Revert "Change CFX_XML Save to take a write stream"

This reverts commit 9a3a7709103a872037dcea1f3cf0b7785a3da191.

Reason for revert: Gerrit did not do what I expected....

Original change's description:
> Change CFX_XML Save to take a write stream
> 
> This CL changes CFX_XML to use an IFX_SeekableWriteStream instead of the more
> generic IFX_SeekableStream.
> 
> Change-Id: I6e4def380c43eca755d91ad5cb6146c2dfdaee10
> Reviewed-on: https://pdfium-review.googlesource.com/30877
> Commit-Queue: dsinclair <dsinclair@chromium.org>
> Reviewed-by: Tom Sepez <tsepez@chromium.org>

TBR=tsepez@chromium.org,dsinclair@chromium.org,hnakashima@chromium.org

Change-Id: I137e53bf93285b88ade6832dedefca66e3b61e13
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://pdfium-review.googlesource.com/31211
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

11 files changed, 92 insertions, 63 deletions

diff --git a/core/fpdfdoc/cpdf_metadata.cpp b/core/fpdfdoc/cpdf_metadata.cpp
index c928952dca..161fc93edd 100644
--- a/core/fpdfdoc/cpdf_metadata.cpp
+++ b/core/fpdfdoc/cpdf_metadata.cpp
@@ -19,11 +19,12 @@ void CheckForSharedFormInternal(CFX_XMLElement* element,
                                 std::vector<UnsupportedFeature>* unsupported) {
   WideString attr = element->GetAttribute(L"xmlns:adhocwf");
   if (attr == L"http://ns.adobe.com/AcrobatAdhocWorkflow/1.0/") {
-    for (const auto& child : *element) {
+    for (const auto* child = element->GetFirstChild(); child;
+         child = child->GetNextSibling()) {
       if (child->GetType() != FX_XMLNODE_Element)
         continue;
 
-      const auto* child_elem = static_cast<const CFX_XMLElement*>(child.get());
+      const auto* child_elem = static_cast<const CFX_XMLElement*>(child);
       if (child_elem->GetName() != L"adhocwf:workflowType")
         continue;
 
@@ -45,11 +46,12 @@ void CheckForSharedFormInternal(CFX_XMLElement* element,
     }
   }
 
-  for (const auto& child : *element) {
+  for (auto* child = element->GetFirstChild(); child;
+       child = child->GetNextSibling()) {
     if (child->GetType() != FX_XMLNODE_Element)
       continue;
 
-    CheckForSharedFormInternal(static_cast<CFX_XMLElement*>(child.get()),
+    CheckForSharedFormInternal(static_cast<CFX_XMLElement*>(child),
                                unsupported);
   }
 }
diff --git a/core/fxcrt/xml/cfx_xmlchardata.cpp b/core/fxcrt/xml/cfx_xmlchardata.cpp
index e62a43ac53..dec2e4618f 100644
--- a/core/fxcrt/xml/cfx_xmlchardata.cpp
+++ b/core/fxcrt/xml/cfx_xmlchardata.cpp
@@ -21,8 +21,7 @@ std::unique_ptr<CFX_XMLNode> CFX_XMLCharData::Clone() {
   return pdfium::MakeUnique<CFX_XMLCharData>(GetText());
 }
 
-void CFX_XMLCharData::Save(
-    const RetainPtr<IFX_SeekableWriteStream>& pXMLStream) {
+void CFX_XMLCharData::Save(const RetainPtr<IFX_SeekableStream>& pXMLStream) {
   pXMLStream->WriteString("<![CDATA[");
   pXMLStream->WriteString(GetText().UTF8Encode().AsStringView());
   pXMLStream->WriteString("]]>");
diff --git a/core/fxcrt/xml/cfx_xmlchardata.h b/core/fxcrt/xml/cfx_xmlchardata.h
index 0cdc348f26..5b00597955 100644
--- a/core/fxcrt/xml/cfx_xmlchardata.h
+++ b/core/fxcrt/xml/cfx_xmlchardata.h
@@ -20,7 +20,7 @@ class CFX_XMLCharData : public CFX_XMLText {
   // CFX_XMLNode
   FX_XMLNODETYPE GetType() const override;
   std::unique_ptr<CFX_XMLNode> Clone() override;
-  void Save(const RetainPtr<IFX_SeekableWriteStream>& pXMLStream) override;
+  void Save(const RetainPtr<IFX_SeekableStream>& pXMLStream) override;
 };
 
