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//! JSON is an ubiquitous format used in many applications.
//! There is no single way of storing JSON values depending on the context,
//! sometimes leading some applications to use multiples representations of JSON values in the same place.
//! This can cause a problem for JSON processing libraries that should not care about the actual internal representation of JSON values,
//! but are forced to stick to a particular format,
//! leading to unwanted and costly conversions between the different formats.
//!
//! This crate abstracts the JSON data structures defined in different library dealing with JSON such as `json`, `serde_json`, etc.
//! The goal is to remove hard dependencies to these libraries when possible,
//! and allow downstream users to choose its preferred library.
//! It basically defines a trait `Json` and a `ValueRef` type abstracting away the implementation details.
//!
//! The `Json` trait must be implemented by the JSON value type
//! and defines what opaque types are used to represent each component of a JSON value.
//! It also provides a function returning the value as a `ValueRef` enum type.
//! Its simplified definition is as follows:
//! ```rust
//! # pub struct ValueRef<'a, T>(std::marker::PhantomData<&'a T>);
//! /// JSON model.
//! pub trait Json: Sized + 'static {
//! /// Literal number type.
//! type Number;
//!
//! /// String type.
//! type String;
//!
//! /// Array type.
//! type Array;
//!
//! /// Object key type.
//! type Key;
//!
//! /// Object type.
//! type Object;
//!
//! /// Returns a reference to this value as a `ValueRef`.
//! fn value(&self) -> ValueRef<'_, Self>;
//!
//! /// Metadata type attached to each value.
//! type MetaData;
//!
//! fn metadata(&self) -> &Self::MetaData;
//! }
//! ```
//!
//! The `ValueRef` exposes the structure of a reference to a JSON value:
//! ```rust
//! # use generic_json::Json;
//! pub enum ValueRef<'v, T: Json> {
//! Null,
//! Bool(bool),
//! Number(&'v T::Number),
//! String(&'v T::String),
//! Array(&'v T::Array),
//! Object(&'v T::Object)
//! }
//! ```
//!
//! In the same way, this crate also defines a `ValueMut` type for mutable references.
//! This allows each implementor to have their own inner representation of values while allowing interoperability.
//!
//! ## Trait aliases
//!
//! When the `nightly` feature is enabled,
//! this crate also defines some trait aliases that define common
//! requirements for JSON data types.
//! For instance the `JsonClone` trait alias ensures that every component
//! of the JSON value implements `Clone`.
#![cfg_attr(feature = "nightly", feature(trait_alias))]
#![feature(generic_associated_types)]
use cc_traits::{Get, Iter, Keyed, Len, MapIter};
use std::{hash::Hash, ops::Deref};
mod impls;
mod number;
mod reference;
mod value;
#[cfg(feature = "nightly")]
mod aliases;
pub use number::*;
pub use reference::*;
pub use value::*;
#[cfg(feature = "nightly")]
pub use aliases::*;
/// JSON object key.
pub trait Key<M>: Eq + Hash + Deref<Target = str> {
fn metadata(&self) -> &M;
}
impl Key<()> for String {
fn metadata(&self) -> &() {
&()
}
}
#[cfg(feature = "smallkey")]
impl<A: smallvec::Array<Item = u8>> Key<()> for smallstr::SmallString<A> {
fn metadata(&self) -> &() {
&()
}
}
/// JSON value attached to some metadata.
pub trait Json: Sized + Eq {
/// Metadata type attached to each value.
