diff options
Diffstat (limited to 'users/Profpatsch/netencode/netencode.rs')
| -rw-r--r-- | users/Profpatsch/netencode/netencode.rs | 891 |
1 files changed, 891 insertions, 0 deletions
diff --git a/users/Profpatsch/netencode/netencode.rs b/users/Profpatsch/netencode/netencode.rs new file mode 100644 index 0000000000..bb08dca4aa --- /dev/null +++ b/users/Profpatsch/netencode/netencode.rs @@ -0,0 +1,891 @@ +extern crate exec_helpers; +extern crate nom; + +use std::collections::HashMap; +use std::fmt::{Debug, Display}; +use std::io::{Read, Write}; + +#[derive(Debug, PartialEq, Eq, Clone)] +pub enum T { + // Unit + Unit, + // Boolean + N1(bool), + // Naturals + N3(u8), + N6(u64), + N7(u128), + // Integers + I3(i8), + I6(i64), + I7(i128), + // Text + // TODO: make into &str + Text(String), + // TODO: rename to Bytes + Binary(Vec<u8>), + // Tags + // TODO: make into &str + // TODO: rename to Tag + Sum(Tag<String, T>), + // TODO: make into &str + Record(HashMap<String, T>), + List(Vec<T>), +} + +impl T { + pub fn to_u<'a>(&'a self) -> U<'a> { + match self { + T::Unit => U::Unit, + T::N1(b) => U::N1(*b), + T::N3(u) => U::N3(*u), + T::N6(u) => U::N6(*u), + T::N7(u) => U::N7(*u), + T::I3(i) => U::I3(*i), + T::I6(i) => U::I6(*i), + T::I7(i) => U::I7(*i), + T::Text(t) => U::Text(t.as_str()), + T::Binary(v) => U::Binary(v), + T::Sum(Tag { tag, val }) => U::Sum(Tag { + tag: tag.as_str(), + val: Box::new(val.to_u()), + }), + T::Record(map) => U::Record(map.iter().map(|(k, v)| (k.as_str(), v.to_u())).collect()), + T::List(l) => U::List(l.iter().map(|v| v.to_u()).collect::<Vec<U<'a>>>()), + } + } + + pub fn encode<'a>(&'a self) -> Vec<u8> { + match self { + // TODO: don’t go via U, inefficient + o => o.to_u().encode(), + } + } +} + +#[derive(Debug, PartialEq, Eq, Clone)] +pub enum U<'a> { + Unit, + // Boolean + N1(bool), + // Naturals + N3(u8), + N6(u64), + N7(u128), + // Integers + I3(i8), + I6(i64), + I7(i128), + // Text + Text(&'a str), + Binary(&'a [u8]), + // TODO: the U-recursion we do here means we can’t be breadth-lazy anymore + // like we originally planned; maybe we want to go `U<'a>` → `&'a [u8]` again? + // Tags + // TODO: rename to Tag + Sum(Tag<&'a str, U<'a>>), + Record(HashMap<&'a str, U<'a>>), + List(Vec<U<'a>>), +} + +impl<'a> U<'a> { + pub fn encode(&self) -> Vec<u8> { + let mut c = std::io::Cursor::new(vec![]); + encode(&mut c, self); + c.into_inner() + } + + pub fn to_t(&self) -> T { + match self { + U::Unit => T::Unit, + U::N1(b) => T::N1(*b), + U::N3(u) => T::N3(*u), + U::N6(u) => T::N6(*u), + U::N7(u) => T::N7(*u), + U::I3(i) => T::I3(*i), + U::I6(i) => T::I6(*i), + U::I7(i) => T::I7(*i), + U::Text(t) => T::Text((*t).to_owned()), + U::Binary(v) => T::Binary((*v).to_owned()), + U::Sum(Tag { tag, val }) => T::Sum(Tag { + tag: (*tag).to_owned(), + val: