Add: EntryHeader::parse()

Introduce Error + Error-kind for it, return Result<> from the ::parse()
function.

libimagstore/src/header.rs

@@ -1,5 +1,75 @@
+use std::error::Error;
+use std::result::Result as RResult;
+
 use toml::Table;
 
+pub mod error {
+    use std::fmt::{Debug, Display, Formatter};
+    use std::fmt;
+    use std::error::Error;
+    use toml;
+
+    #[derive(Clone)]
+    pub enum ParserErrorKind {
+        TOMLParserErrors,
+        MissingMainSection,
+    }
+
+    pub struct ParserError {
+        kind: ParserErrorKind,
+        cause: Option<Box<Error>>,
+    }
+
+    impl ParserError {
+
+        pub fn new(k: ParserErrorKind, cause: Option<Box<Error>>) -> ParserError {
+            ParserError {
+                kind: k,
+                cause: cause,
+            }
+        }
+
+    }
+
+    impl Debug for ParserError {
+
+        fn fmt(&self, f: &mut Formatter) -> Result<(), fmt::Error> {
+            try!(write!(f, "{:?}", self.description()));
+            Ok(())
+        }
+
+    }
+
+    impl Display for ParserError {
+
+        fn fmt(&self, f: &mut Formatter) -> Result<(), fmt::Error> {
+            try!(write!(f, "{}", self.description()));
+            Ok(())
+        }
+
+    }
+
+    impl Error for ParserError {
+
+        fn description(&self) -> &str {
+            match self.kind {
+                ParserErrorKind::MissingMainSection => "Missing main section",
+                ParserErrorKind::TOMLParserErrors   => "Several TOML-Parser-Errors",
+            }
+        }
+
+        fn cause(&self) -> Option<&Error> {
+            self.cause.as_ref().map(|e| &**e)
+        }
+
+    }
+
+}
+
+
+use self::error::ParserErrorKind;
+use self::error::ParserError;
+
 /**
  * EntryHeader
  *
@@ -11,6 +81,11 @@ pub struct EntryHeader {
     toml: Table,
 }
 
+pub type Result<V> = RResult<V, error::ParserError>;
+
+/**
+ * Wrapper type around file header (TOML) object
+ */
 impl EntryHeader {
 
     /**
@@ -29,4 +104,13 @@ impl EntryHeader {
         &self.toml
     }
 
+    pub fn parse(s: &str) -> Result<EntryHeader> {
+        use toml::Parser;
+
+        let mut parser = Parser::new(s);
+        parser.parse()
+            .ok_or(ParserError::new(ParserErrorKind::TOMLParserErrors, None))
+            .map(|table| EntryHeader::new(table))
+    }
+
 }