 #endif  // CORE_FXCRT_XML_CFX_XMLCHARDATA_H_
diff --git a/core/fxcrt/xml/cfx_xmlelement.cpp b/core/fxcrt/xml/cfx_xmlelement.cpp
index 8c8922e0c6..5e79da63cf 100644
--- a/core/fxcrt/xml/cfx_xmlelement.cpp
+++ b/core/fxcrt/xml/cfx_xmlelement.cpp
@@ -33,9 +33,10 @@ std::unique_ptr<CFX_XMLNode> CFX_XMLElement::Clone() {
   // TODO(dsinclair): This clone is wrong. It doesn't clone child nodes just
   // copies text nodes?
   WideString wsText;
-  for (const auto& pChild : *this) {
+  for (CFX_XMLNode* pChild = GetFirstChild(); pChild;
+       pChild = pChild->GetNextSibling()) {
     if (pChild->GetType() == FX_XMLNODE_Text)
-      wsText += static_cast<CFX_XMLText*>(pChild.get())->GetText();
+      wsText += static_cast<CFX_XMLText*>(pChild)->GetText();
   }
   pClone->SetTextData(wsText);
   return std::move(pClone);
@@ -78,10 +79,11 @@ WideString CFX_XMLElement::GetNamespaceURI() const {
 WideString CFX_XMLElement::GetTextData() const {
   CFX_WideTextBuf buffer;
 
-  for (const auto& pChild : *this) {
+  for (CFX_XMLNode* pChild = GetFirstChild(); pChild;
+       pChild = pChild->GetNextSibling()) {
     if (pChild->GetType() == FX_XMLNODE_Text ||
         pChild->GetType() == FX_XMLNODE_CharData) {
-      buffer << static_cast<CFX_XMLText*>(pChild.get())->GetText();
+      buffer << static_cast<CFX_XMLText*>(pChild)->GetText();
     }
   }
   return buffer.MakeString();
@@ -94,8 +96,7 @@ void CFX_XMLElement::SetTextData(const WideString& wsText) {
   AppendChild(pdfium::MakeUnique<CFX_XMLText>(wsText));
 }
 
-void CFX_XMLElement::Save(
-    const RetainPtr<IFX_SeekableWriteStream>& pXMLStream) {
+void CFX_XMLElement::Save(const RetainPtr<IFX_SeekableStream>& pXMLStream) {
   ByteString bsNameEncoded = name_.UTF8Encode();
 
   pXMLStream->WriteString("<");
@@ -108,16 +109,17 @@ void CFX_XMLElement::Save(
         AttributeToString(it.first, it.second).UTF8Encode().AsStringView());
   }
 
-  if (HasChildren()) {
+  if (!GetFirstChild()) {
     pXMLStream->WriteString(" />\n");
     return;
   }
 
   pXMLStream->WriteString(">\n");
 
-  for (const auto& pChild : *this)
+  for (CFX_XMLNode* pChild = GetFirstChild(); pChild;
+       pChild = pChild->GetNextSibling()) {
     pChild->Save(pXMLStream);
-
+  }
   pXMLStream->WriteString("</");
   pXMLStream->WriteString(bsNameEncoded.AsStringView());
   pXMLStream->WriteString(">\n");
@@ -130,11 +132,11 @@ CFX_XMLElement* CFX_XMLElement::GetFirstChildNamed(
 
 CFX_XMLElement* CFX_XMLElement::GetNthChildNamed(const WideStringView& name,
                                                  size_t idx) const {
-  for (const auto& child : *this) {
+  for (auto* child = GetFirstChild(); child; child = child->GetNextSibling()) {
     if (child->GetType() != FX_XMLNODE_Element)
       continue;
 
