Hi Gilles,
I've updated the PR with the new module/package names.
> I don't see the link between "(not) extensible" and "enum": Extensibility is
> provided by API (which classes are public and meant to be reused, e.g. by
> custom IO code) while the "enum" defines the file formats that are "natively"
> supported by this library.
I might not be picturing this correctly so perhaps a code example would help.
Here is what I'd like to be able to do with the IO code:
// add custom handler for my own file format
IO3D.getDefaultManager().registerReadHandler("matt", new MattFileReadHandler());
// read a file using that format
BoundarySource3D result = IO3D.read(Paths.get("mygeometry.matt"));
I don't see how the above could be accomplished if the supported formats are in
an enum. Also, the file extension approach above is similar to that used by
javax.imageio.ImageIO.
Regards,
Matt
________________________________
From: Gilles Sadowski <gillese...@gmail.com>
Sent: Wednesday, January 20, 2021 5:28 PM
To: Commons Developers List <dev@commons.apache.org>
Subject: Re: [geometry] IO Modules
Le mer. 20 janv. 2021 à 22:42, Matt Juntunen
<matt.juntu...@hotmail.com> a écrit :
>
> Hi Gilles,
>
> > package "io" does not belong in "core".
>
> Ah, yes. I'd like to keep the core and euclidean IO modules separate since
> I'm picturing a spherical IO module later on down the road. In that case,
> perhaps we could just put the "io" portion of the module/package name before
> everything else? That would give us
>
> commons-geometry-io-core - contains package o.a.c.geometry.io.core
> commons-geometry-io-euclidean - contains package
> o.a.c.geometry.io.euclidean
Yes; having "io" as the top-level package is what I was suggesting.
>
> > Then, we had also discussed that it would have been more robust to use a
> > parser generator...
>
> Yes. I looked into that and ended up deciding that a full parser-generator
> would be overkill for what I wanted to do and possibly more work to
> maintain/customize. I've placed the current low-level parsing code
> (consisting of the CharReadBuffer and SimpleTextParser classes) in the
> "internal" package o.a.c.geometry.core.io.internal. I don't intend for these
> classes to be part of the public API, which would allow us to switch to a
> parser-generator later if needed.
OK!
>
> > I haven't read all the code (sorry!)
>
> No worries. There is a lot of it :-)
>
> > I'm not convinced by the usage of file "extensions" to determine how the
> > contents should be parsed. At first sight, an "enum"-based approach[3]
> > would be more flexible and clearer from a code design POV.
>
> In contrast to the rest of the library, I'd like to make these IO modules as
> extensible as possible, the reason being that they form the main connection
> between the library and external systems. If we use an enum to indicate the
> format, we restrict usage of the API to only those formats. A string name, on
> the other hand, allows users to define their own formats and use them with
> the API.
[I'm only answering based on the impression I get from your description above.]
I don't see the link between "(not) extensible" and "enum":
Extensibility is provided by
API (which classes are public and meant to be reused, e.g. by custom
IO code) while
the "enum" defines the file formats that are "natively" supported by
this library.
[And, in time, custom code can become part of the supported formats and get its
corresponding "enum" element.]
The file extensions could be supported too, but I would think at a higher level;
mapping to either the "enum", or to custom code.
> For example, we will soon be creating a custom geometry format for an
> application at my day job and I would like to be able to use these IO modules
> to read and write that format (using custom BoundaryReadHandler3D and
> BoundaryWriteHandler3D implementations).
Is what I wrote above preventing that?
Best,
Gilles
>
> Thoughts?
>
> Regards,
> Matt J
>
>
>
> ________________________________
> From: Gilles Sadowski <gillese...@gmail.com>
> Sent: Wednesday, January 20, 2021 9:17 AM
> To: Commons Developers List <dev@commons.apache.org>
> Subject: Re: [geometry] IO Modules
>
> Hi Matt.