///
/// The metadata should be ignored during comparison/ordering/hashing of JSON values.
type MetaData: Clone;
/// Literal number type.
type Number: Number;
/// String type.
type String: Eq + Deref<Target = str> + for<'a> From<&'a str>;
/// Array type.
type Array: Get<usize, Item = Self> + Len + Iter + IntoIterator<Item = Self>;
/// Object key type.
type Key: Key<Self::MetaData>;
/// Object type.
type Object: Keyed<Key = Self::Key, Item = Self>
+ Len
+ for<'a> Get<&'a str>
+ MapIter
+ IntoIterator<Item = (Self::Key, Self)>;
/// Returns a reference to the actual JSON value (without the metadata).
fn as_value_ref(&self) -> ValueRef<'_, Self>;
/// Returns a mutable reference to the actual JSON value (without the metadata).
fn as_value_mut(&mut self) -> ValueMut<'_, Self>;
/// Transforms this JSON value into a `Value` and `MetaData`.
fn into_parts(self) -> (Value<Self>, Self::MetaData);
/// Transforms this JSON value into a `Value`.
fn into_value(self) -> Value<Self> {
self.into_parts().0
}
/// Returns a reference to the metadata associated to the JSON value.
fn metadata(&self) -> &Self::MetaData;
/// Returns a pair containing a reference to the JSON value and a reference to its metadata.
fn as_pair(&self) -> (ValueRef<'_, Self>, &Self::MetaData) {
(self.as_value_ref(), self.metadata())
}
/// Returns a pair containing a mutable reference to the JSON value and a reference to its metadata.
fn as_pair_mut(&mut self) -> (ValueMut<'_, Self>, &Self::MetaData);
/// Returns `true` if the value is a `Null`. Returns `false` otherwise.
fn is_null(&self) -> bool {
self.as_value_ref().is_null()
}
/// Checks if the value is an empty array.
#[inline]
fn is_empty_array(&self) -> bool {
match self.as_value_ref() {
ValueRef::Array(a) => a.is_empty(),
_ => false,
}
}
/// Checks if the value is an empty object.
#[inline]
fn is_empty_object(&self) -> bool {
match self.as_value_ref() {
ValueRef::Array(a) => a.is_empty(),
_ => false,
}
}
/// Checks if the value is an empty array or empty object.
#[inline]
fn is_empty_array_or_object(&self) -> bool {
match self.as_value_ref() {
ValueRef::Array(a) => a.is_empty(),
ValueRef::Object(o) => o.is_empty(),
_ => false,
}
}
/// Returns `true` if the value is a boolean. Returns `false` otherwise.
///
/// For any value on which `is_bool` returns `true`,
/// [`as_bool`](Self::as_bool()) is guaranteed to return the boolean value.
fn is_bool(&self) -> bool {
self.as_value_ref().is_bool()
}
/// Returns `true` if the value is a number. Returns `false` otherwise.
///
/// For any value on which `is_number` returns `true`,
/// [`as_number`](Self::as_number()) is guaranteed to return the number value.
fn is_number(&self) -> bool {
self.as_value_ref().is_number()
}
/// Returns `true` if the value is a string.
/// Returns `false` otherwise.
///
/// For any value on which `is_string` returns `true`,
/// [`as_str`](Self::as_str()) is guaranteed to return the string value.
fn is_string(&self) -> bool {
self.as_value_ref().is_string()
}
/// Returns `true` if the value is an array.
/// Returns `false` otherwise.
///
/// For any value on which `is_array` returns `true`,
/// [`as_array`](Self::as_array()) is guaranteed to return the array value.
fn is_array(&self) -> bool {
self.as_value_ref().is_array()
}
/// Returns `true` if the value is an object.
/// Returns `false` otherwise.
///
/// For any value on which `is_object` returns `true`,
/// [`as_object`](Self::as_object()) is guaranteed to return the object value.
fn is_object(&self) -> bool {
self.as_value_ref().is_object()
}
/// If the value is a boolean, returns the associated `bool`.
/// Returns `None` otherwise.
fn as_bool(&self) -> Option<bool> {
self.as_value_ref().as_bool()
}
/// If the value is a number, returns a reference to it.
