Crate sval 

Structured, streaming values.

sval is a serialization framework that treats data as a flat stream of tokens. The source of that data could be some Rust object or parsed from some encoding. It’s well suited to self-describing, text-based formats like JSON.

Getting started

For a complete introduction, see the project readme.

Add sval to your Cargo.toml:

[dependencies.sval]
version = "2.16.0"

By default, sval doesn’t depend on Rust’s standard library or integrate with its collection types. To include them, add the alloc or std Cargo features:

[dependencies.sval]
version = "2.16.0"
features = ["std"]

sval provides procedural macros for deriving its traits. Add the derive Cargo feature to enable them:

[dependencies.sval]
version = "2.16.0"
features = ["derive"]

The Value trait

Value is a trait for data types to implement that surfaces their structure through visitors called streams. Value is like serde’s Serialize. It can also be used like serde’s Deserialize.

Many standard types in Rust implement the Value trait. It can be derived on your own types using the sval_derive library.

The Stream trait

Stream is a trait for data formats and visitors to implement that observes the structure of values. Stream is like serde’s Serializer. It can also be used like serde’s Deserializer.

Data-model

sval’s data-model is defined by the Stream trait. It includes:

• Null
• Booleans (true, false)
• Text blobs
• Binary blobs
• Integers (u8-u128, i8-i128)
• Binary floating points (f32-f64)
• Sequences
• Maps
• Tags
• Tagged values
• Records
• Tuples
• Enums

Tags

Tag is a type for extending sval’s data-model with new kinds of values. Rust’s own () and Option<T> types are expressed as tags. Other examples of tags include text that encodes RFC3339 timestamps or RFC4122 UUIDs.

The tags module contains built-in tags. Other libraries may define their own tags too.

Modules

default_stream

Default method implementations for Streams.

default_value

Default method implementations for Values.

tags

Built-in tags for fundamental types.

Structs

BinaryArray

An adapter that streams a slice of 8bit unsigned integers as binary with a fixed size.

BinarySlice

An adapter that streams a slice of 8bit unsigned integers as binary.

Display

Adapt a fmt::Display into an [sval::Value].

Error

An error encountered while streaming a value.

Index

The index of a value in its parent context.

Label

A textual label for some value.

MapSlice

An adapter that streams a slice of key-value pairs as a map.

Null

The absence of any meaningful value.

Tag

A type tag for a value.

Traits

Stream

A consumer of structured data.

Value

A producer of structured data.

Functions

error

A streaming result with a generic failure.

stream

Stream a value through a stream.

stream_computed

Stream a value through a stream with an arbitrarily short lifetime.

stream_display

Stream a fmt::Display as text into a Stream.

stream_display_fragments

Stream a fmt::Display as text fragments into a Stream, without calling Stream::text_begin or Stream::text_end.

stream_number

Stream an arbitrary precision number conforming to tags::NUMBER using its fmt::Display implementation.

Type Aliases

Result

A generic streaming result.