Martin Desruisseaux created SIS-487:
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Summary: Define a synchronization policy for WritableRenderedImage
Key: SIS-487
URL: https://issues.apache.org/jira/browse/SIS-487
Project: Spatial Information Systems
Issue Type: Task
Components: Features
Affects Versions: 1.1
Reporter: Martin Desruisseaux
Apache SIS 1.1 provides a {{ComputedImage}} class which manages automatically
the synchronization locks for {{computeTile(tileX, tileY)}} invocations.
However we currently have no synchronization mechanism if users invoke
{{getWritableTile(tileX, tileY)}} method and writes themselves in the image
(outside {{computeTile(tileX, tileY)}} method).
We could easily use {{ReentrantLock}} in {{getWritableTile(…)}} /
{{releaseWritableTile(…)}} methods since those two methods shall be invoked in
pairs. But this lock would not be fully effective, because we would also need
to acquire/release lock in {{getTile(…)}} method (for read-only raster) but
have no easy way of doing that. The problem is that there is no
{{releaseTile(…)}} method for raster acquired in read-only mode.
Some possible actions are:
* *Copy-on-write strategy:* {{getWritableTile(…)}} returns a _copy_ of the tile
and that copy replaces the original tile when {{releaseWritableTile(…)}} is
invoked. Inconvenient is that this strategy may have signification performance
and memory impact because of potentially large amount of copy operations.
* *User responsibility:* Provides a {{ReadWriteLock}} per image and let users
do the synchronization themselves.
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