Using memcpy to copy part of an array and other memory manipulation tools
memmove()
serves for this purpose.
EDIT: memcpy()
works great. Either way, this is probably more optimistic.
In this example, the code will be something like this:
int array1[10] = {0,1,2,3,4,5,6,7,8,9};
int array2[5] = {0,0,0,0,0};
memmove(array2, array1 + 5 * sizeof(int), 5 * sizeof(int));
This will copy 5 lots int
from array1, position 5, to array2, position 0.
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Can memcpy be used to copy part of an array?
No, this is impossible in general. This can only be done when the type of the array elements has a trivial layout.
Let's say, for example, we have an array of 10 integers. Can we create a new array and copy the last 5 integers into it?
int
are trivial types, so it will work for this specific case:
int source[10] = { ::: };
int target[5];
std::memcpy( target, source + 5, 5 * sizeof(int) );
Are there other copy / memory / array manipulation tools available for use with c / C ++?
Of course, the entire set of algorithms in the C ++ standard library will work with arrays. You use pointers to the first and one of the last elements in the array as begin/end
iterators. Or if you are using C ++ 11 then simple std::begin|end( array )
.
std::copy( source + 5, source + 10, target + 0 );
or
std::copy( std::begin(source) + 5, std::end(source), std::begin(target) );
Here is a meta-trick you can use to check if a type is trivial and also to define such a thing: http://en.cppreference.com/w/cpp/types/is_trivial
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