4 files changed, 48 insertions, 46 deletions

diff --git a/core/fxcrt/cfx_bytestring.cpp b/core/fxcrt/cfx_bytestring.cpp
index e031c87d2d..6cbd15e693 100644
--- a/core/fxcrt/cfx_bytestring.cpp
+++ b/core/fxcrt/cfx_bytestring.cpp
@@ -411,26 +411,23 @@ char* CFX_ByteString::GetBuffer(FX_STRSIZE nMinBufLength) {
   return m_pData->m_String;
 }
 
-FX_STRSIZE CFX_ByteString::Delete(FX_STRSIZE nIndex, FX_STRSIZE nCount) {
+FX_STRSIZE CFX_ByteString::Delete(FX_STRSIZE index, FX_STRSIZE count) {
   if (!m_pData)
     return 0;
 
-  if (nIndex < 0)
-    nIndex = 0;
+  FX_STRSIZE old_length = m_pData->m_nDataLength;
+  if (count <= 0 || index != pdfium::clamp(index, 0, old_length))
+    return old_length;
 
-  FX_STRSIZE nOldLength = m_pData->m_nDataLength;
-  if (nCount > 0 && nIndex < nOldLength) {
-    FX_STRSIZE mLength = nIndex + nCount;
-    if (mLength >= nOldLength) {
-      m_pData->m_nDataLength = nIndex;
-      return m_pData->m_nDataLength;
-    }
-    ReallocBeforeWrite(nOldLength);
-    int nCharsToCopy = nOldLength - mLength + 1;
-    memmove(m_pData->m_String + nIndex, m_pData->m_String + mLength,
-            nCharsToCopy);
-    m_pData->m_nDataLength = nOldLength - nCount;
-  }
+  FX_STRSIZE removal_length = index + count;
+  if (removal_length > old_length)
+    return old_length;
+
+  ReallocBeforeWrite(old_length);
+  int chars_to_copy = old_length - removal_length + 1;
+  memmove(m_pData->m_String + index, m_pData->m_String + removal_length,
+          chars_to_copy);
+  m_pData->m_nDataLength = old_length - count;
   return m_pData->m_nDataLength;
 }
 
diff --git a/core/fxcrt/cfx_bytestring_unittest.cpp b/core/fxcrt/cfx_bytestring_unittest.cpp
index 89c8ac6060..d843afef97 100644
--- a/core/fxcrt/cfx_bytestring_unittest.cpp
+++ b/core/fxcrt/cfx_bytestring_unittest.cpp
@@ -454,21 +454,25 @@ TEST(fxcrt, ByteStringInsertAtFrontAndInsertAtBack) {
 
 TEST(fxcrt, ByteStringDelete) {
   CFX_ByteString fred("FRED");
-  fred.Delete(0, 2);
+  EXPECT_EQ(4, fred.Delete(0, 0));
+  EXPECT_EQ("FRED", fred);
+  EXPECT_EQ(2, fred.Delete(0, 2));
   EXPECT_EQ("ED", fred);
-  fred.Delete(1);
+  EXPECT_EQ(1, fred.Delete(1));
+  EXPECT_EQ("E", fred);
+  EXPECT_EQ(1, fred.Delete(-1));
   EXPECT_EQ("E", fred);
-  fred.Delete(-1);
+  EXPECT_EQ(0, fred.Delete(0));
   EXPECT_EQ("", fred);
-  fred.Delete(1);
+  EXPECT_EQ(0, fred.Delete(0));
   EXPECT_EQ("", fred);
 
