Create common CXML_Object base class for CXML_Content and CXML_Element.

They should each know what they are rather than having an
external ChildRecord struct to track the type.

Change-Id: Ic647ba45569764073e944d30af1a96dccdc29eb3
Reviewed-on: https://pdfium-review.googlesource.com/5210
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

7 files changed, 141 insertions, 92 deletions

diff --git a/core/fxcrt/xml/cxml_content.cpp b/core/fxcrt/xml/cxml_content.cpp
new file mode 100644
index 0000000000..fe0c185bb7
--- /dev/null
+++ b/core/fxcrt/xml/cxml_content.cpp
@@ -0,0 +1,20 @@
+// Copyright 2017 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
+
+#include "core/fxcrt/xml/cxml_content.h"
+
+CXML_Content::CXML_Content(bool bCDATA, const CFX_WideStringC& content)
+    : m_bCDATA(bCDATA), m_Content(content) {}
+
+CXML_Content::~CXML_Content() {}
+
+CXML_Content* CXML_Content::AsContent() {
+  return this;
+}
+
+const CXML_Content* CXML_Content::AsContent() const {
+  return this;
+}
diff --git a/core/fxcrt/xml/cxml_content.h b/core/fxcrt/xml/cxml_content.h
index 261c622eca..641efe6720 100644
--- a/core/fxcrt/xml/cxml_content.h
+++ b/core/fxcrt/xml/cxml_content.h
@@ -7,14 +7,17 @@
 #ifndef CORE_FXCRT_XML_CXML_CONTENT_H_
 #define CORE_FXCRT_XML_CXML_CONTENT_H_
 
-class CXML_Content {
+#include "core/fxcrt/fx_string.h"
+#include "core/fxcrt/xml/cxml_object.h"
+
+class CXML_Content : public CXML_Object {
  public:
-  CXML_Content() : m_bCDATA(false), m_Content() {}
+  CXML_Content(bool bCDATA, const CFX_WideStringC& content);
+  ~CXML_Content() override;
 
-  void Set(bool bCDATA, const CFX_WideStringC& content) {
-    m_bCDATA = bCDATA;
-    m_Content = content;
-  }
+  // CXML_Object:
+  CXML_Content* AsContent() override;
+  const CXML_Content* AsContent() const override;
 
   bool m_bCDATA;
   CFX_WideString m_Content;
diff --git a/core/fxcrt/xml/cxml_element.cpp b/core/fxcrt/xml/cxml_element.cpp
index 95a6dba147..ec0a73b00d 100644
--- a/core/fxcrt/xml/cxml_element.cpp
+++ b/core/fxcrt/xml/cxml_element.cpp
@@ -23,25 +23,16 @@ CXML_Element::CXML_Element(const CXML_Element* pParent,
                            const CFX_ByteStringC& tagname)
     : m_pParent(pParent), m_QSpaceName(qSpace), m_TagName(tagname) {}
 
-CXML_Element::~CXML_Element() {
-  Empty();
-}
+CXML_Element::~CXML_Element() {}
 
-void CXML_Element::Empty() {
-  RemoveChildren();
+CXML_Element* CXML_Element::AsElement() {
+  return this;
 }
-void CXML_Element::RemoveChildren() {
-  for (const ChildRecord& record : m_Children) {
-    if (record.type == Content) {
-      delete static_cast<CXML_Content*>(record.child);
-    } else if (record.type == Element) {
-      CXML_Element* child = static_cast<CXML_Element*>(record.child);
-      child->RemoveChildren();
-      delete child;
-    }
-  }
-  m_Children.clear();
+
+const CXML_Element* CXML_Element::AsElement() const {
+  return this;
 }
+
 CFX_ByteString CXML_Element::GetTagName(bool bQualified) const {
   if (!bQualified || m_QSpaceName.IsEmpty()) {
     return m_TagName;
@@ -159,69 +150,47 @@ bool CXML_Element::GetAttrFloat(const CFX_ByteStringC& space,
   return true;
 }
 
