private static BigFraction from()

in commons-numbers-fraction/src/main/java/org/apache/commons/numbers/fraction/BigFraction.java [140:237]
78 lines of code
16 McCabe index (conditional complexity)

    private static BigFraction from(final double value,
                                    final double epsilon,
                                    final int maxDenominator,
                                    final int maxIterations) {
        if (!Double.isFinite(value)) {
            throw new IllegalArgumentException(NOT_FINITE + value);
        }
        if (value == 0) {
            return ZERO;
        }

        // Remove sign, this is restored at the end.
        // (Assumes the value is not zero and thus signum(value) is not zero).
        final double absValue = Math.abs(value);
        double r0 = absValue;
        long a0 = (long) Math.floor(r0);
        if (a0 > OVERFLOW) {
            throw new FractionException(FractionException.ERROR_CONVERSION_OVERFLOW, value, a0, 1);
        }

        // check for (almost) integer arguments, which should not go to iterations.
        if (r0 - a0 <= epsilon) {
            // Restore the sign.
            if (value < 0) {
                a0 = -a0;
            }
            return new BigFraction(BigInteger.valueOf(a0));
        }

        // Support 2^31 as maximum denominator.
        // This is negative as an integer so convert to long.
        final long maxDen = Math.abs((long) maxDenominator);

        long p0 = 1;
        long q0 = 0;
        long p1 = a0;
        long q1 = 1;

        long p2;
        long q2;

        int n = 0;
        boolean stop = false;
        do {
            ++n;
            final double r1 = 1.0 / (r0 - a0);
            final long a1 = (long) Math.floor(r1);
            p2 = (a1 * p1) + p0;
            q2 = (a1 * q1) + q0;
            if (Long.compareUnsigned(p2, OVERFLOW) > 0 ||
                Long.compareUnsigned(q2, OVERFLOW) > 0) {
                // In maxDenominator mode, fall-back to the previous valid fraction.
                if (epsilon == 0) {
                    p2 = p1;
                    q2 = q1;
                    break;
                }
                throw new FractionException(FractionException.ERROR_CONVERSION_OVERFLOW, value, p2, q2);
            }

            final double convergent = (double) p2 / (double) q2;
            if (n < maxIterations &&
                Math.abs(convergent - absValue) > epsilon &&
                q2 < maxDen) {
                p0 = p1;
                p1 = p2;
                q0 = q1;
                q1 = q2;
                a0 = a1;
                r0 = r1;
            } else {
                stop = true;
            }
        } while (!stop);

        if (n >= maxIterations) {
            throw new FractionException(FractionException.ERROR_CONVERSION, value, maxIterations);
        }

        // Use p2 / q2 or p1 / q1 if q2 has grown too large in maxDenominator mode
        long num;
        long den;
        if (q2 <= maxDen) {
            num = p2;
            den = q2;
        } else {
            num = p1;
            den = q1;
        }

        // Restore the sign.
        if (Math.signum(num) * Math.signum(den) != Math.signum(value)) {
            num = -num;
        }

        return new BigFraction(BigInteger.valueOf(num),
                               BigInteger.valueOf(den));
    }