Automatic electronic data type identification process

• US 5,374,916 A
• Filed: 12/18/1992
• Issued: 12/20/1994
• Est. Priority Date: 12/18/1992
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Chu, Ke-Chiang
• Primary Examiner(s): Heyman, John S.
• Application Number:
  US07/993,181
• Time in Patent Office: 732 Days
• Field of Search: 340/146.2, 364/715.02
• US Class Current: 340/146.2
• CPC Class Codes: H03M 7/3086 employing a sliding window, e.g. LZ77
• CPC Class Codes: H03M 7/3088 employing the use of a dictionary, e.g. LZ78
• CPC Class Codes: H03M 7/48 alternating with other codes during the code conversion process, e.g. run-length coding being performed only as long as sufficientlylong runs of digits of the same kind are present

Abstract

A data compression process and system that identifies the data type of an input data stream and then selects in response to the identified data type at least one data compression method from a set of data compression methods that provides an optimal compression ratio for that particular data type, thus maximizing the compression ratio for that input data stream. Moreover, the data compression process also provides means to alter the rate of compression during data compression for added flexibility and data compression efficiency. Furthermore, a system memory allocation process is also provided to allow system or user control over the amount of system memory to be allocated for the memory intensive data compression process. System memory allocation process estimates the memory requirement to compress the input data stream, and allocates only that amount of system memory as needed by the data compression for memory allocation efficiency.

Claims

1. An electronic data type identification process for automatically identifying a data type of information contained in an input data stream, the input data stream including a plurality of bytes of data the process comprising the computer-implemented steps of:

receiving the input data stream;

selecting at least one byte of data of the plurality of byte;

of data in the input data stream;

detecting whether the at least one byte of data represents a corresponding decimal value greater than a predetermined decimal value; and

generating a data type indicator representing a predetermined data type if the at least one byte of data represents a corresponding decimal value greater than the predetermined decimal value.

2. The electronic data identification process of claim 1 wherein the step of detecting whether the at least one byte of data represents a corresponding decimal value greater than a predetermined decimal value includes determining whether any bit of a predetermined subset of bits of said at least one byte is set.

3. The electronic data identification process of claim 1 wherein the plurality of bytes of data includes a first byte of data and a second byte of data, the step of detecting whether the at least one byte of data represents a corresponding decimal value greater than the predetermined decimal value including the steps of:

detecting whether the first byte of data represents a corresponding decimal value greater than the predetermined decimal value; and

detecting whether the second byte of data represents a corresponding decimal value greater than the predetermined decimal value if the first byte of data does not represent a decimal value greater than the predetermined decimal value.

4. An electronic data type identification process for automatically identifying a data type of information contained in an input data stream, the input data stream including a plurality of bytes of data, the process comprising the computer-implemented steps of:

receiving the input data stream;

selecting at least one byte of data Of the plurality of bytes of data in the input data stream;

detecting whether the at least one byte of data represents a corresponding decimal value in a predetermined range of decimal values; and

generating a data type indicator representing a predetermined data type if the at least one byte of data represents a corresponding decimal value in the predetermined range of decimal values.

5. The electronic data identification process of claim 4 wherein the step of detecting whether the at least one byte of data represents a corresponding decimal value in the predetermined range of decimal values includes determining whether any bit of a predetermined subset of bits of said at least one byte is set.

6. The electronic data identification process of claim 4 wherein the plurality of bytes of data includes a first byte of data and a second byte of data, the step of detecting whether the at least one byte of data represents a corresponding decimal value in the predetermined range of decimal values includes the steps of:

detecting whether the first byte of data represents a corresponding decimal value in the predetermined range of decimal values; and

detecting whether the second byte of data represents a corresponding decimal value in the predetermined range of decimal values if the first byte of data represents a decimal value in the predetermined range of decimal values.

7. An electronic data identification process for automatically identifying a data type of information contained in an input data stream, the input data stream representing the information in a plurality of pairs of data bytes, each pair of data bytes of said plurality of pairs of data bytes having a first data byte and a second data byte, the process comprising the computer-implemented steps of:

receiving the input data stream;

selecting at least two pairs of data bytes of said plurality of pairs of data bytes;

detecting whether information contained in the first data bytes of said at least two pairs of data bytes match; and

generating a data type indicator representing a predetermined data type if the information contained in the first data bytes of said at least two pairs of data bytes match.

8. The electronic data identification process of claim 7 wherein the step of detecting whether information contained in the first data bytes of said at least two pairs of data bytes match includes determining whether the first data byte of each pair of data bytes of the plurality of pairs of data bytes match.

9. A method for compressing electronic data contained in an input data stream, the method comprising the computer-implemented steps of:

receiving the input data stream, the electronic data contained in the input data stream representing information of a specific data type, the input data stream including a plurality of bytes of data, each byte of data of said plurality of bytes of data having a plurality of bits;

selecting at least one byte of data of the plurality of bytes of data in the input data stream;

detecting whether any bit of a predetermined subset of bits of the at least one byte of data is set;

generating a data type indicator representing a predetermined data type if any bit of the predetermined subset of bits of the at least one byte of data is set;

selecting a selected data compression method from a plurality of data compression method based upon the data type indicator; and

compressing the input data stream based on the selected data compression method.

10. The method for compressing electronic data of claim 9 wherein the step of compressing the input data stream based on the selected data compression method includes the steps of:

compressing the input data stream according to a first compression method of a first type to produce a first set of compressed data; and

compressing the first set of compressed data according to a second compression method of a second type to produce a second set of compressed data.

11. The method for compressing electronic data of claim 10 wherein the step of compressing the input data stream according to a first compression method of a first type includes compressing the input data stream according to a compression method which associates groups of consecutive characters to a dictionary of indices.

12. The method for compressing electronic data of claim 11 wherein the step of compressing the first set of compressed data according to a second compression method of a second type includes compressing the first set of compressed data according a single symbol coding compression method.