Modularize rustc-serialize support

* Add rustc-serialize as a default feature
* Make room for for serde support

2 files changed, 516 insertions, 0 deletions

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<Value>,
+    cur_field: Option<String>,
+}
+
+/// 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<String>,
+    /// 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<T: ::rustc_serialize::Decodable>(toml: Value) -> Option<T> {
+    ::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<T: ::serde::Deserialize>(toml: Value) -> Option<T> {
+    ::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<T: ::rustc_serialize::Decodable>(s: &str) -> Option<T> {
+    ::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<T: ::serde::Deserialize>(s: &str) -> Option<T> {
+    ::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<Value>, 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<Value>) -> 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",
+        }
+    }
+}
diff --git a/src/decoder/rustc_serialize.rs b/src/decoder/rustc_serialize.rs
new file mode 100644
index 0000000..6e8fe59
--- /dev/null
+++ b/src/decoder/rustc_serialize.rs
@@ -0,0 +1,311 @@
+use rustc_serialize;
+use std::mem;
+
+use super::{Decoder, DecodeError};
+use super::DecodeErrorKind::*;
+use Value;
+
+impl rustc_serialize::Decoder for Decoder {
+    type Error = DecodeError;
+    fn read_nil(&mut self) -> Result<(), DecodeError> {
+        match self.toml {
+            Some(Value::String(ref s)) if s.len() == 0 => {}
+            Some(Value::String(..)) => return Err(self.err(NilTooLong)),
+            ref found => return Err(self.mismatch("string", found)),
+        }
+        self.toml.take();
+        Ok(())
+    }
+    fn read_usize(&mut self) -> Result<usize, DecodeError> {
+        self.read_i64().map(|i| i as usize)
+    }
+    fn read_u64(&mut self) -> Result<u64, DecodeError> {
+        self.read_i64().map(|i| i as u64)
+    }
+    fn read_u32(&mut self) -> Result<u32, DecodeError> {
+        self.read_i64().map(|i| i as u32)
+    }
+    fn read_u16(&mut self) -> Result<u16, DecodeError> {
+        self.read_i64().map(|i| i as u16)
+    }
+    fn read_u8(&mut self) -> Result<u8, DecodeError> {
+        self.read_i64().map(|i| i as u8)
+    }
+    fn read_isize(&mut self) -> Result<isize, DecodeError> {
+        self.read_i64().map(|i| i as isize)
+    }
+    fn read_i64(&mut self) -> Result<i64, DecodeError> {
+        match self.toml {
+            Some(Value::Integer(i)) => { self.toml.take(); Ok(i) }
+            ref found => Err(self.mismatch("integer", found)),
+        }
+    }
+    fn read_i32(&mut self) -> Result<i32, DecodeError> {
+        self.read_i64().map(|i| i as i32)
+    }
+    fn read_i16(&mut self) -> Result<i16, DecodeError> {
+        self.read_i64().map(|i| i as i16)
+    }
+    fn read_i8(&mut self) -> Result<i8, DecodeError> {
+        self.read_i64().map(|i| i as i8)
+    }
+    fn read_bool(&mut self) -> Result<bool, DecodeError> {
+        match self.toml {
+            Some(Value::Boolean(b)) => { self.toml.take(); Ok(b) }
+            ref found => Err(self.mismatch("bool", found)),
+        }
+    }
+    fn read_f64(&mut self) -> Result<f64, DecodeError> {
+        match self.toml {
+            Some(Value::Float(f)) => Ok(f),
+            ref found => Err(self.mismatch("float", found)),
+        }
+    }
+    fn read_f32(&mut self) -> Result<f32, DecodeError> {
+        self.read_f64().map(|f| f as f32)
+    }
+    fn read_char(&mut self) -> Result<char, DecodeError> {
+        let ch = match self.toml {
+            Some(Value::String(ref s)) if s.chars().count() == 1 =>
+                s.chars().next().unwrap(),
+            ref found => return Err(self.mismatch("string", found)),
+        };
+        self.toml.take();
+        Ok(ch)
+    }
+    fn read_str(&mut self) -> Result<String, DecodeError> {
+        match self.toml.take() {
+            Some(Value::String(s)) => Ok(s),
+            found => {
+                let err = Err(self.mismatch("string", &found));
+                self.toml = found;
+                err
+            }
+        }
+    }
+
+    // Compound types:
+    fn read_enum<T, F>(&mut self, _name: &str, f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        f(self)
+    }
+
+    fn read_enum_variant<T, F>(&mut self, names: &[&str], mut f: F)
+        -> Result<T, DecodeError>
+        where F: FnMut(&mut Decoder, usize) -> Result<T, DecodeError>
+    {
+        let mut first_error = None;
+        for i in 0..names.len() {
+            let mut d = self.sub_decoder(self.toml.clone(), "");
+            match f(&mut d, i) {
+                Ok(t) => { self.toml = d.toml; return Ok(t) }
+                Err(e) => {
+                    if first_error.is_none() {
+                        first_error = Some(e);
+                    }
+                }
+            }
+        }
+        Err(first_error.unwrap_or_else(|| self.err(NoEnumVariants)))
+    }
+    fn read_enum_variant_arg<T, F>(&mut self, _a_idx: usize, f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        f(self)
+    }
+
+    fn read_enum_struct_variant<T, F>(&mut self, _names: &[&str], _f: F)
+        -> Result<T, DecodeError>
+        where F: FnMut(&mut Decoder, usize) -> Result<T, DecodeError>
+    {
+        panic!()
+    }
+    fn read_enum_struct_variant_field<T, F>(&mut self,
+                                            _f_name: &str,
+                                            _f_idx: usize,
+                                            _f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        panic!()
+    }
+
