std::copy or <vector>.push_back

[Lorey]

Hi!

just want to know whats the best to use (std::copy or push_back)

this:

std::copy(buf.begin()+pos, buf.begin()+pos+length,
data.begin() )

or :

for (unsigned char size_t index=pos; index < pos+length ; index++)
{
data.push_back(getBufData(index));
}

Also, do i really need to use data.reserve before std::copy

 

[cpjust]

Also, do i really need to use data.reserve before std::copy

Well only if you want to avoid corrupting memory and possibly crashing your program.

Member functions are always preferrable to non-member functions because they can access the internal data structures of the class they're in and therefore can use some optimizations that would leave external functions in the dust. Plus, sometimes external functions simply cannot do what you want. std::remove() would be a good example -- it doesn't actually remove anything from a container because it can't; only the container's erase() member function can truly remove values.
Regardless, std::vector.push_back() & std::copy() don't do the same thing. A better comparison would be the range versions of std::vector.assign() or std::vector.insert()