I am really trying understand pointer to pointer in function arguments. I am seeing a lot in my example projects using double pointer. I want to know what is the main use of them? One example function i have seen is
I could not provide the complete implementation as it is not my project. The function is called when a data is arrived and it will ask the application for buffer. Can someone explain me with simple program how does it work?Code:ProvideRxBuffer(**ptr);
It might be worth trying a related exercise without a pointer to pointer to see why you would need it.
Suppose you want to implement this function to fill a dynamic array with n of a given value:
fill_n will call malloc to allocate space for n ints, then fill with value. It could be used like this:Code:void fill_n(int *array, size_t n, int value);
Try to implement fill_n with the given prototype and see if you can get it to work. You will find that you need fill_n to be:Code:int *array = NULL; fill_n(array, 10, 5); // print the array elements // ... free(array);
insteadCode:void fill_n(int **array, size_t n, int value);
Look up a C++ Reference and learn How To Ask Questions The Smart WayOriginally Posted by Bjarne Stroustrup (2000-10-14)
Pointers are integers used as an address to the first item of an array... Consider arrays of chars... You can have a pointer char *p, pointing to a string (a simple array of chars)... By the same analogy, a pointer to pointers (char **pp, for example), points to an array of pointers, and each of these pointers points to arrays. For example:
