How to convert FILE* to numeric handle in 64 bit system?

Question

I use embedded JavaScript engine, and I used to pass the result of fopen() to JS code as a Number.

int numeric_handle = (int)fopen(*P1, "rb");
return Number::New(numeric_handle); // Return to JavaScript

But now I need to recompile in 64 bit system, and I get

fatal error: cast from pointer to smaller type 'int' loses information

Now I am sort of stuck, how do I keep the design of my system but change as little code as possible? I was thinking of having a hash-map, an array that holds FILE* and return an ID in that array. But that will mean extra memory management, extra lookup.

Answer 1

I would certainly go with "hide the actual type", in other words, use a map, vector or some similar type to store the FILE *, and pass the index or whatever is needed to retrieve the FILE * for the calls that need it. That way, it won't matter HOW you open the file (you may later want to use fstream and C++, for example, which will be much harder to store as a copy of some sort).

Answer 2

long should be enough, but you can use a byte buffer too

FILE *f;
char buffer[sizeof(f)];
memcpy(buffer, &f, sizeof(f));

Why do you need such a hack?

Answer 3

Use a pointer sized integer like intptr_t from cstdint.