Box::new(val.to_t()), + }), + U::Record(map) => T::Record( + map.iter() + .map(|(k, v)| ((*k).to_owned(), v.to_t())) + .collect::<HashMap<String, T>>(), + ), + U::List(l) => T::List(l.iter().map(|v| v.to_t()).collect::<Vec<T>>()), + } + } +} + +#[derive(Debug, PartialEq, Eq, Clone)] +pub struct Tag<S, A> { + // TODO: make into &str + pub tag: S, + pub val: Box<A>, +} + +impl<S, A> Tag<S, A> { + fn map<F, B>(self, f: F) -> Tag<S, B> + where + F: Fn(A) -> B, + { + Tag { + tag: self.tag, + val: Box::new(f(*self.val)), + } + } +} + +fn encode_tag<W: Write>(w: &mut W, tag: &str, val: &U) -> std::io::Result<()> { + write!(w, "<{}:{}|", tag.len(), tag)?; + encode(w, val)?; + Ok(()) +} + +pub fn encode<W: Write>(w: &mut W, u: &U) -> std::io::Result<()> { + match u { + U::Unit => write!(w, "u,"), + U::N1(b) => { + if *b { + write!(w, "n1:1,") + } else { + write!(w, "n1:0,") + } + } + U::N3(n) => write!(w, "n3:{},", n), + U::N6(n) => write!(w, "n6:{},", n), + U::N7(n) => write!(w, "n7:{},", n), + U::I3(i) => write!(w, "i3:{},", i), + U::I6(i) => write!(w, "i6:{},", i), + U::I7(i) => write!(w, "i7:{},", i), + U::Text(s) => { + write!(w, "t{}:", s.len()); + w.write_all(s.as_bytes()); + write!(w, ",") + } + U::Binary(s) => { + write!(w, "b{}:", s.len()); + w.write_all(&s); + write!(w, ",") + } + U::Sum(Tag { tag, val }) => encode_tag(w, tag, val), + U::Record(m) => { + let mut c = std::io::Cursor::new(vec![]); + for (k, v) in m { + encode_tag(&mut c, k, v)?; + } + write!(w, "{{{}:", c.get_ref().len())?; + w.write_all(c.get_ref())?; + write!(w, "}}") + } + U::List(l) => { + let mut c = std::io::Cursor::new(vec![]); + for u in l { + encode(&mut c, u)?; + } + write!(w, "[{}:", c.get_ref().len())?; + w.write_all(c.get_ref())?; + write!(w, "]") + } + } +} + +pub fn text(s: String) -> T { + T::Text(s) +} + +pub fn u_from_stdin_or_die_user_error<'a>(prog_name: &'_ str, stdin_buf: &'a mut Vec<u8>) -> U<'a> { + std::io::stdin().lock().read_to_end(stdin_buf); + let u = match parse::u_u(stdin_buf) { + Ok((rest, u)) => match rest { + b"" => u, + _ => exec_helpers::die_user_error( + prog_name, + format!( + "stdin contained some soup after netencode value: {:?}", + String::from_utf8_lossy(rest) + ), + ), + }, + Err(err) => exec_helpers::die_user_error( + prog_name, + format!("unable to parse netencode from stdin: {:?}", err), + ), + }; + u +} + +pub mod parse { + use super::{Tag, T, U}; + + use std::collections::HashMap; + use std::ops::Neg; + use std::str::FromStr; + + use nom::branch::alt; + use nom::bytes::streaming::{tag, take}; + use nom::character::streaming::{char, digit1}; + use nom::combinator::{flat_map, map, map_parser, map_res, opt}; + use nom::error::{context, ErrorKind, ParseError}; + use nom::sequence::tuple; + use nom::IResult; + + fn unit_t(s: &[u8]) -> IResult<&[u8], ()> { + let (s, _) = context("unit", tag("u,"))(s)?; + Ok((s, ())) + } + + fn usize_t(s: &[u8]) -> IResult<&[u8], usize> { + context( + "usize", + map_res(map_res(digit1, |n| std::str::from_utf8(n)), |s| { + s.parse::<usize>() + }), + )(s) + } + + fn