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//! Generic data structure serialization framework.
//!
//! The two most important traits in this module are [`Serialize`] and
//! [`Serializer`].
//!
//! - **A type that implements `Serialize` is a data structure** that can be
//! serialized to any data format supported by Serde, and conversely
//! - **A type that implements `Serializer` is a data format** that can
//! serialize any data structure supported by Serde.
//!
//! # The Serialize trait
//!
//! Serde provides [`Serialize`] implementations for many Rust primitive and
//! standard library types. The complete list is below. All of these can be
//! serialized using Serde out of the box.
//!
//! Additionally, Serde provides a procedural macro called [`serde_derive`] to
//! automatically generate [`Serialize`] implementations for structs and enums
//! in your program. See the [derive section of the manual] for how to use this.
//!
//! In rare cases it may be necessary to implement [`Serialize`] manually for
//! some type in your program. See the [Implementing `Serialize`] section of the
//! manual for more about this.
//!
//! Third-party crates may provide [`Serialize`] implementations for types that
//! they expose. For example the [`linked-hash-map`] crate provides a
//! [`LinkedHashMap<K, V>`] type that is serializable by Serde because the crate
//! provides an implementation of [`Serialize`] for it.
//!
//! # The Serializer trait
//!
//! [`Serializer`] implementations are provided by third-party crates, for
//! example [`serde_json`], [`serde_yaml`] and [`postcard`].
//!
//! A partial list of well-maintained formats is given on the [Serde
//! website][data formats].
//!
//! # Implementations of Serialize provided by Serde
//!
//! - **Primitive types**:
//! - bool
//! - i8, i16, i32, i64, i128, isize
//! - u8, u16, u32, u64, u128, usize
//! - f32, f64
//! - char
//! - str
//! - &T and &mut T
//! - **Compound types**:
//! - \[T\]
//! - \[T; 0\] through \[T; 32\]
//! - tuples up to size 16
//! - **Common standard library types**:
//! - String
//! - Option\<T\>
//! - Result\<T, E\>
//! - PhantomData\<T\>
//! - **Wrapper types**:
//! - Box\<T\>
//! - Cow\<'a, T\>
//! - Cell\<T\>
//! - RefCell\<T\>
//! - Mutex\<T\>
//! - RwLock\<T\>
//! - Rc\<T\> *(if* features = \["rc"\] *is enabled)*
//! - Arc\<T\> *(if* features = \["rc"\] *is enabled)*
//! - **Collection types**:
//! - BTreeMap\<K, V\>
//! - BTreeSet\<T\>
//! - BinaryHeap\<T\>
//! - HashMap\<K, V, H\>
//! - HashSet\<T, H\>
//! - LinkedList\<T\>
//! - VecDeque\<T\>
//! - Vec\<T\>
//! - **FFI types**:
//! - CStr
//! - CString
//! - OsStr
//! - OsString
//! - **Miscellaneous standard library types**:
//! - Duration
//! - SystemTime
//! - Path
//! - PathBuf
//! - Range\<T\>
//! - RangeInclusive\<T\>
//! - Bound\<T\>
//! - num::NonZero*
//! - `!` *(unstable)*
//! - **Net types**:
//! - IpAddr
//! - Ipv4Addr
//! - Ipv6Addr
//! - SocketAddr
//! - SocketAddrV4
//! - SocketAddrV6
//!
//! [`LinkedHashMap<K, V>`]: https://docs.rs/linked-hash-map/*/linked_hash_map/struct.LinkedHashMap.html
//! [`Serialize`]: ../trait.Serialize.html
//! [`Serializer`]: ../trait.Serializer.html
use crate::lib::*;
mod fmt;
mod impls;
mod impossible;
pub use self::impossible::Impossible;
#[cfg(all(not(feature = "std"), no_core_error))]
#[doc(no_inline)]
pub use crate::std_error::Error as StdError;
#[cfg(not(any(feature = "std", no_core_error)))]
#[doc(no_inline)]
pub use core::error::Error as StdError;
#[cfg(feature = "std")]
#[doc(no_inline)]
pub use std::error::Error as StdError;
////////////////////////////////////////////////////////////////////////////////
macro_rules! declare_error_trait {
(Error: Sized $(+ $($supertrait:ident)::+)*) => {
/// Trait used by `Serialize` implementations to generically construct
/// errors belonging to the `Serializer` against which they are
/// currently running.
///
/// # Example implementation
///
/// The [example data format] presented on the website shows an error
/// type appropriate for a basic JSON data format.
///
pub trait Error: Sized $(+ $($supertrait)::+)* {
/// Used when a [`Serialize`] implementation encounters any error
/// while serializing a type.
///
/// The message should not be capitalized and should not end with a
/// period.
///
/// For example, a filesystem [`Path`] may refuse to serialize
/// itself if it contains invalid UTF-8 data.
///
/// ```edition2021
/// # struct Path;
/// #
/// # impl Path {
/// # fn to_str(&self) -> Option<&str> {
/// # unimplemented!()
/// # }
/// # }
/// #
/// use serde::ser::{self, Serialize, Serializer};
///
/// impl Serialize for Path {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// match self.to_str() {
/// Some(s) => serializer.serialize_str(s),
/// None => Err(ser::Error::custom("path contains invalid UTF-8 characters")),
/// }
/// }
/// }
/// ```
///
/// [`Serialize`]: ../trait.Serialize.html
fn custom<T>(msg: T) -> Self
where
T: Display;
}
}
}
#[cfg(feature = "std")]
declare_error_trait!(Error: Sized + StdError);
#[cfg(not(feature = "std"))]
declare_error_trait!(Error: Sized + Debug + Display);
////////////////////////////////////////////////////////////////////////////////
/// A **data structure** that can be serialized into any data format supported
/// by Serde.
///
/// Serde provides `Serialize` implementations for many Rust primitive and
/// standard library types. The complete list is [here][crate::ser]. All of
/// these can be serialized using Serde out of the box.
///
/// Additionally, Serde provides a procedural macro called [`serde_derive`] to
/// automatically generate `Serialize` implementations for structs and enums in
/// your program. See the [derive section of the manual] for how to use this.
///
/// In rare cases it may be necessary to implement `Serialize` manually for some
/// type in your program. See the [Implementing `Serialize`] section of the
/// manual for more about this.
