Auto merge of servo#111 - servo:stack, r=SimonSapin

Avoid overflowing the stack in consume_until_end_of_block.

Fixes: https://bugzilla.mozilla.org/show_bug.cgi?id=1323705

r? @SimonSapin

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/rust-cssparser/111)
<!-- Reviewable:end -->

Author: bors-servo

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "cssparser"
-version = "0.7.1"
+version = "0.7.2"
 authors = [ "Simon Sapin <simon.sapin@exyr.org>" ]
 
 description = "Rust implementation of CSS Syntax Level 3"

src/parser.rs

@@ -691,15 +691,22 @@ impl<'i, 't> Parser<'i, 't> {
 }
 
 
-/// Return value indicates whether the end of the input was reached.
 fn consume_until_end_of_block(block_type: BlockType, tokenizer: &mut Tokenizer) {
+    let mut stack = vec![block_type];
+
     // FIXME: have a special-purpose tokenizer method for this that does less work.
     while let Ok(ref token) = tokenizer.next() {
-        if BlockType::closing(token) == Some(block_type) {
-            return
+        if let Some(b) = BlockType::closing(token) {
+            if *stack.last().unwrap() == b {
+                stack.pop();
+                if stack.is_empty() {
+                    return;
+                }
+            }
         }
+
         if let Some(block_type) = BlockType::opening(token) {
-            consume_until_end_of_block(block_type, tokenizer);
+            stack.push(block_type);
         }
     }
 }

src/tests.rs

@@ -603,6 +603,16 @@ fn unquoted_url(b: &mut Bencher) {
 
 struct JsonParser;
 
+#[test]
+fn no_stack_overflow_multiple_nested_blocks() {
+    let mut input: String = "{{".into();
+    for _ in 0..20 {
+        let dup = input.clone();
+        input.push_str(&dup);
+    }
+    let mut input = Parser::new(&input);
+    while let Ok(..) = input.next() { }
+}
 
 impl DeclarationParser for JsonParser {
     type Declaration = Json;