No library used, The formula I used is

LC = [Previous CLOSE];
RSI = EWMA(MAX(CLOSE-LC,0),N,1)/EWMA(ABS(CLOSE-LC),N,1) *100;
K = MA(RSI-LLV(RSI,M),P1)/MA(HHV(RSI,M)-LLV(RSI,M),P1)*100;
D = MA(K,P2);

N, M, P1, P2 are parameters.

MA(X,N) = (X1+X2+X3+...+Xn)/N
EWMA(X,N,M) =  Y = [M*X+(N-M)*Y']/N (Y' means previous Y)
HHV - Highest value
LLV - Lowest Value