sized(begin: char, end: char) -> impl Fn(&[u8]) -> IResult<&[u8], &[u8]> { + move |s: &[u8]| { + // This is the point where we check the descriminator; + // if the beginning char does not match, we can immediately return. + let (s, _) = char(begin)(s)?; + let (s, (len, _)) = tuple((usize_t, char(':')))(s)?; + let (s, (res, _)) = tuple((take(len), char(end)))(s)?; + Ok((s, res)) + } + } + + fn uint_t<'a, I: FromStr + 'a>(t: &'static str) -> impl Fn(&'a [u8]) -> IResult<&'a [u8], I> { + move |s: &'a [u8]| { + let (s, (_, _, int, _)) = tuple(( + tag(t.as_bytes()), + char(':'), + map_res(map_res(digit1, |n: &[u8]| std::str::from_utf8(n)), |s| { + s.parse::<I>() + }), + char(','), + ))(s)?; + Ok((s, int)) + } + } + + fn bool_t<'a>() -> impl Fn(&'a [u8]) -> IResult<&'a [u8], bool> { + context( + "bool", + alt((map(tag("n1:0,"), |_| false), map(tag("n1:1,"), |_| true))), + ) + } + + fn int_t<'a, I: FromStr + Neg<Output = I>>( + t: &'static str, + ) -> impl Fn(&'a [u8]) -> IResult<&[u8], I> { + context(t, move |s: &'a [u8]| { + let (s, (_, _, neg, int, _)) = tuple(( + tag(t.as_bytes()), + char(':'), + opt(char('-')), + map_res(map_res(digit1, |n: &[u8]| std::str::from_utf8(n)), |s| { + s.parse::<I>() + }), + char(','), + ))(s)?; + let res = match neg { + Some(_) => -int, + None => int, + }; + Ok((s, res)) + }) + } + + fn tag_t(s: &[u8]) -> IResult<&[u8], Tag<String, T>> { + // recurses into the main parser + map(tag_g(t_t), |Tag { tag, val }| Tag { + tag: tag.to_string(), + val, + })(s) + } + + fn tag_g<'a, P, O>(inner: P) -> impl Fn(&'a [u8]) -> IResult<&'a [u8], Tag<&'a str, O>> + where + P: Fn(&'a [u8]) -> IResult<&'a [u8], O>, + { + move |s: &[u8]| { + let (s, tag) = sized('<', '|')(s)?; + let (s, val) = inner(s)?; + Ok(( + s, + Tag { + tag: std::str::from_utf8(tag) + .map_err(|_| nom::Err::Failure((s, ErrorKind::Char)))?, + val: Box::new(val), + }, + )) + } + } + + /// parse text scalar (`t5:hello,`) + fn text(s: &[u8]) -> IResult<&[u8], T> { + let (s, res) = text_g(s)?; + Ok((s, T::Text(res.to_string()))) + } + + fn text_g(s: &[u8]) -> IResult<&[u8], &str> { + let (s, res) = sized('t', ',')(s)?; + Ok(( + s, + std::str::from_utf8(res).map_err(|_| nom::Err::Failure((s, ErrorKind::Char)))?, + )) + } + + fn binary<'a>() -> impl Fn(&'a [u8]) -> IResult<&'a [u8], T> { + map(binary_g(), |b| T::Binary(b.to_owned())) + } + + fn binary_g() -> impl Fn(&[u8]) -> IResult<&[u8], &[u8]> { + sized('b', ',') + } + + fn list_t(s: &[u8]) -> IResult<&[u8], Vec<T>> { + list_g(t_t)(s) + } + + /// Wrap the inner parser of an `many0`/`fold_many0`, so that the parser + /// is not called when the `s` is empty already, preventing it from + /// returning `Incomplete` on streaming parsing. + fn inner_no_empty_string<'a, P, O>(inner: P) -> impl Fn(&'a [u8]) -> IResult<&'a [u8], O> + where + O: Clone, + P: Fn(&'a [u8]) -> IResult<&'a [u8], O>, + { + move |s: &'a [u8]| { + if