Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1998-09-15
2001-07-24
Choules, Jack (Department: 2771)
Data processing: database and file management or data structures
Database design
Data structure types
Reexamination Certificate
active
06266671
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a data storage apparatus and medium such as a memory card.
Memory cards such as PC (personal computer) cards are useful for storing data in electronic still cameras, audio recorders, and computers. Some memory cards employ battery-backed-up random-access memory, while others employ flash memory. Many include a microcontroller unit that manages the memory and communicates with the outside world. Often, the interface with the outside world is a sector-based interface conforming to a standard originally intended for use with rotating magnetic-disk drives.
Access speed is an important issue in both memory cards and disk drives. The prior art includes methods of increasing access speed by striping data across different memory chips or disks, which can be accessed in parallel, or by dividing records into sub-records which can be stored on different disks or chips, as in Japanese Unexamined Patent Application 28226/1994.
Another important issue is fitting as much data as possible into the available storage space. Data compression techniques have come into widespread use for increasing the storage capacity of memory cards and magnetic disks.
A further issue is the capability to edit data in place. In a sector-based system, this refers to the ability to read a stored sector of data, modify the data contents, and store the modified data at the same sector address. This capability is useful when part of an image is modified, for example.
A problem is that if the sector has been stored in a compressed from, then after decompression, modification, and recompression, the new compressed data may be larger than the old compressed data, even if the decompressed data size is unchanged. Thus the modified compressed sector may not fit into the space allocated to the original compressed sector.
A more general problem is that magnetic disks and memory cards often employ a fixed data storage structure, using clusters or blocks having a single fixed length. This type of structure is unsuitable for storing data of variable size. A known solution is to store data in an unstructured linear format, without subdivision into clusters or blocks, but this solution does not readily provide an edit-in-place capability.
SUMMARY OF THE INVENTION
An object of the present invention is to store data of variable size in a flexible manner.
Another object is to store data in a manner enabling the data to be edited in place.
The invented data storage apparatus comprises a data store having a variable data storage structure, and a data-processing unit. The data processing unit receives data from an external device, processes the received data, stores the processed received data in the data store, using the variable data storage structure, reads the stored data from the data store, processes the read data, and sends the processed read data to the external device.
In processing received data, the data processing unit preferably divides the received data into parts and generates connection information indicating how the parts are connected together, then uses the connection information to reassemble the data when reading the data. The data storage structure is preferably varied by dividing the received data into parts in different ways.
The connection information preferably comprises a flag indicating whether one part is followed by another, and an address indicating the storage location of the following part, if present.
The data processing unit preferably divides received data into first parts having a first fixed length, then divides remaining portions of the received data into second parts having a second fixed length shorter than said first fixed length. The data store preferably comprises a first area for storing the first parts, and a second area for storing the second parts. The connection information may be stored in the data store, or in an internal memory in the data processing unit. Connection information stored in the data store is preferably stored together with respective first parts and second parts.
The invented method of storing data received from an external device divides the data into parts of at least two different lengths, and generates connection information as described above.
The invented data storage medium is a computer-readable medium comprising the invented data storage apparatus.
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patent: 5598549 (1997-01-01), Rathunde
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Choules Jack
Frank Robert J.
OKI Electric Industry Co., Ltd.
Pham Linh M
Sartori Michael A.
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