coding.cpp

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#include <cstdio>
#include <cstdint>
#include <cmath>

using std::printf;

void encodePoint(const double x, const double y, uint32_t& code)
{
        if (((x * 100) < (((double) INT16_MIN) + 1)) ||
                        ((x * 100) > (((double) INT16_MAX) - 1)) ||
                        ((y * 100) < (((double) INT16_MIN) + 1)) ||
                        ((y * 100) > (((double) INT16_MAX) - 1)))
        {
                fprintf(stderr, "Point (%f, %f) cannot be encoded\n", x, y);
        }
        int16_t xint = (int16_t) std::lround(x * 100);
        int16_t yint = (int16_t) std::lround(y * 100);
        code = (xint << 16);
        code |= (yint & 0x0000FFFF);
}

void decodePoint(const uint32_t code, double& x, double& y)
{
        int16_t xint = (int16_t) (code >> 16);
        int16_t yint = (int16_t) code;
        x = ((double) xint) / 100;
        y = ((double) yint) / 100;
}

int main(int argc, char** argv)
{
        double xin = 2.546;
        double yin = 1.20;
        double xout;
        double yout;
        uint32_t code;

        encodePoint(xin, yin, code);
        decodePoint(code, xout, yout);
        printf("encoded x: %f, y: %f\n", xin, yin);
        printf("decoded x: %f, y: %f\n", xout, yout);
        printf("\n");

        xin = -0.02;
        encodePoint(xin, yin, code);
        decodePoint(code, xout, yout);
        printf("encoded x: %f, y: %f\n", xin, yin);
        printf("decoded x: %f, y: %f\n", xout, yout);
        printf("\n");
        
        yin = -57.893;
        encodePoint(xin, yin, code);
        decodePoint(code, xout, yout);
        printf("encoded x: %f, y: %f\n", xin, yin);
        printf("decoded x: %f, y: %f\n", xout, yout);
        printf("\n");

        xin = -1.984;
        encodePoint(xin, yin, code);
        decodePoint(code, xout, yout);
        printf("encoded x: %f, y: %f\n", xin, yin);
        printf("decoded x: %f, y: %f\n", xout, yout);
        printf("\n");

        xin = -700.984;
        encodePoint(xin, yin, code);
        decodePoint(code, xout, yout);
        printf("encoded x: %f, y: %f\n", xin, yin);
        printf("decoded x: %f, y: %f\n", xout, yout);
        printf("\n");

        xin = 0.184421;
        yin = 2.10794;
        encodePoint(xin, yin, code);
        decodePoint(code, xout, yout);
        printf("encoded x: %f, y: %f\n", xin, yin);
        printf("code: %d (%#010x)\n", code, code);
        printf("decoded x: %f, y: %f\n", xout, yout);
        printf("\n");

}