35 lines
1.9 KiB
Markdown
35 lines
1.9 KiB
Markdown
Experimental Rust Serialization Library.
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[](https://travis-ci.org/erickt/rust-serde)
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This is an experiment to modernize rust's `libserialize` library. It is designed to implement https://github.com/rust-lang/rfcs/pull/22. `rust-serde` is an attempt to address a major shortcoming in `libserialize`. For normal structures, when you say you want to deserialize into:
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```rust
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struct Foo {
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x: int,
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y: int,
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}
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```
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`libserialize`'s deserializer essentially asks for:
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* Is the next value a struct named "Foo"? If not, error.
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* Is the next field named "x"? If not, error.
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* Is the next value an "int"? If not, error.
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* Is the next field named "y"? If not, error.
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* Is the next value an "int"? If not, error.
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* Is the struct finished? If not, error.
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While this works for user defined structures, it cannot support deserializing into a value like `json::Json`, which is an enum that can represent every JSON value. In order to support that, it needs to be able to do some lookahead:
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* What is the next value type?
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* If a struct, parse a struct.
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* If an integer, parse an integer.
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* ...
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More formally, `libserialize` implements a LL(0) grammar, whereas `json::Json` requires a LL(1) grammar. `rust-serde` provides this by implementing a serializer and deserializer that produces a tagged token stream of values. This enables a `Deserializable` for `json::Json` to look at the next token before deciding on how to parse the value.
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---
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There is now also a new library variation called `serde2`. This removes the need for tagged values and replaces them with a `Visitor` pattern. This pattern is very similar to the `Iterator` pattern, but it threads some custom state through visiting each type. This gets many of the benefits of the `serde` library without needing to always pay for tagging the variants.
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