   CFX_ByteString empty;
-  empty.Delete(0);
+  EXPECT_EQ(0, empty.Delete(0));
   EXPECT_EQ("", empty);
-  empty.Delete(-1);
+  EXPECT_EQ(0, empty.Delete(-1));
   EXPECT_EQ("", empty);
-  empty.Delete(1);
+  EXPECT_EQ(0, empty.Delete(1));
   EXPECT_EQ("", empty);
 }
 
diff --git a/core/fxcrt/cfx_widestring.cpp b/core/fxcrt/cfx_widestring.cpp
index 6c079b354e..a1fa7ec096 100644
--- a/core/fxcrt/cfx_widestring.cpp
+++ b/core/fxcrt/cfx_widestring.cpp
@@ -538,26 +538,23 @@ wchar_t* CFX_WideString::GetBuffer(FX_STRSIZE nMinBufLength) {
   return m_pData->m_String;
 }
 
-FX_STRSIZE CFX_WideString::Delete(FX_STRSIZE nIndex, FX_STRSIZE nCount) {
+FX_STRSIZE CFX_WideString::Delete(FX_STRSIZE index, FX_STRSIZE count) {
   if (!m_pData)
     return 0;
 
-  if (nIndex < 0)
-    nIndex = 0;
+  FX_STRSIZE old_length = m_pData->m_nDataLength;
+  if (count <= 0 || index != pdfium::clamp(index, 0, old_length))
+    return old_length;
 
-  FX_STRSIZE nOldLength = m_pData->m_nDataLength;
-  if (nCount > 0 && nIndex < nOldLength) {
-    FX_STRSIZE mLength = nIndex + nCount;
-    if (mLength >= nOldLength) {
-      m_pData->m_nDataLength = nIndex;
-      return m_pData->m_nDataLength;
-    }
-    ReallocBeforeWrite(nOldLength);
-    int nCharsToCopy = nOldLength - mLength + 1;
-    wmemmove(m_pData->m_String + nIndex, m_pData->m_String + mLength,
-             nCharsToCopy);
-    m_pData->m_nDataLength = nOldLength - nCount;
-  }
+  FX_STRSIZE removal_length = index + count;
+  if (removal_length > old_length)
+    return old_length;
+
+  ReallocBeforeWrite(old_length);
+  int chars_to_copy = old_length - removal_length + 1;
+  wmemmove(m_pData->m_String + index, m_pData->m_String + removal_length,
+           chars_to_copy);
+  m_pData->m_nDataLength = old_length - count;
   return m_pData->m_nDataLength;
 }
 
diff --git a/core/fxcrt/cfx_widestring_unittest.cpp b/core/fxcrt/cfx_widestring_unittest.cpp
index a763f8abbd..6e7b63c5fa 100644
--- a/core/fxcrt/cfx_widestring_unittest.cpp
+++ b/core/fxcrt/cfx_widestring_unittest.cpp
@@ -414,21 +414,25 @@ TEST(fxcrt, WideStringInsertAtFrontAndInsertAtBack) {
 
 TEST(fxcrt, WideStringDelete) {
   CFX_WideString fred(L"FRED");
-  fred.Delete(0, 2);
+  EXPECT_EQ(4, fred.Delete(0, 0));
+  EXPECT_EQ(L"FRED", fred);
+  EXPECT_EQ(2, fred.Delete(0, 2));
   EXPECT_EQ(L"ED", fred);
-  fred.Delete(1);
+  EXPECT_EQ(1, fred.Delete(1));
+  EXPECT_EQ(L"E", fred);
+  EXPECT_EQ(1, fred.Delete(-1));
   EXPECT_EQ(L"E", fred);
-  fred.Delete(-1);
+  EXPECT_EQ(0, fred.Delete(0));
   EXPECT_EQ(L"", fred);
-  fred.Delete(1);
+  EXPECT_EQ(0, fred.Delete(0));
   EXPECT_EQ(L"", fred);
 
   CFX_WideString empty;
-  empty.Delete(0);
+  EXPECT_EQ(0, empty.Delete(0));
   EXPECT_EQ(L"", empty);
-  empty.Delete(-1);
+  EXPECT_EQ(0, empty.Delete(-1));
   EXPECT_EQ(L"", empty);
-  empty.Delete(1);
+  EXPECT_EQ(0, empty.Delete(1));
   EXPECT_EQ(L"", empty);
 }