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29 lines
1.1 KiB
Markdown
29 lines
1.1 KiB
Markdown
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# Portals may advertise custom iterators
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The `ArrayPortalToIterator` utilities are used to produce STL-style iterators
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from vtk-m's `ArrayHandle` portals. By default, a facade class is constructed
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around the portal API, adapting it to an iterator interface.
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However, some portals use iterators internally, or may be able to construct a
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lightweight iterator easily. For these, it is preferable to directly use the
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specialized iterators instead of going through the generic facade. A portal may
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now declare the following optional API to advertise that it has custom
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iterators:
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```
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struct MyPortal
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{
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using IteratorType = ...; // alias to the portal's specialized iterator type
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IteratorType GetIteratorBegin(); // Return the begin iterator
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IteratorType GetIteratorEnd(); // Return the end iterator
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// ...rest of ArrayPortal API...
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};
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```
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If these members are present, `ArrayPortalToIterators` will forward the portal's
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specialized iterators instead of constructing a facade. This works when using
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the `ArrayPortalToIterators` class directly, and also with the
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`ArrayPortalToIteratorBegin` and `ArrayPortalToIteratorEnd` convenience
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functions.
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