-    CFX_XMLElement* elem = static_cast<CFX_XMLElement*>(child.get());
+    CFX_XMLElement* elem = static_cast<CFX_XMLElement*>(child);
     if (elem->name_ != name)
       continue;
     if (idx == 0)
diff --git a/core/fxcrt/xml/cfx_xmlelement.h b/core/fxcrt/xml/cfx_xmlelement.h
index 678ba6d996..c1d9fea3f0 100644
--- a/core/fxcrt/xml/cfx_xmlelement.h
+++ b/core/fxcrt/xml/cfx_xmlelement.h
@@ -22,7 +22,7 @@ class CFX_XMLElement : public CFX_XMLNode {
   // CFX_XMLNode
   FX_XMLNODETYPE GetType() const override;
   std::unique_ptr<CFX_XMLNode> Clone() override;
-  void Save(const RetainPtr<IFX_SeekableWriteStream>& pXMLStream) override;
+  void Save(const RetainPtr<IFX_SeekableStream>& pXMLStream) override;
 
   WideString GetName() const { return name_; }
 
diff --git a/core/fxcrt/xml/cfx_xmlinstruction.cpp b/core/fxcrt/xml/cfx_xmlinstruction.cpp
index d0f5cbb68b..7b844e6808 100644
--- a/core/fxcrt/xml/cfx_xmlinstruction.cpp
+++ b/core/fxcrt/xml/cfx_xmlinstruction.cpp
@@ -40,8 +40,7 @@ bool CFX_XMLInstruction::IsAcrobat() const {
   return name_ == L"acrobat";
 }
 
-void CFX_XMLInstruction::Save(
-    const RetainPtr<IFX_SeekableWriteStream>& pXMLStream) {
+void CFX_XMLInstruction::Save(const RetainPtr<IFX_SeekableStream>& pXMLStream) {
   if (name_.CompareNoCase(L"xml") == 0) {
     pXMLStream->WriteString("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n");
     return;
diff --git a/core/fxcrt/xml/cfx_xmlinstruction.h b/core/fxcrt/xml/cfx_xmlinstruction.h
index 3be9d48573..045610bd8a 100644
--- a/core/fxcrt/xml/cfx_xmlinstruction.h
+++ b/core/fxcrt/xml/cfx_xmlinstruction.h
@@ -21,7 +21,7 @@ class CFX_XMLInstruction : public CFX_XMLNode {
   // CFX_XMLNode
   FX_XMLNODETYPE GetType() const override;
   std::unique_ptr<CFX_XMLNode> Clone() override;
-  void Save(const RetainPtr<IFX_SeekableWriteStream>& pXMLStream) override;
+  void Save(const RetainPtr<IFX_SeekableStream>& pXMLStream) override;
 
   bool IsOriginalXFAVersion() const;
   bool IsAcrobat() const;
diff --git a/core/fxcrt/xml/cfx_xmlnode.cpp b/core/fxcrt/xml/cfx_xmlnode.cpp
index de0a4acd2f..4f811e608e 100644
--- a/core/fxcrt/xml/cfx_xmlnode.cpp
+++ b/core/fxcrt/xml/cfx_xmlnode.cpp
@@ -6,8 +6,8 @@
 
 #include "core/fxcrt/xml/cfx_xmlnode.h"
 
-#include <algorithm>
 #include <utility>
+#include <vector>
 
 #include "core/fxcrt/xml/cfx_xmlchardata.h"
 #include "core/fxcrt/xml/cfx_xmlelement.h"
@@ -22,7 +22,15 @@ CFX_XMLNode::~CFX_XMLNode() {
 }
 
 void CFX_XMLNode::DeleteChildren() {
-  children_.clear();
+  CFX_XMLNode* child = last_child_.Get();
+  // Clear last child early as it will have been deleted already.
+  last_child_ = nullptr;
+  while (child) {
+    child = child->prev_sibling_.Get();
+    if (child)
+      child->next_sibling_ = nullptr;
+  }
+  first_child_ = nullptr;
 }
 
 void CFX_XMLNode::AppendChild(std::unique_ptr<CFX_XMLNode> pNode) {
@@ -34,38 +42,63 @@ void CFX_XMLNode::InsertChildNode(std::unique_ptr<CFX_XMLNode> pNode,
   ASSERT(!pNode->parent_);
 
