//! Basic types to build the parsers use self::Needed::*; use crate::error::{self, ErrorKind}; use crate::lib::std::fmt; use core::num::NonZeroUsize; /// Holds the result of parsing functions /// /// It depends on the input type `I`, the output type `O`, and the error type `E` /// (by default `(I, nom::ErrorKind)`) /// /// The `Ok` side is a pair containing the remainder of the input (the part of the data that /// was not parsed) and the produced value. The `Err` side contains an instance of `nom::Err`. /// /// Outside of the parsing code, you can use the [Finish::finish] method to convert /// it to a more common result type pub type IResult<I, O, E = error::Error<I>> = Result<(I, O), Err<E>>; /// Helper trait to convert a parser's result to a more manageable type pub trait Finish<I, O, E> { /// converts the parser's result to a type that is more consumable by error /// management libraries. It keeps the same `Ok` branch, and merges `Err::Error` /// and `Err::Failure` into the `Err` side. /// /// *warning*: if the result is `Err(Err::Incomplete(_))`, this method will panic. /// - "complete" parsers: It will not be an issue, `Incomplete` is never used /// - "streaming" parsers: `Incomplete` will be returned if there's not enough data /// for the parser to decide, and you should gather more data before parsing again. /// Once the parser returns either `Ok(_)`, `Err(Err::Error(_))` or `Err(Err::Failure(_))`, /// you can get out of the parsing loop and call `finish()` on the parser's result fn finish(self) -> Result<(I, O), E>; } impl<I, O, E> Finish<I, O, E> for IResult<I, O, E> { fn finish(self) -> Result<(I, O), E> { match self { Ok(res) => Ok(res), Err(Err::Error(e)) | Err(Err::Failure(e)) => Err(e), Err(Err::Incomplete(_)) => { panic!("Cannot call `finish()` on `Err(Err::Incomplete(_))`: this result means that the parser does not have enough data to decide, you should gather more data and try to reapply the parser instead") } } } } /// Contains information on needed data if a parser returned `Incomplete` #[derive(Debug, PartialEq, Eq, Clone, Copy)] #[cfg_attr(nightly, warn(rustdoc::missing_doc_code_examples))] pub enum Needed { /// Needs more data, but we do not know how much Unknown, /// Contains the required data size in bytes Size(NonZeroUsize), } impl Needed { /// Creates `Needed` instance, returns `Needed::Unknown` if the argument is zero pub fn new(s: usize) -> Self { match NonZeroUsize::new(s) { Some(sz) => Needed::Size(sz), None => Needed::Unknown, } } /// Indicates if we know how many bytes we need pub fn is_known(&self) -> bool { *self != Unknown } /// Maps a `Needed` to `Needed` by applying a function to a contained `Size` value. #[inline] pub fn map<F: Fn(NonZeroUsize) -> usize>(self, f: F) -> Needed { match self { Unknown => Unknown, Size(n) => Needed::new(f(n)), } } } /// The `Err` enum indicates the parser was not successful /// /// It has three cases: /// /// * `Incomplete` indicates that more data is needed to decide. The `Needed` enum /// can contain how many additional bytes are necessary. If you are sure your parser /// is working on full data, you can wrap your parser with the `complete` combinator /// to transform that case in `Error` /// * `Error` means some parser did not succeed, but another one might (as an example, /// when testing different branches of an `alt` combinator) /// * `Failure` indicates an unrecoverable error. As an example, if you recognize a prefix /// to decide on the next parser to apply, and that parser fails, you know there's no need /// to try other parsers, you were already in the right branch, so the data is invalid /// #[derive(Debug, Clone, PartialEq)] #[cfg_attr(nightly, warn(rustdoc::missing_doc_code_examples))] pub enum Err<E> { /// There was not enough data Incomplete(Needed), /// The parser had an error (recoverable) Error(E), /// The parser had an unrecoverable error: we got to the right /// branch and we know other branches won't work, so backtrack /// as fast as possible Failure(E), } impl<E> Err<E> { /// Tests if the result is Incomplete pub fn is_incomplete(&self) -> bool { if let Err::Incomplete(_) = self { true } else { false } } /// Applies the given function to the inner error pub fn map<E2, F>(self, f: F) -> Err<E2> where F: FnOnce(E) -> E2, { match