40 lines
1.2 KiB
Markdown
40 lines
1.2 KiB
Markdown
Sand-Boxing - Block Access to External Data
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==========================================
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{{#include ../links.md}}
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Rhai is _sand-boxed_ so a script can never read from outside its own environment.
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Furthermore, an [`Engine`] created non-`mut` cannot mutate any state, including itself
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(and therefore it is also _re-entrant_).
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It is highly recommended that [`Engine`]'s be created immutable as much as possible.
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```rust
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let mut engine = Engine::new();
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// Use the fluent API to configure an 'Engine'
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engine.register_get("field", get_field)
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.register_set("field", set_field)
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.register_fn("do_work", action);
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// Then turn it into an immutable instance
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let engine = engine;
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// 'engine' is immutable...
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```
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Using Rhai to Control External Environment
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-----------------------------------------
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How does a _sand-boxed_, immutable [`Engine`] control the external environment?
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This is necessary in order to use Rhai as a _dynamic control layer_ over a Rust core system.
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There are two general patterns, both involving wrapping the external system
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in a shared, interior-mutated object (e.g. `Rc<RefCell<T>>`):
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* [Control Layer]({{rootUrl}}/patterns/control.md) pattern.
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* [Singleton Command Object]({{rootUrl}}/patterns/singleton.md) pattern.
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