r_missing_value.hpp

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#ifndef RITSUKO_R_MISSING_HPP
#define RITSUKO_R_MISSING_HPP
 
#include <cstdint>
#include <cstring>
 
namespace ritsuko {
 
inline double r_missing_value() {
    uint32_t tmp_value = 1;
    auto tmp_ptr = reinterpret_cast<unsigned char*>(&tmp_value);
 
    // Mimic R's generation of these values, but we can't use type punning as
    // this is not legal in C++, and we don't have bit_cast yet.
    double missing_value = 0;
    auto missing_ptr = reinterpret_cast<unsigned char*>(&missing_value);
 
    int step = 1;
    if (tmp_ptr[0] == 1) { // little-endian. 
        missing_ptr += sizeof(double) - 1;
        step = -1;
    }
 
    *missing_ptr = 0x7f;
    *(missing_ptr += step) = 0xf0;
    *(missing_ptr += step) = 0x00;
    *(missing_ptr += step) = 0x00;
    *(missing_ptr += step) = 0x00;
    *(missing_ptr += step) = 0x00;
    *(missing_ptr += step) = 0x07;
    *(missing_ptr += step) = 0xa2;
 
    return missing_value;
}
 
template<typename Float_>
bool are_floats_identical(const Float_* x, const Float_* y) {
    auto xptr = reinterpret_cast<const unsigned char*>(x);
    auto yptr = reinterpret_cast<const unsigned char*>(y);
    return std::memcmp(xptr, yptr, sizeof(Float_)) == 0;
}
 
}
 
#endif