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//! Decoder-based structs and traits.
mod decoder;
mod impl_core;
mod impl_tuples;
mod impls;
use self::read::{BorrowReader, Reader};
use crate::{
config::{Config, InternalLimitConfig},
error::DecodeError,
utils::Sealed,
};
pub mod read;
pub use self::decoder::DecoderImpl;
/// Trait that makes a type able to be decoded, akin to serde's `DeserializeOwned` trait.
///
/// This trait should be implemented for types which do not have references to data in the reader. For types that contain e.g. `&str` and `&[u8]`, implement [BorrowDecode] instead.
///
/// Whenever you implement `Decode` for your type, the base trait `BorrowDecode` is automatically implemented.
///
/// This trait will be automatically implemented if you enable the `derive` feature and add `#[derive(bincode::Decode)]` to your type. Note that if the type contains any lifetimes, `BorrowDecode` will be implemented instead.
///
/// # Implementing this trait manually
///
/// If you want to implement this trait for your type, the easiest way is to add a `#[derive(bincode::Decode)]`, build and check your `target/generated/bincode/` folder. This should generate a `<Struct name>_Decode.rs` file.
///
/// For this struct:
///
/// ```
/// struct Entity {
/// pub x: f32,
/// pub y: f32,
/// }
/// ```
///
/// It will look something like:
///
/// ```
/// # struct Entity {
/// # pub x: f32,
/// # pub y: f32,
/// # }
/// impl bincode::Decode for Entity {
/// fn decode<D: bincode::de::Decoder>(
/// decoder: &mut D,
/// ) -> core::result::Result<Self, bincode::error::DecodeError> {
/// Ok(Self {
/// x: bincode::Decode::decode(decoder)?,
/// y: bincode::Decode::decode(decoder)?,
/// })
/// }
/// }
/// impl<'de> bincode::BorrowDecode<'de> for Entity {
/// fn borrow_decode<D: bincode::de::BorrowDecoder<'de>>(
/// decoder: &mut D,
/// ) -> core::result::Result<Self, bincode::error::DecodeError> {
/// Ok(Self {
/// x: bincode::BorrowDecode::borrow_decode(decoder)?,
/// y: bincode::BorrowDecode::borrow_decode(decoder)?,
/// })
/// }
/// }
/// ```
///
/// From here you can add/remove fields, or add custom logic.
///
/// To get specific integer types, you can use:
/// ```
/// # struct Foo;
/// # impl bincode::Decode for Foo {
/// # fn decode<D: bincode::de::Decoder>(
/// # decoder: &mut D,
/// # ) -> core::result::Result<Self, bincode::error::DecodeError> {
/// let x: u8 = bincode::Decode::decode(decoder)?;
/// let x = <u8 as bincode::Decode>::decode(decoder)?;
/// # Ok(Foo)
/// # }
/// # }
/// # bincode::impl_borrow_decode!(Foo);
/// ```
pub trait Decode: Sized {
/// Attempt to decode this type with the given [Decode].
fn decode<D: Decoder>(decoder: &mut D) -> Result<Self, DecodeError>;
}
/// Trait that makes a type able to be decoded, akin to serde's `Deserialize` trait.
///
/// This trait should be implemented for types that contain borrowed data, like `&str` and `&[u8]`. If your type does not have borrowed data, consider implementing [Decode] instead.
///
/// This trait will be automatically implemented if you enable the `derive` feature and add `#[derive(bincode::Decode)]` to a type with a lifetime.
pub trait BorrowDecode<'de>: Sized {
/// Attempt to decode this type with the given [BorrowDecode].
fn borrow_decode<D: BorrowDecoder<'de>>(decoder: &mut D) -> Result<Self, DecodeError>;
}
/// Helper macro to implement `BorrowDecode` for any type that implements `Decode`.
#[macro_export]
macro_rules! impl_borrow_decode {
($ty:ty) => {
impl<'de> $crate::BorrowDecode<'de> for $ty {
fn borrow_decode<D: $crate::de::BorrowDecoder<'de>>(
decoder: &mut D,
) -> core::result::Result<Self, $crate::error::DecodeError> {
$crate::Decode::decode(decoder)
}
}
};
}
/// Any source that can decode basic types. This type is most notably implemented for [Decoder].
pub trait Decoder: Sealed {
/// The concrete [Reader] type
type R: Reader;
/// The concrete [Config] type
type C: Config;
/// Returns a mutable reference to the reader
fn reader(&mut self) -> &mut Self::R;
/// Returns a reference to the config
fn config(&self) -> &Self::C;
/// Claim that `n` bytes are going to be read from the decoder.
/// This can be used to validate `Configuration::Limit<N>()`.
fn claim_bytes_read(&mut self, n: usize) -> Result<(), DecodeError>;
/// Claim that we're going to read a container which contains `len` entries of `T`.
