Question

In C++, arrays cannot be passed simply as parameters. Meaning if I create a function like so:

void doSomething(char charArray[]) {     // if I want the array size     int size = sizeof(charArray);     // NO GOOD, will always get 4 (as in 4 bytes in the pointer) } 

I have no way of knowing how big the array is, since I have only a pointer to the array.

Which way do I have, without changing the method signature, to get the size of the array and iterate over it’s data?

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EDIT: just an addition regarding the solution. If the char array, specifically, was initialized like so:

char charArray[] = 'i am a string'; 

then the \0 is already appended to the end of the array. In this case the answer (marked as accepted) works out of the box, so to speak.

Answer 1

Without changing the signature? Append a sentinel element. For char arrays specifically, it could be the null-terminating '\0' which is used for standard C strings.

void doSomething(char charArray[]) {     char* p = charArray;     for (; *p != '\0'; ++p)     {          // if '\0' happens to be valid data for your app,           // then you can (maybe) use some other value as          // sentinel     }     int arraySize = p - charArray;      // now we know the array size, so we can do some thing } 

Of course, then your array itself cannot contain the sentinel element as content. For other kinds of (i.e., non-char) arrays, it could be any value which is not legal data. If no such value exists, then this method does not work.

Moreover, this requires co-operation on the caller side. You really have to make sure that the caller reserves an array of arraySize + 1 elements, and always sets the sentinel element.

However, if you really cannot change the signature, your options are rather limited.