer identifying memory allocated at said
lower hierarchical level.
20. A method for processing a document in a hierarchically structured
language, comprising the steps of:
determining a beginning of one of a picture and pageset structure elements
in the document;
pushing onto a stack, an entry used for keeping track of processing
parameters for a particular hierarchical level, said entry corresponding
to said one of the picture and pageset structure elements; and
processing said one of the picture and pageset structure elements;
popping said entry off of the stack after processing of said one of said
picture and pageset structure elements is complete.
21. An apparatus for processing a document in a hierarchically structured
language, comprising:
means for determining a beginning of one of a picture and pageset structure
elements in the document; means for pushing onto a stack, an entry used
for keeping track of processing parameters for a particular hierarchical
level, said entry corresponding to said one of the picture and pageset
structure elements;
means for processing said one of the picture and pageset structure
elements; and
means for popping said entry off of the stack after processing of said one
of said picture and pageset structure elements is complete.
22. A method of processing a hierarchically structured document, comprising
the steps of:
processing a first hierarchical level of the document using a first set of
system parameters;
copying the first set of system parameters to a second set of system
parameters;
processing a second hierarchical level of the document using the second set
of system parameters, during which the second set of system parameters are
modified;
continuing processing of the first hierarchical level of the document,
after the processing of the second hierarchical level of the document,
using system parameters which are equal to the first set of system
parameters.
23. An apparatus for processing a hierarchically structured document,
comprising:
means for processing a first hierarchical level of the document using a
first set of system parameters;
means for copying the first set of system parameters to a second set of
system parameters;
means for processing a second hierarchical level of the document using the
second set of system parameters, during which the second set of system
parameters are modified;
means for continuing processing of the first hierarchical level of the
document, after the processing of the second hierarchical level of the
document, using system parameters which are equal to the first set of
system parameters. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the computer controlled printing,
displaying or other presentation of documents which may have text,
graphical components, and/or images and more particularly to a method and
systems for processing the beginning and ending of pictures or pagesets in
a document data stream, as well as other data which might be defined in
the document data stream. This invention also relates to methodology for
keeping track of the scope or status of the presentation device. In this
context the presentation of a document on a page involves the printing on
a fixed medium such as paper, transparency or the like, the page, or
presenting on a visual display the page or transmitting to another device
the document in a form to be presented or stored. The present application
is related to commonly owned co-pending U.S. patent application Ser. No.
07/778,578 filed on Oct. 17, 1991, the disclosure of which is incorporated
by reference herein. The present application is also related to commonly
owned concurrently filed U.S. patent application Ser. No. 07/876,251
entitled "A Method and System to Handle Inclusion of External Files into a
Document Processing Language", filed Apr. 30, 1992, also incorporated by
reference herein.
2. Discussion of the Background
The development of laser printers in the early 1970s provided an
opportunity for high quality and low cost printing of documents which
contain not only character data but also generalized graphical material.
The primary method of controlling these types of printers was by means of
commands employing a so-called "escape sequence", which commands are
similar to the type of commands used in a DIABLO.RTM. command sequence.
These commands were distinguished from typical character data in a data
stream by preceding the command with a special byte, generally an escape
character (ASCII 27). This methodology was acceptable for low speed
devices and for devices which print limited amounts of graphics, such as
daisy wheel or dot matrix printers, but was not well suited for printing
documents that combine significant amounts of text and graphical materials
because no provision was made for the large amount of data that a graphic
might employ.
In response to the limitations inherent in the escape sequence type of
control, different types of "page description language" (PDL) were
developed in general to control laser or other types of page printers. A
backward compatibility was provided in most of these laser printers in
that they were able to simulate conventional escape sequence commands such
as might be found in the aforementioned DIABLO.RTM. or EPSON.RTM. type of
printers. Examples of the conventional page description language which
were developed in response to the limitations inherent in escape sequence
commands were the PostScript.RTM. system from Adobe Systems, Inc. and
Interpress.RTM. from Xerox. Other types of proprietary PDL's were also
created to circumvent the limitations attendant to the use of escape
sequence commends.
