Implement a character stream for external one byte streams

src/parsing/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_PARSING_SCANNER_CHARACTER_STREAMS_H_
 #define V8_PARSING_SCANNER_CHARACTER_STREAMS_H_
 
 #include "src/handles.h"
 #include "src/parsing/scanner.h"
 #include "src/vector.h"
 
 namespace v8 {
 namespace internal {
 
 // Forward declarations.
 class ExternalTwoByteString;
+class ExternalOneByteString;
 
 // A buffered character stream based on a random access character
 // source (ReadBlock can be called with pos_ pointing to any position,
 // even positions before the current).
 class BufferedUtf16CharacterStream: public Utf16CharacterStream {
  public:
   BufferedUtf16CharacterStream();
   ~BufferedUtf16CharacterStream() override;
 
   void PushBack(uc32 character) override;
@@ skipping 133 matching lines @@
     DCHECK(buffer_cursor_ > raw_data_);
     pos_--;
     if (character != kEndOfInput) {
       buffer_cursor_--;
     }
   }
 
   bool SetBookmark() override;
   void ResetToBookmark() override;
 
- protected:
+ private:
   size_t SlowSeekForward(size_t delta) override {
     // Fast case always handles seeking.
     return 0;
   }
   bool ReadBlock() override {
     // Entire string is read at start.
     return false;
   }
-  Handle<ExternalTwoByteString> source_;
   const uc16* raw_data_;  // Pointer to the actual array of characters.
 
- private:
   static const size_t kNoBookmark = -1;
 
   size_t bookmark_;
 };
 
+// UTF16 buffer to read characters from an external latin1 string.
+class ExternalOneByteStringUtf16CharacterStream
+    : public BufferedUtf16CharacterStream {
+ public:
+  ExternalOneByteStringUtf16CharacterStream(Handle<ExternalOneByteString> data,
+                                            int start_position,
+                                            int end_position);
+  ~ExternalOneByteStringUtf16CharacterStream() override;
+
+  bool SetBookmark() override;
+  void ResetToBookmark() override;
+
+ private:
+  static const size_t kNoBookmark = -1;
+
+  size_t BufferSeekForward(size_t delta) override;
+  size_t FillBuffer(size_t position) override;
+
+  const uint8_t* raw_data_;  // Pointer to the actual array of characters.
+  size_t length_;
+  size_t bookmark_;
+};
+
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_SCANNER_CHARACTER_STREAMS_H_