///
/// Third-party crates may provide `Serialize` implementations for types that
/// they expose. For example the [`linked-hash-map`] crate provides a
/// [`LinkedHashMap<K, V>`] type that is serializable by Serde because the crate
/// provides an implementation of `Serialize` for it.
///
/// [`LinkedHashMap<K, V>`]: https://docs.rs/linked-hash-map/*/linked_hash_map/struct.LinkedHashMap.html
#[cfg_attr(
not(no_diagnostic_namespace),
diagnostic::on_unimplemented(
note = "for local types consider adding `#[derive(serde::Serialize)]` to your `{Self}` type",
note = "for types from other crates check whether the crate offers a `serde` feature flag",
)
)]
pub trait Serialize {
/// Serialize this value into the given Serde serializer.
///
/// See the [Implementing `Serialize`] section of the manual for more
/// information about how to implement this method.
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeStruct, Serializer};
///
/// struct Person {
/// name: String,
/// age: u8,
/// phones: Vec<String>,
/// }
///
/// // This is what #[derive(Serialize)] would generate.
/// impl Serialize for Person {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut s = serializer.serialize_struct("Person", 3)?;
/// s.serialize_field("name", &self.name)?;
/// s.serialize_field("age", &self.age)?;
/// s.serialize_field("phones", &self.phones)?;
/// s.end()
/// }
/// }
/// ```
///
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: Serializer;
}
////////////////////////////////////////////////////////////////////////////////
/// A **data format** that can serialize any data structure supported by Serde.
///
/// The role of this trait is to define the serialization half of the [Serde
/// data model], which is a way to categorize every Rust data structure into one
/// of 29 possible types. Each method of the `Serializer` trait corresponds to
/// one of the types of the data model.
///
/// Implementations of `Serialize` map themselves into this data model by
/// invoking exactly one of the `Serializer` methods.
///
/// The types that make up the Serde data model are:
///
/// - **14 primitive types**
/// - bool
/// - i8, i16, i32, i64, i128
/// - u8, u16, u32, u64, u128
/// - f32, f64
/// - char
/// - **string**
/// - UTF-8 bytes with a length and no null terminator.
/// - When serializing, all strings are handled equally. When deserializing,
/// there are three flavors of strings: transient, owned, and borrowed.
/// - **byte array** - \[u8\]
/// - Similar to strings, during deserialization byte arrays can be
/// transient, owned, or borrowed.
/// - **option**
/// - Either none or some value.
/// - **unit**
/// - The type of `()` in Rust. It represents an anonymous value containing
/// no data.
/// - **unit_struct**
/// - For example `struct Unit` or `PhantomData<T>`. It represents a named
/// value containing no data.
/// - **unit_variant**
/// - For example the `E::A` and `E::B` in `enum E { A, B }`.
/// - **newtype_struct**
/// - For example `struct Millimeters(u8)`.
/// - **newtype_variant**
/// - For example the `E::N` in `enum E { N(u8) }`.
/// - **seq**
/// - A variably sized heterogeneous sequence of values, for example
/// `Vec<T>` or `HashSet<T>`. When serializing, the length may or may not
/// be known before iterating through all the data. When deserializing,
/// the length is determined by looking at the serialized data.
/// - **tuple**
/// - A statically sized heterogeneous sequence of values for which the
/// length will be known at deserialization time without looking at the
/// serialized data, for example `(u8,)` or `(String, u64, Vec<T>)` or
/// `[u64; 10]`.
/// - **tuple_struct**
/// - A named tuple, for example `struct Rgb(u8, u8, u8)`.
/// - **tuple_variant**
/// - For example the `E::T` in `enum E { T(u8, u8) }`.
/// - **map**
/// - A heterogeneous key-value pairing, for example `BTreeMap<K, V>`.
/// - **struct**
/// - A heterogeneous key-value pairing in which the keys are strings and
/// will be known at deserialization time without looking at the
/// serialized data, for example `struct S { r: u8, g: u8, b: u8 }`.
/// - **struct_variant**
/// - For example the `E::S` in `enum E { S { r: u8, g: u8, b: u8 } }`.
///
/// Many Serde serializers produce text or binary data as output, for example
/// JSON or Postcard. This is not a requirement of the `Serializer` trait, and
/// there are serializers that do not produce text or binary output. One example
/// is the `serde_json::value::Serializer` (distinct from the main `serde_json`
/// serializer) that produces a `serde_json::Value` data structure in memory as
/// output.
///
///
/// # Example implementation
///
/// The [example data format] presented on the website contains example code for
/// a basic JSON `Serializer`.
///
pub trait Serializer: Sized {
/// The output type produced by this `Serializer` during successful
/// serialization. Most serializers that produce text or binary output
/// should set `Ok = ()` and serialize into an [`io::Write`] or buffer
/// contained within the `Serializer` instance. Serializers that build
/// in-memory data structures may be simplified by using `Ok` to propagate
/// the data structure around.
///
type Ok;
/// The error type when some error occurs during serialization.
type Error: Error;
/// Type returned from [`serialize_seq`] for serializing the content of the
/// sequence.
///
/// [`serialize_seq`]: #tymethod.serialize_seq
type SerializeSeq: SerializeSeq<Ok = Self::Ok, Error = Self::Error>;
/// Type returned from [`serialize_tuple`] for serializing the content of
/// the tuple.
///
/// [`serialize_tuple`]: #tymethod.serialize_tuple
type SerializeTuple: SerializeTuple<Ok = Self::Ok, Error = Self::Error>;
/// Type returned from [`serialize_tuple_struct`] for serializing the
/// content of the tuple struct.
///
/// [`serialize_tuple_struct`]: #tymethod.serialize_tuple_struct
type SerializeTupleStruct: SerializeTupleStruct<Ok = Self::Ok, Error = Self::Error>;
/// Type returned from [`serialize_tuple_variant`] for serializing the
/// content of the tuple variant.
///
/// [`serialize_tuple_variant`]: #tymethod.serialize_tuple_variant
type SerializeTupleVariant: SerializeTupleVariant<Ok = Self::Ok, Error = Self::Error>;
/// Type returned from [`serialize_map`] for serializing the content of the
/// map.
