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

src/scanner-character-streams.h

 // 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.
 
 #ifndef V8_SCANNER_CHARACTER_STREAMS_H_
 #define V8_SCANNER_CHARACTER_STREAMS_H_
 
 #include "src/scanner.h"
 
 namespace v8 {
@@ skipping 25 matching lines @@
 };
 
 
 // Generic string stream.
 class GenericStringUtf16CharacterStream: public BufferedUtf16CharacterStream {
  public:
   GenericStringUtf16CharacterStream(Handle<String> data, size_t start_position,
                                     size_t end_position);
   virtual ~GenericStringUtf16CharacterStream();
 
+  virtual bool SetBookmark();
+  virtual bool CanResetToBookmark();
+  virtual bool ResetToBookmark();
+
  protected:
   virtual size_t BufferSeekForward(size_t delta);
   virtual size_t FillBuffer(size_t position);
 
   Handle<String> string_;
   size_t length_;
+  size_t bookmark_;
 };
 
 
 // Utf16 stream based on a literal UTF-8 string.
 class Utf8ToUtf16CharacterStream: public BufferedUtf16CharacterStream {
  public:
   Utf8ToUtf16CharacterStream(const byte* data, size_t length);
   virtual ~Utf8ToUtf16CharacterStream();
 
   static size_t CopyChars(uint16_t* dest, size_t length, const byte* src,
                           size_t* src_pos, size_t src_length);
 
  protected:
   virtual size_t BufferSeekForward(size_t delta);
   virtual size_t FillBuffer(size_t char_position);
   void SetRawPosition(size_t char_position);
 
   const byte* raw_data_;
   size_t raw_data_length_;  // Measured in bytes, not characters.
   size_t raw_data_pos_;
   // The character position of the character at raw_data[raw_data_pos_].
   // Not necessarily the same as pos_.
   size_t raw_character_position_;
 };
 
 
 // ExternalStreamingStream is a wrapper around an ExternalSourceStream (see
 // include/v8.h) subclass implemented by the embedder.
 class ExternalStreamingStream : public BufferedUtf16CharacterStream {

[marja, 2015/04/22 16:40:55]

Pls add a todo here to implement bookmarking for this stream too; it should be
easy, since we can just ask the embedder to give us data from a given position.
(That might require transmitting the position in the API..)

  public:
   ExternalStreamingStream(ScriptCompiler::ExternalSourceStream* source_stream,
                           v8::ScriptCompiler::StreamedSource::Encoding encoding)
       : source_stream_(source_stream),
         encoding_(encoding),
         current_data_(NULL),
         current_data_offset_(0),
         current_data_length_(0),
         utf8_split_char_buffer_length_(0) {}
 
@@ skipping 31 matching lines @@
                                             int start_position,
                                             int end_position);
   virtual ~ExternalTwoByteStringUtf16CharacterStream();
 
   virtual void PushBack(uc32 character) {
     DCHECK(buffer_cursor_ > raw_data_);
     buffer_cursor_--;
     pos_--;
   }
 
+  virtual bool SetBookmark();
+  virtual bool CanResetToBookmark();
+  virtual bool ResetToBookmark();
+
  protected:
   virtual size_t SlowSeekForward(size_t delta) {
     // Fast case always handles seeking.
     return 0;
   }
   virtual bool ReadBlock() {
     // Entire string is read at start.
     return false;
   }
   Handle<ExternalTwoByteString> source_;
   const uc16* raw_data_;  // Pointer to the actual array of characters.
+
+ private:
+  int bookmark_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCANNER_CHARACTER_STREAMS_H_