1 files changed, 82 insertions, 0 deletions
diff --git a/src/tools/rustfmt/src/source_map.rs b/src/tools/rustfmt/src/source_map.rs
new file mode 100644
index 000000000..76e0d24cf
--- /dev/null
+++ b/src/tools/rustfmt/src/source_map.rs
@@ -0,0 +1,82 @@
+//! This module contains utilities that work with the `SourceMap` from `libsyntax`/`syntex_syntax`.
+//! This includes extension traits and methods for looking up spans and line ranges for AST nodes.
+
+use rustc_span::{BytePos, Span};
+
+use crate::comment::FindUncommented;
+use crate::config::file_lines::LineRange;
+use crate::visitor::SnippetProvider;
+
+pub(crate) trait SpanUtils {
+    fn span_after(&self, original: Span, needle: &str) -> BytePos;
+    fn span_after_last(&self, original: Span, needle: &str) -> BytePos;
+    fn span_before(&self, original: Span, needle: &str) -> BytePos;
+    fn span_before_last(&self, original: Span, needle: &str) -> BytePos;
+    fn opt_span_after(&self, original: Span, needle: &str) -> Option<BytePos>;
+    fn opt_span_before(&self, original: Span, needle: &str) -> Option<BytePos>;
+}
+
+pub(crate) trait LineRangeUtils {
+    /// Returns the `LineRange` that corresponds to `span` in `self`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `span` crosses a file boundary, which shouldn't happen.
+    fn lookup_line_range(&self, span: Span) -> LineRange;
+}
+
+impl SpanUtils for SnippetProvider {
+    fn span_after(&self, original: Span, needle: &str) -> BytePos {
+        self.opt_span_after(original, needle).unwrap_or_else(|| {
+            panic!(
+                "bad span: `{}`: `{}`",
+                needle,
+                self.span_to_snippet(original).unwrap()
+            )
+        })
+    }
+
+    fn span_after_last(&self, original: Span, needle: &str) -> BytePos {
+        let snippet = self.span_to_snippet(original).unwrap();
+        let mut offset = 0;
+
+        while let Some(additional_offset) = snippet[offset..].find_uncommented(needle) {
+            offset += additional_offset + needle.len();
+        }
+
+        original.lo() + BytePos(offset as u32)
+    }
+
+    fn span_before(&self, original: Span, needle: &str) -> BytePos {
+        self.opt_span_before(original, needle).unwrap_or_else(|| {
+            panic!(
+                "bad span: `{}`: `{}`",
+                needle,
+                self.span_to_snippet(original).unwrap()
+            )
+        })
+    }
+
+    fn span_before_last(&self, original: Span, needle: &str) -> BytePos {
+        let snippet = self.span_to_snippet(original).unwrap();
+        let mut offset = 0;
+
+        while let Some(additional_offset) = snippet[offset..].find_uncommented(needle) {
+            offset += additional_offset + needle.len();
+        }
+
+        original.lo() + BytePos(offset as u32 - 1)
+    }
+
+    fn opt_span_after(&self, original: Span, needle: &str) -> Option<BytePos> {
+        self.opt_span_before(original, needle)
+            .map(|bytepos| bytepos + BytePos(needle.len() as u32))
+    }
+
+    fn opt_span_before(&self, original: Span, needle: &str) -> Option<BytePos> {
+        let snippet = self.span_to_snippet(original)?;
+        let offset = snippet.find_uncommented(needle)?;
+
+        Some(original.lo() + BytePos(offset as u32))
+    }
+}