///
/// [`serialize_map`]: #tymethod.serialize_map
type SerializeMap: SerializeMap<Ok = Self::Ok, Error = Self::Error>;
/// Type returned from [`serialize_struct`] for serializing the content of
/// the struct.
///
/// [`serialize_struct`]: #tymethod.serialize_struct
type SerializeStruct: SerializeStruct<Ok = Self::Ok, Error = Self::Error>;
/// Type returned from [`serialize_struct_variant`] for serializing the
/// content of the struct variant.
///
/// [`serialize_struct_variant`]: #tymethod.serialize_struct_variant
type SerializeStructVariant: SerializeStructVariant<Ok = Self::Ok, Error = Self::Error>;
/// Serialize a `bool` value.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for bool {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_bool(*self)
/// }
/// }
/// ```
fn serialize_bool(self, v: bool) -> Result<Self::Ok, Self::Error>;
/// Serialize an `i8` value.
///
/// If the format does not differentiate between `i8` and `i64`, a
/// reasonable implementation would be to cast the value to `i64` and
/// forward to `serialize_i64`.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for i8 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_i8(*self)
/// }
/// }
/// ```
fn serialize_i8(self, v: i8) -> Result<Self::Ok, Self::Error>;
/// Serialize an `i16` value.
///
/// If the format does not differentiate between `i16` and `i64`, a
/// reasonable implementation would be to cast the value to `i64` and
/// forward to `serialize_i64`.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for i16 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_i16(*self)
/// }
/// }
/// ```
fn serialize_i16(self, v: i16) -> Result<Self::Ok, Self::Error>;
/// Serialize an `i32` value.
///
/// If the format does not differentiate between `i32` and `i64`, a
/// reasonable implementation would be to cast the value to `i64` and
/// forward to `serialize_i64`.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for i32 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_i32(*self)
/// }
/// }
/// ```
fn serialize_i32(self, v: i32) -> Result<Self::Ok, Self::Error>;
/// Serialize an `i64` value.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for i64 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_i64(*self)
/// }
/// }
/// ```
fn serialize_i64(self, v: i64) -> Result<Self::Ok, Self::Error>;
/// Serialize an `i128` value.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for i128 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_i128(*self)
/// }
/// }
/// ```
///
/// The default behavior unconditionally returns an error.
fn serialize_i128(self, v: i128) -> Result<Self::Ok, Self::Error> {
let _ = v;
Err(Error::custom("i128 is not supported"))
}
/// Serialize a `u8` value.
///
/// If the format does not differentiate between `u8` and `u64`, a
/// reasonable implementation would be to cast the value to `u64` and
/// forward to `serialize_u64`.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for u8 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_u8(*self)
/// }
/// }
/// ```
fn serialize_u8(self, v: u8) -> Result<Self::Ok, Self::Error>;
/// Serialize a `u16` value.
///
/// If the format does not differentiate between `u16` and `u64`, a
/// reasonable implementation would be to cast the value to `u64` and
/// forward to `serialize_u64`.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for u16 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_u16(*self)
/// }
/// }
/// ```
fn serialize_u16(self, v: u16) -> Result<Self::Ok, Self::Error>;
/// Serialize a `u32` value.
///
/// If the format does not differentiate between `u32` and `u64`, a
/// reasonable implementation would be to cast the value to `u64` and
/// forward to `serialize_u64`.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for u32 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_u32(*self)
/// }
/// }
/// ```
fn serialize_u32(self, v: u32) -> Result<Self::Ok, Self::Error>;
/// Serialize a `u64` value.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for u64 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_u64(*self)
/// }
/// }
/// ```
fn serialize_u64(self, v: u64) -> Result<Self::Ok, Self::Error>;
/// Serialize a `u128` value.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for u128 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_u128(*self)
/// }
/// }
/// ```
///
/// The default behavior unconditionally returns an error.
fn serialize_u128(self, v: u128) -> Result<Self::Ok, Self::Error> {
let _ = v;
Err(Error::custom("u128 is not supported"))
}
/// Serialize an `f32` value.
///
/// If the format does not differentiate between `f32` and `f64`, a
/// reasonable implementation would be to cast the value to `f64` and
/// forward to `serialize_f64`.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for f32 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_f32(*self)
/// }
/// }
/// ```
fn serialize_f32(self, v: f32) -> Result<Self::Ok, Self::Error>;
/// Serialize an `f64` value.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for f64 {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_f64(*self)
/// }
/// }
/// ```
fn serialize_f64(self, v: f64) -> Result<Self::Ok, Self::Error>;
/// Serialize a character.
///
/// If the format does not support characters, it is reasonable to serialize
/// it as a single element `str` or a `u32`.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for char {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_char(*self)
/// }
/// }
/// ```
fn serialize_char(self, v: char) -> Result<Self::Ok, Self::Error>;
/// Serialize a `&str`.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for str {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_str(self)
/// }
/// }
/// ```
fn serialize_str(self, v: &str) -> Result<Self::Ok, Self::Error>;
/// Serialize a chunk of raw byte data.
///
/// Enables serializers to serialize byte slices more compactly or more
/// efficiently than other types of slices. If no efficient implementation
/// is available, a reasonable implementation would be to forward to
/// `serialize_seq`. If forwarded, the implementation looks usually just
/// like this:
///
/// ```edition2021
/// # use serde::ser::{Serializer, SerializeSeq};
/// # use serde::__private::doc::Error;
/// #
/// # struct MySerializer;
/// #
/// # impl Serializer for MySerializer {
/// # type Ok = ();
/// # type Error = Error;
/// #
/// fn serialize_bytes(self, v: &[u8]) -> Result<Self::Ok, Self::Error> {
/// let mut seq = self.serialize_seq(Some(v.len()))?;
/// for b in v {
/// seq.serialize_element(b)?;
/// }
/// seq.end()
/// }
/// #
/// # serde::__serialize_unimplemented! {
/// # bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str none some
/// # unit unit_struct unit_variant newtype_struct newtype_variant
/// # seq tuple tuple_struct tuple_variant map struct struct_variant
/// # }
/// # }
/// ```
fn serialize_bytes(self, v: &[u8]) -> Result<Self::Ok, Self::Error>;
/// Serialize a [`None`] value.
