Make trim_end_unescaped more readable

Author: ratmice

lrlex/src/lib/parser.rs

@@ -686,39 +686,17 @@ where
 }
 
 fn trim_end_unescaped(s: &str) -> &str {
-    let mut cbuf = [0; 4];
-    let mut total_ws_bytes = 0;
-    let mut last_ws_char_len = 0;
-    // First loop over spaces
-    for ch in s.chars().rev().into_iter() {
-        if RE_SPACE_SEP.is_match(ch.encode_utf8(&mut cbuf)) {
-            last_ws_char_len = ch.len_utf8();
-            total_ws_bytes += last_ws_char_len;
-        } else {
-            break;
-        }
-    }
-    if total_ws_bytes == 0 {
+    let trimmed = s.trim_end_matches(matches_whitespace);
+    if trimmed.len() == s.len() {
         return s;
     }
-    let mut preceeding_backslashes = 0;
-    // Next loop over escaped slashes or spaces,
-    // an even number of backslashes are all escaping slashes,
-    // and an odd number of backslashes must have a trailing escaped space.
-    for c in s[..s.len() - total_ws_bytes].chars().rev() {
-        if c == '\\' {
-            preceeding_backslashes += 1
-        } else {
-            break;
-        }
+    // If the number of backslashes is odd then the first space in the trimmed portion is escaped so re-add it.
+    if trimmed.chars().rev().take_while(|&c| c == '\\').count() % 2 == 1 {
+        // Panic safety: the trimmed portion is at least one char long.
+        &s[..trimmed.len() + s[trimmed.len()..].chars().next().unwrap().len_utf8()]
+    } else {
+        trimmed
     }
-    // The backslash count was odd, the last must escape a space.
-    // Drop one of the intial spaces from the trim.
-    if preceeding_backslashes % 2 == 1 {
-        total_ws_bytes -= last_ws_char_len;
-    }
-
-    &s[..s.len() - total_ws_bytes]
 }
 
 #[cfg(test)]