self { Err::Incomplete(n) => Err::Incomplete(n), Err::Failure(t) => Err::Failure(f(t)), Err::Error(t) => Err::Error(f(t)), } } /// Automatically converts between errors if the underlying type supports it pub fn convert<F>(e: Err<F>) -> Self where E: From<F>, { e.map(crate::lib::std::convert::Into::into) } } impl<T> Err<(T, ErrorKind)> { /// Maps `Err<(T, ErrorKind)>` to `Err<(U, ErrorKind)>` with the given `F: T -> U` pub fn map_input<U, F>(self, f: F) -> Err<(U, ErrorKind)> where F: FnOnce(T) -> U, { match self { Err::Incomplete(n) => Err::Incomplete(n), Err::Failure((input, k)) => Err::Failure((f(input), k)), Err::Error((input, k)) => Err::Error((f(input), k)), } } } impl<T> Err<error::Error<T>> { /// Maps `Err<error::Error<T>>` to `Err<error::Error<U>>` with the given `F: T -> U` pub fn map_input<U, F>(self, f: F) -> Err<error::Error<U>> where F: FnOnce(T) -> U, { match self { Err::Incomplete(n) => Err::Incomplete(n), Err::Failure(error::Error { input, code }) => Err::Failure(error::Error { input: f(input), code, }), Err::Error(error::Error { input, code }) => Err::Error(error::Error { input: f(input), code, }), } } } #[cfg(feature = "alloc")] use crate::lib::std::{borrow::ToOwned, string::String, vec::Vec}; #[cfg(feature = "alloc")] impl Err<(&[u8], ErrorKind)> { /// Obtaining ownership #[cfg_attr(feature = "docsrs", doc(cfg(feature = "alloc")))] pub fn to_owned(self) -> Err<(Vec<u8>, ErrorKind)> { self.map_input(ToOwned::to_owned) } } #[cfg(feature = "alloc")] impl Err<(&str, ErrorKind)> { /// Obtaining ownership #[cfg_attr(feature = "docsrs", doc(cfg(feature = "alloc")))] pub fn to_owned(self) -> Err<(String, ErrorKind)> { self.map_input(ToOwned::to_owned) } } #[cfg(feature = "alloc")] impl Err<error::Error<&[u8]>> { /// Obtaining ownership #[cfg_attr(feature = "docsrs", doc(cfg(feature = "alloc")))] pub fn to_owned(self) -> Err<error::Error<Vec<u8>>> { self.map_input(ToOwned::to_owned) } } #[cfg(feature = "alloc")] impl Err<error::Error<&str>> { /// Obtaining ownership #[cfg_attr(feature = "docsrs", doc(cfg(feature = "alloc")))] pub fn to_owned(self) -> Err<error::Error<String>> { self.map_input(ToOwned::to_owned) } } impl<E: Eq> Eq for Err<E> {} impl<E> fmt::Display for Err<E> where E: fmt::Debug, { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match self { Err::Incomplete(Needed::Size(u)) => write!(f, "Parsing requires {} bytes/chars", u), Err::Incomplete(Needed::Unknown) => write!(f, "Parsing requires more data"), Err::Failure(c) => write!(f, "Parsing Failure: {:?}", c), Err::Error(c) => write!(f, "Parsing Error: {:?}", c), } } } #[cfg(feature = "std")] use std::error::Error; #[cfg(feature = "std")] impl<E> Error for Err<E> where E: fmt::Debug, { fn source(&self) -> Option<&(dyn Error + 'static)> { None // no underlying error } } /// All nom parsers implement this trait pub trait Parser<I, O, E> { /// A parser takes in input type, and returns a `Result` containing /// either the remaining input and the output value, or an error fn parse(&mut self, input: I) -> IResult<I, O, E>; /// Maps a function over the result of a parser fn map<G, O2>(self, g: G) -> Map<Self, G, O> where G: Fn(O) -> O2, Self: core::marker::Sized, { Map { f: self, g, phantom: core::marker::PhantomData, } } /// Creates a second parser from the output of the first one, then apply over the rest of the input fn flat_map<G, H, O2>(self, g: G) -> FlatMap<Self, G, O> where G: FnMut(O) -> H, H: Parser<I, O2, E>, Self: core::marker::Sized, { FlatMap { f: self, g, phantom: core::marker::PhantomData, } } /// Applies a second parser over the output of the first one fn and_then<G, O2>(self, g: G) -> AndThen<Self, G, O> where G: Parser<O, O2, E>, Self: core::marker::Sized, { AndThen { f: self, g, phantom: core::marker::PhantomData, } } /// Applies a second parser after the first one, return their results as a tuple fn and<G, O2>(self, g: G) -> And<Self, G> where G: Parser<I, O2, E>, Self: core::marker::Sized, { And { f: self, g } } /// Applies a second parser over the input if the first one failed fn or<G>(self, g: G) -> Or<Self, G> where G: Parser<I, O, E>, Self: core::marker::Sized, { Or { f: self, g } } /// automatically converts the parser's output and error values to another type, as long as they /// implement the `From` trait fn into<O2: From<O>, E2: From<E>>(self) -> Into<Self, O, O2, E, E2> where Self: core::marker::Sized, { Into { f: self, phantom_out1: core::marker::PhantomData, phantom_err1: core::marker::PhantomData, phantom_out2: core::marker::PhantomData, phantom_err2: core::marker::PhantomData, } } } impl<'a, I, O, E, F> Parser<I, O, E> for F where F: FnMut(I) -> IResult<I, O, E> + 'a, { fn parse(&mut self, i: I) -> IResult<I, O, E> { self(i) } } #[cfg(feature = "alloc")] use alloc::boxed::Box; #[cfg(feature = "alloc")] impl<'a, I, O, E> Parser<I, O, E> for Box<dyn Parser<I, O, E> + 'a> { fn parse(&mut self, input: I) -> IResult<I, O, E> { (**self).parse(input) } } /// Implementation of `Parser::map` #[cfg_attr(nightly, warn(rustdoc::missing_doc_code_examples))] pub struct Map<F, G, O1> { f: F, g: G, phantom: core::marker::PhantomData<O1>, } impl<'a, I, O1, O2, E, F: Parser<I, O1, E>, G: Fn(O1) -> O2> Parser<I, O2, E> for Map<F, G, O1> { fn parse(&mut self, i: I) -> IResult<I, O2, E> { match self.f.parse(i) { Err(e) => Err(e), Ok((i, o)) => Ok((i, (self.g)(o))), } } } /// Implementation of `Parser::flat_map` #[cfg_attr(nightly, warn(rustdoc::missing_doc_code_examples))] pub struct FlatMap<F, G, O1> { f: F, g: G, phantom: core::marker::PhantomData<O1>, } impl<'a, I, O1, O2, E, F: Parser<I, O1, E>, G: Fn(O1) -> H, H: Parser<I, O2, E>> Parser<I, O2, E> for FlatMap<F, G, O1> { fn parse(&mut self, i: I) -> IResult<I, O2, E> { let (i, o1) = self.f.parse(i)?; (self.g)(o1).parse(i) } } /// Implementation of `Parser::and_then` #[cfg_attr(nightly, warn(rustdoc::missing_doc_code_examples))] pub struct AndThen<F, G, O1> { f: F, g: G, phantom: core::marker::PhantomData<O1>, } impl<'a, I, O1, O2, E, F: Parser<I, O1, E>, G: Parser<O1, O2, E>> Parser<I, O2, E> for AndThen<F, G, O1> { fn parse(&mut self, i: I) -> IResult<I, O2, E> { let (i, o1) = self.f.parse(i)?; let (_, o2) = self.g.parse(o1)?; Ok((i, o2)) } } /// Implementation of `Parser::and` #[cfg_attr(nightly, warn(rustdoc::missing_doc_code_examples))] pub struct And<F, G> { f: F, g: G, } impl<'a, I, O1, O2, E, F: Parser<I, O1, E>, G: Parser<I, O2, E>> Parser<I, (O1, O2), E> for And<F, G> { fn parse(&mut self, i: I) -> IResult<I, (O1, O2), E> { let (i, o1) = self.f.parse(i)?; let (i, o2) = self.g.parse(i)?; Ok((i, (o1, o2))) } } /// Implementation of `Parser::or` #[cfg_attr(nightly, warn(rustdoc::missing_doc_code_examples))] pub struct Or<F, G> { f: F, g: G, } impl<'a, I: Clone, O, E: crate::error::ParseError<I>, F: Parser<I, O, E>, G: Parser<I, O, E>> Parser<I, O, E> for Or<F, G> { fn parse(&mut self, i: I) -> IResult<I, O, E> { match self.f.parse(i.clone()) { Err(Err::Error(e1)) => match self.g.parse(i) { Err(Err::Error(e2)) => Err(Err::Error(e1.or(e2))), res => res, }, res => res, } } } /// Implementation of `Parser::into` #[cfg_attr(nightly, warn(rustdoc::missing_doc_code_examples))] pub struct Into<F, O1, O2: From<O1>, E1, E2: From<E1>> { f: F, phantom_out1: core::marker::PhantomData<O1>, phantom_err1: core::marker::PhantomData<E1>, phantom_out2: core::marker::PhantomData<O2>, phantom_err2: core::marker::PhantomData<E2>, } impl< 'a, I: Clone, O1, O2: From<O1>, E1, E2: crate::error::ParseError<I> + From<E1>, F: Parser<I, O1, E1>, > Parser<I, O2, E2> for Into<F, O1, O2, E1, E2> { fn parse(&mut self, i: I) -> IResult<I, O2, E2> { match self.f.parse(i) { Ok((i, o)) => Ok((i, o.into())), Err(Err::Error(e)) => Err(Err::Error(e.into())), Err(Err::Failure(e)) => Err(Err::Failure(e.into())), Err(Err::Incomplete(e)) => Err(Err::Incomplete(e)), } } } #[cfg(test)] mod tests { use super::*; use crate::error::ErrorKind; #[doc(hidden)] #[macro_export] macro_rules! assert_size ( ($t:ty, $sz:expr) => ( assert_eq!(crate::lib::std::mem::size_of::<$t>(), $sz); ); ); #[test] #[cfg(target_pointer_width = "64")] fn size_test() { assert_size!(IResult<&[u8], &[u8], (&[u8], u32)>, 40); //FIXME: since rust 1.65, this is now 32 bytes, likely thanks to https://github.com/rust-lang/rust/pull/94075 // deactivating that test for now because it'll have different values depending on the rust version // assert_size!(IResult<&str, &str, u32>, 40); assert_size!(Needed, 8); assert_size!(Err<u32>, 16); assert_size!(ErrorKind, 1); } #[test] fn err_map_test() { let e = Err::Error(1); assert_eq!(e.map(|v| v + 1), Err::Error(2)); } }