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A method to reduce media directory search time for directories which may include multiple entries for the same file name.

IP.com Disclosure Number: IPCOM000014035D
Original Publication Date: 1999-Nov-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Related People

Leon Gregg: AUTHOR [+2]

Abstract

Disclosed is a method for greatly reducing the time required to search a media directory which might include multiple entries for the "same" file. For file systems of this type, a "simple" find file "A" necessitates a complete search of the entire directory because finding one entry for file "A" does not satisfy the search requirement. It is necessary to keep searching because normal access requires the most recent version of a file and more entries for "A" could still remain to be found. For example, the High Performace Optical File System (HPOFS) may include multiple entries for one file because it is designed for a write once, read many (WORM) media. To allow a file to be "deleted", another entry is added to the directory indicating that a particular file is to be considered deleted, but there is no actual change to the original directory entry, or the file data already on the media. Should a file of that same name be created again, then another entry would be added to the directory describing the "new" file. The Universal Disk Format (UDF) for Direct View Display (DVD) media also has the possibility of multiple entries for the "same" file name. In this case the multiple entries exist because the file system permits multiple "versions" of the same file.

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  A method to reduce media directory search time for directories which may include multiple entries for the same file name.

Disclosed is a method for greatly reducing the time required to search a media directory which might include multiple entries for the "same" file. For file systems of this type, a "simple" find file "A" necessitates a complete search of the entire directory because finding one entry for file "A" does not satisfy the search requirement. It is necessary to keep searching because normal access requires the most recent version of a file and more entries for "A" could still remain to be found. For example, the High Performace Optical File System (HPOFS) may include multiple entries for one file because it is designed for a write once, read many (WORM) media. To allow a file to be "deleted", another entry is added to the directory indicating that a particular file is to be considered deleted, but there is no actual change to the original directory entry, or the file data already on the media. Should a file of that same name be created again, then another entry would be added to the directory describing the "new" file. The Universal Disk Format (UDF) for Direct View Display (DVD) media also has the possibility of multiple entries for the "same" file name. In this case the multiple entries exist because the file system permits multiple "versions" of the same file.

The shortened search hinges on one key observation. With a very minor enhancement, the d...