fxcrt::{Byte,Wide}String missing move-assign operator

This hasn't been a big deal, since no data is copied, but avoids
some ref-count churn in the process.

Change-Id: I53c059284aa6806793c59a0c19b3e0d7fe4191d6
Reviewed-on: https://pdfium-review.googlesource.com/35350
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

6 files changed, 101 insertions, 8 deletions

diff --git a/core/fxcrt/bytestring.cpp b/core/fxcrt/bytestring.cpp
index 872de065ba..984acf9c69 100644
--- a/core/fxcrt/bytestring.cpp
+++ b/core/fxcrt/bytestring.cpp
@@ -11,6 +11,7 @@
 #include <algorithm>
 #include <cctype>
 #include <string>
+#include <utility>
 
 #include "core/fxcrt/cfx_utf8decoder.h"
 #include "core/fxcrt/fx_codepage.h"
@@ -244,9 +245,16 @@ const ByteString& ByteString::operator=(const ByteStringView& stringSrc) {
   return *this;
 }
 
-const ByteString& ByteString::operator=(const ByteString& stringSrc) {
-  if (m_pData != stringSrc.m_pData)
-    m_pData = stringSrc.m_pData;
+const ByteString& ByteString::operator=(const ByteString& that) {
+  if (m_pData != that.m_pData)
+    m_pData = that.m_pData;
+
+  return *this;
+}
+
+const ByteString& ByteString::operator=(ByteString&& that) {
+  if (m_pData != that.m_pData)
+    m_pData = std::move(that.m_pData);
 
   return *this;
 }
@@ -493,6 +501,10 @@ void ByteString::Concat(const char* pSrcData, size_t nSrcLen) {
   m_pData.Swap(pNewData);
 }
 
+intptr_t ByteString::ReferenceCountForTesting() const {
+  return m_pData ? m_pData->m_nRefs : 0;
+}
+
 ByteString ByteString::Mid(size_t first, size_t count) const {
   if (!m_pData)
     return ByteString();
diff --git a/core/fxcrt/bytestring.h b/core/fxcrt/bytestring.h
index 99b87b1d4c..5722c4925d 100644
--- a/core/fxcrt/bytestring.h
+++ b/core/fxcrt/bytestring.h
@@ -21,6 +21,7 @@
 
 namespace fxcrt {
 
+class ByteString_Assign_Test;
 class ByteString_Concat_Test;
 class StringPool_ByteString_Test;
 class WideString;
@@ -133,7 +134,8 @@ class ByteString {
 
   const ByteString& operator=(const char* str);
   const ByteString& operator=(const ByteStringView& bstrc);
-  const ByteString& operator=(const ByteString& stringSrc);
+  const ByteString& operator=(const ByteString& that);
+  const ByteString& operator=(ByteString&& that);
 
   const ByteString& operator+=(char ch);
   const ByteString& operator+=(const char* str);
@@ -209,9 +211,11 @@ class ByteString {
   void AllocCopy(ByteString& dest, size_t nCopyLen, size_t nCopyIndex) const;
   void AssignCopy(const char* pSrcData, size_t nSrcLen);
   void Concat(const char* lpszSrcData, size_t nSrcLen);
+  intptr_t ReferenceCountForTesting() const;
 
   RetainPtr<StringData> m_pData;
 
+  friend ByteString_Assign_Test;
   friend ByteString_Concat_Test;
   friend class StringPool_ByteString_Test;
 };
diff --git a/core/fxcrt/bytestring_unittest.cpp b/core/fxcrt/bytestring_unittest.cpp
index ed3f375434..2b7d4f7836 100644
--- a/core/fxcrt/bytestring_unittest.cpp
+++ b/core/fxcrt/bytestring_unittest.cpp
@@ -59,6 +59,37 @@ TEST(ByteString, ElementAccess) {
 #endif
 }
 
+TEST(ByteString, Assign) {
+  {
+    // Copy-assign.
+    ByteString string1;
+    EXPECT_EQ(0, string1.ReferenceCountForTesting());
+    {
+      ByteString string2("abc");
+      EXPECT_EQ(1, string2.ReferenceCountForTesting());
+
+      string1 = string2;
+      EXPECT_EQ(2, string1.ReferenceCountForTesting());
+      EXPECT_EQ(2, string2.ReferenceCountForTesting());
+    }
+    EXPECT_EQ(1, string1.ReferenceCountForTesting());
+  }
+  {
+    // Move-assign.
+    ByteString string1;
+    EXPECT_EQ(0, string1.ReferenceCountForTesting());
+    {
+      ByteString string2("abc");
+      EXPECT_EQ(1, string2.ReferenceCountForTesting());
+
+      string1 = std::move(string2);
+      EXPECT_EQ(1, string1.ReferenceCountForTesting());
+      EXPECT_EQ(0, string2.ReferenceCountForTesting());
+    }
+    EXPECT_EQ(1, string1.ReferenceCountForTesting());
+  }
+}
+
 TEST(ByteString, OperatorLT) {
   ByteString empty;
   ByteString a("a");
diff --git a/core/fxcrt/widestring.cpp b/core/fxcrt/widestring.cpp
index 25f253ea11..cde1973d26 100644
--- a/core/fxcrt/widestring.cpp
+++ b/core/fxcrt/widestring.cpp
@@ -441,9 +441,16 @@ const WideString& WideString::operator=(const WideStringView& stringSrc) {
   return *this;
 }
 
