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Re: [jgit-dev] Java NIO Options


----- Ursprungligt meddelande -----
> FrÃn: "Aaron Tull" <atull@xxxxxxxxxxx>
> Till: jgit-dev@xxxxxxxxxxx
> Skickat: onsdag, 28 maj 2014 1:59:14
> Ãmne: [jgit-dev] Java NIO Options
> 
> I was trying to use JimFS with JGit to see if I could get an efficient in
> memory repository built. All documentation states that the
> InMemoryRepository should not be used outside of testing or simple

The InMemoryRepository is meant for testing. What's the compelling reason
for using it?

> experiments while for some use cases it is also not sufficiently secure to
> access the default file system.

Why?

> Currently JGit's interface and implementation is coded directly against the
> java.io.File. This precludes any possibility of interopping directly with
> nio classes. While a java.nio.Path has a toFile option, the toFile
> implementation in JimFS correctly throws an UnsupportedOperationException.
> When the java.io.File instance is created, the FileSystem is set to the
> DefaultFileSystem and cannot be overridden (private static final).
> 
> Has there been any thought to adding additional operations to support Paths
> as arguments and changing the File based api to call to the Path api?

Sure we have "thought" about it, but to actually do it there must be an compelling
need, rather than a "it'd be nice to"-need.

As for one part of NIO, JGit has supported memory mapping of pack files for a long time, but it's not the
default. You can enable it using core.packedgitmmap = true. I'm mostly on Mac nowadays and
as I recall it, memory mapping only helps on Linux. On Windows and OS X it doesn't buy anything,
because the remapping call is so expensive. Only Linux does it efficiently.

The we do use some NIO2 stuff too, through the Java7 bundle. That's how we support symbolic
links if your JRE supports it, but the API is till Java 5/Java 6 compatible.

-- robin