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snix/users/Profpatsch/netencode/netencode.rs
Profpatsch 59a9955d75 feat(users/Profpatsch/netencode): fully streaming parser 
In order to arbitrarily split netencode over multiple reads, we need
to make the parser completely streaming, so that it recognizes all
cases where it needs more input.

Luckily, this is fairly trivial, after working around a bunch of
overeager parsing.

The tricky part was the giant `alt`, where inner parsers would start
consuming input and thus become incomplete when they fail afterwards.
Sinc the format *always* starts the different types with one
discriminator char, we can use that to instantly return the parser and
try the next one instead.

The other tricky part was that lists and records would parse all inner
elements and then choke on the empty string after the last element,
because the inner parser would consume at least the descriminator, and
an empty string is always `Incomplete`. We wrap these into a small
combinator which plays nice with `many0` in that regard.

Change-Id: Ib8d15d9a7cab19d432c6b24a35fcad6a5a72b246
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2704
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>
Reviewed-by: sterni <sternenseemann@systemli.org>
2021-04-01 07:28:07 +00:00

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extern crate nom;
extern crate exec_helpers;
use std::collections::HashMap;
use std::io::{Write, Read};
use std::fmt::{Display, Debug};
#[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
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]),
// Tags
// 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?
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(s.as_bytes());
write!(w, ",")
}
U::Binary(s) => {
write!(w, "b{}:", s.len());
w.write(&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(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(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: {:?}", rest))
},
Err(err) => exec_helpers::die_user_error(prog_name, format!("unable to parse netencode from stdin: {:?}", err))
};
u
}
pub mod parse {
use super::{T, Tag, U};
use std::str::FromStr;
use std::ops::Neg;
use std::collections::HashMap;
use nom::{IResult};
use nom::branch::{alt};
use nom::bytes::streaming::{tag, take};
use nom::character::streaming::{digit1, char};
use nom::sequence::{tuple};
use nom::combinator::{map, map_res, flat_map, map_parser, opt};
use nom::error::{context, ErrorKind, ParseError};
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 duplicated tag names that appear later
// according to netencode spec
if ! acc.contains_key(tag) {
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::Unit),
("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>;
}
#[derive(Clone, Copy)]
pub struct AnyT;
#[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)
}
}
#[derive(Clone, Copy)]
pub struct Text;
// 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))),
}
}
}
#[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))),
}
}
}
#[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)))
}
}
}
#[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),
}
}
}
#[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)
}
}
}
#[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)
}
}
}
}
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