-const WideString& WideString::operator=(const WideString& stringSrc) {
-  if (m_pData != stringSrc.m_pData)
-    m_pData = stringSrc.m_pData;
+const WideString& WideString::operator=(const WideString& that) {
+  if (m_pData != that.m_pData)
+    m_pData = that.m_pData;
+
+  return *this;
+}
+
+const WideString& WideString::operator=(WideString&& that) {
+  if (m_pData != that.m_pData)
+    m_pData = std::move(that.m_pData);
 
   return *this;
 }
@@ -662,6 +669,10 @@ void WideString::Concat(const wchar_t* pSrcData, size_t nSrcLen) {
   m_pData.Swap(pNewData);
 }
 
+intptr_t WideString::ReferenceCountForTesting() const {
+  return m_pData ? m_pData->m_nRefs : 0;
+}
+
 ByteString WideString::UTF8Encode() const {
   return FX_UTF8Encode(AsStringView());
 }
diff --git a/core/fxcrt/widestring.h b/core/fxcrt/widestring.h
index 4b097c4430..b531292c57 100644
--- a/core/fxcrt/widestring.h
+++ b/core/fxcrt/widestring.h
@@ -23,6 +23,7 @@ namespace fxcrt {
 
 class ByteString;
 class StringPool_WideString_Test;
+class WideString_Assign_Test;
 class WideString_ConcatInPlace_Test;
 
 // A mutable string with shared buffers using copy-on-write semantics that
@@ -111,8 +112,9 @@ class WideString {
   bool IsValidLength(size_t length) const { return length <= GetLength(); }
 
   const WideString& operator=(const wchar_t* str);
-  const WideString& operator=(const WideString& stringSrc);
   const WideString& operator=(const WideStringView& stringSrc);
+  const WideString& operator=(const WideString& that);
+  const WideString& operator=(WideString&& that);
 
   const WideString& operator+=(const wchar_t* str);
   const WideString& operator+=(wchar_t ch);
@@ -208,10 +210,12 @@ class WideString {
   void AllocCopy(WideString& dest, size_t nCopyLen, size_t nCopyIndex) const;
   void AssignCopy(const wchar_t* pSrcData, size_t nSrcLen);
   void Concat(const wchar_t* lpszSrcData, size_t nSrcLen);
+  intptr_t ReferenceCountForTesting() const;
 
   RetainPtr<StringData> m_pData;
 
   friend WideString_ConcatInPlace_Test;
+  friend WideString_Assign_Test;
   friend StringPool_WideString_Test;
 };
 
diff --git a/core/fxcrt/widestring_unittest.cpp b/core/fxcrt/widestring_unittest.cpp
index 4572305530..b044a81bb0 100644
--- a/core/fxcrt/widestring_unittest.cpp
+++ b/core/fxcrt/widestring_unittest.cpp
@@ -53,6 +53,37 @@ TEST(WideString, ElementAccess) {
 #endif
 }
 
+TEST(WideString, Assign) {
+  {
+    // Copy-assign.
+    WideString string1;
+    EXPECT_EQ(0, string1.ReferenceCountForTesting());
+    {
+      WideString string2(L"abc");
+      EXPECT_EQ(1, string2.ReferenceCountForTesting());
+
+      string1 = string2;
+      EXPECT_EQ(2, string1.ReferenceCountForTesting());
+      EXPECT_EQ(2, string2.ReferenceCountForTesting());
+    }
+    EXPECT_EQ(1, string1.ReferenceCountForTesting());
+  }
+  {
+    // Move-assign.
+    WideString string1;
+    EXPECT_EQ(0, string1.ReferenceCountForTesting());
+    {
+      WideString string2(L"abc");
+      EXPECT_EQ(1, string2.ReferenceCountForTesting());
+
+      string1 = std::move(string2);
+      EXPECT_EQ(1, string1.ReferenceCountForTesting());
+      EXPECT_EQ(0, string2.ReferenceCountForTesting());
+    }
+    EXPECT_EQ(1, string1.ReferenceCountForTesting());
+  }
+}
+
 TEST(WideString, OperatorLT) {
   WideString empty;
   WideString a(L"a");