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2011-03-28vcs-svn: let deltas use data from preimageLibravatar Jonathan Nieder1-0/+35
The copyfrom_source instruction appends data from the preimage buffer to the end of output. Its arguments are a length and an offset relative to the beginning of the source view. With this change, the delta applier is able to reproduce all 5,636,613 blobs in the early history of the ASF repository. Tested with mkfifo backflow svn-fe <svn-asf-public-r0:940166 3<backflow | git fast-import --cat-blob-fd=3 3>backflow with svn-asf-public-r0:940166 produced by whatever version of Subversion the dumps in /dump/ on svn.apache.org use (presumably 1.6.something). Improved-by: Ramkumar Ramachandra <artagnon@gmail.com> Improved-by: David Barr <david.barr@cordelta.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Acked-by: Ramkumar Ramachandra <artagnon@gmail.com>
2011-03-27vcs-svn: let deltas use data from postimageLibravatar Jonathan Nieder1-0/+42
The copyfrom_target instruction copies appends data that is already present in the current output view to the end of output. (The offset argument is relative to the beginning of output produced in the current window.) The region copied is allowed to run past the end of the existing output. To support that case, copy one character at a time rather than calling memcpy or memmove. This allows copyfrom_target to be used once to repeat a string many times. For example: COPYFROM_DATA 2 COPYFROM_OUTPUT 10, 0 DATA "ab" would produce the output "ababababababababababab". Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Acked-by: Ramkumar Ramachandra <artagnon@gmail.com>
2011-03-27vcs-svn: verify that deltas consume all inline dataLibravatar Jonathan Nieder1-3/+2
By constraining the format of deltas, we can more easily detect corruption and other breakage. Requiring deltas not to provide unconsumed data also opens the possibility of ignoring the declared amount of novel data and simply streaming the data as needed to fulfill copyfrom_data requests. Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Acked-by: Ramkumar Ramachandra <artagnon@gmail.com>
2011-03-27vcs-svn: implement copyfrom_data delta instructionLibravatar Jonathan Nieder1-0/+31
The copyfrom_data instruction copies a few bytes verbatim from the novel text section of a window to the postimage. [jn: with memory leak fix from David] Improved-by: David Barr <david.barr@cordelta.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Acked-by: Ramkumar Ramachandra <artagnon@gmail.com>
2011-03-27vcs-svn: read instructions from deltasLibravatar Jonathan Nieder1-0/+5
Buffer the instruction section upon encountering it for later interpretation. An alternative design would involve parsing the instructions at this point and buffering them in some processed form. Using the unprocessed form is simpler. Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Acked-by: Ramkumar Ramachandra <artagnon@gmail.com>
2011-03-27vcs-svn: read inline data from deltasLibravatar Jonathan Nieder1-0/+12
Each window of an svndiff0-format delta includes a section for novel text to be copied to the postimage (in the order it appears in the window, possibly interspersed with other data). Slurp in this data when encountering it. It is not actually necessary to do so --- it would be just as easy to copy from delta to output as part of interpreting the relevant instructions --- but this way, the code that interprets svndiff0 instructions can proceed very quickly because it does not require I/O. Subversion's svndiff0 parser rejects deltas that do not consume all the novel text that was provided. Omit that check for now so we can test the new functionality right away, rather than waiting to learn instructions that consume data. Do check for truncated data sections. Subversion's parser rejects deltas that end in the middle of a declared novel-text section, so it should be safe for us to reject them, too. Improved-by: Ramkumar Ramachandra <artagnon@gmail.com> Improved-by: David Barr <david.barr@cordelta.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Acked-by: Ramkumar Ramachandra <artagnon@gmail.com>
2011-03-27vcs-svn: read the preimage when applying deltasLibravatar Jonathan Nieder1-0/+35
The source view offset heading each svndiff0 window represents a number of bytes past the beginning of the preimage. Together with the source view length, it dictates to the delta applier what portion of the preimage instructions will refer to. Read that portion right away using the sliding window code. Maybe some day we will use mmap to read data more lazily. Subversion's implementation tolerates source view offsets pointing past the end of the preimage file but we do not, for simplicity. This does not teach the delta applier to read instructions or copy data from the source view. Deltas that could produce nonempty output will still be rejected. Improved-by: Ramkumar Ramachandra <artagnon@gmail.com> Improved-by: David Barr <david.barr@cordelta.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Acked-by: Ramkumar Ramachandra <artagnon@gmail.com>
2011-03-27vcs-svn: parse svndiff0 window headerLibravatar Jonathan Nieder1-1/+55
Each window in a subversion delta (svndiff0-format file) starts with a window header, consisting of five integers with variable-length representation: source view offset source view length output length instructions length auxiliary data length Parse it. The result is not usable for deltas with nonempty postimage yet; in fact, this only adds support for deltas without any instructions or auxiliary data. This is a good place to stop, though, since that little support lets us add some simple passing tests concerning error handling to the test suite. Improved-by: Ramkumar Ramachandra <artagnon@gmail.com> Improved-by: David Barr <david.barr@cordelta.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
2011-03-27vcs-svn: skeleton of an svn delta parserLibravatar Jonathan Nieder1-0/+35
A delta in the subversion delta (svndiff0) format consists of the magic bytes SVN\0 followed by a sequence of windows of a certain well specified format (starting with five integers). Add an svndiff0_apply function and test-svn-fe -d commandline tool to parse such a delta in the special case of not including any windows. Later patches will add features to turn this into a fully functional delta applier for svn-fe to use to parse the streams produced by "svnrdump dump" and "svnadmin dump --deltas". The content of symlinks starts with the word "link " in Subversion's worldview, so we need to be able to prepend that text to input for the sake of delta application. So initialization of the input state of the delta preimage is left to the calling program, giving callers a chance to seed the buffer with text of their choice. Improved-by: Ramkumar Ramachandra <artagnon@gmail.com> Improved-by: David Barr <david.barr@cordelta.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>