static void yy_png_delay_to_fraction()

in iOS/WAStickersThirdParty/YYImageCoder.m [262:298]

• 33 lines of code
• 9 McCabe index (conditional complexity)

static void yy_png_delay_to_fraction(double duration, uint16_t *num, uint16_t *den) {
    if (duration >= 0xFF) {
        *num = 0xFF;
        *den = 1;
    } else if (duration <= 1.0 / (double)0xFF) {
        *num = 1;
        *den = 0xFF;
    } else {
        // Use continued fraction to calculate the num and den.
        long MAX = 10;
        double eps = (0.5 / (double)0xFF);
        long p[MAX], q[MAX], a[MAX], i, numl = 0, denl = 0;
        // The first two convergents are 0/1 and 1/0
        p[0] = 0; q[0] = 1;
        p[1] = 1; q[1] = 0;
        // The rest of the convergents (and continued fraction)
        for (i = 2; i < MAX; i++) {
            a[i] = lrint(floor(duration));
            p[i] = a[i] * p[i - 1] + p[i - 2];
            q[i] = a[i] * q[i - 1] + q[i - 2];
            if (p[i] <= 0xFF && q[i] <= 0xFF) { // uint16_t
                numl = p[i];
                denl = q[i];
            } else break;
            if (fabs(duration - a[i]) < eps) break;
            duration = 1.0 / (duration - a[i]);
        }
        
        if (numl != 0 && denl != 0) {
            *num = numl;
            *den = denl;
        } else {
            *num = 1;
            *den = 100;
        }
    }
}