Variable-length record, corruption recovery apparatus, system, and method

1. A method for identifying variable-length records within a data block containing corrupted data, the method comprising:

scanning, by at least one processor, backward from an end of a data block comprising records of variable length, one record at a time, to identify a first span of good records;

scanning, by the at least one processor, forward from a front of the data block, one record at a time, to identify a second span of good records;

identifying, by the at least one processor, a problem region by identifying data that resides between the first span and the second span, wherein the problem region comprises at least one variable-length record having a corrupt control information field; and

creating, by the at least one processor, a new record between the first span and the second span that encapsulates the problem region, wherein creating the new record comprises creating a control information field for the new record with a length indicator storing the length of the problem region.

2. The method of claim 1 , wherein scanning backward from the end of the data block comprises:

maintaining a count value of units traversed while reading bit patterns in the data block, backward from the end of the data block;

recording the count value and resetting the count value upon reading a bit pattern having a value equal to the count value; and

determining, upon arriving at the front of the data block, a length of the first span by summing each recorded count value.

3. The method of claim 1 , wherein scanning forward from the front of the data block comprises;

scanning forward from bit pattern to bit pattern by scanning a number of units equal to the value of each bit pattern;

storing a running total of units from the front of the data block to a present location;

obtaining a result, upon arriving at each bit pattern, by subtracting from a total block length a sum of both the running total and a length of the first span; and

determining a length of the second span based on the running total upon a number of units equal to the value of a bit pattern at the present location being greater than the result.

4. The method of claim 3 , further comprising selecting a first bit pattern from which to traverse forward using one of a default offset and user input.

5. The method of claim 1 , further comprising skipping over the new record after the data block has been read into a memory.

6. The method of claim 1 , further comprising applying one or more data recovery algorithms to the new record.

7. A computer program product for identifying variable-length records within a data block containing corrupted data, the computer program product comprising a non-transitory computer-readable storage medium storing computer instructions which when executed by at least one computer cause the at least one computer to perform the following:

scan backward from an end of a data block comprising records of variable length, one record at a time, to identify a first span of good records;

scan forward from a front of the data block, one record at a time, to identify a second span of good records;

identify a problem region by identifying data that resides between the first span and the second span, wherein the problem region comprises at least one variable-length record having corrupt control information field; and

create a new record between the first span and the second span that encapsulates the problem region, wherein creating the new record comprises creating a control information field for the new record with a length indicator storing the length of the problem region.

8. The computer program product of claim 7 , wherein scanning backward from the end of the data block comprises:

maintaining a count value of units traversed while reading bit patterns in the data block, backward from the end of the data block;

recording the count value and resetting the count value upon reading a bit pattern having a value equal to the count value; and

determining, upon arriving at the front of the data block, a length of the first span by summing each recorded count.

9. The computer program product of claim 7 , wherein scanning forward from the front of the data block comprises:

scanning forward from bit pattern to bit pattern by scanning a number of units equal to the value of each bit pattern;

storing a running total of units from the front of the data block to a present location;

obtaining a result, upon arriving at each bit pattern, by subtracting from a total block length a sum of both the running total and a length of the first span; and

determining a length of the second span based on the running total upon a number of units equal to the value of a bit pattern at the present location being greater than the result.

10. The computer program product of claim 9 , wherein the computer instructions further cause the at least one computer to select a first bit pattern from which to scan forward using one of a default offset and user input.

11. The computer program product of claim 7 , wherein the computer instructions further cause the at least one computer to skip over the new record after the data block has been read into a memory.

12. The computer program product of claim 7 , wherein the computer instructions further cause the at least one computer to apply one or more data recovery algorithms to the new record.

13. An apparatus for identifying variable-length records within a data block containing corrupted data, the apparatus comprising:

at least one processor; and

at least one memory device coupled to the at least one processor and storing modules for execution on the at least one processor, the modules comprising:

a backward scan module configured to scan backward from an end of a data block comprising records of variable length, one record at a time, to identify a first span of good records;

a forward scan module configured to scan forward from a front of the data block, one record at a time, to identify a second span of good records;

an identification module configured to identify a problem region by identifying data that resides between the first span and the second span, wherein the problem region comprises at least one variable-length record having a corrupt control information field; and

a record creation module configured to create a new record between the first span and the second span that encapsulates the problem region, wherein creating the new record comprises creating a control information field for the new record with a length indicator storing the length of the problem region.

14. The apparatus of claim 13 , wherein the backward scan module further comprises:

a count module configured to maintain a record of a count value of units traversed while reading bit patterns in the data block, backward from the end of the data block;

a detection module configured to record the count value and to reset the count value upon reading a bit pattern having a value equal to the count value; and

a determination module configured to determine, upon arriving at the front of the data block, a length of the first span by summing each recorded count value.

15. The apparatus of claim 13 , wherein the forward scan module further comprises:

a step module configured to scan forward from bit pattern to bit pattern by scanning a number of units equal to the value of each bit pattern;

a count module configured to store a running total of units from the front of the data block to a present location;

a computation module configured to obtain a result, upon arriving at each bit pattern, by subtracting from a total block length a sum of both the running total and a length of the first span; and

a determination module configured to determine a length of the second span based on the running total upon a number of units equal to the value of a bit pattern at the present location being greater than the result.

16. The apparatus of claim 13 , wherein the modules further comprise a skip module configured to skip over the new record after the data block has been read into a memory.

17. A system for identifying variable-length records within a data block containing corrupted data, the system comprising:

a storage device configured to store a data block comprising variable-length records;

a memory configured to receive the data block;

a transfer module configured to transfer the data block between the memory and the storage device;

a recovery module configured to:

scan backward from an end of a data block comprising variable-length records, one record at a time, to identify a first span of good records;

scan forward from a front of the data block, one record at a time, to identify a second span of good records;

identify a problem region by identifying data that resides between the first span and the second span, wherein the problem region comprises at least one variable-length record having a corrupt control information field; and

create a new record between the first span and the second span that encapsulates the problem region, wherein creating the new record comprises creating a control information field for the new record with a length indicator storing the length of the problem region.

18. The system of claim 17 , further comprising a skip module configured to skip over the new record after the data block has been read into the memory.