One of the shortcomings of the conventional page description languages such
as PostScript.RTM., becomes evident in relation to the provisions that are
made so that a particular document may contain a new definition, such as a
new resource definition (e.g., an additional font or graphic which is to
be used in the document) or a new dictionary definition. These new
definitions might appear anywhere within a document data stream and are
difficult to process and identify. As a result, the entire contents of a
document must be inspected in order to determine whether or not a given
printer has resources which are capable and necessary to print a
particular document or to process the document in the manner desired. As a
consequence, it is possible for the printing of a document to fail at any
point during the printing process, including near the very end of
processing, due to the inability of the printer to comply with the
commands contained within the document's page description language.
Another problem associated with a PostScript.RTM. type system is that in
order to print a given page of a document, if it is not the first page, it
is necessary to read the entire PDL description of all the preceding pages
of the document in order to determine the state of the document page set
up parameters (i.e., resource declaration, dictionary definition or the
like) before the processing for a specified page can be accomplished. In
other words, the print controller or a print driver program must read the
entire PDL document data stream to take into account the effect of every
page set up command which might change the state of the printing between
the beginning of the document and the specified page. Although this
scanning is relatively straightforward, it requires a significant amount
of processing and consequently is an ineffective solution to the problem.
It further is complicated in that identification of the beginning and end
of pages and graphics in PostScript.RTM. documents is not very
straightforward and involves significant processing. PostScript developed
the Document Structuring Convention using comments to distinguish various
resources and page breaks. However, this is the convention and there is
nothing in the description language to enforce this convention. The
violation of convention does not flag the errors.
The prior art page description languages including PostScript and
InterPress providing various improvements to the conventional escape
sequences, such as providing tools for such items as resource
declarations, context declarations, dictionaries, the use of memory stacks
or the like. These languages also in some cases allowed for dynamic
changes in the printers state such as the ability to add fonts or to add
graphical images to the resources that might be available to the printer.
Some of these features are documented in such generally available
reference works as Adobe System Incorporated's "PostScript Language
Reference Manual" and the "PostScript Language Program Design", both by
Addison-Wesley Publishing Company. Other PDL's are likewise described in
various technical and reference books such as "Interpress, The Source
Book" by Harrington et. al. (Simon and Schuster, Inc. ,1988)
One of the problems as noted above with respect to the PostScript system is
that an identification of the beginning and end of an image or a page
requires a significant amount of processing and these languages do not
provided a logical manner in which the preparation of the document may
require significant extra processing to determine these items. In fact a
processing "as if printing" of the entire document is needed even if only
one page or a section of pages such as a chapter in a long document are
needed. Further the processing may not be straightforward or simple enough
to allow for lower cost processors to be used at the printer/display
device. This problem adds to the cost or reduces the flexibility of the
prior art systems. A basis for a proposed standardized page description
language has been made by several people including the inventors herein
and is in the process of being developed as an international standard. The
proposal at this stage is in draft form before a section of the ISO as
ISO/IEC DIS 10180 labeled as "Information Processing- Text Communication-
Standard Page Description Language". The current draft is dated 1991.
SUMMARY OF THE INVENTION
Accordingly, one object of this invention is to provide a method and
apparatus for the determination and the efficient processing of the
beginning and ending of pictures and/or pagesets in a document data stream
so as to speed up the processing of document data streams.
It is another object of this invention to provide an efficient method and
apparatus which can keep track of the scope and status of material defined
within the definition for each document data stream (called prologues) in
an efficient manner.
It is yet another object of this invention to provide an apparatus and
methodology for selecting in an input data document stream a given page or
picture for processing in an efficient manner without the requirement of
processing all preceding pages in the document.
