Implement a 'trial parse' step, that will abort pre-parsing excessively

src/scanner.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Features shared by parsing and pre-parsing scanners.
 
 #include <stdint.h>
 
 #include <cmath>
 
@@ skipping 11 matching lines @@
 
 
 Handle<String> LiteralBuffer::Internalize(Isolate* isolate) const {
   if (is_one_byte()) {
     return isolate->factory()->InternalizeOneByteString(one_byte_literal());
   }
   return isolate->factory()->InternalizeTwoByteString(two_byte_literal());
 }
 
 
+// Default implementation for streams that do not support bookmarks.
+bool Utf16CharacterStream::SetBookmark() { return false; }
+void Utf16CharacterStream::ResetToBookmark() { UNREACHABLE(); }
+
+
 // ----------------------------------------------------------------------------
 // Scanner
 
 Scanner::Scanner(UnicodeCache* unicode_cache)
     : unicode_cache_(unicode_cache),
+      bookmark_c0_(-1),
       octal_pos_(Location::invalid()),
       harmony_modules_(false),
       harmony_classes_(false),
-      harmony_unicode_(false) {}
+      harmony_unicode_(false) {
+  bookmark_current_.literal_chars = &bookmark_current_literal_;
+  bookmark_current_.raw_literal_chars = &bookmark_current_raw_literal_;
+  bookmark_next_.literal_chars = &bookmark_next_literal_;
+  bookmark_next_.raw_literal_chars = &bookmark_next_raw_literal_;
+}
 
 
 void Scanner::Initialize(Utf16CharacterStream* source) {
   source_ = source;
   // Need to capture identifiers in order to recognize "get" and "set"
   // in object literals.
   Init();
   // Skip initial whitespace allowing HTML comment ends just like
   // after a newline and scan first token.
   has_line_terminator_before_next_ = true;
@@ skipping 1368 matching lines @@
 
 
 int Scanner::FindSymbol(DuplicateFinder* finder, int value) {
   if (is_literal_one_byte()) {
     return finder->AddOneByteSymbol(literal_one_byte_string(), value);
   }
   return finder->AddTwoByteSymbol(literal_two_byte_string(), value);
 }
 
 
+bool Scanner::SetBookmark() {
+  if (bookmark_c0_ == -1 && source_->SetBookmark()) {
+    bookmark_c0_ = c0_;
+    CopyTokenDesc(&bookmark_current_, &current_);
+    CopyTokenDesc(&bookmark_next_, &next_);
+    return true;
+  }
+  return false;
+}
+
+
+void Scanner::ResetToBookmark() {
+  DCHECK(bookmark_c0_ >= 0);  // Caller hasn't called SetBookmark.
+
+  source_->ResetToBookmark();
+  c0_ = bookmark_c0_;
+  StartLiteral();
+  StartRawLiteral();
+  CopyTokenDesc(&next_, &bookmark_current_);
+  current_ = next_;
+  StartLiteral();
+  StartRawLiteral();
+  CopyTokenDesc(&next_, &bookmark_next_);
+
+  bookmark_c0_ = -2;
+}
+
+
+bool Scanner::BookmarkHasBeenSet() { return bookmark_c0_ >= 0; }
+
+
+bool Scanner::BookmarkHasBeenReset() { return bookmark_c0_ == -2; }
+
+
+void Scanner::DropBookmark() { bookmark_c0_ = -1; }
+
+
+void Scanner::CopyTokenDesc(TokenDesc* to, TokenDesc* from) {
+  DCHECK_NOT_NULL(to);
+  DCHECK_NOT_NULL(from);
+  to->token = from->token;
+  to->location = from->location;
+  to->literal_chars->CopyFrom(from->literal_chars);
+  to->raw_literal_chars->CopyFrom(from->raw_literal_chars);
+}
+
+
 int DuplicateFinder::AddOneByteSymbol(Vector<const uint8_t> key, int value) {
   return AddSymbol(key, true, value);
 }
 
 
 int DuplicateFinder::AddTwoByteSymbol(Vector<const uint16_t> key, int value) {
   return AddSymbol(Vector<const uint8_t>::cast(key), false, value);
 }
 
 
@@ skipping 120 matching lines @@
     }
     backing_store_.Add(static_cast<uint8_t>((one_byte_length >> 7) | 0x80u));
   }
   backing_store_.Add(static_cast<uint8_t>(one_byte_length & 0x7f));
 
   backing_store_.AddBlock(bytes);
   return backing_store_.EndSequence().start();
 }
 
 } }  // namespace v8::internal