1 files changed, 94 insertions, 0 deletions
diff --git a/src/ir/comment.rs b/src/ir/comment.rs
new file mode 100644
index 00000000..15237b91
--- /dev/null
+++ b/src/ir/comment.rs
@@ -0,0 +1,94 @@
+//! Utilities for manipulating C/C++ comments.
+
+/// The type of a comment.
+#[derive(Debug, PartialEq, Eq)]
+enum Kind {
+    /// A `///` comment, or something of the like.
+    /// All lines in a comment should start with the same symbol.
+    SingleLines,
+    /// A `/**` comment, where each other line can start with `*` and the
+    /// entire block ends with `*/`.
+    MultiLine,
+}
+/// Preprocesses a C/C++ comment so that it is a valid Rust comment.
+pub fn preprocess(comment: String) -> String {
+    match self::kind(&comment) {
+        Some(Kind::SingleLines) => preprocess_single_lines(&comment),
+        Some(Kind::MultiLine) => preprocess_multi_line(&comment),
+        None => comment.to_owned(),
+    }
+}
+
+/// Gets the kind of the doc comment, if it is one.
+fn kind(comment: &str) -> Option<Kind> {
+    if comment.starts_with("/*") {
+        Some(Kind::MultiLine)
+    } else if comment.starts_with("//") {
+        Some(Kind::SingleLines)
+    } else {
+        None
+    }
+}
+
+/// Preprocesses mulitple single line comments.
+///
+/// Handles lines starting with both `//` and `///`.
+fn preprocess_single_lines(comment: &str) -> String {
+    assert!(comment.starts_with("//"), "comment is not single line");
+
+    let lines: Vec<_> = comment.lines()
+                               .map(|l| l.trim_left_matches('/').trim())
+                               .map(|l| format!("/// {}", l).trim().to_owned())
+                               .collect();
+    lines.join("\n")
+}
+
+fn preprocess_multi_line(comment: &str) -> String {
+    let comment = comment.trim_left_matches('/')
+                         .trim_left_matches("*")
+                         .trim_left_matches("!")
+                         .trim_right_matches('/')
+                         .trim_right_matches('*')
+                         .trim();
+
+    // Strip any potential `*` characters preceding each line.
+    let mut lines: Vec<_> = comment.lines()
+        .map(|line| line.trim().trim_left_matches('*').trim())
+        .skip_while(|line| line.is_empty()) // Skip the first empty lines.
+        .map(|line| format!("/// {}", line).trim().to_owned())
+        .collect();
+
+    // Remove the trailing `*/`.
+    let last_idx = lines.len() - 1;
+    if lines[last_idx].is_empty() {
+        lines.remove(last_idx);
+    }
+
+    lines.join("\n")
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn picks_up_single_and_multi_line_doc_comments() {
+        assert_eq!(kind("/// hello"), Some(Kind::SingleLines));
+        assert_eq!(kind("/** world */"), Some(Kind::MultiLine));
+    }
+
+    #[test]
+    fn processes_single_lines_correctly() {
+        assert_eq!(preprocess("/// hello".to_owned()), "/// hello");
+        assert_eq!(preprocess("// hello".to_owned()), "/// hello");
+    }
+
+    #[test]
+    fn processes_multi_lines_correctly() {
+        assert_eq!(preprocess("/** hello \n * world \n * foo \n */".to_owned()),
+                   "/// hello\n/// world\n/// foo");
+
+        assert_eq!(preprocess("/**\nhello\n*world\n*foo\n*/".to_owned()),
+                   "/// hello\n/// world\n/// foo");
+    }
+}