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//! Generic serialization framework. //! # For Developers who want to serialize objects //! Implement the `Serialize` trait for the type of objects you want to serialize. Call methods of //! the `serializer` object. For which methods to call and how to do so, look at the documentation //! of the `Serializer` trait. //! //! # For Serialization Format Developers //! Implement the `Serializer` trait for a structure that contains fields that enable it to write //! the serialization result to your target. When a method's argument is an object of type //! `Serialize`, you can either forward the serializer object (`self`) or create a new one, //! depending on the quirks of your format. #[cfg(feature = "std")] use std::error; #[cfg(not(feature = "std"))] use error; #[cfg(all(feature = "collections", not(feature = "std")))] use collections::String; pub mod impls; /////////////////////////////////////////////////////////////////////////////// /// `Error` is a trait that allows a `Serialize` to generically create a /// `Serializer` error. pub trait Error: Sized + error::Error { /// Raised when there is a general error when serializing a type. #[cfg(any(feature = "std", feature = "collections"))] fn custom<T: Into<String>>(msg: T) -> Self; /// Raised when there is a general error when serializing a type. #[cfg(all(not(feature = "std"), not(feature = "collections")))] fn custom<T: Into<&'static str>>(msg: T) -> Self; /// Raised when a `Serialize` was passed an incorrect value. fn invalid_value(msg: &str) -> Self { Error::custom(format!("invalid value: {}", msg)) } } /////////////////////////////////////////////////////////////////////////////// /// A trait that describes a type that can be serialized by a `Serializer`. pub trait Serialize { /// Serializes this value into this serializer. fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error> where S: Serializer; } /////////////////////////////////////////////////////////////////////////////// /// A trait that describes a type that can serialize a stream of values into the underlying format. /// /// # For `Serialize` Developers /// Non-aggrergate types like integers and strings can be serialized directly by calling the /// appropriate function. For Aggregate types there's an initial `serialize_T` method that yields /// a State object that you should not interact with. For each part of the aggregate there's a /// `serialize_T_elt` method that allows you to pass values or key/value pairs. The types of the /// values or the keys may change between calls, but the serialization format may not necessarily /// accept it. The `serialize_T_elt` method also takes a mutable reference to the state object. /// Make sure that you always use the same state object and only the state object that was returned /// by the `serialize_T` method. Finally, when your object is done, call the `serialize_T_end` /// method and pass the state object by value /// /// # For Serialization Format Developers /// If your format has different situations where it accepts different types, create a /// `Serializer` for each situation. You can create the sub-`Serializer` in one of the aggregate /// `serialize_T` methods and return it as a state object. Remember to also set the corresponding /// associated type `TState`. In the `serialize_T_elt` methods you will be given a mutable /// reference to that state. You do not need to do any additional checks for the correctness of the /// state object, as it is expected that the user will not modify it. Due to the generic nature /// of the `Serialize` impls, modifying the object is impossible on stable Rust. pub trait Serializer { /// The error type that can be returned if some error occurs during serialization. type Error: Error; /// A state object that is initialized by `serialize_seq`, passed to /// `serialize_seq_elt`, and consumed by `serialize_seq_end`. Use `()` if no /// state is required. type SeqState; /// A state object that is initialized by `serialize_tuple`, passed to /// `serialize_tuple_elt`, and consumed by `serialize_tuple_end`. Use `()` /// if no state is required. type TupleState; /// A state object that is initialized by `serialize_tuple_struct`, passed /// to `serialize_tuple_struct_elt`, and consumed by /// `serialize_tuple_struct_end`. Use `()` if no state is required. type TupleStructState; /// A state object that is initialized by `serialize_tuple_variant`, passed /// to `serialize_tuple_variant_elt`, and consumed by /// `serialize_tuple_variant_end`. Use `()` if no state is required. type TupleVariantState; /// A state object that is initialized by `serialize_map`, passed to /// `serialize_map_elt`, and consumed by `serialize_map_end`. Use `()` if no /// state is required. type MapState; /// A state object that is initialized by `serialize_struct`, passed to /// `serialize_struct_elt`, and consumed by `serialize_struct_end`. Use `()` /// if no state is required. type StructState; /// A state object that is initialized by `serialize_struct_variant`, passed /// to `serialize_struct_variant_elt`, and consumed by /// `serialize_struct_variant_end`. Use `()` if no state is required. type StructVariantState; /// Serializes a `bool` value. fn serialize_bool(&mut self, v: bool) -> Result<(), Self::Error>; /// Serializes an `isize` value. If the format does not differentiate /// between `isize` and `i64`, a reasonable implementation would be to cast /// the value to `i64` and forward to `serialize_i64`. fn serialize_isize(&mut self, v: isize) -> Result<(), Self::Error>; /// Serializes 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`. fn serialize_i8(&mut self, v: i8) -> Result<(), Self::Error>; /// Serializes 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`. fn serialize_i16(&mut self, v: i16) -> Result<(), Self::Error>; /// Serializes 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`. fn serialize_i32(&mut self, v: i32) -> Result<(), Self::Error>; /// Serializes an `i64` value. fn serialize_i64(&mut self, v: i64) -> Result<(), Self::Error>; /// Serializes a `usize` value. If the format does not differentiate between /// `usize` and `u64`, a reasonable implementation would be to cast the /// value to `u64` and forward to `serialize_u64`. fn serialize_usize(&mut self, v: usize) -> Result<(), Self::Error>; /// Serializes 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`. fn serialize_u8(&mut self, v: u8) -> Result<(), Self::Error>; /// Serializes 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`. fn serialize_u16(&mut self, v: u16) -> Result<(), Self::Error>; /// Serializes 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`. fn serialize_u32(&mut self, v: u32) -> Result<(), Self::Error>; /// `Serializes a `u64` value. fn serialize_u64(&mut self, v: u64) -> Result<(), Self::Error>; /// Serializes 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`. fn serialize_f32(&mut self, v: f32) -> Result<(), Self::Error>; /// Serializes an `f64` value. fn serialize_f64(&mut self, v: f64) -> Result<(), Self::Error>; /// Serializes a character. If the format does not support characters, /// it is reasonable to serialize it as a single element `str` or a `u32`. fn serialize_char(&mut self, v: char) -> Result<(), Self::Error>; /// Serializes a `&str`. fn serialize_str(&mut self, value: &str) -> Result<(), Self::Error>; /// 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: /// ```rust /// let mut state = try!(self.serialize_seq(value)); /// for b in value { /// try!(self.serialize_seq_elt(&mut state, b)); /// } /// self.serialize_seq_end(state) /// ``` fn serialize_bytes(&mut self, value: &[u8]) -> Result<(), Self::Error>; /// Serializes a `()` value. It's reasonable to just not serialize anything. fn serialize_unit(&mut self) -> Result<(), Self::Error>; /// Serializes a unit struct value. A reasonable implementation would be to /// forward to `serialize_unit`. fn serialize_unit_struct( &mut self, name: &'static str, ) -> Result<(), Self::Error>; /// Serializes a unit variant, otherwise known as a variant with no /// arguments. A reasonable implementation would be to forward to /// `serialize_unit`. fn serialize_unit_variant( &mut self, name: &'static str, variant_index: usize, variant: &'static str, ) -> Result<(), Self::Error>; /// Allows a tuple struct with a single element, also known as a newtype /// struct, to be more efficiently serialized than a tuple struct with /// multiple items. A reasonable implementation would be to forward to /// `serialize_tuple_struct` or to just serialize the inner value without wrapping. fn serialize_newtype_struct<T: Serialize>( &mut self, name: &'static str, value: T, ) -> Result<(), Self::Error>; /// Allows a variant with a single item to be more efficiently serialized /// than a variant with multiple items. A reasonable implementation would be /// to forward to `serialize_tuple_variant`. fn serialize_newtype_variant<T: Serialize>( &mut self, name: &'static str, variant_index: usize, variant: &'static str, value: T, ) -> Result<(), Self::Error>; /// Serializes a `None` value. fn serialize_none(&mut self) -> Result<(), Self::Error>; /// Serializes a `Some(...)