   pNode->parent_ = this;
-  if (static_cast<size_t>(index) >= children_.size()) {
-    if (!children_.empty())
-      children_.back()->next_sibling_ = pNode.get();
-    children_.push_back(std::move(pNode));
+  // No existing children, add node as first child.
+  if (!first_child_) {
+    ASSERT(!last_child_);
+
+    first_child_ = std::move(pNode);
+    last_child_ = first_child_.get();
+    first_child_->prev_sibling_ = nullptr;
+    first_child_->next_sibling_ = nullptr;
+    return;
+  }
+
+  if (index == 0) {
+    first_child_->prev_sibling_ = pNode.get();
+    pNode->next_sibling_ = std::move(first_child_);
+    pNode->prev_sibling_ = nullptr;
+    first_child_ = std::move(pNode);
     return;
   }
-  index = std::max(index, 0);
 
-  pNode->next_sibling_ = children_[index].get();
-  children_.insert(children_.begin() + index, std::move(pNode));
-  if (index > 0)
-    children_[index - 1]->next_sibling_ = children_[index].get();
+  int32_t iCount = 0;
+  CFX_XMLNode* pFind = first_child_.get();
+  // Note, negative indexes, and indexes after the end of the list will result
+  // in appending to the list.
+  while (++iCount != index && pFind->next_sibling_)
+    pFind = pFind->next_sibling_.get();
+
+  pNode->prev_sibling_ = pFind;
+  if (pFind->next_sibling_)
+    pFind->next_sibling_->prev_sibling_ = pNode.get();
+  pNode->next_sibling_ = std::move(pFind->next_sibling_);
+
+  pFind->next_sibling_ = std::move(pNode);
+  if (pFind == last_child_.Get())
+    last_child_ = pFind->next_sibling_.get();
 }
 
 void CFX_XMLNode::RemoveChildNode(CFX_XMLNode* pNode) {
+  ASSERT(first_child_);
   ASSERT(pNode);
 
-  auto it = std::find(children_.begin(), children_.end(),
-                      pdfium::FakeUniquePtr<CFX_XMLNode>(pNode));
-  if (it != children_.end()) {
-    if (it != children_.begin()) {
-      CFX_XMLNode* prev = (*(it - 1)).get();
-      prev->next_sibling_ = (*it)->next_sibling_;
-    }
-
-    children_.erase(it);
+  if (first_child_.get() == pNode) {
+    first_child_.release();
+    first_child_ = std::move(pNode->next_sibling_);
+  } else {
+    CFX_XMLNode* prev = pNode->prev_sibling_.Get();
+    prev->next_sibling_.release();  // Release pNode
+    prev->next_sibling_ = std::move(pNode->next_sibling_);
   }
-}
 
-void CFX_XMLNode::MoveChildrenTo(CFX_XMLNode* root) {
-  ASSERT(root->children_.empty());
-  std::swap(root->children_, children_);
+  if (last_child_.Get() == pNode)
+    last_child_ = pNode->prev_sibling_.Get();
+
+  if (pNode->next_sibling_)
+    pNode->next_sibling_->prev_sibling_ = pNode->prev_sibling_;
+
+  pNode->parent_ = nullptr;
+  pNode->prev_sibling_ = nullptr;
 }
 
 CFX_XMLNode* CFX_XMLNode::GetRoot() {
diff --git a/core/fxcrt/xml/cfx_xmlnode.h b/core/fxcrt/xml/cfx_xmlnode.h
index cbf89adb5e..288095403c 100644
--- a/core/fxcrt/xml/cfx_xmlnode.h
+++ b/core/fxcrt/xml/cfx_xmlnode.h
@@ -8,7 +8,6 @@
 #define CORE_FXCRT_XML_CFX_XMLNODE_H_
 
