| Issue 62: | Forward and backward patches (enhancement) | |
| 3 people starred this issue and may be notified of changes. | Back to list |
What is the posibility of creating the vcdiff files for two files for both directions at the same time, e.g. a forward patch and reverse patch at the same time, I guess it must be posible it is just how complicated is it to do. It would be the same as doing xdelta3.exe file1.exe -s file2.exe output1.vcdiff and xelta3.exe file2.exe -s file1.exe output2.vcdiff doing this in a single step would improve the performance in my case as I want to keep 2 copies of each of the source files one locally with reverse patches and one updated on a server located on the internet updated with the forward patch. thanks |
|
,
Jan 09, 2008
I am more interested in a utility to reverse a patch, given its source file. Then you could run something like: xdelta3.exe -s file1 file2 out2.vcdiff xdelta3.exe reverse -s file1 out2.vcdiff out1.vcdiff But first, I need to finish the "merge" command, which I'm working on.
Status: Accepted
Labels: -Type-Defect Type-Enhancement |
|
,
Jan 10, 2008
so let me understand this better, with your idea of reverse a single patch could roll a file forward or backward?, if this is the case and the merge command did what I expect there could be a single command to take a file forward or backward and many versions. Rather than having to process the file forward and then backward to create both patches and having to roll x patches forward or backward to make a specific revision of the file. Am I right? |
|
,
Jan 10, 2008
Yes, correct. |
|
,
May 08, 2008
Hi Josh, the idea of being able to reverse a patch interests me too. Have you any idea when you might have this available? Is the diff structure such that everything can be reliably reversed (e.g. Insert n bytes at offset m -> remove n bytes at offset m) etc... or will additional info be required inside the diff file - if the file has got smaller, I assume you don't store the data that was removed in the diff file so addional info would be required in to go backwards?? I guess what I'm driving at is do you think it might work with existing diff files produced with an older version of xdelta? I suspect not. |
|
,
Jun 09, 2008
A reverse patching mechanism would be very helpful indeed. I have an application by which I want to take a patch file and be able to use it to: given A create B, or if given B, create A. An excellent program btw, thanks for the time and effort you've put into this. |
|
,
Jun 10, 2008
There seem to be several approaches: 1. Modify the software and file format to support bi-directional patches 2. Modify the software to support a "reverse" operation #2 is easier. You would compute the forward differences and then compute the reverse. It's not a single step and it's a little less efficient, but it's much more flexible. Computing the reverse would require the target file to be present. I.e., xdelta3 -s SOURCE TARGET FORWARD.vcdiff xdelta3 reverse -s TARGET FORWARD.vcdiff REVERSE.vcdiff The code to compute the reverse operation would be useful for computing reversals in a chain of deltas. For example, if you have v1->v2, v2->v3 stored, and you would like to prepare a v3->v1 difference file...
Owner: josh.macdonald
|
|
 Sign in to add a comment
|