///
/// ```edition2021
/// # use serde::{Serialize, Serializer};
/// #
/// # enum Option<T> {
/// # Some(T),
/// # None,
/// # }
/// #
/// # use self::Option::{Some, None};
/// #
/// impl<T> Serialize for Option<T>
/// where
/// T: Serialize,
/// {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// match *self {
/// Some(ref value) => serializer.serialize_some(value),
/// None => serializer.serialize_none(),
/// }
/// }
/// }
/// #
/// # fn main() {}
/// ```
///
fn serialize_none(self) -> Result<Self::Ok, Self::Error>;
/// Serialize a [`Some(T)`] value.
///
/// ```edition2021
/// # use serde::{Serialize, Serializer};
/// #
/// # enum Option<T> {
/// # Some(T),
/// # None,
/// # }
/// #
/// # use self::Option::{Some, None};
/// #
/// impl<T> Serialize for Option<T>
/// where
/// T: Serialize,
/// {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// match *self {
/// Some(ref value) => serializer.serialize_some(value),
/// None => serializer.serialize_none(),
/// }
/// }
/// }
/// #
/// # fn main() {}
/// ```
///
fn serialize_some<T>(self, value: &T) -> Result<Self::Ok, Self::Error>
where
T: ?Sized + Serialize;
/// Serialize a `()` value.
///
/// ```edition2021
/// # use serde::Serializer;
/// #
/// # serde::__private_serialize!();
/// #
/// impl Serialize for () {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_unit()
/// }
/// }
/// ```
fn serialize_unit(self) -> Result<Self::Ok, Self::Error>;
/// Serialize a unit struct like `struct Unit` or `PhantomData<T>`.
///
/// A reasonable implementation would be to forward to `serialize_unit`.
///
/// ```edition2021
/// use serde::{Serialize, Serializer};
///
/// struct Nothing;
///
/// impl Serialize for Nothing {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_unit_struct("Nothing")
/// }
/// }
/// ```
fn serialize_unit_struct(self, name: &'static str) -> Result<Self::Ok, Self::Error>;
/// Serialize a unit variant like `E::A` in `enum E { A, B }`.
///
/// The `name` is the name of the enum, the `variant_index` is the index of
/// this variant within the enum, and the `variant` is the name of the
/// variant.
///
/// ```edition2021
/// use serde::{Serialize, Serializer};
///
/// enum E {
/// A,
/// B,
/// }
///
/// impl Serialize for E {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// match *self {
/// E::A => serializer.serialize_unit_variant("E", 0, "A"),
/// E::B => serializer.serialize_unit_variant("E", 1, "B"),
/// }
/// }
/// }
/// ```
fn serialize_unit_variant(
self,
name: &'static str,
variant_index: u32,
variant: &'static str,
) -> Result<Self::Ok, Self::Error>;
/// Serialize a newtype struct like `struct Millimeters(u8)`.
///
/// Serializers are encouraged to treat newtype structs as insignificant
/// wrappers around the data they contain. A reasonable implementation would
/// be to forward to `value.serialize(self)`.
///
/// ```edition2021
/// use serde::{Serialize, Serializer};
///
/// struct Millimeters(u8);
///
/// impl Serialize for Millimeters {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.serialize_newtype_struct("Millimeters", &self.0)
/// }
/// }
/// ```
fn serialize_newtype_struct<T>(
self,
name: &'static str,
value: &T,
) -> Result<Self::Ok, Self::Error>
where
T: ?Sized + Serialize;
/// Serialize a newtype variant like `E::N` in `enum E { N(u8) }`.
///
/// The `name` is the name of the enum, the `variant_index` is the index of
/// this variant within the enum, and the `variant` is the name of the
/// variant. The `value` is the data contained within this newtype variant.
///
/// ```edition2021
/// use serde::{Serialize, Serializer};
///
/// enum E {
/// M(String),
/// N(u8),
/// }
///
/// impl Serialize for E {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// match *self {
/// E::M(ref s) => serializer.serialize_newtype_variant("E", 0, "M", s),
/// E::N(n) => serializer.serialize_newtype_variant("E", 1, "N", &n),
/// }
/// }
/// }
/// ```
fn serialize_newtype_variant<T>(
self,
name: &'static str,
variant_index: u32,
variant: &'static str,
value: &T,
) -> Result<Self::Ok, Self::Error>
where
T: ?Sized + Serialize;
/// Begin to serialize a variably sized sequence. This call must be
/// followed by zero or more calls to `serialize_element`, then a call to
/// `end`.
///
/// The argument is the number of elements in the sequence, which may or may
/// not be computable before the sequence is iterated. Some serializers only
/// support sequences whose length is known up front.
///
/// ```edition2021
/// # use std::marker::PhantomData;
/// #
/// # struct Vec<T>(PhantomData<T>);
/// #
/// # impl<T> Vec<T> {
/// # fn len(&self) -> usize {
/// # unimplemented!()
/// # }
/// # }
/// #
/// # impl<'a, T> IntoIterator for &'a Vec<T> {
/// # type Item = &'a T;
/// # type IntoIter = Box<dyn Iterator<Item = &'a T>>;
/// #
/// # fn into_iter(self) -> Self::IntoIter {
/// # unimplemented!()
/// # }
/// # }
/// #
/// use serde::ser::{Serialize, SerializeSeq, Serializer};
///
/// impl<T> Serialize for Vec<T>
/// where
/// T: Serialize,
/// {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut seq = serializer.serialize_seq(Some(self.len()))?;
/// for element in self {
/// seq.serialize_element(element)?;
/// }
/// seq.end()
/// }
/// }
/// ```
fn serialize_seq(self, len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error>;
/// Begin to serialize a statically sized sequence whose length will be
/// known at deserialization time without looking at the serialized data.
/// This call must be followed by zero or more calls to `serialize_element`,
/// then a call to `end`.
