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/*! A small, no-std, object-safe, serialization-only framework. The `sval` API is built around two key traits: - [`Value`] is a trait for data with a streamable structure. It's like `serde::Serialize`. - [`Stream`] is a trait for receiving the structure of a value. It's like `serde::Serializer`. # Getting started Add `sval` to your `Cargo.toml`: ```toml,ignore [dependencies.sval] version = "0.5.2" ``` # Supported formats - [JSON](https://crates.io/crates/sval_json), the ubiquitous JavaScript Object Notation used by many HTTP APIs. # Streaming values The structure of a [`Value`] can be streamed to a [`Stream`]. ## in a single call For simple use-cases, use the [`stream`](function.stream.html) function to stream the structure of a value: ```no_run # #[cfg(not(feature = "std"))] # fn main() {} # #[cfg(feature = "std")] # fn main() -> Result<(), Box<dyn std::error::Error>> { sval::stream(MyStream, 42)?; # Ok(()) # } # use sval::stream::{self, Stream}; # struct MyStream; # impl Stream for MyStream { # fn fmt(&mut self, _: stream::Arguments) -> stream::Result { unimplemented!() } # } ``` where `42` is a [`Value`] and `MyStream` is a [`Stream`]. ## over multiple calls More involved use-cases may want to build up structure over time. Use a [`stream::OwnedStream`](stream/struct.OwnedStream.html) to hang on to a stream and pass it values over time: ```no_run # #[cfg(not(feature = "std"))] # fn main() {} # #[cfg(feature = "std")] # fn main() -> Result<(), Box<dyn std::error::Error>> { use sval::{ Value, stream::{self, OwnedStream}, }; // We begin the wrapper over `MyStream` let mut stream = StreamPairs::new()?; // Pairs can be streamed independently stream.pair("a", 42)?; stream.pair("b", 17)?; // Eventually we end the wrapper and return the underlying `MyStream` let my_stream = stream.end()?; struct StreamPairs { // Using `OwnedStream<MyStream>` instead of just `MyStream` // gives us better ergonomics and validation stream: OwnedStream<MyStream>, } impl StreamPairs { fn new() -> Result<Self, stream::Error> { let mut stream = OwnedStream::new(MyStream); stream.map_begin(None)?; Ok(StreamPairs { stream, }) } fn pair(&mut self, k: impl Value, v: impl Value) -> Result<(), stream::Error> { self.stream.map_key(k)?; self.stream.map_value(v)?; Ok(()) } fn end(mut self) -> Result<MyStream, stream::Error> { self.stream.map_end()?; Ok(self.stream.into_inner()) } } # Ok(()) # } # use sval::stream::{self, Stream}; # struct MyStream; # impl Stream for MyStream { # fn fmt(&mut self, _: stream::Arguments) -> stream::Result { unimplemented!() } # } ``` The above example captures an `OwnedStream<MyStream>` and then allows multiple key-value pairs to be streamed through it before finishing. # `serde` integration Use the `serde` Cargo feature to enable integration with `serde`: ```toml,ignore [dependencies.sval] features = ["serde"] ``` When `serde` is available, the `Value` trait can also be derived based on an existing `Serialize` implementation: ```ignore use sval::Value; #[derive(Serialize, Value)] #[sval(derive_from = "serde")] pub enum Data { Variant(i32, String), } # } ``` # `std::fmt` integration Use the `fmt` Cargo feature to enable extended integration with `std::fmt`: ```toml,ignore [dependencies.sval] features = ["fmt"] ``` When `fmt` is available, arbitrary `Value`s can be treated like `std::fmt::Debug`: ``` # fn main() {} # #[cfg(feature = "fmt")] # mod test { fn with_value(value: impl sval::Value) { dbg!(sval::fmt::to_debug(&value)); // Do something with the value } # } ``` */ #![doc(html_root_url = "https://docs.rs/sval/0.5.2")] #![no_std] #[doc(hidden)] #[macro_export] #[cfg(feature = "alloc")] macro_rules! sval_if_alloc { ( if #[cfg(feature = "alloc")] { $($with:tt)* } else { $($without:tt)* } ) => { $($with)* }; } #[doc(hidden)] #[macro_export] #[cfg(not(feature = "alloc"))] macro_rules! sval_if_alloc { ( if #[cfg(feature = "alloc")] { $($with:tt)* } else { $($without:tt)* } ) => { $($without)* }; } #[doc(hidden)] #[cfg(feature = "derive")] pub mod derive; #[doc(inline)] #[cfg(feature = "derive")] pub use sval_derive::*; #[cfg(feature = "std")] #[macro_use] #[allow(unused_imports)] extern crate std; #[macro_use] #[allow(unused_imports)] #[cfg(all(feature = "alloc", not(feature = "std")))] extern crate alloc as alloc_lib; #[macro_use] #[allow(unused_imports)] #[cfg(all(feature = "alloc", not(feature = "std")))] extern crate core as core_lib; #[cfg(all(feature = "alloc", not(feature = "std")))] mod std { pub use crate::alloc_lib::{ boxed, collections, rc, string, vec, }; pub use crate::core_lib::*; } #[cfg(all(not(feature = "std"), not(feature = "alloc")))] #[macro_use] #[allow(unused_imports)] extern crate core as std; #[macro_use] mod error; mod collect; #[cfg(any(test, feature = "test"))] pub mod test; #[cfg(feature = "fmt")] pub mod fmt; #[cfg(feature = "serde_lib")] pub mod serde; pub mod stream; pub mod value; pub use self::{ error::Error, stream::Stream, value::Value, }; /** Stream the structure of a [`Value`] using the given [`Stream`]. This method is a convenient way of calling [`OwnedStream::stream`](stream/struct.OwnedStream.html#method.stream). */ pub fn stream<S>(stream: S, value: impl Value) -> Result<S, Error> where S: Stream, { crate::stream::OwnedStream::stream(stream, value) }