/// This will correctly handle overflowing if `len * size_of::<T>() > usize::max_value`
fn claim_container_read<T>(&mut self, len: usize) -> Result<(), DecodeError> {
if <Self::C as InternalLimitConfig>::LIMIT.is_some() {
match len.checked_mul(core::mem::size_of::<T>()) {
Some(val) => self.claim_bytes_read(val),
None => Err(DecodeError::LimitExceeded),
}
} else {
Ok(())
}
}
/// Notify the decoder that `n` bytes are being reclaimed.
///
/// When decoding container types, a typical implementation would claim to read `len * size_of::<T>()` bytes.
/// This is to ensure that bincode won't allocate several GB of memory while constructing the container.
///
/// Because the implementation claims `len * size_of::<T>()`, but then has to decode each `T`, this would be marked
/// as double. This function allows us to un-claim each `T` that gets decoded.
///
/// We cannot check if `len * size_of::<T>()` is valid without claiming it, because this would mean that if you have
/// a nested container (e.g. `Vec<Vec<T>>`), it does not know how much memory is already claimed, and could easily
/// allocate much more than the user intends.
/// ```
/// # use bincode::de::{Decode, Decoder};
/// # use bincode::error::DecodeError;
/// # struct Container<T>(Vec<T>);
/// # impl<T> Container<T> {
/// # fn with_capacity(cap: usize) -> Self {
/// # Self(Vec::with_capacity(cap))
/// # }
/// #
/// # fn push(&mut self, t: T) {
/// # self.0.push(t);
/// # }
/// # }
/// impl<T: Decode> Decode for Container<T> {
/// fn decode<D: Decoder>(decoder: &mut D) -> Result<Self, DecodeError> {
/// let len = u64::decode(decoder)?;
/// let len: usize = len.try_into().map_err(|_| DecodeError::OutsideUsizeRange(len))?;
/// // Make sure we don't allocate too much memory
/// decoder.claim_bytes_read(len * core::mem::size_of::<T>());
///
/// let mut result = Container::with_capacity(len);
/// for _ in 0..len {
/// // un-claim the memory
/// decoder.unclaim_bytes_read(core::mem::size_of::<T>());
/// result.push(T::decode(decoder)?)
/// }
/// Ok(result)
/// }
/// }
/// impl<'de, T: bincode::BorrowDecode<'de>> bincode::BorrowDecode<'de> for Container<T> {
/// fn borrow_decode<D: bincode::de::BorrowDecoder<'de>>(
/// decoder: &mut D,
/// ) -> core::result::Result<Self, bincode::error::DecodeError> {
/// let len = u64::borrow_decode(decoder)?;
/// let len: usize = len.try_into().map_err(|_| DecodeError::OutsideUsizeRange(len))?;
/// // Make sure we don't allocate too much memory
/// decoder.claim_bytes_read(len * core::mem::size_of::<T>());
///
/// let mut result = Container::with_capacity(len);
/// for _ in 0..len {
/// // un-claim the memory
/// decoder.unclaim_bytes_read(core::mem::size_of::<T>());
/// result.push(T::borrow_decode(decoder)?)
/// }
/// Ok(result)
/// }
/// }
/// ```
fn unclaim_bytes_read(&mut self, n: usize);
}
/// Any source that can decode basic types. This type is most notably implemented for [Decoder].
///
/// This is an extension of [Decode] that can also return borrowed data.
pub trait BorrowDecoder<'de>: Decoder {
/// The concrete [BorrowReader] type
type BR: BorrowReader<'de>;
/// Rerturns a mutable reference to the borrow reader
fn borrow_reader(&mut self) -> &mut Self::BR;
}
impl<'a, T> Decoder for &'a mut T
where
T: Decoder,
{
type R = T::R;
type C = T::C;
fn reader(&mut self) -> &mut Self::R {
T::reader(self)
}
fn config(&self) -> &Self::C {
T::config(self)
}
#[inline]
fn claim_bytes_read(&mut self, n: usize) -> Result<(), DecodeError> {
T::claim_bytes_read(self, n)
}
#[inline]
fn unclaim_bytes_read(&mut self, n: usize) {
T::unclaim_bytes_read(self, n)
}
}
impl<'a, 'de, T> BorrowDecoder<'de> for &'a mut T
where
T: BorrowDecoder<'de>,
{
type BR = T::BR;
fn borrow_reader(&mut self) -> &mut Self::BR {
T::borrow_reader(self)
}
}
/// Decodes only the option variant from the decoder. Will not read any more data than that.
#[inline]
pub(crate) fn decode_option_variant<D: Decoder>(
decoder: &mut D,
type_name: &'static str,
) -> Result<Option<()>, DecodeError> {
let is_some = u8::decode(decoder)?;
match is_some {
0 => Ok(None),
1 => Ok(Some(())),
x => Err(DecodeError::UnexpectedVariant {
found: x as u32,
allowed: &crate::error::AllowedEnumVariants::Range { max: 1, min: 0 },
type_name,
}),
}
}
/// Decodes the length of any slice, container, etc from the decoder
#[inline]
pub(crate) fn decode_slice_len<D: Decoder>(decoder: &mut D) -> Result<usize, DecodeError> {
let v = u64::decode(decoder)?;
v.try_into().map_err(|_| DecodeError::OutsideUsizeRange(v))
}