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use crate::{hint, Error, Settings};
use std::io::prelude::*;
use std::io;
/// A value which can be read and written.
///
/// All of the expected standard Rust types implement this.
///
/// Types that implement `Parcel` include (not exhaustive):
///
/// * The Rust primitive types
/// * `u8`, `i8`, `u16`, `i16` ... `u64`
/// * `bool`, `char`
/// * `f32`, `f64`
/// * Tuples
/// * `(T1) where T1: Parcel`
/// * `(T1, T2) where T1: Parcel, T2: Parcel`
/// * `(T1, T2, ... Tn) where T1: Parcel, T2: Parcel, ... Tn: Parcel`
/// * Arrays
/// * `[T; 0] where T: Parcel`
/// * `[T; 1] where T: Parcel`
/// * `[T; 2] where T: Parcel`
/// * `[T; 32] where T: Parcel`
/// * `[T; 40] where T: Parcel`
/// * `[T; 42] where T: Parcel`
/// * ...
/// * `[T; 64] where T: Parcel`
/// * ...
/// * `[T; 1024] where T: Parcel`
/// * `String`
/// * `Option<T: Parcel>`
/// * `Box<T: Parcel>`
/// * Smart pointers
/// * `std::rc::Rc`
/// * `std::sync::Arc`
/// * `std::collections`
/// * `Vec<T: Parcel>`
/// * `VecDeque<T: Parcel>`
/// * `HashMap<T: Parcel>`
/// * `BTreeMap<T: Parcel>`
pub trait Parcel : Sized
{
/// The textual name of the type.
const TYPE_NAME: &'static str;
/// Reads a new item with a fresh set of hints.
///
/// Blocks until a value is received.
fn read(read: &mut dyn Read,
settings: &Settings) -> Result<Self, Error> {
Self::read_field(read, settings, &mut hint::Hints::default())
}
/// Reads a value from a stream.
///
/// Parameters:
///
/// * `hints` - a list of hints accessible by the current
/// parcel chain only.
///
/// Blocks until a value is received.
fn read_field(read: &mut dyn Read,
settings: &Settings,
hints: &mut hint::Hints) -> Result<Self, Error>;
/// Writes a value to a stream.
fn write(&self, write: &mut dyn Write,
settings: &Settings) -> Result<(), Error> {
self.write_field(write, settings, &mut hint::Hints::default())
}
/// Writes a value to a stream.
fn write_field(&self, write: &mut dyn Write,
settings: &Settings,
hints: &mut hint::Hints) -> Result<(), Error>;
/// Convers the value into a byte stream that implements `std::io::Read`.
fn into_stream(self, settings: &Settings)
-> Result<io::Cursor<Vec<u8>>, Error> {
self.raw_bytes(settings).map(io::Cursor::new)
}
/// Parses a new value from its raw byte representation.
///
/// Returns `Err` if the bytes represent an invalid value.
fn from_raw_bytes(bytes: &[u8],
settings: &Settings) -> Result<Self, Error> {
let mut hints = hint::Hints::default();
Self::field_from_raw_bytes(bytes, settings, &mut hints)
}
/// Parses a new value from its raw byte representation.
///
/// Returns `Err` if the bytes represent an invalid value.
fn field_from_raw_bytes(bytes: &[u8],
settings: &Settings,
hints: &mut hint::Hints) -> Result<Self, Error> {
let mut buffer = ::std::io::Cursor::new(bytes);
Self::read_field(&mut buffer, settings, hints)
}
/// Gets the raw byte representation of the value.
fn raw_bytes(&self, settings: &Settings) -> Result<Vec<u8>, Error> {
self.raw_bytes_field(settings, &mut hint::Hints::default())
}
/// Gets the raw bytes of this type as a field of a larger type.
fn raw_bytes_field(&self,
settings: &Settings,
hints: &mut hint::Hints) -> Result<Vec<u8>, Error> {
let mut buffer = io::Cursor::new(Vec::new());
self.write_field(&mut buffer, settings, hints)?;
Ok(buffer.into_inner())
}
/// Gets the name of the type; `Parcel::TYPE_NAME`.
fn type_name(&self) -> &'static str { Self::TYPE_NAME }
}