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optimize Replace() for the common case of replacing one character with another one (#9802)

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@54860 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Vadim Zeitlin
2008-07-30 21:41:07 +00:00
parent 6a7e5ea2f5
commit 8a6270322b
1 changed files with 45 additions and 16 deletions
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61
src/common/string.cpp
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@@ -1239,27 +1239,56 @@ size_t wxString::Replace(const wxString& strOld,
size_t uiCount = 0; // count of replacements made
const size_t uiOldLen = strOld.m_impl.length();
const size_t uiNewLen = strNew.m_impl.length();
for ( size_t dwPos = 0; dwPos < m_impl.length(); )
// optimize the special common case: replacement of one character by
// another one (in UTF-8 case we can only do this for ASCII characters)
//
// benchmarks show that this special version is around 3 times faster
// (depending on the proportion of matching characters and UTF-8/wchar_t
// build)
if ( strOld.m_impl.length() == 1 && strNew.m_impl.length() == 1 )
{
dwPos = m_impl.find(strOld.m_impl, dwPos);
if ( dwPos == npos )
break;
const wxStringCharType chOld = strOld.m_impl[0],
chNew = strNew.m_impl[0];
// replace this occurance of the old string with the new one
m_impl.replace(dwPos, uiOldLen, strNew.m_impl);
// this loop is the simplified version of the one below
for ( size_t pos = 0; ; )
{
pos = m_impl.find(chOld, pos);
if ( pos == npos )
break;
// move up pos past the string that was replaced
dwPos += uiNewLen;
m_impl[pos++] = chNew;
// increase replace count
++uiCount;
uiCount++;
// stop after the first one?
if ( !bReplaceAll )
break;
if ( !bReplaceAll )
break;
}
}
else // general case
{
const size_t uiOldLen = strOld.m_impl.length();
const size_t uiNewLen = strNew.m_impl.length();
for ( size_t pos = 0; ; )
{
pos = m_impl.find(strOld.m_impl, pos);
if ( pos == npos )
break;
// replace this occurrence of the old string with the new one
m_impl.replace(pos, uiOldLen, strNew.m_impl);
// move up pos past the string that was replaced
pos += uiNewLen;
// increase replace count
uiCount++;
// stop after the first one?
if ( !bReplaceAll )
break;
}
}
return uiCount;