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeTuple, Serializer};
///
/// # mod fool {
/// # trait Serialize {}
/// impl<A, B, C> Serialize for (A, B, C)
/// # {}
/// # }
/// #
/// # struct Tuple3<A, B, C>(A, B, C);
/// #
/// # impl<A, B, C> Serialize for Tuple3<A, B, C>
/// where
/// A: Serialize,
/// B: Serialize,
/// C: Serialize,
/// {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut tup = serializer.serialize_tuple(3)?;
/// tup.serialize_element(&self.0)?;
/// tup.serialize_element(&self.1)?;
/// tup.serialize_element(&self.2)?;
/// tup.end()
/// }
/// }
/// ```
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeTuple, Serializer};
///
/// const VRAM_SIZE: usize = 386;
/// struct Vram([u16; VRAM_SIZE]);
///
/// impl Serialize for Vram {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut seq = serializer.serialize_tuple(VRAM_SIZE)?;
/// for element in &self.0[..] {
/// seq.serialize_element(element)?;
/// }
/// seq.end()
/// }
/// }
/// ```
fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple, Self::Error>;
/// Begin to serialize a tuple struct like `struct Rgb(u8, u8, u8)`. This
/// call must be followed by zero or more calls to `serialize_field`, then a
/// call to `end`.
///
/// The `name` is the name of the tuple struct and the `len` is the number
/// of data fields that will be serialized.
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeTupleStruct, Serializer};
///
/// struct Rgb(u8, u8, u8);
///
/// impl Serialize for Rgb {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut ts = serializer.serialize_tuple_struct("Rgb", 3)?;
/// ts.serialize_field(&self.0)?;
/// ts.serialize_field(&self.1)?;
/// ts.serialize_field(&self.2)?;
/// ts.end()
/// }
/// }
/// ```
fn serialize_tuple_struct(
self,
name: &'static str,
len: usize,
) -> Result<Self::SerializeTupleStruct, Self::Error>;
/// Begin to serialize a tuple variant like `E::T` in `enum E { T(u8, u8)
/// }`. This call must be followed by zero or more calls to
/// `serialize_field`, then a call to `end`.
///
/// The `name` is the name of the enum, the `variant_index` is the index of
/// this variant within the enum, the `variant` is the name of the variant,
/// and the `len` is the number of data fields that will be serialized.
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeTupleVariant, Serializer};
///
/// enum E {
/// T(u8, u8),
/// U(String, u32, u32),
/// }
///
/// impl Serialize for E {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// match *self {
/// E::T(ref a, ref b) => {
/// let mut tv = serializer.serialize_tuple_variant("E", 0, "T", 2)?;
/// tv.serialize_field(a)?;
/// tv.serialize_field(b)?;
/// tv.end()
/// }
/// E::U(ref a, ref b, ref c) => {
/// let mut tv = serializer.serialize_tuple_variant("E", 1, "U", 3)?;
/// tv.serialize_field(a)?;
/// tv.serialize_field(b)?;
/// tv.serialize_field(c)?;
/// tv.end()
/// }
/// }
/// }
/// }
/// ```
fn serialize_tuple_variant(
self,
name: &'static str,
variant_index: u32,
variant: &'static str,
len: usize,
) -> Result<Self::SerializeTupleVariant, Self::Error>;
/// Begin to serialize a map. This call must be followed by zero or more
/// calls to `serialize_key` and `serialize_value`, then a call to `end`.
///
/// The argument is the number of elements in the map, which may or may not
/// be computable before the map is iterated. Some serializers only support
/// maps whose length is known up front.
///
/// ```edition2021
/// # use std::marker::PhantomData;
/// #
/// # struct HashMap<K, V>(PhantomData<K>, PhantomData<V>);
/// #
/// # impl<K, V> HashMap<K, V> {
/// # fn len(&self) -> usize {
/// # unimplemented!()
/// # }
/// # }
/// #
/// # impl<'a, K, V> IntoIterator for &'a HashMap<K, V> {
/// # type Item = (&'a K, &'a V);
/// # type IntoIter = Box<dyn Iterator<Item = (&'a K, &'a V)>>;
/// #
/// # fn into_iter(self) -> Self::IntoIter {
/// # unimplemented!()
/// # }
/// # }
/// #
/// use serde::ser::{Serialize, SerializeMap, Serializer};
///
/// impl<K, V> Serialize for HashMap<K, V>
/// where
/// K: Serialize,
/// V: Serialize,
/// {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut map = serializer.serialize_map(Some(self.len()))?;
/// for (k, v) in self {
/// map.serialize_entry(k, v)?;
/// }
/// map.end()
/// }
/// }
/// ```
fn serialize_map(self, len: Option<usize>) -> Result<Self::SerializeMap, Self::Error>;
/// Begin to serialize a struct like `struct Rgb { r: u8, g: u8, b: u8 }`.
/// This call must be followed by zero or more calls to `serialize_field`,
/// then a call to `end`.
///
/// The `name` is the name of the struct and the `len` is the number of
/// data fields that will be serialized. `len` does not include fields
/// which are skipped with [`SerializeStruct::skip_field`].
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeStruct, Serializer};
///
/// struct Rgb {
/// r: u8,
/// g: u8,
/// b: u8,
/// }
///
/// impl Serialize for Rgb {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut rgb = serializer.serialize_struct("Rgb", 3)?;
/// rgb.serialize_field("r", &self.r)?;
/// rgb.serialize_field("g", &self.g)?;
/// rgb.serialize_field("b", &self.b)?;
/// rgb.end()
/// }
/// }
/// ```
fn serialize_struct(
self,
name: &'static str,
len: usize,
) -> Result<Self::SerializeStruct, Self::Error>;
/// Begin to serialize a struct variant like `E::S` in `enum E { S { r: u8,
/// g: u8, b: u8 } }`. This call must be followed by zero or more calls to
/// `serialize_field`, then a call to `end`.
///
/// The `name` is the name of the enum, the `variant_index` is the index of
/// this variant within the enum, the `variant` is the name of the variant,
/// and the `len` is the number of data fields that will be serialized.
/// `len` does not include fields which are skipped with
/// [`SerializeStructVariant::skip_field`].
