sqrt16()

LIB8STATIC uint8_t sqrt16

(

uint16_t

x

)

Square root for 16-bit integers.

About three times faster and five times smaller than Arduino's general sqrt on AVR.

Definition at line 540 of file math8.h.

                                      {
    if (x <= 1) {
        return x;
    }
 
    uint8_t low = 1; // lower bound
    uint8_t hi, mid;
 
    if (x > 7904) {
        hi = 255;
    } else {
        hi = (x >> 5) + 8; // initial estimate for upper bound
    }
 
    do {
        mid = (low + hi) >> 1;
        if ((uint16_t)(mid * mid) > x) {
            hi = mid - 1;
        } else {
            if (mid == 255) {
                return 255;
            }
            low = mid + 1;
        }
    } while (hi >= low);
 
    return low - 1;
}

References LIB8STATIC, and x.

Referenced by rgb2hsv_approximate(), and sqrt8().

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