1 files changed, 119 insertions, 0 deletions
diff --git a/bindgen/ir/comment.rs b/bindgen/ir/comment.rs
new file mode 100644
index 00000000..c96e3ebb
--- /dev/null
+++ b/bindgen/ir/comment.rs
@@ -0,0 +1,119 @@
+//! 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: &str, indent: usize) -> String {
+    match self::kind(comment) {
+        Some(Kind::SingleLines) => preprocess_single_lines(comment, indent),
+        Some(Kind::MultiLine) => preprocess_multi_line(comment, indent),
+        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
+    }
+}
+
+fn make_indent(indent: usize) -> String {
+    const RUST_INDENTATION: usize = 4;
+    " ".repeat(indent * RUST_INDENTATION)
+}
+
+/// Preprocesses multiple single line comments.
+///
+/// Handles lines starting with both `//` and `///`.
+fn preprocess_single_lines(comment: &str, indent: usize) -> String {
+    debug_assert!(comment.starts_with("//"), "comment is not single line");
+
+    let indent = make_indent(indent);
+    let mut is_first = true;
+    let lines: Vec<_> = comment
+        .lines()
+        .map(|l| l.trim().trim_start_matches('/'))
+        .map(|l| {
+            let indent = if is_first { "" } else { &*indent };
+            is_first = false;
+            format!("{}///{}", indent, l)
+        })
+        .collect();
+    lines.join("\n")
+}
+
+fn preprocess_multi_line(comment: &str, indent: usize) -> String {
+    let comment = comment
+        .trim_start_matches('/')
+        .trim_end_matches('/')
+        .trim_end_matches('*');
+
+    let indent = make_indent(indent);
+    // Strip any potential `*` characters preceding each line.
+    let mut is_first = true;
+    let mut lines: Vec<_> = comment
+        .lines()
+        .map(|line| line.trim().trim_start_matches('*').trim_start_matches('!'))
+        .skip_while(|line| line.trim().is_empty()) // Skip the first empty lines.
+        .map(|line| {
+            let indent = if is_first { "" } else { &*indent };
+            is_first = false;
+            format!("{}///{}", indent, line)
+        })
+        .collect();
+
+    // Remove the trailing line corresponding to the `*/`.
+    if lines
+        .last()
+        .map_or(false, |l| l.trim().is_empty() || l.trim() == "///")
+    {
+        lines.pop();
+    }
+
+    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", 0), "/// hello");
+        assert_eq!(preprocess("// hello", 0), "/// hello");
+        assert_eq!(preprocess("//    hello", 0), "///    hello");
+    }
+
+    #[test]
+    fn processes_multi_lines_correctly() {
+        assert_eq!(
+            preprocess("/** hello \n * world \n * foo \n */", 0),
+            "/// hello\n/// world\n/// foo"
+        );
+
+        assert_eq!(
+            preprocess("/**\nhello\n*world\n*foo\n*/", 0),
+            "///hello\n///world\n///foo"
+        );
+    }
+}