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Shawn O. Pearce e0970cd1b4 Micro-optimize reduceCommonStartEnd for RawText 
This is a faster exact match based form that tries to improve
performance for the common case of the header and trailer of
a text file not changing at all. After this fast path we use
the slower path based on the super class' using equals() to
allow for whitespace ignore modes to still work.

Some simple performance testing showed a major improvement over the
older implementation for a common edit we see in JGit.  The test
compared blob 29a89bc and 372a978, which is the ObjectDirectory.java
file difference in commit 41dd9ed1c0.
The two text files are approximately 22 KiB in size.

  DEFAULT        old   203900 ns
  DEFAULT        new   100400 ns

This new version is 2x faster for the DEFAULT comparator, which does
not treat space specially.  This is because we can now examine a
larger swath of text with fewer instructions per byte compared.  The
older algorithm had to stop at each line break and recompute how to
examine the next line, while the new algorithm only stops when the
first difference is found.

  WS_IGNORE_ALL  old   298500 ns
  WS_IGNORE_ALL  new    63300 ns

Its 4.7x faster for the whitespace ignore comparator, as the common
header and footer do not have a whitespace difference.  Avoiding the
special case handling for whitespace on each byte considered saves a
lot of time.

Since most edits to source code (and other text like files) appears in
the interior of the file, fast elimination of common header/footer
means faster diff throughput.  In the less common case of an actual
header or footer edit, the common header/footer elimination is stopped
rather quickly either way, so there is very little downside to the
optimiation applied here.

Change-Id: I1d501b4c3ff80ed086b20bf12faf51ae62167db7
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
 		2010-09-20 18:05:41 -07:00
org.eclipse.jgit Micro-optimize reduceCommonStartEnd for RawText 2010-09-20 18:05:41 -07:00
org.eclipse.jgit.console Qualify builds as 0.10.0 2010-09-16 17:26:53 -07:00
org.eclipse.jgit.http.server Qualify builds as 0.10.0 2010-09-16 17:26:53 -07:00
org.eclipse.jgit.http.test Qualify builds as 0.10.0 2010-09-16 17:26:53 -07:00
org.eclipse.jgit.iplog Merge "Define DiffAlgorithm as an abstract function" 2010-09-17 15:08:27 -04:00
org.eclipse.jgit.junit Qualify builds as 0.10.0 2010-09-16 17:26:53 -07:00
org.eclipse.jgit.packaging Fix dependency to jgit source bundle 2010-09-17 22:01:40 +02:00
org.eclipse.jgit.pgm Qualify builds as 0.10.0 2010-09-16 17:26:53 -07:00
org.eclipse.jgit.test Micro-optimize reduceCommonStartEnd for RawText 2010-09-20 18:05:41 -07:00
org.eclipse.jgit.ui Qualify builds as 0.10.0 2010-09-16 17:26:53 -07:00
tools Clean up LICENSE file 2010-07-02 14:52:49 -07:00
.eclipse_iplog Update .eclipse_iplog for 0.9 2010-09-08 23:17:54 +02:00
.gitattributes Initial JGit contribution to eclipse.org 2009-09-29 16:47:03 -07:00
LICENSE Clean up LICENSE file 2010-07-02 14:52:49 -07:00
README Initial JGit contribution to eclipse.org 2009-09-29 16:47:03 -07:00
SUBMITTING_PATCHES Correcting explanation of EDL 2009-10-28 14:12:07 +01:00
pom.xml Qualify builds as 0.10.0 2010-09-16 17:26:53 -07:00

README 

            == Java GIT ==

This package is licensed under the BSD.

  org.eclipse.jgit/

    A pure Java library capable of being run standalone, with no
    additional support libraries.  Some JUnit tests are provided
    to exercise the library.  The library provides functions to
    read and write a GIT formatted repository.

    All portions of jgit are covered by the BSD.  Absolutely no GPL,
    LGPL or EPL contributions are accepted within this package.

  org.eclipse.jgit.test/
    Unit tests for org.eclipse.jgit and the same licensing rules.

            == WARNINGS / CAVEATS              ==

- Symbolic links are not supported because java does not support it.
  Such links could be damaged.

- Only the timestamp of the index is used by jgit check if  the index
  is dirty.

- Don't try the library with a JDK other than 1.6 (Java 6) unless you
  are prepared to investigate problems yourself. JDK 1.5.0_11 and later
  Java 5 versions *may* work. Earlier versions do not. JDK 1.4 is *not*
  supported. Apple's Java 1.5.0_07 is reported to work acceptably. We
  have no information about other vendors. Please report your findings
  if you try.

- CRLF conversion is never performed. On Windows you should thereforc
  make sure your projects and workspaces are configured to save files
  with Unix (LF) line endings.

            == Package Features                ==

  org.eclipse.jgit/

    * Read loose and packed commits, trees, blobs, including
      deltafied objects.

    * Read objects from shared repositories

    * Write loose commits, trees, blobs.

    * Write blobs from local files or Java InputStreams.

    * Read blobs as Java InputStreams.

    * Copy trees to local directory, or local directory to a tree.

    * Lazily loads objects as necessary.

    * Read and write .git/config files.

    * Create a new repository.

    * Read and write refs, including walking through symrefs.

    * Read, update and write the Git index.

    * Checkout in dirty working directory if trivial.

    * Walk the history from a given set of commits looking for commits
      introducing changes in files under a specified path.

    * Object transport
      Fetch via ssh, git, http, Amazon S3 and bundles.
      Push via ssh, git and Amazon S3. JGit does not yet deltify
      the pushed packs so they may be a lot larger than C Git packs.

  org.eclipse.jgit.pgm/

    * Assorted set of command line utilities. Mostly for ad-hoc testing of jgit
      log, glog, fetch etc.

            == Missing Features                ==

There are a lot of missing features. You need the real Git for this.
For some operations it may just be the preferred solution also. There
are not just a command line, there is e.g. git-gui that makes committing
partial files simple.

- Merging. 

- Repacking.

- Generate a GIT format patch.

- Apply a GIT format patch.

- Documentation. :-)

- gitattributes support
  In particular CRLF conversion is not implemented. Files are treated
  as byte sequences.

- submodule support
  Submodules are not supported or even recognized.

            == Support                         ==

  Post question, comments or patches to the git@vger.kernel.org mailing list.


            == Contributing                    ==

  See SUBMITTING_PATCHES in this directory. However, feedback and bug reports
  are also contributions.


            == About GIT                       ==

More information about GIT, its repository format, and the canonical
C based implementation can be obtained from the GIT websites:

  http://git.or.cz/
  http://www.kernel.org/pub/software/scm/git/
  http://www.kernel.org/pub/software/scm/git/docs/