s.is_empty() { + // This is a bit hacky, `many0` considers the inside done + // when a parser returns `Err::Error`, ignoring the actual error content + Err(nom::Err::Error((s, nom::error::ErrorKind::Many0))) + } else { + inner(s) + } + } + } + + fn list_g<'a, P, O>(inner: P) -> impl Fn(&'a [u8]) -> IResult<&'a [u8], Vec<O>> + where + O: Clone, + P: Fn(&'a [u8]) -> IResult<&'a [u8], O>, + { + map_parser( + sized('[', ']'), + nom::multi::many0(inner_no_empty_string(inner)), + ) + } + + fn record_t<'a>(s: &'a [u8]) -> IResult<&'a [u8], HashMap<String, T>> { + let (s, r) = record_g(t_t)(s)?; + Ok(( + s, + r.into_iter() + .map(|(k, v)| (k.to_string(), v)) + .collect::<HashMap<_, _>>(), + )) + } + + fn record_g<'a, P, O>(inner: P) -> impl Fn(&'a [u8]) -> IResult<&'a [u8], HashMap<&'a str, O>> + where + O: Clone, + P: Fn(&'a [u8]) -> IResult<&'a [u8], O>, + { + move |s: &'a [u8]| { + let (s, map) = map_parser( + sized('{', '}'), + nom::multi::fold_many0( + inner_no_empty_string(tag_g(&inner)), + HashMap::new(), + |mut acc: HashMap<_, _>, Tag { tag, mut val }| { + // ignore earlier tags with the same name + // according to netencode spec + let _ = acc.insert(tag, *val); + acc + }, + ), + )(s)?; + if map.is_empty() { + // records must not be empty, according to the spec + Err(nom::Err::Failure((s, nom::error::ErrorKind::Many1))) + } else { + Ok((s, map)) + } + } + } + + pub fn u_u(s: &[u8]) -> IResult<&[u8], U> { + alt(( + map(text_g, U::Text), + map(binary_g(), U::Binary), + map(unit_t, |()| U::Unit), + map(tag_g(u_u), |t| U::Sum(t)), + map(list_g(u_u), U::List), + map(record_g(u_u), U::Record), + map(bool_t(), |u| U::N1(u)), + map(uint_t("n3"), |u| U::N3(u)), + map(uint_t("n6"), |u| U::N6(u)), + map(uint_t("n7"), |u| U::N7(u)), + map(int_t("i3"), |u| U::I3(u)), + map(int_t("i6"), |u| U::I6(u)), + map(int_t("i7"), |u| U::I7(u)), + // less common + map(uint_t("n2"), |u| U::N3(u)), + map(uint_t("n4"), |u| U::N6(u)), + map(uint_t("n5"), |u| U::N6(u)), + map(int_t("i1"), |u| U::I3(u)), + map(int_t("i2"), |u| U::I3(u)), + map(int_t("i4"), |u| U::I6(u)), + map(int_t("i5"), |u| U::I6(u)), + // TODO: 8, 9 not supported + ))(s) + } + + pub fn t_t(s: &[u8]) -> IResult<&[u8], T> { + alt(( + text, + binary(), + map(unit_t, |_| T::Unit), + map(tag_t, |t| T::Sum(t)), + map(list_t, |l| T::List(l)), + map(record_t, |p| T::Record(p)), + map(bool_t(), |u| T::N1(u)), + // 8, 64 and 128 bit + map(uint_t("n3"), |u| T::N3(u)), + map(uint_t("n6"), |u| T::N6(u)), + map(uint_t("n7"), |u| T::N7(u)), + map(int_t("i3"), |u| T::I3(u)), + map(int_t("i6"), |u| T::I6(u)), + map(int_t("i7"), |u| T::I7(u)), + // less common + map(uint_t("n2"), |u| T::N3(u)), + map(uint_t("n4"), |u| T::N6(u)), + map(uint_t("n5"), |u| T::N6(u)), + map(int_t("i1"), |u| T::I3(u)), + map(int_t("i2"), |u| T::I3(u)), + map(int_t("i4"), |u| T::I6(u)), + map(int_t("i5"), |u| T::I6(u)), + // TODO: 8, 9 not supported + ))(s) + } + + #[cfg(test)] + mod tests { + use super::*; + + #[test] + fn test_parse_unit_t() { + assert_eq!