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Algorithm for Nested Overlay Management

IP.com Disclosure Number: IPCOM000034459D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 130K

Publishing Venue

IBM

Related People

Miller, BA: AUTHOR

Abstract

An algorithm is disclosed which detects cyclic paths in a singly-linked list. By utilizing the algorithm many overlays may be nested and merged together. (Image Omitted) An overlay is a series of print objects which are stored in the printer's memory and when called up will print stored print objects such as text, graphics, images and bar codes. This is important when the printer is required to print the same print objects repeatedly on different pages such as is necessary when printing a series of forms. By having an algorithm to control the output, a whole series of overlays and data may be combined, and the entire data stream may be controlled by a simple host directive rather than resending the data stream multiple times.

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Algorithm for Nested Overlay Management

An algorithm is disclosed which detects cyclic paths in a singly-linked list. By utilizing the algorithm many overlays may be nested and merged together.

(Image Omitted)

An overlay is a series of print objects which are stored in the printer's memory and when called up will print stored print objects such as text, graphics, images and bar codes. This is important when the printer is required to print the same print objects repeatedly on different pages such as is necessary when printing a series of forms. By having an algorithm to control the output, a whole series of overlays and data may be combined, and the entire data stream may be controlled by a simple host directive rather than resending the data stream multiple times. Overlays may be nested, that is, there may be a series of smaller overlays combined together to compose a larger overlay. This allows the user to reuse subsections of print objects which are common to more than one page but which are not needed on every page. The restriction to nesting is that no overlay inclusion path be cyclic so that the overlay includes itself or includes any other overlay in the current inclusion path. The present algorithm is intended to detect such cyclic paths. Referring to Fig. 1, the basic data structure consists of a list of lists with a header record for each overlay (OV1 to OV4 .) This list using a "next task" pointer points to a list of print objects or "tasks" which define the overlay. In addition, a "dummy" header record is maintained, and each list is terminated by a nil pointer. Now referring to the flow diagram of Fig. 2, the use of the algorithm will be described. Initially, the original included overlay has its "included by" pointer (hereinafter, I.B. pointer) set to point at the dummy header record and its "examine next" pointer (E.N....