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Parsable -> FromStream

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AF 2023-08-01 11:15:05 +00:00
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src/exercises/mode.md
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@ -1,4 +1,4 @@
# Parsing modes # Deserialisation modes
Merge implementations of `ConsumesStream` and `Deterministic` for tuple. Merge implementations of `ConsumesStream` and `Deterministic` for tuple.
It's recommended to first solve [this exercise](./multiple_blanket.md). It's recommended to first solve [this exercise](./multiple_blanket.md).
@ -17,23 +17,24 @@ trait Stream: Sized {
fn read_all<A>(self, ok: impl FnOnce(&[u8]) -> A) -> A; fn read_all<A>(self, ok: impl FnOnce(&[u8]) -> A) -> A;
} }
trait Parsable: Sized { /// Can be read from a stream.
trait FromStream: Sized {
type Error; type Error;
} }
/// Can parse any length of data. /// Can be formed from any length of data. Always consumes the stream.
trait ConsumesStream: Parsable { trait ConsumesStream: FromStream {
/// Try to parse the value. Can handle EOF, can ask for all data the stream has. /// Try to read the value. Can handle EOF, can ask for all data the stream has.
fn parse(stream: impl Stream) -> Result<Self, Self::Error>; fn read_from(stream: impl Stream) -> Result<Self, Self::Error>;
/// Push extra data into the value. /// Push extra data into the value.
fn extend(self, data: &[u8]) -> Result<Self, Self::Error>; fn extend(self, data: &[u8]) -> Result<Self, Self::Error>;
} }
/// Whether the parsing is terminated, is only determined by the data already parsed. /// Whether the reading is terminated, is only determined by the data already read.
trait Deterministic: Parsable { trait Deterministic: FromStream {
/// Returns the stream, as it shouldn't succeed on unexpected EOF. /// Returns the stream, as it shouldn't succeed on unexpected EOF.
fn parse<S: Stream>(stream: S) -> Result<(Self, S), Self::Error>; fn read_from<S: Stream>(stream: S) -> Result<(Self, S), Self::Error>;
/// Always fail on extra data. /// Always fail on extra data.
fn fail(data: &[u8]) -> Self::Error; fn fail(data: &[u8]) -> Self::Error;
@ -44,14 +45,14 @@ enum Either<L, R> {
Right(R), Right(R),
} }
impl<A: Parsable, B: Parsable> Parsable for (A, B) { impl<A: FromStream, B: FromStream> FromStream for (A, B) {
type Error = Either<A::Error, B::Error>; type Error = Either<A::Error, B::Error>;
} }
impl<A: Deterministic, B: ConsumesStream> ConsumesStream for (A, B) { impl<A: Deterministic, B: ConsumesStream> ConsumesStream for (A, B) {
fn parse(stream: impl Stream) -> Result<Self, Self::Error> { fn read_from(stream: impl Stream) -> Result<Self, Self::Error> {
let (a, stream) = A::parse(stream).map_err(Either::Left)?; let (a, stream) = A::read_from(stream).map_err(Either::Left)?;
B::parse(stream).map_err(Either::Right).map(|b| (a, b)) B::read_from(stream).map_err(Either::Right).map(|b| (a, b))
} }
fn extend(self, data: &[u8]) -> Result<Self, Self::Error> { fn extend(self, data: &[u8]) -> Result<Self, Self::Error> {
@ -60,9 +61,9 @@ impl<A: Deterministic, B: ConsumesStream> ConsumesStream for (A, B) {
} }
impl<A: Deterministic, B: Deterministic> Deterministic for (A, B) { impl<A: Deterministic, B: Deterministic> Deterministic for (A, B) {
fn parse<S: Stream>(stream: S) -> Result<(Self, S), Self::Error> { fn read_from<S: Stream>(stream: S) -> Result<(Self, S), Self::Error> {
let (a, stream) = A::parse(stream).map_err(Either::Left)?; let (a, stream) = A::read_from(stream).map_err(Either::Left)?;
B::parse(stream).map_err(Either::Right).map(|(b, stream)| ((a, b), stream)) B::read_from(stream).map_err(Either::Right).map(|(b, stream)| ((a, b), stream))
} }
fn fail(data: &[u8]) -> Self::Error { fn fail(data: &[u8]) -> Self::Error {