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

Don't try to copy the string until we are sure we need to
change it.

Review URL: https://codereview.chromium.org/1877993002

1 files changed, 15 insertions, 2 deletions

diff --git a/core/fxcrt/fx_basic_wstring.cpp b/core/fxcrt/fx_basic_wstring.cpp
index 08a9d212d4..069b9fa42d 100644
--- a/core/fxcrt/fx_basic_wstring.cpp
+++ b/core/fxcrt/fx_basic_wstring.cpp
@@ -672,17 +672,30 @@ FX_STRSIZE CFX_WideString::Remove(FX_WCHAR chRemove) {
   if (!m_pData || m_pData->m_nDataLength < 1)
     return 0;
 
-  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;
   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);
+  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;