std::string usage in DataFactoryImpl.cpp allocates/deallocates heap and copys
memoery too frequently
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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
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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