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This tries to address #7.
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Erick Tryzelaar 2014-09-07 22:15:16 -07:00
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@ -2,5 +2,33 @@ Experimental Rust Serialization Library.
[![Build Status](https://travis-ci.org/erickt/rust-serde.png?branch=master)](https://travis-ci.org/erickt/rust-serde) [![Build Status](https://travis-ci.org/erickt/rust-serde.png?branch=master)](https://travis-ci.org/erickt/rust-serde)
This is an experiment to modernize rust's `libserialize` library. It is 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:
designed to implement https://github.com/rust-lang/rfcs/pull/22.
```rust
struct Foo {
x: int,
y: int,
}
```
`libserialize`'s deserializer essentially asks for:
* Is the next value a struct named "Foo"? If not, error.
* Is the next field named "x"? If not, error.
* Is the next value an "int"? If not, error.
* Is the next field named "y"? If not, error.
* Is the next value an "int"? If not, error.
* Is the struct finished? If not, error.
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:
* What is the next value type?
* If a struct, parse a struct.
* If an integer, parse an integer.
* ...
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.
---
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.