(unit_t("u,".as_bytes()), Ok(("".as_bytes(), ()))); + } + + #[test] + fn test_parse_bool_t() { + assert_eq!(bool_t()("n1:0,".as_bytes()), Ok(("".as_bytes(), false))); + assert_eq!(bool_t()("n1:1,".as_bytes()), Ok(("".as_bytes(), true))); + } + + #[test] + fn test_parse_usize_t() { + assert_eq!(usize_t("32foo".as_bytes()), Ok(("foo".as_bytes(), 32))); + } + + #[test] + fn test_parse_int_t() { + assert_eq!( + uint_t::<u8>("n3")("n3:42,abc".as_bytes()), + Ok(("abc".as_bytes(), 42)) + ); + assert_eq!( + uint_t::<u8>("n3")("n3:1024,abc".as_bytes()), + Err(nom::Err::Error(( + "1024,abc".as_bytes(), + nom::error::ErrorKind::MapRes + ))) + ); + assert_eq!( + int_t::<i64>("i6")("i6:-23,abc".as_bytes()), + Ok(("abc".as_bytes(), -23)) + ); + assert_eq!( + int_t::<i128>("i3")("i3:0,:abc".as_bytes()), + Ok((":abc".as_bytes(), 0)) + ); + assert_eq!( + uint_t::<u8>("n7")("n7:09,".as_bytes()), + Ok(("".as_bytes(), 9)) + ); + // assert_eq!( + // length("c"), + // Err(nom::Err::Error(("c", nom::error::ErrorKind::Digit))) + // ); + // assert_eq!( + // length(":"), + // Err(nom::Err::Error((":", nom::error::ErrorKind::Digit))) + // ); + } + + #[test] + fn test_parse_text() { + assert_eq!( + text("t5:hello,".as_bytes()), + Ok(("".as_bytes(), T::Text("hello".to_owned()))), + "{}", + r"t5:hello," + ); + assert_eq!( + text("t4:fo".as_bytes()), + // The content of the text should be 4 long + Err(nom::Err::Incomplete(nom::Needed::Size(4))), + "{}", + r"t4:fo," + ); + assert_eq!( + text("t9:今日は,".as_bytes()), + Ok(("".as_bytes(), T::Text("今日は".to_owned()))), + "{}", + r"t9:今日は," + ); + } + + #[test] + fn test_parse_binary() { + assert_eq!( + binary()("b5:hello,".as_bytes()), + Ok(("".as_bytes(), T::Binary(Vec::from("hello".to_owned())))), + "{}", + r"b5:hello," + ); + assert_eq!( + binary()("b4:fo".as_bytes()), + // The content of the byte should be 4 long + Err(nom::Err::Incomplete(nom::Needed::Size(4))), + "{}", + r"b4:fo," + ); + assert_eq!( + binary()("b4:foob".as_bytes()), + // The content is 4 bytes now, but the finishing , is missing + Err(nom::Err::Incomplete(nom::Needed::Size(1))), + "{}", + r"b4:fo," + ); + assert_eq!( + binary()("b9:今日は,".as_bytes()), + Ok(("".as_bytes(), T::Binary(Vec::from("今日は".as_bytes())))), + "{}", + r"b9:今日は," + ); + } + + #[test] + fn test_list() { + assert_eq!( + list_t("[0:]".as_bytes()), + Ok(("".as_bytes(), vec![])), + "{}", + r"[0:]" + ); + assert_eq!( + list_t("[6:u,u,u,]".as_bytes()), + Ok(("".as_bytes(), vec![T::Unit, T::Unit, T::Unit,])), + "{}", + r"[6:u,u,u,]" + ); + assert_eq!( + list_t("[15:u,[7:t3:foo,]u,]".as_bytes()), + Ok(( + "".as_bytes(), + vec![T::Unit, T::List(vec![T::Text("foo".to_owned())]), T::Unit,] + )), + "{}", + r"[15:u,[7:t3:foo,]u,]" + ); + } + + #[test] + fn test_record() { + assert_eq!