1 files changed, 140 insertions, 0 deletions
diff --git a/src/spanned.rs b/src/spanned.rs
new file mode 100644
index 0000000..abbbd49
--- /dev/null
+++ b/src/spanned.rs
@@ -0,0 +1,140 @@
+//! ```
+//! #[macro_use]
+//! extern crate serde_derive;
+//!
+//! extern crate toml;
+//! use toml::Spanned;
+//!
+//! #[derive(Deserialize)]
+//! struct Value {
+//!     s: Spanned<String>,
+//! }
+//!
+//! fn main() {
+//!     let t = "s = \"value\"\n";
+//!
+//!     let u: Value = toml::from_str(t).unwrap();
+//!
+//!     assert_eq!(u.s.start(), 4);
+//!     assert_eq!(u.s.end(), 11);
+//!     assert_eq!(u.s.get_ref(), "value");
+//!     assert_eq!(u.s.into_inner(), String::from("value"));
+//! }
+//! ```
+
+use serde::{de, ser};
+use std::fmt;
+
+#[doc(hidden)]
+pub const NAME: &'static str = "$__toml_private_Spanned";
+#[doc(hidden)]
+pub const START: &'static str = "$__toml_private_start";
+#[doc(hidden)]
+pub const END: &'static str = "$__toml_private_end";
+#[doc(hidden)]
+pub const VALUE: &'static str = "$__toml_private_value";
+
+/// A spanned value, indicating the range at which it is defined in the source.
+#[derive(Debug)]
+pub struct Spanned<T> {
+    /// The start range.
+    start: usize,
+    /// The end range (exclusive).
+    end: usize,
+    /// The spanned value.
+    value: T,
+}
+
+impl<T> Spanned<T> {
+    /// Access the start of the span of the contained value.
+    pub fn start(&self) -> usize {
+        self.start
+    }
+
+    /// Access the end of the span of the contained value.
+    pub fn end(&self) -> usize {
+        self.end
+    }
+
+    /// Get the span of the contained value.
+    pub fn span(&self) -> (usize, usize) {
+        (self.start, self.end)
+    }
+
+    /// Consumes the spanned value and returns the contained value.
+    pub fn into_inner(self) -> T {
+        self.value
+    }
+
+    /// Returns a reference to the contained value.
+    pub fn get_ref(&self) -> &T {
+        &self.value
+    }
+
+    /// Returns a mutable reference to the contained value.
+    pub fn get_mut(&self) -> &T {
+        &self.value
+    }
+}
+
+impl<'de, T> de::Deserialize<'de> for Spanned<T>
+    where T: de::Deserialize<'de>
+{
+    fn deserialize<D>(deserializer: D) -> Result<Spanned<T>, D::Error>
+        where D: de::Deserializer<'de>
+    {
+        struct SpannedVisitor<T>(::std::marker::PhantomData<T>);
+
+        impl<'de, T> de::Visitor<'de> for SpannedVisitor<T>
+            where T: de::Deserialize<'de>
+        {
+            type Value = Spanned<T>;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter.write_str("a TOML spanned")
+            }
+
+            fn visit_map<V>(self, mut visitor: V) -> Result<Spanned<T>, V::Error>
+                where V: de::MapAccess<'de>
+            {
+                if visitor.next_key()? != Some(START) {
+                    return Err(de::Error::custom("spanned start key not found"))
+                }
+
+                let start: usize = visitor.next_value()?;
+
+                if visitor.next_key()? != Some(END) {
+                    return Err(de::Error::custom("spanned end key not found"))
+                }
+
+                let end: usize = visitor.next_value()?;
+
+                if visitor.next_key()? != Some(VALUE) {
+                    return Err(de::Error::custom("spanned value key not found"))
+                }
+
+                let value: T = visitor.next_value()?;
+
+                Ok(Spanned {
+                    start: start,
+                    end: end,
+                    value: value
+                })
+            }
+        }
+
+        let visitor = SpannedVisitor(::std::marker::PhantomData);
+
+        static FIELDS: [&'static str; 3] = [START, END, VALUE];
+        deserializer.deserialize_struct(NAME, &FIELDS, visitor)
+    }
+}
+
+impl<T: ser::Serialize> ser::Serialize for Spanned<T> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: ser::Serializer,
+    {
+        self.value.serialize(serializer)
+    }
+}