Integrated block checking system for rapid file transfer of compressed data

• US 6,711,709 B1
• Filed: 06/24/1998
• Issued: 03/23/2004
• Est. Priority Date: 06/24/1998
• Status: Expired due to Term

• Current Assignee: Unisys Corporation
• Original Assignee: Unisys Corporation
• Inventors: York, Kenneth Lindsay
• Primary Examiner(s): Baker, Stephen M.
• Application Number:
  US09/104,116
• Time in Patent Office: 2,099 Days
• Field of Search: 714/748
• US Class Current: 714/748
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/18 Automatic repetition systems, e.g. Van Duuren systems

Abstract

In a system for enhancing the integrity of transmitted data files from one memory to a remotely located memory there is provided an original data stream which is compressed by a known data compression code. The compressed data stream may be in a variable length format and is not provided with the usual parity code bits. To assure that compressed data is received both without loss and error free, the compressed data stream is divided into groups of n blocks having N bytes. At the end of the group of nN byte blocks, a block or check code is inserted into the compressed data stream. The transmitted and received compressed data stream is processed as n blocks of N bytes having a received block check code. The received blocks of data are used to generate new block check codes which are compared with the transmitted block check codes to determine if a one bit error has occurred in any of the n blocks of N bytes. If an error occurs in the transmission of compressed data, the block is not stored in the memory of the receiver and the transmitter is requested to resend the entire group of n blocks of N bytes until no error in transmission is detected. The same system for enhancing the integrity of a transmitted data file can be employed with data that is double data compressed and/or encrypted.

Claims

1. The method of decoding a compressed data stream representative of a data file being transmitted from a remote site over conventional network framing protocol lines, comprising the steps of:

a. extracting n blocks of variable bit length encoded compressed data and an accompanying block error code from network protocol frames,

b. storing said extracted n blocks and accompanying block error code in a first memory of a computer,

c. stripping the block error code from the end of said n blocks of said compressed data stream,

d. generating a new block error code from the data in said compressed data stream as it is received,

e. comparing the newly generated block error code with the block error code stripped from the end of said n block compressed data to determine if each block of compression code values is valid and usable,

f. decoding the n blocks of compressed data as long as the block error codes match,

g. storing blocks of compressed data after said block error codes do not match,

h. requesting a retransmittal of the blocks of data in which the block error codes do not match,

i. repeating steps d, e and f until the block error codes match,

j. decoding the retransmitted blocks of compressed data, and

k. then decoding the stored blocks of compressed data before decoding new blocks of compressed data in said compressed data stream.

2. The method as set forth in claim 1 which further includes the step of,

raising an error signal in a computer so that the stored compressed data stream which included the block error will not be used.

3. The method as set forth in claim 2 wherein raising said error signal further includes means for requesting a retransmittal of the block of data which included the block error.

4. The method as set forth in claim 1 which further includes raising a signal indicating an error free transmission, and

storing the compressed data stream in a data file.

5. The method as set forth in claim 4 which further includes the step of decoding the compressed data stream for use or for storage in a data file.