From 2d49247b92f74cf760202b7d1a08d61804f45bca Mon Sep 17 00:00:00 2001 From: Alex Crichton Date: Thu, 2 Apr 2015 17:04:17 -0700 Subject: Modularize rustc-serialize support * Add rustc-serialize as a default feature * Make room for for serde support --- src/decoder/mod.rs | 205 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 205 insertions(+) create mode 100644 src/decoder/mod.rs (limited to 'src/decoder/mod.rs') diff --git a/src/decoder/mod.rs b/src/decoder/mod.rs new file mode 100644 index 0000000..675e0ca --- /dev/null +++ b/src/decoder/mod.rs @@ -0,0 +1,205 @@ +use std::error; +use std::fmt; + +use Value; +use self::DecodeErrorKind::*; + +#[cfg(feature = "rustc-serialize")] mod rustc_serialize; + +/// A structure to transform TOML values into Rust values. +/// +/// This decoder implements the serialization `Decoder` interface, allowing +/// `Decodable` types to be generated by this decoder. The input is any +/// arbitrary TOML value. +pub struct Decoder { + /// The TOML value left over after decoding. This can be used to inspect + /// whether fields were decoded or not. + pub toml: Option, + cur_field: Option, +} + +/// Description for errors which can occur while decoding a type. +#[derive(PartialEq, Debug)] +pub struct DecodeError { + /// Field that this error applies to. + pub field: Option, + /// The type of error which occurred while decoding, + pub kind: DecodeErrorKind, +} + +/// Enumeration of possible errors which can occur while decoding a structure. +#[derive(PartialEq, Debug)] +pub enum DecodeErrorKind { + /// An error flagged by the application, e.g. value out of range + ApplicationError(String), + /// A field was expected, but none was found. + ExpectedField(/* type */ Option<&'static str>), + /// A field was found, but it had the wrong type. + ExpectedType(/* expected */ &'static str, /* found */ &'static str), + /// The nth map key was expected, but none was found. + ExpectedMapKey(usize), + /// The nth map element was expected, but none was found. + ExpectedMapElement(usize), + /// An enum decoding was requested, but no variants were supplied + NoEnumVariants, + /// The unit type was being decoded, but a non-zero length string was found + NilTooLong, + /// There was an error with the syntactical structure of the TOML. + SyntaxError, + /// The end of the TOML input was reached too soon + EndOfStream, +} + +/// Decodes a TOML value into a decodable type. +/// +/// This function will consume the given TOML value and attempt to decode it +/// into the type specified. If decoding fails, `None` will be returned. If a +/// finer-grained error is desired, then it is recommended to use `Decodable` +/// directly. +#[cfg(feature = "rustc-serialize")] +pub fn decode(toml: Value) -> Option { + ::rustc_serialize::Decodable::decode(&mut Decoder::new(toml)).ok() +} + +/// Decodes a TOML value into a decodable type. +/// +/// This function will consume the given TOML value and attempt to decode it +/// into the type specified. If decoding fails, `None` will be returned. If a +/// finer-grained error is desired, then it is recommended to use `Decodable` +/// directly. +#[cfg(all(not(feature = "rustc-serialize"), feature = "serde"))] +pub fn decode(toml: Value) -> Option { + ::serde::Deserialize::deserialize(&mut Decoder::new(toml)).ok() +} + +/// Decodes a string into a toml-encoded value. +/// +/// This function will parse the given string into a TOML value, and then parse +/// the TOML value into the desired type. If any error occurs `None` is return. +/// +/// If more fine-grained errors are desired, these steps should be driven +/// manually. +#[cfg(feature = "rustc-serialize")] +pub fn decode_str(s: &str) -> Option { + ::Parser::new(s).parse().and_then(|t| decode(Value::Table(t))) +} + +/// Decodes a string into a toml-encoded value. +/// +/// This function will parse the given string into a TOML value, and then parse +/// the TOML value into the desired type. If any error occurs `None` is return. +/// +/// If more fine-grained errors are desired, these steps should be driven +/// manually. +#[cfg(all(not(feature = "rustc-serialize"), feature = "serde"))] +pub fn decode_str(s: &str) -> Option { + ::Parser::new(s).parse().and_then(|t| decode(Value::Table(t))) +} + +impl Decoder { + /// Creates a new decoder, consuming the TOML value to decode. + /// + /// This decoder can be passed to the `Decodable` methods or driven + /// manually. + pub fn new(toml: Value) -> Decoder { + Decoder { toml: Some(toml), cur_field: None } + } + + fn sub_decoder(&self, toml: Option, field: &str) -> Decoder { + Decoder { + toml: toml, + cur_field: if field.len() == 0 { + self.cur_field.clone() + } else { + match self.cur_field { + None => Some(format!("{}", field)), + Some(ref s) => Some(format!("{}.{}", s, field)) + } + } + } + } + + fn err(&self, kind: DecodeErrorKind) -> DecodeError { + DecodeError { + field: self.cur_field.clone(), + kind: kind, + } + } + + fn mismatch(&self, expected: &'static str, + found: &Option) -> DecodeError{ + match *found { + Some(ref val) => self.err(ExpectedType(expected, val.type_str())), + None => self.err(ExpectedField(Some(expected))), + } + } +} + +impl fmt::Display for DecodeError { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + try!(match self.kind { + ApplicationError(ref err) => { + write!(f, "{}", err) + } + ExpectedField(expected_type) => { + match expected_type { + Some("table") => write!(f, "expected a section"), + Some(e) => write!(f, "expected a value of type `{}`", e), + None => write!(f, "expected a value"), + } + } + ExpectedType(expected, found) => { + fn humanize(s: &str) -> String { + if s == "section" { + format!("a section") + } else { + format!("a value of type `{}`", s) + } + } + write!(f, "expected {}, but found {}", + humanize(expected), + humanize(found)) + } + ExpectedMapKey(idx) => { + write!(f, "expected at least {} keys", idx + 1) + } + ExpectedMapElement(idx) => { + write!(f, "expected at least {} elements", idx + 1) + } + NoEnumVariants => { + write!(f, "expected an enum variant to decode to") + } + NilTooLong => { + write!(f, "expected 0-length string") + } + SyntaxError => { + write!(f, "syntax error") + } + EndOfStream => { + write!(f, "end of stream") + } + }); + match self.field { + Some(ref s) => { + write!(f, " for the key `{}`", s) + } + None => Ok(()) + } + } +} + +impl error::Error for DecodeError { + fn description(&self) -> &str { + match self.kind { + ApplicationError(ref s) => &**s, + ExpectedField(..) => "expected a field", + ExpectedType(..) => "expected a type", + ExpectedMapKey(..) => "expected a map key", + ExpectedMapElement(..) => "expected a map element", + NoEnumVariants => "no enum variants to decode to", + NilTooLong => "nonzero length string representing nil", + SyntaxError => "syntax error", + EndOfStream => "end of stream", + } + } +} -- cgit v1.2.3