c++ - Proper casting for fstream read and write member functions

Question

Although there was a lot of lines written on the topic of reinterpret_cast, and how bad it is, I'm still puzzled with best way to avoid it, especially when dealing with functions like read and write from fstream. So, here is my dilemma...

Let's say we have an integer array that we want to fill with some data from a file.

std::ifstream iFile( ... );

// presume that the type of this array is not a matter of choice
int *a = new int[ 100 ]; 

We can read with a few different casts:

iFile.read( (char *)a, sizeof( int ) * 100 );
iFile.read( reinterpret_cast< char * >( a ), sizeof( int ) * 100 );
iFile.read( static_cast< char * >( static_cast< void * >( ( a ) ), sizeof( int ) * 100 );

The first one (C-style) is outdated and new style casts we're introduced in C++ for good reasons. The second one is unportable and offers no guarantees. The third one is tedious to write and spoils the fun.

Is there any alternative to this and how should I go about it?

EDIT:

The goal is to achieve code as portable and as standard-conforming as possible.

Answer 1

Why don't you declare a as char* instead, like this:

//int *a = new int[100]; 
char *a = new char[100];
iFile.read(a, 100 ); 

No casting required now.

---

EDIT:

Okay, I read your comment and the commented line in your post. In that case:

iFile.read(reinterpret_cast<char*>(a), sizeof(int)*100);

should suffice.

However,I personally would choose C-style cast:

iFile.read((char*)a, sizeof(int)*100);

That is because I don't see any danger here. Everything seems fine even with C-Style cast!

---

Best yet less tedious cast

Define this function template:

template<class To, class From>
To any_cast(From v)
{
    return static_cast<To>(static_cast<void*>(v));
}

Then use it:

//`From` type will be inferred from the function argument. :-) 
iFile.read(any_cast<char*>(a), sizeof(int)*100);

Looks good?

I think this any_cast can be used to cast from any-type to any-type!