>
> Le mer. 20 janv. 2021 à 05:03, Matt Juntunen
> <matt.juntu...@hotmail.com> a écrit :
> >
> > Hello,
> >
> > I've created GEOMETRY-115 and an associated PR [1] containing new modules
> > for IO functionality. The new modules are
> >
> > * commons-geometry-core-io - Common space-independent interfaces and
> > classes
> > * commons-geometry-euclidean-io - Euclidean IO classes; currently
> > contains support for the 3D formats TXT, CSV, and OBJ
> >
> > The API is based on a core BoundaryIOManager class that delegates to
> > BoundaryReadHandler and BoundaryWriteHandler implementations based on the
> > requested data format. For Euclidean 3D space, a convenience IO3D class is
> > provided with static methods that delegate to a default manager instance.
> > In addition to reading and writing the core geometric types for the library
> > (ConvexPolygon3D, Triangle3D), the Euclidean module also supports reading
> > and writing a FacetDefinition interface, which exposes simple, unvalidated
> > geometric data. This is intended for accessing raw (possibly invalid)
> > geometric data from files and writing data contained in external data
> > structures (for example, a custom facet class). The example below is from
> > the IO3D class documentation and demonstrates a read, transform, write
> > operation using streams.
> >
> > final Path origFile = tempDir.resolve("orig.obj");
> > final Path scaledFile = tempDir.resolve("scaled.csv");
> >
> > final DoublePrecisionContext precision = new
> > EpsilonDoublePrecisionContext(1e-10);
> > final BoundarySource3D src = Parallelepiped.unitCube(precision);
> >
> > IO3D.write(src, origFile);
> >
> > final AffineTransformMatrix3D transform =
> > AffineTransformMatrix3D.createScale(2);
> >
> > try (Stream<Triangle3D> stream = IO3D.triangles(origFile,
> > precision)) {
> > IO3D.write(stream.map(t -> t.transform(transform)), scaledFile);
> > }
> >
> > Feedback is welcome.
>
> The high-level API, illustrated in the example above, looks quite fine.
> But we should enforce "separation of concerns"; in this particular case:
> package "io" does not belong in "core".
>
> The Java package
> org.apache.commons.geometry.core
> is defined the within the (maven) module
> commons-geometry-core
> The new Java package
> org.apache.commons.geometry.core.io
> is defined the within the (maven) module
> commons-geometry-core-io
>
> The (maven) module name is also often used to define the
> Java 9+ module name for JPMS.[1]
> IIUC, the package
> org.apache.commons.geometry.core
> and its "sub-package"
> org.apache.commons.geometry.core.io
> cannot belong to different (JPMS) modules, because (IIUC) a package
> hierarchy cannot be shared across modules (since one of the purposes
> is to organize "visibility").
> Components should be JPMS-compatible.[2]
>
> Fixing that would just require to
> 1. remove the two modules introduced in PR #130
> commons-geometry-core-io
> commons-geometry-euclidean-io
> 2. create one (maven) module
> commons-geometry-io
> owning the Java packages
> org.apache.commons.geometry.io
> org.apache.commons.geometry.io.core
> org.apache.commons.geometry.io.euclidean
>
> [If you think that it's really worth having separate modules for loading
> "euclidean" data vs other space-types (not yet implemented IIUC),
> point (2) would be adapted accordingly.]
>
> This would fix both the JPMS issue, and the design issue.
>
> Then, we had also discussed that it would have been more robust to
> use a parser generator...
> In either case, I'd suggest that we put the actual I/O classes in an
> "internal" package, and only advertize the above high-level API (i.e. we
> should not be expected to maintain compatibility of the parser code).
>
> I haven't read all the code (sorry!), but in class "IO3D", I'm not convinced
> by the usage of file "extensions" to determine how the contents should be
> parsed. At first sight, an "enum"-based approach[3] would be more flexible
> and clearer from a code design POV.
>
> Regards,
> Gilles
>
> [1]
> https://www.oracle.com/corporate/features/understanding-java-9-modules.html
> [2] See
> https://gitbox.apache.org/repos/asf?p=commons-rng.git;a=tree;f=commons-rng-examples/examples-jpms;hb=HEAD
> [3] See
> https://gitbox.apache.org/repos/asf?p=commons-rng.git;a=blob;f=commons-rng-simple/src/main/java/org/apache/commons/rng/simple/RandomSource.java;h=65ca02fdc285fbb7ea8305008dbce21f571191d7;hb=HEAD
>
> >
> > Regards,
> > Matt J
> >
> > [1] https://github.com/apache/commons-geometry/pull/130
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