7
votes
Accepted
Compression algorithm from very old tape backup?
Just to close the loop on this:
I ended up successfully reverse-engineering this compression format, which turned out to be written by an extremely obscure tape backup tool from the early 90s called ...
- 201
2
votes
Algorithm for decoding database like file structure
You're going to have to get heuristic on this I think. My approach would be to generate a parse tree for the first record, where you tokenize the data and create nodes for valid interpretations. Then ...
- 161
2
votes
Trying to reverse engineer dump of a timestamp
Following up alahel's answer, the date is indeed a number of milliseconds, but it includes 1 further bit to the left and is from the standard epoch of 1 Jan 1970. For example:
08014273ed2071a6800017
...
- 121
2
votes
Accepted
Decoding a list of integer values in unknown format
it is clear that if the high bit of the first byte is not set then it is just the value of the byte
So we can suspect that the high bit is a signal for extending the number
checking the lone 1428 ...
- 617
1
vote
Decoding a list of integer values in unknown format
The answer from @ratchet freak is correct.
To add a little more information, this format is known as LEB128. It's not uncommon and pops up in various places. For example, DWARF3 debug info and ...
- 2,503
1
vote
Algorithm for decoding database like file structure
You know the number of columns from the metadata file (is that really all it contains? A single integer?). Generate the set of all possible schemas with that number of columns. For each line, parse ...
- 191
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