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeStructVariant, Serializer};
///
/// enum E {
/// S { r: u8, g: u8, b: u8 },
/// }
///
/// impl Serialize for E {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// match *self {
/// E::S {
/// ref r,
/// ref g,
/// ref b,
/// } => {
/// let mut sv = serializer.serialize_struct_variant("E", 0, "S", 3)?;
/// sv.serialize_field("r", r)?;
/// sv.serialize_field("g", g)?;
/// sv.serialize_field("b", b)?;
/// sv.end()
/// }
/// }
/// }
/// }
/// ```
fn serialize_struct_variant(
self,
name: &'static str,
variant_index: u32,
variant: &'static str,
len: usize,
) -> Result<Self::SerializeStructVariant, Self::Error>;
/// Collect an iterator as a sequence.
///
/// The default implementation serializes each item yielded by the iterator
/// using [`serialize_seq`]. Implementors should not need to override this
/// method.
///
/// ```edition2021
/// use serde::{Serialize, Serializer};
///
/// struct SecretlyOneHigher {
/// data: Vec<i32>,
/// }
///
/// impl Serialize for SecretlyOneHigher {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.collect_seq(self.data.iter().map(|x| x + 1))
/// }
/// }
/// ```
///
/// [`serialize_seq`]: #tymethod.serialize_seq
fn collect_seq<I>(self, iter: I) -> Result<Self::Ok, Self::Error>
where
I: IntoIterator,
<I as IntoIterator>::Item: Serialize,
{
let mut iter = iter.into_iter();
let mut serializer = tri!(self.serialize_seq(iterator_len_hint(&iter)));
tri!(iter.try_for_each(|item| serializer.serialize_element(&item)));
serializer.end()
}
/// Collect an iterator as a map.
///
/// The default implementation serializes each pair yielded by the iterator
/// using [`serialize_map`]. Implementors should not need to override this
/// method.
///
/// ```edition2021
/// use serde::{Serialize, Serializer};
/// use std::collections::BTreeSet;
///
/// struct MapToUnit {
/// keys: BTreeSet<i32>,
/// }
///
/// // Serializes as a map in which the values are all unit.
/// impl Serialize for MapToUnit {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.collect_map(self.keys.iter().map(|k| (k, ())))
/// }
/// }
/// ```
///
/// [`serialize_map`]: #tymethod.serialize_map
fn collect_map<K, V, I>(self, iter: I) -> Result<Self::Ok, Self::Error>
where
K: Serialize,
V: Serialize,
I: IntoIterator<Item = (K, V)>,
{
let mut iter = iter.into_iter();
let mut serializer = tri!(self.serialize_map(iterator_len_hint(&iter)));
tri!(iter.try_for_each(|(key, value)| serializer.serialize_entry(&key, &value)));
serializer.end()
}
/// Serialize a string produced by an implementation of `Display`.
///
/// The default implementation builds a heap-allocated [`String`] and
/// delegates to [`serialize_str`]. Serializers are encouraged to provide a
/// more efficient implementation if possible.
///
/// ```edition2021
/// # struct DateTime;
/// #
/// # impl DateTime {
/// # fn naive_local(&self) -> () { () }
/// # fn offset(&self) -> () { () }
/// # }
/// #
/// use serde::{Serialize, Serializer};
///
/// impl Serialize for DateTime {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.collect_str(&format_args!("{:?}{:?}", self.naive_local(), self.offset()))
/// }
/// }
/// ```
///
/// [`serialize_str`]: #tymethod.serialize_str
#[cfg(any(feature = "std", feature = "alloc"))]
fn collect_str<T>(self, value: &T) -> Result<Self::Ok, Self::Error>
where
T: ?Sized + Display,
{
self.serialize_str(&value.to_string())
}
/// Serialize a string produced by an implementation of `Display`.
///
/// Serializers that use `no_std` are required to provide an implementation
/// of this method. If no more sensible behavior is possible, the
/// implementation is expected to return an error.
///
/// ```edition2021
/// # struct DateTime;
/// #
/// # impl DateTime {
/// # fn naive_local(&self) -> () { () }
/// # fn offset(&self) -> () { () }
/// # }
/// #
/// use serde::{Serialize, Serializer};
///
/// impl Serialize for DateTime {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// serializer.collect_str(&format_args!("{:?}{:?}", self.naive_local(), self.offset()))
/// }
/// }
/// ```
#[cfg(not(any(feature = "std", feature = "alloc")))]
fn collect_str<T>(self, value: &T) -> Result<Self::Ok, Self::Error>
where
T: ?Sized + Display;
/// Determine whether `Serialize` implementations should serialize in
/// human-readable form.
///
/// Some types have a human-readable form that may be somewhat expensive to
/// construct, as well as a binary form that is compact and efficient.
/// Generally text-based formats like JSON and YAML will prefer to use the
/// human-readable one and binary formats like Postcard will prefer the
/// compact one.
///
/// ```edition2021
/// # use std::fmt::{self, Display};
/// #
/// # struct Timestamp;
/// #
/// # impl Timestamp {
/// # fn seconds_since_epoch(&self) -> u64 { unimplemented!() }
/// # }
/// #
/// # impl Display for Timestamp {
/// # fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
/// # unimplemented!()
/// # }
/// # }
/// #
/// use serde::{Serialize, Serializer};
///
/// impl Serialize for Timestamp {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// if serializer.is_human_readable() {
/// // Serialize to a human-readable string "2015-05-15T17:01:00Z".
/// self.to_string().serialize(serializer)
/// } else {
/// // Serialize to a compact binary representation.
/// self.seconds_since_epoch().serialize(serializer)
/// }
/// }
/// }
/// ```
///
/// The default implementation of this method returns `true`. Data formats
/// may override this to `false` to request a compact form for types that
/// support one. Note that modifying this method to change a format from
/// human-readable to compact or vice versa should be regarded as a breaking
/// change, as a value serialized in human-readable mode is not required to
/// deserialize from the same data in compact mode.
#[inline]
fn is_human_readable(&self) -> bool {
true
}
}
/// Returned from `Serializer::serialize_seq`.
