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#' @export
library(bitops)
require(signal)
idin.prbs<-function(n,band=c(0,1),levels=c(0,1)){
u=vector()
for(i in 1:18){
if(n / (2^i) < 1){
u=idin.prbs12(i,band,levels)
break
}
}
return(u[1:n])
}
idin.prbs12 <- function(N,band=c(0,1),levels=c(0,1)){
first=ceiling(abs(rnorm(1)*10)) #some non-zero initial state
x= first
v = vector()
n=2^N-1
i=1
clock=floor(1/band[2])
k=1
M=rbind(c(0,0,0,0),c(1,2,0,0),c(1,3,0,0),c(1,4,0,0),c(2,5,0,0),c(1,6,0,0),
c(1,7,0,0),c(1,2,7,8),c(4,9,0,0),c(3,10,0,0),c(9,11,0,0),
c(6,8,11,12),c(9,10,12,13),c(4,8,13,14),c(14,15,0,0),c(4,13,15,16),
c(14,17,0,0),c(11,18,0,0))
repeat{
a=M[N,1]
b=M[N,2]
c=M[N,3]
d=M[N,4]
four=c(8,12,13,14,16)
if(N %in% four){
e=bitwXor(bitwShiftR(x,N-a),bitwShiftR(x,N-b))
f=bitwXor(bitwShiftR(x,N-c),bitwShiftR(x,N-d))
newbit=bitwAnd(bitwXor(e,f),1)
}else{
newbit=bitwAnd(bitwXor(bitwShiftR(x,N-a),bitwShiftR(x,N-b)),1)
}
if(k>=clock || i==1){
# newbit=bitwAnd(bitwXor(bitwShiftR(x,0),bitwShiftR(x,1)),1)
v[i]=newbit
i=i+1
# x=bitwOr(bitwShiftR(x,1),bitwShiftL(newbit,6))
k=1
}else{
v[i]=v[i-1]
i=i+1
k=k+1
}
x=bitwOr(bitwShiftR(x,1),bitwShiftL(newbit,N-1))
#checking if it exceeds the repetition period or reaches
#required no. of bits first
if(x==first){
cat("Repetition period is ",i-1)
break
}
# else if(i-1==n){
# break
# }
}
v=sapply(v, function(x){if (x==0) levels[1] else levels[2]})
return(v)
}
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