( + record_t("{21:<1:a|u,<1:b|u,<1:c|u,}".as_bytes()), + Ok(( + "".as_bytes(), + vec![ + ("a".to_owned(), T::Unit), + ("b".to_owned(), T::Unit), + ("c".to_owned(), T::Unit), + ] + .into_iter() + .collect::<HashMap<String, T>>() + )), + "{}", + r"{21:<1:a|u,<1:b|u,<1:c|u,}" + ); + // duplicated keys are ignored (first is taken) + assert_eq!( + record_t("{25:<1:a|u,<1:b|u,<1:a|i1:-1,}".as_bytes()), + Ok(( + "".as_bytes(), + vec![("a".to_owned(), T::I3(-1)), ("b".to_owned(), T::Unit),] + .into_iter() + .collect::<HashMap<_, _>>() + )), + "{}", + r"{25:<1:a|u,<1:b|u,<1:a|i1:-1,}" + ); + // empty records are not allowed + assert_eq!( + record_t("{0:}".as_bytes()), + Err(nom::Err::Failure(( + "".as_bytes(), + nom::error::ErrorKind::Many1 + ))), + "{}", + r"{0:}" + ); + } + + #[test] + fn test_parse() { + assert_eq!( + t_t("n3:255,".as_bytes()), + Ok(("".as_bytes(), T::N3(255))), + "{}", + r"n3:255," + ); + assert_eq!( + t_t("t6:halloo,".as_bytes()), + Ok(("".as_bytes(), T::Text("halloo".to_owned()))), + "{}", + r"t6:halloo," + ); + assert_eq!( + t_t("<3:foo|t6:halloo,".as_bytes()), + Ok(( + "".as_bytes(), + T::Sum(Tag { + tag: "foo".to_owned(), + val: Box::new(T::Text("halloo".to_owned())) + }) + )), + "{}", + r"<3:foo|t6:halloo," + ); + // { a: Unit + // , foo: List <A: Unit | B: List i3> } + assert_eq!( + t_t("{52:<1:a|u,<3:foo|[33:<1:A|u,<1:A|n1:1,<1:B|[7:i3:127,]]}".as_bytes()), + Ok(( + "".as_bytes(), + T::Record( + vec![ + ("a".to_owned(), T::Unit), + ( + "foo".to_owned(), + T::List(vec![ + T::Sum(Tag { + tag: "A".to_owned(), + val: Box::new(T::Unit) + }), + T::Sum(Tag { + tag: "A".to_owned(), + val: Box::new(T::N1(true)) + }), + T::Sum(Tag { + tag: "B".to_owned(), + val: Box::new(T::List(vec![T::I3(127)])) + }), + ]) + ) + ] + .into_iter() + .collect::<HashMap<String, T>>() + ) + )), + "{}", + r"{52:<1:a|u,<3:foo|[33:<1:A|u,<1:A|n1:1,<1:B|[7:i3:127,]]}" + ); + } + } +} + +pub mod dec { + use super::*; + use std::collections::HashMap; + + pub struct DecodeError(pub String); + + pub trait Decoder<'a> { + type A; + fn dec(&self, u: U<'a>) -> Result<Self::A, DecodeError>; + } + + /// Any netencode, as `T`. + #[derive(Clone, Copy)] + pub struct AnyT; + /// Any netencode, as `U`. + #[derive(Clone, Copy)] + pub struct AnyU; + + impl<'a> Decoder<'a> for AnyT { + type A = T; + fn dec(&self, u: U<'a>) -> Result<Self::A, DecodeError> { + Ok(u.to_t()) + } + } + + impl<'a> Decoder<'a> for AnyU { + type A = U<'a>; + fn dec(&self, u: U<'a>) -> Result<Self::A, DecodeError> { + Ok(u) + } + } + + /// A text + #[derive(Clone, Copy)] + pub struct Text; + + /// A bytestring + // TODO: rename to Bytes + #[derive(Clone, Copy)] + pub struct Binary; + + impl<'a> Decoder<'a> for Text { + type A = &'a str; + fn dec(&self, u: U<'a>) -> Result<Self::A, DecodeError> { + match u { + U::Text(t) => Ok(t), + other => Err(DecodeError(format!("Cannot decode {:?} into Text", other))), + } + } + } + + impl<'a> Decoder<'a> for Binary { + type A = &'a [u8]; + fn dec(&self, u: U<'a>) -> Result<Self::A, DecodeError> { + match u { + U::Binary(b) => Ok(b), + other => Err(DecodeError(format!