These and other objects are achieved according to the present invention by
providing an efficient method of processing in DIS 10180. According to DIS
10180, each document data stream is provided in a structure which is
either a pageset or a picture. The pageset and a picture elements consist
of an optional prologue which contains definitions and declaratory
commands and an optional body. A pageset body consists of zero or more
pagesets or pictures while a picture body consists of zero or more
pictures or tokensequences. The tokensequence which contain specific
tokens or commands for defining specific images along with necessary
operators is called Content while other elements are called Structure. The
Structure sets up the environment for Content to generate the appropriate
output images. The effects of prologue within a picture or a pageset is
until the end of the picture or the pageset. Therefore, the prologue of a
picture in the hierarchical tree does not influence the peer picture,
while the prologue of a parent picture or pageset influences the
child-pictures. This invention efficiently handles this hierarchical tree
structure along with the scope of the prologue by using a stack and
various pointers.
A tree-linked hierarchy advantageously enables the processing of any
portion of the document by directly addressing that portion of the
document and those portions which are higher in the hierarchy without the
necessity of processing the other items in the different branches of the
hierarchical tree. In other words, only structural definitions which occur
in the hierarchical tree which are above a given portion of the document
need be processed. This increases the efficiency of the processing of the
document and also facilitates the determination of the type of resources
which will be needed in the printing device or the display device prior to
the commencement of the actual printing of the document. This increases
the speed and efficiency by which the various devices print or display the
document.
DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and many of the attendant
advantages thereof will be readily obtained as the same becomes better
understood by reference to the following detailed description when
considered in connection with the accompanying drawings, wherein:
FIG. 1 is an illustration of the basic structure of a document data stream
where a document is defined as either a pageset or a picture as
represented in the structured standard page description language form of
this invention;
FIG. 2 is an illustration of the hierarchical structure of a document shown
in FIG. 1;
FIG. 3 is an illustration of a representative grammar of a picture and
pageset according to the structure shown in FIG. 2;
FIG. 4 is a schematic illustration of the general architecture of the
picture pageset stack arrangement according to this invention;
FIG. 5 is an illustration of the structure of a picture pageset prologue
data structure and the linked list that accompanies this structure;
FIG. 6 is an illustration of the data structure of the link list which
supports a connection to an external declaration which can be included
into a document data stream;
FIG. 7 is a flow chart of the processing necessary for the processor to
handle the beginning of a picture;
FIG. 8 is a flow chart of the routines necessary for the processor to
handle the beginning of a pageset;
FIG. 9 is a flow chart showing the processing necessary for a picture end
routine;
FIG. 10 is a flow chart of the processing necessary for a pageset end
routine;
FIG. 11 is an exemplary implementation of this system in either a host
computer, print server or printer controller for this invention;
FIGS. 12A, 12B, and 12C are drawings showing three possible implementation
environments; and
FIG. 13 is an expanded top level breakdown of a document data stream, such
as is shown in FIG. 2 as processed by this invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In reference to FIG. 1 a basic document data stream layout is shown in
which a document may be defined as being a grouping of Pagesets. With a
reference now to FIG. 11, it is clear that a target system which is to
accept the document's data stream will have generally at least a CPU,
memory generally in the form of ROM and RAM, input/output means to receive
the document data stream, and a means for displaying/printing a resultant
output. The resultant output image may be produced by an image raster
device which may be directly connected to the CPU or may have its own
distinct native type of imaging which would then, of course, require a
translation of a document data stream into the type of imaging commands
which the individual imaging device might have. An example of this might
be a PostScript.RTM. type of device connected to a system which transmits
the document description data stream as called for in this invention and
which then processes and prints the data after a translation into
PostScript.RTM. language. This, of course, allows for means of supporting
existing printers.
As stated above individual document description data stream may be defined
as either a pageset or a picture, as shown in FIG. 1. When a document is
defined as a picture, the document would then be a one page or single page
document. An individual document may be made up of a single picture (page)
or a single pageset. A picture, however does not cross pages.
