Method and system for ensuring cache file integrity

Details Method and system for ensuring cache file integrity Method and system for ensuring cache file integrity

1998-09-28

2001-08-07

Ray, Gopal C. (Department: 2181)

Error detection/correction and fault detection/recovery

Data processing system error or fault handling

Reliability and availability

C707S793000, C711S141000

Reexamination Certificate

active

06272649

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to cache files, and more particularly to ensuring valid data in a cache file.
BACKGROUND OF THE INVENTION
Current computer systems provide individuals with opportunities to produce documents of professional quality, such as with desktop publishing software and graphics software programs. Input/Output (I/O) devices that support image input or output for production of such documents typically include, for example, monitors, printers, scanners, and digital cameras. Usually, a profile of each such I/O device known to the computer system is stored in the system, e.g., in a system folder, to identify particular characteristics of each device. By way of example, profiles typically include color matching information.
Color matching information is data, such as red, green, and blue (RGB) values and CMYK (cyan, magenta, yellow, black) values that are associated with objects and text in the document to control how the objects and text will appear when they are displayed and printed. Because RGB and CMYK values may differ depending on the particular device involved, color matching is offered as a standard component of some operating systems, such as through a ColorSync™ component of MacOS from Apple Computer, for example.
Utilization of the profiles normally occurs through the ColorSync™ component. ColorSync™ refers to a system level API (application program interface) that application programs and device drivers of a computer system call. A device profile typically provides a set of characteristics, such as RGB or CMYK values in the document, to describe the device to which the values are associated and enable the document to be portable, i.e., so that it will have the same appearance when drawn by different devices.
For example, application programs, such as Adobe Photoshop™, running on the computer system typically request a list of profiles in the computer system. Normally, ColorSync™ responds to such a request by opening every profile, retrieving the data, and returning it to the requesting application program. For systems with a small number of profiles, relatively little time is needed to perform these tasks. Unfortunately, performance speed becomes hampered as the number of profiles increases, e.g., to 100 or more.
One way of increasing performance includes the use of a cache file. Basically, the cache file stores the most necessary/desired information from each profile in a single file. Thus, requests for the profile data are responded to more quickly by retrieving the single cache file. While decreasing time constraints, use of the cache file is not without problems.
While cache files are intended to save time by putting frequently requested or slow to access information in a quickly accessible place, like a single file, the cache is only relevant as long as it accurately reflects the data it is meant to cache. To verify a cache file's integrity by brute force every time the cache file was used would significantly lower the benefit of the cache file. Further, to save time by rebuilding the cache file every time the system is booted, rather than every time the cache file is used, does not guarantee integrity, since changes can be made after booting that would not be reflected until the next next boot. Also, such rebuilding of the cache file is inefficient when no change has been made.
Accordingly, a need exists for an efficient, reliable, and accurate manner of utilizing a cache file. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention provides aspects for ensuring the integrity of a cache file utilized by an application program interface of a computer system. A method aspect includes forming a checksum with a modification date value of each of a plurality of files, storing the checksum in the cache file, and utilizing the checksum to validate data in the cache file.
With the present invention, a relatively quick calculation utilizing modification dates determines whether a cache file is up-to-date with a large measure of confidence. The maintenance of modification dates by a computer's file manager, combined with the ease with which the modification dates may be accessed, results in a convenient and reliable access point to profiles in a system that facilitates cache file integrity determinations. These and other advantages of the aspects of the present invention will be more fully understood in conjunction with the following detailed description and accompanying drawings.


REFERENCES:
patent: 5845128 (1998-12-01), Noble et al.
patent: 5878050 (1999-03-01), Brahme et al.
patent: 5946697 (1999-08-01), Shen
“Apple Unveils ColorSync 2.5,” Apple Press Release, Sep. 29, 1997.

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