( + "Cannot decode {:?} into Binary", + other + ))), + } + } + } + + /// Any scalar, converted to bytes. + #[derive(Clone, Copy)] + pub struct ScalarAsBytes; + + impl<'a> Decoder<'a> for ScalarAsBytes { + type A = Vec<u8>; + fn dec(&self, u: U<'a>) -> Result<Self::A, DecodeError> { + match u { + U::N3(u) => Ok(format!("{}", u).into_bytes()), + U::N6(u) => Ok(format!("{}", u).into_bytes()), + U::N7(u) => Ok(format!("{}", u).into_bytes()), + U::I3(i) => Ok(format!("{}", i).into_bytes()), + U::I6(i) => Ok(format!("{}", i).into_bytes()), + U::I7(i) => Ok(format!("{}", i).into_bytes()), + U::Text(t) => Ok(t.as_bytes().to_owned()), + U::Binary(b) => Ok(b.to_owned()), + o => Err(DecodeError(format!("Cannot decode {:?} into scalar", o))), + } + } + } + + /// A map of Ts (TODO: rename to map) + #[derive(Clone, Copy)] + pub struct Record<T>(pub T); + + impl<'a, Inner> Decoder<'a> for Record<Inner> + where + Inner: Decoder<'a>, + { + type A = HashMap<&'a str, Inner::A>; + fn dec(&self, u: U<'a>) -> Result<Self::A, DecodeError> { + match u { + U::Record(map) => map + .into_iter() + .map(|(k, v)| self.0.dec(v).map(|v2| (k, v2))) + .collect::<Result<Self::A, _>>(), + o => Err(DecodeError(format!("Cannot decode {:?} into record", o))), + } + } + } + + /// Assume a record and project out the field with the given name and type. + #[derive(Clone, Copy)] + pub struct RecordDot<'a, T> { + pub field: &'a str, + pub inner: T, + } + + impl<'a, Inner> Decoder<'a> for RecordDot<'_, Inner> + where + Inner: Decoder<'a> + Clone, + { + type A = Inner::A; + fn dec(&self, u: U<'a>) -> Result<Self::A, DecodeError> { + match Record(self.inner.clone()).dec(u) { + Ok(mut map) => match map.remove(self.field) { + Some(inner) => Ok(inner), + None => Err(DecodeError(format!( + "Cannot find `{}` in record map", + self.field + ))), + }, + Err(err) => Err(err), + } + } + } + + /// Equals one of the listed `A`s exactly, after decoding. + #[derive(Clone)] + pub struct OneOf<T, A> { + pub inner: T, + pub list: Vec<A>, + } + + impl<'a, Inner> Decoder<'a> for OneOf<Inner, Inner::A> + where + Inner: Decoder<'a>, + Inner::A: Display + Debug + PartialEq, + { + type A = Inner::A; + fn dec(&self, u: U<'a>) -> Result<Self::A, DecodeError> { + match self.inner.dec(u) { + Ok(inner) => match self.list.iter().any(|x| x.eq(&inner)) { + true => Ok(inner), + false => Err(DecodeError(format!( + "{} is not one of {:?}", + inner, self.list + ))), + }, + Err(err) => Err(err), + } + } + } + + /// Try decoding as `T`. + #[derive(Clone)] + pub struct Try<T>(pub T); + + impl<'a, Inner> Decoder<'a> for Try<Inner> + where + Inner: Decoder<'a>, + { + type A = Option<Inner::A>; + fn dec(&self, u: U<'a>) -> Result<Self::A, DecodeError> { + match self.0.dec(u) { + Ok(inner) => Ok(Some(inner)), + Err(err) => Ok(None), + } + } + } +} |