The hierarchical structure of a document data stream such as is shown in
FIG. 1 is illustrated in FIG. 2. Pages are defined as, and are set as, the
highest level within a picture hierarchy. Tokensequences (211) and (214)
are individual elements which may describe portions of an individual page.
These may be, for example a drawing, text or image. Other portions of the
document are also handled by way of tokensequences which create image
descriptions which are used to define individual elements within a
picture. The translation of pictures into a tokensequence allows for a
more efficient processing of the document data stream and also allows for
a rapid change of elements within a document data stream, if needed or
desired, far easier than has been available in prior art systems.
For purposes of this discussion and in particular with reference to FIGS. 2
and 13 the "clear text" processing will be shown, however it should be
apparent based upon the token structure and stack implementation discussed
below a binary data stream having, for example, a first set of information
in binary form as to its type, its value and then a length indicator the
processing that will occur will be identical.
As shown in FIG. 3, the picture and pageset have a set "grammar" where a
picture is defined as having an optional prologue and an optional picture
body, a pageset is defined as having an optional prologue and an optional
pageset body, and a prologue has elements such as an external declaration,
informative declaration, resource declaration, document production
instruction declaration, context declaration, dictionary generation
declaration or set-up procedure. All of these elements in the prologue are
optional and, in fact, may be repeated in the sense that there may be
multiple instances of the same item. Consequently, multiple levels of a
prologue may be present and the handling of these multiple instances can
be accomplished as set forth below.
A picture body is made up of a picture or tokensequence which may occur
either zero or more times as does the pageset body which has pagesets or
pictures which may occur either zero or more times. FIG. 3 illustrates
that a picture consists of an optional prologue and optional
picture.sub.-- bodies, and a pageset consists of optional prologues and
optional pageset.sub.-- bodies. Each prologue consists of zero or more
prologue elements with a picture.sub.-- body consisting of zero or more
picture or tokensequences as shown as 210 of FIG. 2. If a picture is
present in the definition or data stream making up the picture.sub.-- body
that picture will be placed one level below the parent picture in the
hierarchial structure as shown in FIG. 2. A Pageset body may consist of
zero or more pagesets as shown in element 201 of FIG. 2.
The general architecture of the system and the data structure is shown in
FIG. 4. The parser 400 accepts a byte stream and identifies various
tokens. In the context of this disclosure, the most important tokens
processed by the parser are the picture.sub.-- begin, picture.sub.-- end,
pageset.sub.-- begin and pageset.sub.-- end. When these tokens are
recognized by the parser 400, the parser will call an appropriate routine
to handle the processing of the data stream and to set up a structure as
is shown in FIG. 13 for example. A conventional type of parsing which is
easily implemented, either in software or in hardware is used at this
point. Accordingly, no further discussion of parsing is made here for the
sake of brevity.
When a "begin", for example, as shown in FIG. 13 is encountered and is
recognized by the CPU 1110 of FIG. 11 and more particularly to that
portion of the CPU 1110 which acts as a structure processor, an
appropriate pointer is pushed onto a picture pageset stack (401). It
should be noted that the functions of the structure processor may be
implemented in CPU 1110 or can be implemented in a separate, but connected
processor, however for simplicity it can be assumed that the structure
processor is implemented as part of the operation functions of CPU 1110.
When an "end" is recognized, an appropriate pointer is popped from the
stack and the necessary memory is erased. In a clear text encoding of a
document, <picture> and <pageset> tags may, for example, be used to denote
a beginning while <picture> and <pageset> may be used to denote an ending.
In a binary encoding scheme for the document data stream, special tags
along with a byte count may be used to identify a "begin" and "end"
condition for a picture and pageset. Accordingly, a stack arrangement
employing push and pop techniques being used for the manipulation of items
within the stack may be employed to determine the beginning and end of a
given pageset or picture, which allows for the handling and identification
of the "begins" and "ends" in a very expeditious manner.