-CXML_Element::ChildType CXML_Element::GetChildType(uint32_t index) const {
-  return index < m_Children.size() ? m_Children[index].type : Invalid;
-}
-
-CFX_WideString CXML_Element::GetContent(uint32_t index) const {
-  if (index < m_Children.size() && m_Children[index].type == Content) {
-    CXML_Content* pContent =
-        static_cast<CXML_Content*>(m_Children[index].child);
-    if (pContent)
-      return pContent->m_Content;
-  }
-  return CFX_WideString();
-}
-
-CXML_Element* CXML_Element::GetElement(uint32_t index) const {
-  if (index < m_Children.size() && m_Children[index].type == Element)
-    return static_cast<CXML_Element*>(m_Children[index].child);
-  return nullptr;
-}
-
 uint32_t CXML_Element::CountElements(const CFX_ByteStringC& space,
                                      const CFX_ByteStringC& tag) const {
   int count = 0;
-  for (const ChildRecord& record : m_Children) {
-    if (record.type != Element)
-      continue;
-
-    CXML_Element* pKid = static_cast<CXML_Element*>(record.child);
-    if ((space.IsEmpty() || pKid->m_QSpaceName == space) &&
-        pKid->m_TagName == tag) {
+  for (const auto& pChild : m_Children) {
+    const CXML_Element* pKid = pChild->AsElement();
+    if (pKid && pKid->m_TagName == tag &&
+        (space.IsEmpty() || pKid->m_QSpaceName == space)) {
       count++;
     }
   }
   return count;
 }
 
+CXML_Object* CXML_Element::GetChild(uint32_t index) const {
+  return index < m_Children.size() ? m_Children[index].get() : nullptr;
+}
+
 CXML_Element* CXML_Element::GetElement(const CFX_ByteStringC& space,
                                        const CFX_ByteStringC& tag,
-                                       int index) const {
-  if (index < 0)
+                                       int nth) const {
+  if (nth < 0)
     return nullptr;
 
-  for (const ChildRecord& record : m_Children) {
-    if (record.type != Element)
-      continue;
-
-    CXML_Element* pKid = static_cast<CXML_Element*>(record.child);
-    if ((space.IsEmpty() || pKid->m_QSpaceName == space) &&
-        pKid->m_TagName == tag) {
-      if (index-- == 0)
+  for (const auto& pChild : m_Children) {
+    CXML_Element* pKid = pChild->AsElement();
+    if (pKid && pKid->m_TagName == tag &&
+        (space.IsEmpty() || pKid->m_QSpaceName == space)) {
+      if (nth-- == 0)
         return pKid;
     }
   }
   return nullptr;
 }
 
-uint32_t CXML_Element::FindElement(CXML_Element* pChild) const {
+uint32_t CXML_Element::FindElement(CXML_Element* pElement) const {
   int index = 0;
-  for (const ChildRecord& record : m_Children) {
-    if (record.type == Element &&
-        static_cast<CXML_Element*>(record.child) == pChild) {
+  for (const auto& pChild : m_Children) {
+    CXML_Element* pKid = pChild->AsElement();
+    if (pKid && pKid == pElement)
       return index;
-    }
+
     ++index;
   }
   return 0xFFFFFFFF;
diff --git a/core/fxcrt/xml/cxml_element.h b/core/fxcrt/xml/cxml_element.h
index 349deba2c8..2eb6caf74c 100644
--- a/core/fxcrt/xml/cxml_element.h
+++ b/core/fxcrt/xml/cxml_element.h
@@ -12,19 +12,21 @@
 
 #include "core/fxcrt/fx_basic.h"
 #include "core/fxcrt/xml/cxml_attrmap.h"
+#include "core/fxcrt/xml/cxml_object.h"
 
-class CXML_Element {
+class CXML_Element : public CXML_Object {
  public:
-  enum ChildType { Invalid, Element, Content };
-
   static std::unique_ptr<CXML_Element> Parse(const void* pBuffer, size_t size);
 
   CXML_Element(const CXML_Element* pParent,
                const CFX_ByteStringC& qSpace,
                const CFX_ByteStringC& tagname);
-  ~CXML_Element();
+  ~CXML_Element() override;
+
+  // CXML_Object:
+  CXML_Element* AsElement() override;
+  const CXML_Element* AsElement() const override;
 
-  void Empty();
   CFX_ByteString GetTagName(bool bQualified = false) const;
   CFX_ByteString GetNamespace(bool bQualified = false) const;
   CFX_ByteString GetNamespaceURI(const CFX_ByteString& qName) const;
@@ -88,39 +90,25 @@ class CXML_Element {
   }
 
   uint32_t CountChildren() const { return m_Children.size(); }
-  ChildType GetChildType(uint32_t index) const;
-  CFX_WideString GetContent(uint32_t index) const;
-  CXML_Element* GetElement(uint32_t index) const;
-  CXML_Element* GetElement(const CFX_ByteStringC& space,
-                           const CFX_ByteStringC& tag) const {
-    return GetElement(space, tag, 0);
-  }
-
   uint32_t CountElements(const CFX_ByteStringC& space,
                          const CFX_ByteStringC& tag) const;
+  CXML_Object* GetChild(uint32_t index) const;
   CXML_Element* GetElement(const CFX_ByteStringC& space,
                            const CFX_ByteStringC& tag,
-                           int index) const;
-
-  uint32_t FindElement(CXML_Element* pChild) const;
+                           int nth) const;
+  uint32_t FindElement(CXML_Element* pElement) const;
   void SetTag(const CFX_ByteStringC& qTagName);
-  void RemoveChildren();
   void RemoveChild(uint32_t index);
 
  private:
   friend class CXML_Parser;
   friend class CXML_Composer;
 
