41 lines
1.8 KiB
Markdown
41 lines
1.8 KiB
Markdown
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Maximum Size of Object Maps
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==========================
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{{#include ../links.md}}
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Limiting How Large Object Maps Can Grow
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--------------------------------------
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Rhai by default does not limit how large (i.e. the number of properties) an [object map] can be.
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This can be changed via the `Engine::set_max_map_size` method, with zero being unlimited (the default).
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A script attempting to create an object map literal with more properties than the maximum will terminate with a parse error.
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Any script operation that produces an object map with more properties than the maximum also terminates the script with an error result.
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This check can be disabled via the [`unchecked`] feature for higher performance (but higher risks as well).
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```rust
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let mut engine = Engine::new();
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engine.set_max_map_size(500); // allow object maps with only up to 500 properties
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engine.set_max_map_size(0); // allow unlimited object maps
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```
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Setting Maximum Size
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-------------------
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Be conservative when setting a maximum limit and always consider the fact that a registered function may grow
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an object map's size without Rhai noticing until the very end.
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For instance, the built-in '`+`' operator for object maps concatenates two object maps together to form one larger object map;
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if both object maps are _slightly_ below the maximum size limit, the resultant object map may be almost _twice_ the maximum size.
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As a malicious script may create a deeply-nested object map which consumes huge amounts of memory while each individual
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object map still stays under the maximum size limit, Rhai also recursively adds up the sizes of all [strings], [arrays]
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and [object maps] contained within each object map to make sure that the _aggregate_ sizes of none of these data structures
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exceed their respective maximum size limits (if any).
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