As shown in FIG. 5, a pointer to a picture/pageset prologue contains a
series of pointers which may be set to "null" or to the memory allocated
for external declarations, informative declarations, resource definitions,
resource declarations, context declarations, dictionary generation
declaration, set-up procedures or machine states, as may be necessary. As
these items are optional in nature and may occur either zero or more
times, a pointer arrangement is used in this invention to allow for
multiple instances to occur or for zero instances to occur without the
resultant waste of memory that might occur if this were not the case. If
zero instances are the case, the value of the pointers is "null" and, of
course, no memory need be allocated for these items. These pointers are
identified by means of reference numeral designations 503 through 510 in
FIG. 5. Numeral 501 in FIG. 5 refers to the pageset level and numeral 502
refers to the picture level of the individual picture/pageset prologue
which allows for an expeditious processing of the individual
picture/pagesets in the structure.
This identification that occurs with respect to each of the levels 501 and
502 in FIG. 5 becomes important when one understands that an individual
page to be processed may have many constituent parts, such as is shown in
FIG. 13. The Picture.sub.-- levels processed in FIG. 13 will vary from a
top level of one to a lower level of two, however it is apparent that the
level may in a more complex page having graphics containing other graphics
or the like to have many Picture.sub.-- levels and that the level for
processing purposes may increase substantially beyond two. In fact by
having the stack arrangement, the limits on the number of levels becomes
virtually unlimited and is only limited to the amount of memory 1120
available to the stack used by the CPU 1110 of FIG. 11.
As shown in FIG. 6, a linked list is used to keep track of the individual
items within the structure shown in FIG. 5. A pointer, for example, to an
external declaration 503 shown in FIG. 5, is used as an example in FIG. 6.
It should be noted that the pointers 504 through 510 would be handled in a
similar manner as the pointer 503. All the pointers 503 through 510 in
FIG. 5 have pageset levels and picture levels included in the data
structure which will allow the memory allocated to these items to be
released when an "end" is recognized for a given pageset or picture. This
allows for a greater use of available memory resources by allowing the
"reuse" of memory through conventional memory "garbage" collection
procedures. It further allows for a type of internal error checking to
occur in that a mismatched group of "begins" and "ends" can be easily
determined by the CPU 1110 of FIG. 11 and more particularly to that
section of the CPU 1110 which may be acting as a structure processor. This
type of arrangement may be as shown in the embodiments of FIGS. 12A, 12B
and 12C where the processing can be accomplished in many different forms
or environments, for example, at the printer end, the main processor end
(i.e. the document data stream creator) or at some other location in
between.
As shown in FIG. 6 the pointer 503 from FIG. 5 points to a data structure
of a link list. In the structure 600, 601 is the Pageset.sub.-- level for
the external declaration. The Picture.sub.-- level 602 is also present in
this link structure. An external identifier 603 and the structure type 604
are likewise provided. The pointer to external data 605 allows for the
allocation of memory for the external data itself and 606 allows for a
linking of multiple external declarations by providing a pointer to the
next group of elements which would be similar to the element 600 but would
be for the next level "down" in the data structure.
