// zRSplitByFixedSizeBars

// By Zlatomir Zlatev

// Source: https://github.com/zzlatev/zRSplitByFixedSizeBars.c

#include <R.h>

#include <Rdefines.h>

SEXP zSplitByFixedSizeBars(SEXP xIntVect, SEXP nBy, SEXP nCount)

{

int i, j, N, NBy, intSplitTo, intSplitTo2, startI;

long long int sum=0;

int *pNUM, *pResult;

SEXP result;

PROTECT(xIntVect = AS_INTEGER(xIntVect));

NBy = INTEGER_VALUE(nBy);

N = INTEGER_VALUE(nCount);

pNUM = INTEGER(xIntVect);

//get sum

for(i=0; i<N; i++)

{

sum += pNUM[i];

}

//how many rows we'll need to split the volume bars to

intSplitTo = sum/NBy;

if(sum % NBy > 0)

intSplitTo += 1;

//reserve space for the results

PROTECT(result = allocMatrix(INTSXP, intSplitTo, 3));

pResult = INTEGER(result);

intSplitTo2 = intSplitTo * 2;

//split

j=0; //j is the index for the split matrix

i=0; // i is the index of the original vector

sum = 0;

startI = 1;

while(1)

{

if(sum >= NBy) //split

{

pResult[j] = startI;

pResult[j+intSplitTo] = i;

pResult[j+intSplitTo2] = NBy;

sum -= NBy;

if(sum == 0)

startI = i+1;

else

startI = i;

j++;

continue;

}

if(i==N && sum <= NBy) {

if(sum != 0) { // final split

pResult[intSplitTo-1] = startI;

pResult[intSplitTo2-1] = i;

pResult[intSplitTo*3-1] = sum;

}

break;

}

if(i<N) {

sum += pNUM[i];

i++;

}

}

UNPROTECT(2);

return result;

}