Algorithm for an Automatic Variable Length Truncation of a Composite Document Size While Closing It
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
A method is described which permits unused media space to be freed from the end of the document and made available for general use. When a document is closed, Data Management Services (DMS), knows that there might be several unused sectors at the end of a document. The unused sectors (storage space) contain trash and need to be truncated from a document. In accordance with the new method, DMS builds a table which tracks the allocation of sectors within a document starting at OPEN time. This table known as the Free Space Map can be scanned to locate the highest Logical Sector Number (LSN) used within the document and then used to truncate the document to a smaller size. An undocumented function of DOS supported file truncation by seeking to the position in the file to truncate and writing a data length of 0.