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Posted to dev@tuscany.apache.org by "Geoff Winn (JIRA)" <tu...@ws.apache.org> on 2006/12/08 20:27:22 UTC
[jira] Commented: (TUSCANY-946) std::string usage in
DataFactoryImpl.cpp allocates/deallocates heap and copys memoery too
frequently
[ http://issues.apache.org/jira/browse/TUSCANY-946?page=comments#action_12456953 ]
Geoff Winn commented on TUSCANY-946:
------------------------------------
Patch applied.
> 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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