A shallow copy is a type of copy operation and the opposite of a deep copy.

Both types of copy operations work on a class, with a pointer to data member. When this class is copied, two things can happen:

A shallow copy only copies the pointer, so both copies work on the same data
A deep copy copies the data pointed to as well, so both copies work on different data

The code below shows a shallow copy:


struct Huge

{

  //Huge contains much data and is hard to copy.

};



struct MyClass

{

  //MyClass holds a pointer to a Huge.

  Huge * mp_huge;

};



int main()

{

  //My class 'a' points to a Huge.

  MyClass a;

  //A second class 'b' points to the same Huge:

  //the Huge is _not_ copied: only the pointer pointing

  //the the Huge is copied.

  MyClass b = a;

}

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(C++) Shallow copy