[ http://issues.apache.org/jira/browse/TUSCANY-946?page=all ]
Geoff Winn resolved TUSCANY-946.
--------------------------------
Resolution: Fixed
> std::string usage in DataFactoryImpl.cpp allocates/deallocates heap and copys
> memoery too frequently
> ----------------------------------------------------------------------------------------------------
>
> Key: TUSCANY-946
> URL: http://issues.apache.org/jira/browse/TUSCANY-946
> Project: Tuscany
> Issue Type: Improvement
> Components: C++ SDO
> Affects Versions: Cpp-current
> Reporter: Yang ZHONG
> Priority: Minor
> Attachments: DataFactoryImpl.946
>
>
> Thanks to Geoffrey Winn and Pete Robbins; see the thread
> http://www.mail-archive.com/tuscany-dev%40ws.apache.org/msg11015.html(Use
> std::string as an example to discuss object vs. &/* to reduce heap
> allocation/release and memory copying)
> for more info.
> Here's an example:
>
> typedef std::string SDOString;
> SDOString DataFactoryImpl::getFullTypeName(const SDOString& uri, const
> SDOString& inTypeName) const
> {
> return uri + "#" + inTypeName;
> }
> void DataFactoryImpl::addType(const char* pccUri, const char*
> pccTypeName,...)
> {
> SDOString fullTypeName = getFullTypeName(pccUri, pccTypeName);
> ...
> }
>
> 1. getFullTypeName(pccUri,pccTypeName) call will allocate stack for
> std::string instance uri and inTypeName.
> Since a URI is likely longer than 16(see std::string implementation), a
> heap(5-1) piece will be allocated.
> pccUri and pccTypeName will be copied into uri(7-1) and inTypeName(7-2)
> respectively
> 2. uri+"#" will allocate stack and *heap*(5-2) for a new std::string
> instance, and uri will be copied(7-3)
> 3. ...+inTypeName will allocate stack and *heap*(5-3) for another new
> std::string instance, and above(2.) std::string(7-4) and inTypeName(7-5) will
> be copied
> 4. getFullTypeName return will allocate stack and *heap*(5-4) for yet another
> new std::string instance, and return value will be copied(7-6)
> 5. The assignment to local variable fullTypeName, will allocate stack and
> *heap*(5-5) for one more new std::string instance, and value will be
> copied(7-7)
>
> It's too frequent that simple 2 lines of code allocate/deallocate heap *five*
> times and copy memory *seven* times.
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