jmacd
Forward and backward patches (enhancement)
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
Original issue reported on code.google.com by [email protected] on 8 Jan 2008 at 5:57
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.
Original comment by [email protected] on 10 Jan 2008 at 2:51
- Changed state: Accepted
- Added labels: Type-Enhancement
- Removed labels: Type-Defect
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?
Original comment by [email protected] on 10 Jan 2008 at 8:05
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.
Original comment by [email protected] on 8 May 2008 at 12:55
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.
Original comment by [email protected] on 9 Jun 2008 at 9:13
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...
Original comment by [email protected] on 11 Jun 2008 at 4:54
Is there any progression?
I'm interesting in reversing xdelta patch.
Original comment by [email protected] on 11 Jun 2010 at 7:10
same here
is not possible revert the xdelta like patch can do with patch -R?