///
/// # Example use
///
/// ```edition2021
/// # use std::marker::PhantomData;
/// #
/// # struct Vec<T>(PhantomData<T>);
/// #
/// # impl<T> Vec<T> {
/// # fn len(&self) -> usize {
/// # unimplemented!()
/// # }
/// # }
/// #
/// # impl<'a, T> IntoIterator for &'a Vec<T> {
/// # type Item = &'a T;
/// # type IntoIter = Box<dyn Iterator<Item = &'a T>>;
/// # fn into_iter(self) -> Self::IntoIter {
/// # unimplemented!()
/// # }
/// # }
/// #
/// use serde::ser::{Serialize, SerializeSeq, Serializer};
///
/// impl<T> Serialize for Vec<T>
/// where
/// T: Serialize,
/// {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut seq = serializer.serialize_seq(Some(self.len()))?;
/// for element in self {
/// seq.serialize_element(element)?;
/// }
/// seq.end()
/// }
/// }
/// ```
///
/// # Example implementation
///
/// The [example data format] presented on the website demonstrates an
/// implementation of `SerializeSeq` for a basic JSON data format.
///
pub trait SerializeSeq {
/// Must match the `Ok` type of our `Serializer`.
type Ok;
/// Must match the `Error` type of our `Serializer`.
type Error: Error;
/// Serialize a sequence element.
fn serialize_element<T>(&mut self, value: &T) -> Result<(), Self::Error>
where
T: ?Sized + Serialize;
/// Finish serializing a sequence.
fn end(self) -> Result<Self::Ok, Self::Error>;
}
/// Returned from `Serializer::serialize_tuple`.
///
/// # Example use
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeTuple, Serializer};
///
/// # mod fool {
/// # trait Serialize {}
/// impl<A, B, C> Serialize for (A, B, C)
/// # {}
/// # }
/// #
/// # struct Tuple3<A, B, C>(A, B, C);
/// #
/// # impl<A, B, C> Serialize for Tuple3<A, B, C>
/// where
/// A: Serialize,
/// B: Serialize,
/// C: Serialize,
/// {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut tup = serializer.serialize_tuple(3)?;
/// tup.serialize_element(&self.0)?;
/// tup.serialize_element(&self.1)?;
/// tup.serialize_element(&self.2)?;
/// tup.end()
/// }
/// }
/// ```
///
/// ```edition2021
/// # use std::marker::PhantomData;
/// #
/// # struct Array<T>(PhantomData<T>);
/// #
/// # impl<T> Array<T> {
/// # fn len(&self) -> usize {
/// # unimplemented!()
/// # }
/// # }
/// #
/// # impl<'a, T> IntoIterator for &'a Array<T> {
/// # type Item = &'a T;
/// # type IntoIter = Box<dyn Iterator<Item = &'a T>>;
/// # fn into_iter(self) -> Self::IntoIter {
/// # unimplemented!()
/// # }
/// # }
/// #
/// use serde::ser::{Serialize, SerializeTuple, Serializer};
///
/// # mod fool {
/// # trait Serialize {}
/// impl<T> Serialize for [T; 16]
/// # {}
/// # }
/// #
/// # impl<T> Serialize for Array<T>
/// where
/// T: Serialize,
/// {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut seq = serializer.serialize_tuple(16)?;
/// for element in self {
/// seq.serialize_element(element)?;
/// }
/// seq.end()
/// }
/// }
/// ```
///
/// # Example implementation
///
/// The [example data format] presented on the website demonstrates an
/// implementation of `SerializeTuple` for a basic JSON data format.
///
pub trait SerializeTuple {
/// Must match the `Ok` type of our `Serializer`.
type Ok;
/// Must match the `Error` type of our `Serializer`.
type Error: Error;
/// Serialize a tuple element.
fn serialize_element<T>(&mut self, value: &T) -> Result<(), Self::Error>
where
T: ?Sized + Serialize;
/// Finish serializing a tuple.
fn end(self) -> Result<Self::Ok, Self::Error>;
}
/// Returned from `Serializer::serialize_tuple_struct`.
///
/// # Example use
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeTupleStruct, Serializer};
///
/// struct Rgb(u8, u8, u8);
///
/// impl Serialize for Rgb {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut ts = serializer.serialize_tuple_struct("Rgb", 3)?;
/// ts.serialize_field(&self.0)?;
/// ts.serialize_field(&self.1)?;
/// ts.serialize_field(&self.2)?;
/// ts.end()
/// }
/// }
/// ```
///
/// # Example implementation
///
/// The [example data format] presented on the website demonstrates an
/// implementation of `SerializeTupleStruct` for a basic JSON data format.
///
pub trait SerializeTupleStruct {
/// Must match the `Ok` type of our `Serializer`.
type Ok;
/// Must match the `Error` type of our `Serializer`.
type Error: Error;
/// Serialize a tuple struct field.
fn serialize_field<T>(&mut self, value: &T) -> Result<(), Self::Error>
where
T: ?Sized + Serialize;
/// Finish serializing a tuple struct.
fn end(self) -> Result<Self::Ok, Self::Error>;
}
/// Returned from `Serializer::serialize_tuple_variant`.
///
/// # Example use
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeTupleVariant, Serializer};
///
/// enum E {
/// T(u8, u8),
/// U(String, u32, u32),
/// }
///
/// impl Serialize for E {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// match *self {
/// E::T(ref a, ref b) => {
/// let mut tv = serializer.serialize_tuple_variant("E", 0, "T", 2)?;
/// tv.serialize_field(a)?;
/// tv.serialize_field(b)?;
/// tv.end()
/// }
/// E::U(ref a, ref b, ref c) => {
/// let mut tv = serializer.serialize_tuple_variant("E", 1, "U", 3)?;
/// tv.serialize_field(a)?;
/// tv.serialize_field(b)?;
/// tv.serialize_field(c)?;
/// tv.end()
/// }
/// }
/// }
/// }
/// ```
///
/// # Example implementation
///
/// The [example data format] presented on the website demonstrates an
/// implementation of `SerializeTupleVariant` for a basic JSON data format.
///
pub trait SerializeTupleVariant {
/// Must match the `Ok` type of our `Serializer`.
type Ok;
/// Must match the `Error` type of our `Serializer`.
type Error: Error;
/// Serialize a tuple variant field.
fn serialize_field<T>(&mut self, value: &T) -> Result<(), Self::Error>
where
T: ?Sized + Serialize;
/// Finish serializing a tuple variant.
fn end(self) -> Result<Self::Ok, Self::Error>;
}
/// Returned from `Serializer::serialize_map`.
///
/// # Example use
///
/// ```edition2021
/// # use std::marker::PhantomData;
/// #
/// # struct HashMap<K, V>(PhantomData<K>, PhantomData<V>);
/// #
/// # impl<K, V> HashMap<K, V> {
/// # fn len(&self) -> usize {
/// # unimplemented!()
/// # }
/// # }
/// #
/// # impl<'a, K, V> IntoIterator for &'a HashMap<K, V> {
/// # type Item = (&'a K, &'a V);
/// # type IntoIter = Box<dyn Iterator<Item = (&'a K, &'a V)>>;
/// #
/// # fn into_iter(self) -> Self::IntoIter {
/// # unimplemented!()
/// # }
/// # }
/// #
/// use serde::ser::{Serialize, SerializeMap, Serializer};
///
/// impl<K, V> Serialize for HashMap<K, V>
/// where
/// K: Serialize,
/// V: Serialize,
/// {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut map = serializer.serialize_map(Some(self.len()))?;
/// for (k, v) in self {
/// map.serialize_entry(k, v)?;
/// }
/// map.end()
/// }
/// }
/// ```
///
/// # Example implementation
///
/// The [example data format] presented on the website demonstrates an
/// implementation of `SerializeMap` for a basic JSON data format.
///
pub trait SerializeMap {
/// Must match the `Ok` type of our `Serializer`.
type Ok;
/// Must match the `Error` type of our `Serializer`.
type Error: Error;
/// Serialize a map key.
///
/// If possible, `Serialize` implementations are encouraged to use
/// `serialize_entry` instead as it may be implemented more efficiently in
/// some formats compared to a pair of calls to `serialize_key` and
/// `serialize_value`.
fn serialize_key<T>(&mut self, key: &T) -> Result<(), Self::Error>
where
T: ?Sized + Serialize;
/// Serialize a map value.
///
/// # Panics
///
/// Calling `serialize_value` before `serialize_key` is incorrect and is
/// allowed to panic or produce bogus results.
fn serialize_value<T>(&mut self, value: &T) -> Result<(), Self::Error>
where
T: ?Sized + Serialize;
/// Serialize a map entry consisting of a key and a value.
///
/// Some [`Serialize`] types are not able to hold a key and value in memory
/// at the same time so `SerializeMap` implementations are required to
/// support [`serialize_key`] and [`serialize_value`] individually. The
/// `serialize_entry` method allows serializers to optimize for the case
/// where key and value are both available. [`Serialize`] implementations
/// are encouraged to use `serialize_entry` if possible.
///
/// The default implementation delegates to [`serialize_key`] and
/// [`serialize_value`]. This is appropriate for serializers that do not
/// care about performance or are not able to optimize `serialize_entry` any
/// better than this.
///
/// [`Serialize`]: ../trait.Serialize.html
/// [`serialize_key`]: #tymethod.serialize_key
/// [`serialize_value`]: #tymethod.serialize_value
fn serialize_entry<K, V>(&mut self, key: &K, value: &V) -> Result<(), Self::Error>
where
K: ?Sized + Serialize,
V: ?Sized + Serialize,
{
tri!(self.serialize_key(key));
self.serialize_value(value)
}
/// Finish serializing a map.
fn end(self) -> Result<Self::Ok, Self::Error>;
}
/// Returned from `Serializer::serialize_struct`.
///
/// # Example use
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeStruct, Serializer};
///
/// struct Rgb {
/// r: u8,
/// g: u8,
/// b: u8,
/// }
///
/// impl Serialize for Rgb {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// let mut rgb = serializer.serialize_struct("Rgb", 3)?;
/// rgb.serialize_field("r", &self.r)?;
/// rgb.serialize_field("g", &self.g)?;
/// rgb.serialize_field("b", &self.b)?;
/// rgb.end()
/// }
/// }
/// ```
///
/// # Example implementation
///
/// The [example data format] presented on the website demonstrates an
/// implementation of `SerializeStruct` for a basic JSON data format.
///
pub trait SerializeStruct {
/// Must match the `Ok` type of our `Serializer`.
type Ok;
/// Must match the `Error` type of our `Serializer`.
type Error: Error;
/// Serialize a struct field.
fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<(), Self::Error>
where
T: ?Sized + Serialize;
/// Indicate that a struct field has been skipped.
///
/// The default implementation does nothing.
#[inline]
fn skip_field(&mut self, key: &'static str) -> Result<(), Self::Error> {
let _ = key;
Ok(())
}
/// Finish serializing a struct.
fn end(self) -> Result<Self::Ok, Self::Error>;
}
/// Returned from `Serializer::serialize_struct_variant`.
///
/// # Example use
///
/// ```edition2021
/// use serde::ser::{Serialize, SerializeStructVariant, Serializer};
///
/// enum E {
/// S { r: u8, g: u8, b: u8 },
/// }
///
/// impl Serialize for E {
/// fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
/// where
/// S: Serializer,
/// {
/// match *self {
/// E::S {
/// ref r,
/// ref g,
/// ref b,
/// } => {
/// let mut sv = serializer.serialize_struct_variant("E", 0, "S", 3)?;
/// sv.serialize_field("r", r)?;
/// sv.serialize_field("g", g)?;
/// sv.serialize_field("b", b)?;
/// sv.end()
/// }
/// }
/// }
/// }
/// ```
///
/// # Example implementation
///
/// The [example data format] presented on the website demonstrates an
/// implementation of `SerializeStructVariant` for a basic JSON data format.
///
pub trait SerializeStructVariant {
/// Must match the `Ok` type of our `Serializer`.
type Ok;
/// Must match the `Error` type of our `Serializer`.
type Error: Error;
/// Serialize a struct variant field.
fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<(), Self::Error>
where
T: ?Sized + Serialize;
/// Indicate that a struct variant field has been skipped.
///
/// The default implementation does nothing.
#[inline]
fn skip_field(&mut self, key: &'static str) -> Result<(), Self::Error> {
let _ = key;
Ok(())
}
/// Finish serializing a struct variant.
fn end(self) -> Result<Self::Ok, Self::Error>;
}
fn iterator_len_hint<I>(iter: &I) -> Option<usize>
where
I: Iterator,
{
match iter.size_hint() {
(lo, Some(hi)) if lo == hi => Some(lo),
_ => None,
}
}