[Isolates] Merge from bleeding_edge, revisions 5934-6100.

src/preparser-api.cc

Index: src/preparser-api.cc
===================================================================
--- src/preparser-api.cc	(revision 6904)
+++ src/preparser-api.cc	(working copy)
@@ -39,39 +39,121 @@
 namespace internal {
 
 // UTF16Buffer based on a v8::UnicodeInputStream.
-class InputStreamUTF16Buffer : public UTF16Buffer {
+class InputStreamUTF16Buffer : public UC16CharacterStream {
  public:
-  explicit InputStreamUTF16Buffer(UnicodeInputStream* stream)
-      : UTF16Buffer(),
-        stream_(stream) { }
+  /* The InputStreamUTF16Buffer maintains an internal buffer
+   * that is filled in chunks from the UC16CharacterStream.
+   * It also maintains unlimited pushback capability, but optimized
+   * for small pushbacks.
+   * The pushback_buffer_ pointer points to the limit of pushbacks
+   * in the current buffer. There is room for a few pushback'ed chars before
+   * the buffer containing the most recently read chunk. If this is overflowed,
+   * an external buffer is allocated/reused to hold further pushbacks, and
+   * pushback_buffer_ and buffer_cursor_/buffer_end_ now points to the
+   * new buffer. When this buffer is read to the end again, the cursor is
+   * switched back to the internal buffer
+   */
+  explicit InputStreamUTF16Buffer(v8::UnicodeInputStream* stream)
+      : UC16CharacterStream(),
+        stream_(stream),
+        pushback_buffer_(buffer_),
+        pushback_buffer_end_cache_(NULL),
+        pushback_buffer_backing_(NULL),
+        pushback_buffer_backing_size_(0) {
+    buffer_cursor_ = buffer_end_ = buffer_ + kPushBackSize;
+  }
 
-  virtual ~InputStreamUTF16Buffer() { }
+  virtual ~InputStreamUTF16Buffer() {
+    if (pushback_buffer_backing_ != NULL) {
+      DeleteArray(pushback_buffer_backing_);
+    }
+  }
 
-  virtual void PushBack(uc32 ch) {
-    stream_->PushBack(ch);
+  virtual void PushBack(uc16 ch) {
+    ASSERT(pos_ > 0);
+    if (buffer_cursor_ <= pushback_buffer_) {
+      // No more room in the current buffer to do pushbacks.
+      if (pushback_buffer_end_cache_ == NULL) {
+        // We have overflowed the pushback space at the beginning of buffer_.
+        // Switch to using a separate allocated pushback buffer.
+        if (pushback_buffer_backing_ == NULL) {
+          // Allocate a buffer the first time we need it.
+          pushback_buffer_backing_ = NewArray<uc16>(kPushBackSize);
+          pushback_buffer_backing_size_ = kPushBackSize;
+        }
+        pushback_buffer_ = pushback_buffer_backing_;
+        pushback_buffer_end_cache_ = buffer_end_;
+        buffer_end_ = pushback_buffer_backing_ + pushback_buffer_backing_size_;
+        buffer_cursor_ = buffer_end_ - 1;
+      } else {
+        // Hit the bottom of the allocated pushback buffer.
+        // Double the buffer and continue.
+        uc16* new_buffer = NewArray<uc16>(pushback_buffer_backing_size_ * 2);
+        memcpy(new_buffer + pushback_buffer_backing_size_,
+               pushback_buffer_backing_,
+               pushback_buffer_backing_size_);
+        DeleteArray(pushback_buffer_backing_);
+        buffer_cursor_ = new_buffer + pushback_buffer_backing_size_;
+        pushback_buffer_backing_ = pushback_buffer_ = new_buffer;
+        buffer_end_ = pushback_buffer_backing_ + pushback_buffer_backing_size_;
+      }
+    }
+    pushback_buffer_[buffer_cursor_ - pushback_buffer_- 1] = ch;
     pos_--;
   }
 
-  virtual uc32 Advance() {
-    uc32 result = stream_->Next();
-    if (result >= 0) pos_++;
-    return result;
+ protected:
+  virtual bool ReadBlock() {
+    if (pushback_buffer_end_cache_ != NULL) {
+      buffer_cursor_ = buffer_;
+      buffer_end_ = pushback_buffer_end_cache_;
+      pushback_buffer_end_cache_ = NULL;
+      return buffer_end_ > buffer_cursor_;
+    }
+    // Copy the top of the buffer into the pushback area.
+    int32_t value;
+    uc16* buffer_start = buffer_ + kPushBackSize;
+    buffer_cursor_ = buffer_end_ = buffer_start;
+    while ((value = stream_->Next()) >= 0) {
+      if (value > static_cast<int32_t>(unibrow::Utf8::kMaxThreeByteChar)) {
+        value = unibrow::Utf8::kBadChar;
+      }
+      // buffer_end_ is a const pointer, but buffer_ is writable.
+      buffer_start[buffer_end_++ - buffer_start] = static_cast<uc16>(value);
+      if (buffer_end_ == buffer_ + kPushBackSize + kBufferSize) break;
+    }
+    return buffer_end_ > buffer_start;
   }
 
-  virtual void SeekForward(int pos) {
+  virtual unsigned SlowSeekForward(unsigned pos) {
     // Seeking in the input is not used by preparsing.
     // It's only used by the real parser based on preparser data.
     UNIMPLEMENTED();
+    return 0;
   }
 
  private:
+  static const unsigned kBufferSize = 512;
+  static const unsigned kPushBackSize = 16;
   v8::UnicodeInputStream* const stream_;
+  // Buffer holding first kPushBackSize characters of pushback buffer,
+  // then kBufferSize chars of read-ahead.
+  // The pushback buffer is only used if pushing back characters past
+  // the start of a block.
+  uc16 buffer_[kPushBackSize + kBufferSize];
+  // Limit of pushbacks before new allocation is necessary.
+  uc16* pushback_buffer_;
+  // Only if that pushback buffer at the start of buffer_ isn't sufficient
+  // is the following used.
+  const uc16* pushback_buffer_end_cache_;
+  uc16* pushback_buffer_backing_;
+  unsigned pushback_buffer_backing_size_;
 };
 
 
 class StandAloneJavaScriptScanner : public JavaScriptScanner {
  public:
-  void Initialize(UTF16Buffer* source) {
+  void Initialize(UC16CharacterStream* source) {
     source_ = source;
     literal_flags_ = kLiteralString | kLiteralIdentifier;
     Init();
@@ -92,7 +174,6 @@
 
 bool EnableSlowAsserts() { return true; }
 
-
 }  // namespace internal.