/// Returns `None` otherwise.
fn as_number(&self) -> Option<&Self::Number> {
self.as_value_ref().as_number()
}
/// Returns this number as an `u32` if it can be exactly represented as such.
fn as_u32(&self) -> Option<u32> {
self.as_value_ref().as_u32()
}
/// Returns this number as an `u64` if it can be exactly represented as such.
fn as_u64(&self) -> Option<u64> {
self.as_value_ref().as_u64()
}
/// Returns this number as an `i32` if it can be exactly represented as such.
fn as_i32(&self) -> Option<i32> {
self.as_value_ref().as_i32()
}
/// Returns this number as an `i64` if it can be exactly represented as such.
fn as_i64(&self) -> Option<i64> {
self.as_value_ref().as_i64()
}
/// Returns this number as an `f32` if it can be exactly represented as such.
fn as_f32(&self) -> Option<f32> {
self.as_value_ref().as_f32()
}
/// Returns this number as an `f32` if it is a number, potentially losing precision in the process.
fn as_f32_lossy(&self) -> Option<f32> {
self.as_value_ref().as_f32_lossy()
}
/// Returns this number as an `f64` if it can be exactly represented as such.
fn as_f64(&self) -> Option<f64> {
self.as_value_ref().as_f64()
}
/// Returns this number as an `f64` if it is a number, potentially losing precision in the process.
fn as_f64_lossy(&self) -> Option<f64> {
self.as_value_ref().as_f64_lossy()
}
/// If the value is a string, returns its associated [`str`].
/// Returns `None` otherwise.
fn as_str(&self) -> Option<&str> {
self.as_value_ref().into_str()
}
/// If the value is an array, returns a reference to it.
/// Returns `None` otherwise.
fn as_array(&self) -> Option<&Self::Array> {
self.as_value_ref().as_array()
}
/// If the value is an array, returns a mutable reference to it.
/// Returns `None` otherwise.
fn as_array_mut(&mut self) -> Option<&mut Self::Array> {
self.as_value_mut().into_array_mut()
}
/// If the value is an object, returns a reference to it.
/// Returns `None` otherwise.
fn as_object(&self) -> Option<&Self::Object> {
self.as_value_ref().as_object()
}
/// If the value is an object, returns a mutable reference to it.
/// Returns `None` otherwise.
fn as_object_mut(&mut self) -> Option<&mut Self::Object> {
self.as_value_mut().into_object_mut()
}
}
impl<J: Json> From<J> for Value<J> {
fn from(j: J) -> Value<J> {
j.into_value()
}
}
/// Constructible JSON type.
pub trait JsonNew: Json {
/// Creates a new "meta value" from a `Value` and its associated metadata.
fn new(value: Value<Self>, metadata: Self::MetaData) -> Self;
/// Creates a new object key.
fn new_key(key: &str, metadata: Self::MetaData) -> Self::Key;
/// Creates a new `null` value.
fn null(metadata: Self::MetaData) -> Self {
Self::new(Value::Null, metadata)
}
/// Creates a new boolean value.
fn boolean(b: bool, metadata: Self::MetaData) -> Self {
Self::new(Value::Boolean(b), metadata)
}
/// Creates a new number value.
fn number(n: Self::Number, metadata: Self::MetaData) -> Self {
Self::new(Value::Number(n), metadata)
}
/// Creates a new string value.
fn string(s: Self::String, metadata: Self::MetaData) -> Self {
Self::new(Value::String(s), metadata)
}
/// Creates a new array value.
fn array(a: Self::Array, metadata: Self::MetaData) -> Self {
Self::new(Value::Array(a), metadata)
}
/// Creates a new empty object value.
fn empty_array(metadata: Self::MetaData) -> Self
where
Self::Array: Default,
{
Self::array(Self::Array::default(), metadata)
}
/// Creates a new object value.
fn object(o: Self::Object, metadata: Self::MetaData) -> Self {
Self::new(Value::Object(o), metadata)
}
/// Creates a new empty object value.
fn empty_object(metadata: Self::MetaData) -> Self
where
Self::Object: Default,
{
Self::object(Self::Object::default(), metadata)
}
}