Question

I’m getting data from a binary file, reading from file and writing in a vector of unsigned char. I can’t edit it, because I’m using a external library.

But the data that I’m reading from file is a 16 bits image, and I’d like to put the data in a vector of unsigned short

Maybe I can do a cast for it?

Rgds.

Answer 1

A generic approach (not bullet proof):

#include <vector>
#include <iostream>
#include <iterator>
#include <algorithm>

typedef unsigned char u8;
typedef unsigned short u16;

u16 combine_two_bytes(u8 a, u8 b) {
    return a | (b << 8);
}

template<typename InIter, typename OutIter, typename InT, typename OutT>
void combine_pairs(InIter in, InIter in_end, OutIter out, OutT (*func)(InT, InT)) {
    while(1) {
        if(in == in_end) {
            break;
        }

        InT &left = *in++;

        if(in == in_end) {
            break;
        }

        InT &right = *in++;

        *out++ = func(left, right);
    }
}

int main() {
    using namespace std;    // lazy

    u8 input[] = { 1, 2, 3, 4, 5, 6, 7, 8 };
    const size_t in_size = sizeof(input) / sizeof(*input);
    u16 output[in_size / 2];

    cout << "Original: ";
    copy(input, input + in_size, ostream_iterator<int>(cout, " "));
    cout << endl;

    combine_pairs(input, input + in_size, output, combine_two_bytes);

    cout << "Transformed: ";
    copy(output, output + in_size / 2, ostream_iterator<int>(cout, " "));
    cout << endl;

    return 0;
}