realTransform(out, data) {
        if (out === data)
            throw new Error('Input and output buffers must be different');

        this._realTransform4(out, data, 1 /* DONE */);
    }
Performs a real-valued forward FFT on the given input buffer and stores the result in the given output buffer.
The input buffer must contain real values only, while the output buffer will contain complex values. The input and
output buffers must be different.

@param {Float64Array} out The output buffer.
@param {Float64Array} data The input buffer containing real values.

@throws {Error} If the input and output buffers are the same.