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|
//! Decoding: reading protocol values from a byte stream.
use crate::context::Context;
use std::{io::Read, sync::Arc};
use crate::{DEFAULT_BUFFER_LEN, codec::error::Result};
macro_rules! impl_decode {
($type: ty) => {
impl<Data> Decode<Data> for $type {
// decode number using big endian
fn decode(reader: &mut dyn Read, _: &Context<Data>) -> Result<Self>
where
Self: Sized,
{
const BYTES: usize = (<$type>::BITS / 8) as usize;
let mut bytes = [0; BYTES];
reader.read_exact(&mut bytes)?;
Ok(<$type>::from_be_bytes(bytes))
}
}
};
}
/// Read a value from a byte stream
pub trait Decode<Data> {
fn decode(reader: &mut dyn Read, ctx: &Context<Data>) -> Result<Self>
where
Self: Sized;
}
impl<Data> Decode<Data> for bool {
fn decode(reader: &mut dyn Read, _: &Context<Data>) -> Result<Self>
where
Self: Sized,
{
let mut byte = [0_u8];
reader.read_exact(&mut byte)?;
Ok(byte[0] != 0)
}
}
impl<Data, T: Decode<Data>> Decode<Data> for Option<T> {
fn decode(reader: &mut dyn Read, ctx: &Context<Data>) -> Result<Self>
where
Self: Sized,
{
let tag = u8::decode(reader, ctx)?;
if tag == 0 {
Ok(None)
} else {
Ok(Some(T::decode(reader, ctx)?))
}
}
}
impl<Data, T: Decode<Data>> Decode<Data> for Vec<T> {
fn decode(reader: &mut dyn Read, ctx: &Context<Data>) -> Result<Self>
where
Self: Sized,
{
let len = usize::decode(reader, ctx)?;
let mut vec = Vec::with_capacity(len);
for _ in 0..len {
vec.push(T::decode(reader, ctx)?);
}
Ok(vec)
}
}
impl<Data> Decode<Data> for String {
fn decode(reader: &mut dyn Read, _: &Context<Data>) -> Result<Self>
where
Self: Sized,
{
let mut bytes: Vec<u8> = Vec::new();
reader.read_to_end(&mut bytes)?;
Ok(String::from_utf8_lossy(&bytes).to_string())
}
}
impl<Data> Decode<Data> for Arc<[u8]> {
fn decode(reader: &mut dyn Read, _: &Context<Data>) -> Result<Self> {
let mut buf = Vec::with_capacity(DEFAULT_BUFFER_LEN);
reader.read_to_end(&mut buf)?;
Ok(Arc::<[u8]>::from(buf.into_boxed_slice()))
}
}
impl<Data, const S: usize> Decode<Data> for [u8; S] {
fn decode(reader: &mut dyn Read, _: &Context<Data>) -> Result<Self>
where
Self: Sized,
{
let mut slice = [0_u8; S];
reader.read_exact(&mut slice)?;
Ok(slice)
}
}
impl_decode!(u8);
impl_decode!(u16);
impl_decode!(u32);
impl_decode!(u64);
impl_decode!(u128);
impl_decode!(usize);
impl_decode!(i8);
impl_decode!(i16);
impl_decode!(i32);
impl_decode!(i64);
impl_decode!(i128);
impl_decode!(isize);
impl<Data> Decode<Data> for f64 {
fn decode(reader: &mut dyn Read, ctx: &Context<Data>) -> Result<Self>
where
Self: Sized,
{
let bits = u64::decode(reader, ctx)?;
let value = f64::from_bits(bits);
Ok(value)
}
}
impl<Data> Decode<Data> for f32 {
fn decode(reader: &mut dyn Read, ctx: &Context<Data>) -> Result<Self>
where
Self: Sized,
{
let bits = u32::decode(reader, ctx)?;
let value = f32::from_bits(bits);
Ok(value)
}
}
|