The processing that is necessary for a picture.sub.-- begin routine is
shown in FIG. 7 and in FIG. 13. Global variables such as the picture level
(Pic.sub.-- level) are available for use by any of the routines while the
Picture.sub.-- level (501) and the Pageset.sub.-- level (502) are local
variables contained within the data structure (500) pointed to by the
entry in the picture/pageset stack (401) found in FIG. 4. After starting
in step 700, in step 701 the Pic.sub.-- level is initialized to zero at
the initialization of all processing for a document data stream or on
"power up". An error check occurs in step 702 and an error flag is set in
step 703, if a problem occurs, followed by a return to other processing by
the CPU 1110 of FIG. 11 in step 704. Otherwise processing continues and
the global variable Pic.sub.-- level is incremented at step 705. When the
selection of pages is needed, the following process should be inserted
after step 705. [If (Pic.sub.-- level==1) then page-number++]This means,
after step 705, that Pic.sub.-- level is examined to see if it is one. If
it is one, then the "picture begin" denotes the beginning of the highest
level of picture hierarchy, that is, start of page. Therefore the
page-number is incremented. "Page-number" is initialized to be zero at
power on initialization or at a reset. The "Page-number" should be a
global variable which can be accessed by any routine. This return allows
for the continuation of processing of the document data stream. As the
Pic.sub.-- level is a global variable, this level is available through all
other routines and allows for multiple levels to be implemented. An
allocation of memory occurs in step 706 for the picture/pageset prologue
data structure (500) from FIG. 5. A pointer to the data structure is
pushed to the stack (401) in step 706. The Picture.sub.-- level and the
Pageset.sub.-- level of the data structure (500) are set in step 707.
Then, in step 708, it is determined if the entry is the first entry of the
stack. If so, in step 710 a pointer.sub.-- to.sub.-- machine.sub.-- state
is set to point to the copy of the default values for the display/print
device and the other pointers are set to null. If not, in step 709, all
pointers are set to point to the same objects as the one entry which is
below that entry in the stack. This allows for an efficient "search"
through the stack by the structured processing routines/section of CPU
1110. It should be noted at this point that the structure processing that
occurs in processor 1110 of FIG. 11 may also be accomplished by a separate
processor working in conjunction with the CPU 1110 of FIG. 11, although in
a general scheme this would not be necessary.
As shown in FIG. 8, the processing that occurs for a "Pageset begin" is
similar to that shown in FIG. 7 except that the error check is to the
PS.sub.-- level in 802 and it is the PS.sub.-- level that is incremented
in step 805. Otherwise, processing is the same for Pagesets and "Picture"
and is not further discussed for the sake of brevity.
FIGS. 9 and 10 illustrate the processing that occurs as a result of an
"end" routine. As shown in FIG. 9, after start (step 900) the condition of
the stack is checked in step 901 with the current Pic.sub.-- level to
ensure the correct use of the picture structure in the document data
stream and to detect and to note any possible corruption of the data. This
becomes especially important if the document data stream is not in clear
text but rather is a binary data stream in which the length of the data
stream is not known or is known incorrectly due to faulty transmission or
the like. An error checking also occurs in step 904 before proceeding to
the actual processing of the "picture-end" command. The error flag is set
in step 902 with a return to processing occurring in step 903. The top
entry of the picture/pageset stack 401 will be popped in step 905 and
consequently the memory which was previously being used is freed for
"garbage collection". The related memory in the picture/pageset prologue
data structure pointed to by the popped entry and the link list pointed to
by the pointers in the data structure which have a Pageset.sub.-- level
equal to PS.sub.-- level and the Picture.sub.-- level equal to Pic level
is accomplished and the Pic.sub.-- level is then decreased by one in step
906. In step 907, it is determined if the resulting Pic.sub.-- level is
then zero. If so, in step 908 the picture which has just been processed is
the highest level picture (i.e., a page) the image data may then be
forwarded to the output device for printing/display and the image data
area will be reset indicating that a new page is to be processed. If
selection of pages is needed, the "page-number" should be examined in step
908 to determine if the page-number is among the selected pages.
The flow that occurs in FIG. 10 is similar to that as shown in FIG. 9
except the picture and error checking as shown in steps 1001 and 1004
relate to the pageset end, and the pageset level decrement in step 1006
does not cause the printing of a page or an image reset as does steps 907
and 908 in the picture.sub.-- end routine discussed in FIG. 9.
Obviously, numerous modifications and variations of the present invention
are possible in light of the above teachings. It is therefore to be
understood that within the scope of the appended claims, the invention may
be practiced otherwise than as specifically described herein.
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