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Shawn O. Pearce 3cb59216f5 Avoid unnecessary second read on OBJ_OFS_DELTA headers
When we read the object header we copy 20 bytes from the pack data,
then start parsing out the type and the inflated size.  For most
objects, this is only going to require 3 bytes, which is sufficient
to represent objects with inflated sizes of up to 2^16.  The local
buffer however still has 17 bytes remaining in it, and that can be
used to satisfy the OBJ_OFS_DELTA header.

We shouldn't need to worry about walking off the end of the buffer
here, because delta offsets cannot be larger than 64 bits, and that
requires only 9 bytes in the OFS_DELTA encoding.

Assuming worst-case scenarios of 9 bytes for the OFS_DELTA encoding,
the pack file itself must be approaching 2^64 bytes, an infeasible
size to store on any current technology.  However, even if this
were the case we still have 11 bytes for the type/size header.
In that encoding we can represent an object as large as 2^74 bytes,
which is also an infeasible size to process in JGit.

So drop the second read here.

The data offsets we pass into the ObjectLoaders being constructed
need to be computed individually now.  This saves a local variable,
but pushes the addition operation into each branch of the switch.

Change-Id: I6cf64697a9878db87bbf31c7636c03392b47a062
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
2010-05-15 16:09:07 -07:00
org.eclipse.jgit Avoid unnecessary second read on OBJ_OFS_DELTA headers 2010-05-15 16:09:07 -07:00
org.eclipse.jgit.console JGit plugin not compatible with Eclipse 3.4 2010-04-05 12:25:06 +02:00
org.eclipse.jgit.http.server Qualify builds as 0.8.0 2010-03-20 19:06:58 -07:00
org.eclipse.jgit.http.test Qualify builds as 0.8.0 2010-03-20 19:06:58 -07:00
org.eclipse.jgit.iplog Qualify builds as 0.8.0 2010-03-20 19:06:58 -07:00
org.eclipse.jgit.junit Fix unit tests using MockSystemReader with user configuation 2010-04-14 18:39:19 -07:00
org.eclipse.jgit.packaging Add missing pom dependency to org.eclipse.jgit.junit 2010-05-11 21:53:42 +02:00
org.eclipse.jgit.pgm Add commit command to the pgm package 2010-05-12 16:05:54 -07:00
org.eclipse.jgit.test Add builder-style API to jgit and Commit & Log cmd 2010-05-10 15:17:55 +02:00
org.eclipse.jgit.ui JGit plugin not compatible with Eclipse 3.4 2010-04-05 12:25:06 +02:00
tools tools/version.sh: Update OSGi manifest files 2010-03-18 19:20:32 -07:00
.eclipse_iplog JGit plugin not compatible with Eclipse 3.4 2010-04-05 12:25:06 +02:00
.gitattributes Initial JGit contribution to eclipse.org 2009-09-29 16:47:03 -07:00
LICENSE Initial JGit contribution to eclipse.org 2009-09-29 16:47:03 -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 Fix Maven Javadoc generation problem 2010-05-11 18:06:28 -05:00

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/