1 files changed, 73 insertions, 0 deletions
diff --git a/core/fxcrt/fx_bidi.h b/core/fxcrt/fx_bidi.h
new file mode 100644
index 0000000000..309c6f518d
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+++ b/core/fxcrt/fx_bidi.h
@@ -0,0 +1,73 @@
+// Copyright 2014 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#ifndef CORE_FXCRT_FX_BIDI_H_
+#define CORE_FXCRT_FX_BIDI_H_
+
+#include <memory>
+#include <vector>
+
+#include "core/fxcrt/include/fx_string.h"
+#include "core/fxcrt/include/fx_system.h"
+
+// Processes characters and group them into segments based on text direction.
+class CFX_BidiChar {
+ public:
+  enum Direction { NEUTRAL, LEFT, RIGHT };
+  struct Segment {
+    int32_t start;        // Start position.
+    int32_t count;        // Character count.
+    Direction direction;  // Segment direction.
+  };
+
+  CFX_BidiChar();
+
+  // Append a character and classify it as left, right, or neutral.
+  // Returns true if the character has a different direction than the
+  // existing direction to indicate there is a segment to process.
+  bool AppendChar(FX_WCHAR wch);
+
+  // Call this after the last character has been appended. AppendChar()
+  // must not be called after this.
+  // Returns true if there is still a segment to process.
+  bool EndChar();
+
+  // Call after a change in direction is indicated by the above to get
+  // information about the segment to process.
+  Segment GetSegmentInfo() const { return m_LastSegment; }
+
+ private:
+  void StartNewSegment(CFX_BidiChar::Direction direction);
+
+  Segment m_CurrentSegment;
+  Segment m_LastSegment;
+};
+
+class CFX_BidiString {
+ public:
+  using const_iterator = std::vector<CFX_BidiChar::Segment>::const_iterator;
+  explicit CFX_BidiString(const CFX_WideString& str);
+
+  // Overall direction is always LEFT or RIGHT, never NEUTRAL.
+  CFX_BidiChar::Direction OverallDirection() const {
+    return m_eOverallDirection;
+  }
+
+  // Force the overall direction to be R2L regardless of what was detected.
+  void SetOverallDirectionRight();
+
+  FX_WCHAR CharAt(size_t x) const { return m_Str[x]; }
+  const_iterator begin() const { return m_Order.begin(); }
+  const_iterator end() const { return m_Order.end(); }
+
+ private:
+  const CFX_WideString m_Str;
+  std::unique_ptr<CFX_BidiChar> m_pBidiChar;
+  std::vector<CFX_BidiChar::Segment> m_Order;
+  CFX_BidiChar::Direction m_eOverallDirection;
+};
+
+#endif  // CORE_FXCRT_FX_BIDI_H_