Get array size inside a function using C++

Question

If I have the following function in C++:

void functionName(HANDLE arr[100])
{
}

HANDLE hHandles[100];
functionName(hHandles);

Is there any way to know the size of 'arr' inside the functionName? (Without hardcoding it there)

Not without passing it in as an arg, no. That is why std containers store the array size. — crush, Feb 16 '12 at 18:28
@crush: if you change the function parameters it can be done. — Mooing Duck, Feb 16 '12 at 18:51
possible duplicate of [determine size of array if passed to function](http://stackoverflow.com/questions/968001/determine-size-of-array-if-passed-to-function) — Bo Persson, Feb 16 '12 at 21:37

score 8 · Accepted Answer · answered Feb 16 '12 at 18:38

8

Use template to catch the N in T[N]

template <size_t N>
void function(HANDLE (&arr)[N]) 
{
  std::cout << N << " is here\n";
}

answered Feb 16 '12 at 18:38

Joel Falcou

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OK, yeah, this one uses templates though. – ahmd0 Feb 17 '12 at 04:51
you dont have many options anyway. The fact the size of an array is part of the array type in C++ is a very strong informations. Not using it result in subpar solution. – Joel Falcou Feb 17 '12 at 06:24

score 1 · Answer 2 · answered Feb 16 '12 at 18:29

1

No. Unless you have put a delimiter at the end yourself before passing. In case of strings (which are character arrays)the delimiter is the null character '\0' so the size can be checked. But normally for arrays this can't be done.

answered Feb 16 '12 at 18:29

vjain27

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Terminator is a good suggestion, but there's several ways to do this. – Mooing Duck Feb 16 '12 at 18:54

score 0 · Answer 3 · answered Feb 16 '12 at 18:37

0

Consider sending the size as a separate parameter instead.

void functionName(HANDLE arr[100], size_t size)
{
}

answered Feb 16 '12 at 18:37

Muhammad Hewedy

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2

Consider instead using `std::vector`. – Cheers and hth. - Alf Feb 16 '12 at 18:59

score 0 · Answer 4 · answered Feb 16 '12 at 20:06

0

You could also use a global variable or a class attribute.

size_t size = 100;
void functionName(HANDLE* arr)
{
//size will be visible here and in any other
// functions and you can change its value during run-time

}

answered Feb 16 '12 at 20:06

Mihai

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Get array size inside a function using C++

4 Answers4