` value. fn serialize_some<T: Serialize>( &mut self, value: T, ) -> Result<(), Self::Error>; /// Begins to serialize a sequence. This call must be followed by zero or /// more calls to `serialize_seq_elt`, then a call to `serialize_seq_end`. fn serialize_seq( &mut self, len: Option<usize>, ) -> Result<Self::SeqState, Self::Error>; /// Serializes a sequence element. Must have previously called /// `serialize_seq`. fn serialize_seq_elt<T: Serialize>( &mut self, state: &mut Self::SeqState, value: T, ) -> Result<(), Self::Error>; /// Finishes serializing a sequence. fn serialize_seq_end( &mut self, state: Self::SeqState, ) -> Result<(), Self::Error>; /// Begins to serialize a sequence whose length will be known at /// deserialization time. This call must be followed by zero or more calls /// to `serialize_seq_elt`, then a call to `serialize_seq_end`. A reasonable /// implementation would be to forward to `serialize_seq`. fn serialize_seq_fixed_size( &mut self, size: usize, ) -> Result<Self::SeqState, Self::Error>; /// Begins to serialize a tuple. This call must be followed by zero or more /// calls to `serialize_tuple_elt`, then a call to `serialize_tuple_end`. A /// reasonable implementation would be to forward to `serialize_seq`. fn serialize_tuple( &mut self, len: usize, ) -> Result<Self::TupleState, Self::Error>; /// Serializes a tuple element. Must have previously called /// `serialize_tuple`. fn serialize_tuple_elt<T: Serialize>( &mut self, state: &mut Self::TupleState, value: T, ) -> Result<(), Self::Error>; /// Finishes serializing a tuple. fn serialize_tuple_end( &mut self, state: Self::TupleState, ) -> Result<(), Self::Error>; /// Begins to serialize a tuple struct. This call must be followed by zero /// or more calls to `serialize_tuple_struct_elt`, then a call to /// `serialize_tuple_struct_end`. A reasonable implementation would be to /// forward to `serialize_tuple`. fn serialize_tuple_struct( &mut self, name: &'static str, len: usize, ) -> Result<Self::TupleStructState, Self::Error>; /// Serializes a tuple struct element. Must have previously called /// `serialize_tuple_struct`. fn serialize_tuple_struct_elt<T: Serialize>( &mut self, state: &mut Self::TupleStructState, value: T, ) -> Result<(), Self::Error>; /// Finishes serializing a tuple struct. fn serialize_tuple_struct_end( &mut self, state: Self::TupleStructState, ) -> Result<(), Self::Error>; /// Begins to serialize a tuple variant. This call must be followed by zero /// or more calls to `serialize_tuple_variant_elt`, then a call to /// `serialize_tuple_variant_end`. A reasonable implementation would be to /// forward to `serialize_tuple_struct`. fn serialize_tuple_variant( &mut self, name: &'static str, variant_index: usize, variant: &'static str, len: usize, ) -> Result<Self::TupleVariantState, Self::Error>; /// Serializes a tuple variant element. Must have previously called /// `serialize_tuple_variant`. fn serialize_tuple_variant_elt<T: Serialize>( &mut self, state: &mut Self::TupleVariantState, value: T, ) -> Result<(), Self::Error>; /// Finishes serializing a tuple variant. fn serialize_tuple_variant_end( &mut self, state: Self::TupleVariantState, ) -> Result<(), Self::Error>; /// Begins to serialize a map. This call must be followed by zero or more /// calls to `serialize_map_key` and `serialize_map_value`, then a call to /// `serialize_map_end`. fn serialize_map( &mut self, len: Option<usize>, ) -> Result<Self::MapState, Self::Error>; /// Serialize a map key. Must have previously called `serialize_map`. fn serialize_map_key<T: Serialize>( &mut self, state: &mut Self::MapState, key: T ) -> Result<(), Self::Error>; /// Serialize a map value. Must have previously called `serialize_map`. fn serialize_map_value<T: Serialize>( &mut self, state: &mut Self::MapState, value: T ) -> Result<(), Self::Error>; /// Finishes serializing a map. fn serialize_map_end( &mut self, state: Self::MapState, ) -> Result<(), Self::Error>; /// Begins to serialize a struct. This call must be followed by zero or more /// calls to `serialize_struct_elt`, then a call to `serialize_struct_end`. fn serialize_struct( &mut self, name: &'static str, len: usize, ) -> Result<Self::StructState, Self::Error>; /// Serializes a struct field. Must have previously called /// `serialize_struct`. fn serialize_struct_elt<V: Serialize>( &mut self, state: &mut Self::StructState, key: &'static str, value: V, ) -> Result<(), Self::Error>; /// Finishes serializing a struct. fn serialize_struct_end( &mut self, state: Self::StructState, ) -> Result<(), Self::Error>; /// Begins to serialize a struct variant. This call must be followed by zero /// or more calls to `serialize_struct_variant_elt`, then a call to /// `serialize_struct_variant_end`. fn serialize_struct_variant( &mut self, name: &'static str, variant_index: usize, variant: &'static str, len: usize, ) -> Result<Self::StructVariantState, Self::Error>; /// Serialize a struct variant element. Must have previously called /// `serialize_struct_variant`. fn serialize_struct_variant_elt<V: Serialize>( &mut self, state: &mut Self::StructVariantState, key: &'static str, value: V, ) -> Result<(), Self::Error>; /// Finishes serializing a struct variant. fn serialize_struct_variant_end( &mut self, state: Self::StructVariantState, ) -> Result<(), Self::Error>; }