 #include <memory>
-#include <vector>
 
 #include "core/fxcrt/fx_stream.h"
 #include "core/fxcrt/retain_ptr.h"
@@ -23,39 +22,34 @@ enum FX_XMLNODETYPE {
 
 class CFX_XMLNode {
  public:
-  using const_iterator =
-      std::vector<std::unique_ptr<CFX_XMLNode>>::const_iterator;
-
   CFX_XMLNode();
   virtual ~CFX_XMLNode();
 
   virtual FX_XMLNODETYPE GetType() const = 0;
   virtual std::unique_ptr<CFX_XMLNode> Clone() = 0;
-  virtual void Save(const RetainPtr<IFX_SeekableWriteStream>& pXMLStream) = 0;
+  virtual void Save(const RetainPtr<IFX_SeekableStream>& pXMLStream) = 0;
 
   CFX_XMLNode* GetRoot();
   CFX_XMLNode* GetParent() const { return parent_.Get(); }
-  CFX_XMLNode* GetNextSibling() const { return next_sibling_; }
-  bool HasChildren() const { return !children_.empty(); }
-  const_iterator begin() const { return children_.begin(); }
-  const_iterator end() const { return children_.end(); }
+  CFX_XMLNode* GetFirstChild() const { return first_child_.get(); }
+  CFX_XMLNode* GetNextSibling() const { return next_sibling_.get(); }
 
   void AppendChild(std::unique_ptr<CFX_XMLNode> pNode);
   void InsertChildNode(std::unique_ptr<CFX_XMLNode> pNode, int32_t index);
   void RemoveChildNode(CFX_XMLNode* pNode);
   void DeleteChildren();
-  // Note |root| must not have any children.
-  void MoveChildrenTo(CFX_XMLNode* root);
 
  protected:
   WideString EncodeEntities(const WideString& value);
 
  private:
+  // A node owns its first child and it owns its next sibling. The rest
+  // are unowned pointers.
   UnownedPtr<CFX_XMLNode> parent_;
-  // The next_sibling is owned by the vector. We don't use an UnownedPtr
-  // because we don't know the destruction order of the vector.
-  CFX_XMLNode* next_sibling_;
-  std::vector<std::unique_ptr<CFX_XMLNode>> children_;
+  UnownedPtr<CFX_XMLNode> last_child_;
+  UnownedPtr<CFX_XMLNode> prev_sibling_;
+  std::unique_ptr<CFX_XMLNode> first_child_;
+  std::unique_ptr<CFX_XMLNode> next_sibling_;
 };
 
 #endif  // CORE_FXCRT_XML_CFX_XMLNODE_H_
diff --git a/core/fxcrt/xml/cfx_xmltext.cpp b/core/fxcrt/xml/cfx_xmltext.cpp
index 2c324be1c9..9bed941dd4 100644
--- a/core/fxcrt/xml/cfx_xmltext.cpp
+++ b/core/fxcrt/xml/cfx_xmltext.cpp
@@ -21,7 +21,7 @@ std::unique_ptr<CFX_XMLNode> CFX_XMLText::Clone() {
   return pdfium::MakeUnique<CFX_XMLText>(m_wsText);
 }
 
-void CFX_XMLText::Save(const RetainPtr<IFX_SeekableWriteStream>& pXMLStream) {
+void CFX_XMLText::Save(const RetainPtr<IFX_SeekableStream>& pXMLStream) {
   pXMLStream->WriteString(
       EncodeEntities(GetText()).UTF8Encode().AsStringView());
 }
diff --git a/core/fxcrt/xml/cfx_xmltext.h b/core/fxcrt/xml/cfx_xmltext.h
index cc9c71d01c..bbf14be257 100644
--- a/core/fxcrt/xml/cfx_xmltext.h
+++ b/core/fxcrt/xml/cfx_xmltext.h
@@ -20,7 +20,7 @@ class CFX_XMLText : public CFX_XMLNode {
   // CFX_XMLNode
   FX_XMLNODETYPE GetType() const override;
   std::unique_ptr<CFX_XMLNode> Clone() override;
-  void Save(const RetainPtr<IFX_SeekableWriteStream>& pXMLStream) override;
+  void Save(const RetainPtr<IFX_SeekableStream>& pXMLStream) override;
 
   WideString GetText() const { return m_wsText; }
   void SetText(const WideString& wsText) { m_wsText = wsText; }