+    fn read_struct<T, F>(&mut self, _s_name: &str, _len: usize, f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        match self.toml {
+            Some(Value::Table(..)) => {
+                let ret = try!(f(self));
+                match self.toml {
+                    Some(Value::Table(ref t)) if t.len() == 0 => {}
+                    _ => return Ok(ret)
+                }
+                self.toml.take();
+                Ok(ret)
+            }
+            ref found => Err(self.mismatch("table", found)),
+        }
+    }
+    fn read_struct_field<T, F>(&mut self, f_name: &str, _f_idx: usize, f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        let field = format!("{}", f_name);
+        let toml = match self.toml {
+            Some(Value::Table(ref mut table)) => {
+                table.remove(&field)
+                    .or_else(|| table.remove(&f_name.replace("_", "-")))
+            },
+            ref found => return Err(self.mismatch("table", found)),
+        };
+        let mut d = self.sub_decoder(toml, f_name);
+        let ret = try!(f(&mut d));
+        if let Some(value) = d.toml {
+            if let Some(Value::Table(ref mut table)) = self.toml {
+                table.insert(field, value);
+            }
+        }
+        Ok(ret)
+    }
+
+    fn read_tuple<T, F>(&mut self, tuple_len: usize, f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        self.read_seq(move |d, len| {
+            assert!(len == tuple_len,
+                    "expected tuple of length `{}`, found tuple \
+                         of length `{}`", tuple_len, len);
+            f(d)
+        })
+    }
+    fn read_tuple_arg<T, F>(&mut self, a_idx: usize, f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        self.read_seq_elt(a_idx, f)
+    }
+
+    fn read_tuple_struct<T, F>(&mut self, _s_name: &str, _len: usize, _f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        panic!()
+    }
+    fn read_tuple_struct_arg<T, F>(&mut self, _a_idx: usize, _f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        panic!()
+    }
+
+    // Specialized types:
+    fn read_option<T, F>(&mut self, mut f: F)
+        -> Result<T, DecodeError>
+        where F: FnMut(&mut Decoder, bool) -> Result<T, DecodeError>
+    {
+        match self.toml {
+            Some(..) => f(self, true),
+            None => f(self, false),
+        }
+    }
+
+    fn read_seq<T, F>(&mut self, f: F) -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder, usize) -> Result<T, DecodeError>
+    {
+        let len = match self.toml {
+            Some(Value::Array(ref arr)) => arr.len(),
+            None => 0,
+            ref found => return Err(self.mismatch("array", found)),
+        };
+        let ret = try!(f(self, len));
+        match self.toml {
+            Some(Value::Array(ref mut arr)) => {
+                arr.retain(|slot| slot.as_integer() != Some(0));
+                if arr.len() != 0 { return Ok(ret) }
+            }
+            _ => return Ok(ret)
+        }
+        self.toml.take();
+        Ok(ret)
+    }
+    fn read_seq_elt<T, F>(&mut self, idx: usize, f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        let toml = match self.toml {
+            Some(Value::Array(ref mut arr)) => {
+                mem::replace(&mut arr[idx], Value::Integer(0))
+            }
+            ref found => return Err(self.mismatch("array", found)),
+        };
+        let mut d = self.sub_decoder(Some(toml), "");
+        let ret = try!(f(&mut d));
+        match d.toml {
+            Some(toml) => match self.toml {
+                Some(Value::Array(ref mut arr)) => arr[idx] = toml,
+                _ => {}
+            },
+            _ => {}
+        }
+        Ok(ret)
+    }
+
+    fn read_map<T, F>(&mut self, f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder, usize) -> Result<T, DecodeError>
+    {
+        let len = match self.toml {
+            Some(Value::Table(ref table)) => table.len(),
+            ref found => return Err(self.mismatch("table", found)),
+        };
+        let ret = try!(f(self, len));
+        self.toml.take();
+        Ok(ret)
+    }
+    fn read_map_elt_key<T, F>(&mut self, idx: usize, f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        match self.toml {
+            Some(Value::Table(ref table)) => {
+                match table.iter().skip(idx).next() {
+                    Some((key, _)) => {
+                        let val = Value::String(format!("{}", key));
+                        f(&mut self.sub_decoder(Some(val), &**key))
+                    }
+                    None => Err(self.err(ExpectedMapKey(idx))),
+                }
+            }
+            ref found => Err(self.mismatch("table", found)),
+        }
+    }
+    fn read_map_elt_val<T, F>(&mut self, idx: usize, f: F)
+        -> Result<T, DecodeError>
+        where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
+    {
+        match self.toml {
+            Some(Value::Table(ref table)) => {
+                match table.iter().skip(idx).next() {
+                    Some((_, value)) => {
+                        // XXX: this shouldn't clone
+                        f(&mut self.sub_decoder(Some(value.clone()), ""))
+                    }
+                    None => Err(self.err(ExpectedMapElement(idx))),
+                }
+            }
+            ref found => Err(self.mismatch("table", found)),
+        }
+    }
+
+    fn error(&mut self, err: &str) -> DecodeError {
+        DecodeError {
+            field: self.cur_field.clone(),
+            kind: ApplicationError(format!("{}", err))
+        }
+    }
+}