sval

A prototype, lightweight, no-std, object-safe, serialization-only API for structured values with serde support.

Producers of structured values use the value module. Consumers of structured values use the stream module. sval offers a json-like data model, which is more limiting than serde's, but capable enough to represent Rust datastructures in one form or another.

This library is designed to plug a no-std-object-safe sized hole in Rust's current serialization ecosystem. The driving use-case is structured logging, where individual events are typically small, and there's no complete schema that can tie values in any one event to values in another.

sval_json and sval_derive are mostly pilfered from dtolnay's excellent miniserde project.

Minimum rustc

This library requires Rust 1.31.0.

See also

• serde
• miniserde

Crate features

• std: assume std is available and add support for std types.
• derive: add support for #[derive(Value)].
• serde: enable integration with serde.
• arbitrary-depth: support stateful values with any depth.
• test: add helpers for testing implementations of Value.

How to use it

Add sval to your crate dependencies:

toml [dependencies.sval] version = "0.1.0"

To support my datastructures

Simple struct-like datastructures can derive sval::Value:

toml [dependencies.sval] features = ["derive"]

```rust

[macro_use]

extern crate sval;

[derive(Value)]

struct MyData { id: u64, name: String, } ```

Other datastructures can implement sval::Value manually:

```rust use sval::value::{self, Value};

struct MyId(u64);

impl Value for MyId { fn stream(&self, stream: &mut value::Stream) -> Result<(), value::Error> { stream.u64(self.0) } } ```

To format my data

The sval_json crate can format any sval::Value as json:

toml [dependencies.sval_json] version = "0.1.0" features = ["std"]

rust let my_json = sval_json::to_string(my_data)?;

To integrate with serde

sval has out-of-the-box serde integration between sval::Values and serde::Serializes. Add the serde feature to sval to enable it:

toml [dependencies.sval] features = ["serde"]

Use the to_serialize function to turn any sval::Value into a serde::Serialize:

rust let my_serialize = sval::serde::to_serialize(my_data);

Use the to_value function to turn any serde::Serialize into a sval::Value:

rust let my_value = sval::serde::to_value(my_data);