Make CFX_{Byte,Wide}String::Remove() no-touch if possible

core/fxcrt/fx_basic_wstring.cpp

 // 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
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <cctype>
@@ skipping 654 matching lines @@
     return;
 
   ReallocBeforeWrite(m_pData->m_nDataLength);
   FXSYS_wcsupr(m_pData->m_String);
 }
 
 FX_STRSIZE CFX_WideString::Remove(FX_WCHAR chRemove) {
   if (!m_pData || m_pData->m_nDataLength < 1)
     return 0;
 
+  FX_WCHAR* pstrSource = m_pData->m_String;
+  FX_WCHAR* pstrEnd = m_pData->m_String + m_pData->m_nDataLength;
+  while (pstrSource < pstrEnd) {
+    if (*pstrSource == chRemove)
+      break;
+    pstrSource++;
+  }
+  if (pstrSource == pstrEnd)
+    return 0;
+
+  ptrdiff_t copied = pstrSource - m_pData->m_String;
   ReallocBeforeWrite(m_pData->m_nDataLength);
-  FX_WCHAR* pstrSource = m_pData->m_String;
-  FX_WCHAR* pstrDest = m_pData->m_String;
-  FX_WCHAR* pstrEnd = m_pData->m_String + m_pData->m_nDataLength;
+  pstrSource = m_pData->m_String + copied;
+  pstrEnd = m_pData->m_String + m_pData->m_nDataLength;
+
+  FX_WCHAR* pstrDest = pstrSource;
   while (pstrSource < pstrEnd) {
     if (*pstrSource != chRemove) {
       *pstrDest = *pstrSource;
       pstrDest++;
     }
     pstrSource++;
   }
+
   *pstrDest = 0;
   FX_STRSIZE nCount = (FX_STRSIZE)(pstrSource - pstrDest);
   m_pData->m_nDataLength -= nCount;
   return nCount;
 }
 
 FX_STRSIZE CFX_WideString::Replace(const CFX_WideStringC& pOld,
                                    const CFX_WideStringC& pNew) {
   if (!m_pData || pOld.IsEmpty())
     return 0;
@@ skipping 274 matching lines @@
       FXSYS_MultiByteToWideChar(codepage, 0, bstr.c_str(), src_len, nullptr, 0);
   CFX_WideString wstr;
   if (dest_len) {
     FX_WCHAR* dest_buf = wstr.GetBuffer(dest_len);
     FXSYS_MultiByteToWideChar(codepage, 0, bstr.c_str(), src_len, dest_buf,
                               dest_len);
     wstr.ReleaseBuffer(dest_len);
   }
   return wstr;
 }