-  struct ChildRecord {
-    ChildType type;
-    void* child;  // CXML_Element and CXML_Content lack a common ancestor.
-  };
-
   const CXML_Element* const m_pParent;
   CFX_ByteString m_QSpaceName;
   CFX_ByteString m_TagName;
   CXML_AttrMap m_AttrMap;
-  std::vector<ChildRecord> m_Children;
+  std::vector<std::unique_ptr<CXML_Object>> m_Children;
 };
 
 #endif  // CORE_FXCRT_XML_CXML_ELEMENT_H_
diff --git a/core/fxcrt/xml/cxml_object.cpp b/core/fxcrt/xml/cxml_object.cpp
new file mode 100644
index 0000000000..61e88cb407
--- /dev/null
+++ b/core/fxcrt/xml/cxml_object.cpp
@@ -0,0 +1,25 @@
+// Copyright 2017 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
+
+#include "core/fxcrt/xml/cxml_object.h"
+
+CXML_Object::~CXML_Object() {}
+
+CXML_Content* CXML_Object::AsContent() {
+  return nullptr;
+}
+
+CXML_Element* CXML_Object::AsElement() {
+  return nullptr;
+}
+
+const CXML_Content* CXML_Object::AsContent() const {
+  return nullptr;
+}
+
+const CXML_Element* CXML_Object::AsElement() const {
+  return nullptr;
+}
diff --git a/core/fxcrt/xml/cxml_object.h b/core/fxcrt/xml/cxml_object.h
new file mode 100644
index 0000000000..e7f23aa988
--- /dev/null
+++ b/core/fxcrt/xml/cxml_object.h
@@ -0,0 +1,45 @@
+// Copyright 2017 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_XML_CXML_OBJECT_H_
+#define CORE_FXCRT_XML_CXML_OBJECT_H_
+
+#include "core/fxcrt/fx_basic.h"
+
+class CXML_Content;
+class CXML_Element;
+
+class CXML_Object {
+ public:
+  virtual ~CXML_Object();
+
+  virtual CXML_Content* AsContent();
+  virtual const CXML_Content* AsContent() const;
+
+  virtual CXML_Element* AsElement();
+  virtual const CXML_Element* AsElement() const;
+
+ protected:
+  CXML_Object() {}
+};
+
+inline CXML_Content* ToContent(CXML_Object* pObj) {
+  return pObj ? pObj->AsContent() : nullptr;
+}
+
+inline const CXML_Content* ToContent(const CXML_Object* pObj) {
+  return pObj ? pObj->AsContent() : nullptr;
+}
+
+inline CXML_Element* ToElement(CXML_Object* pObj) {
+  return pObj ? pObj->AsElement() : nullptr;
+}
+
+inline const CXML_Element* ToElement(const CXML_Object* pObj) {
+  return pObj ? pObj->AsElement() : nullptr;
+}
+
+#endif  // CORE_FXCRT_XML_CXML_OBJECT_H_
diff --git a/core/fxcrt/xml/cxml_parser.cpp b/core/fxcrt/xml/cxml_parser.cpp
index 3c91d744ec..d43fbd6581 100644
--- a/core/fxcrt/xml/cxml_parser.cpp
+++ b/core/fxcrt/xml/cxml_parser.cpp
@@ -6,6 +6,7 @@
 
 #include <algorithm>
 #include <memory>
+#include <utility>
 #include <vector>
 
 #include "core/fxcrt/fx_extension.h"
@@ -493,8 +494,7 @@ std::unique_ptr<CXML_Element> CXML_Parser::ParseElementInternal(
             if (!pSubElement)
               break;
 
-            pElement->m_Children.push_back(
-                {CXML_Element::Element, pSubElement.release()});
+            pElement->m_Children.push_back(std::move(pSubElement));
             SkipWhiteSpaces();
           }
           break;
@@ -537,7 +537,6 @@ void CXML_Parser::InsertContentSegment(bool bCDATA,
   if (content.IsEmpty())
     return;
 
-  CXML_Content* pContent = new CXML_Content;
-  pContent->Set(bCDATA, content);
-  pElement->m_Children.push_back({CXML_Element::Content, pContent});
+  pElement->m_Children.push_back(
+      pdfium::MakeUnique<CXML_Content>(bCDATA, content));
 }