#include "data.table.h"

SEXP vecseq(SEXP x, SEXP len, SEXP clamp)

{

// Name taken from bit::vecseq, but,

// * implemented in C rather than R

// * takes len rather than y endpoints

// * no concat=FALSE or eval arguments as not needed.

// * Adds clamp to prevent very large vectors being created (unless allow.cartesian=TRUE)

// Specially for use by [.data.table after binary search. Now so specialized that for general use

// bit::vecseq is recommended (Jens has coded it in C now).

if (!isInteger(x))

error(_("x must be an integer vector")); // # nocov

if (!isInteger(len))

error(_("len must be an integer vector")); // # nocov

if (LENGTH(x) != LENGTH(len))

error(_("x and len must be the same length")); // # nocov

const int *ix = INTEGER_RO(x);

const int *ilen = INTEGER_RO(len), nlen=LENGTH(len);

int reslen = 0;

for (int i=0; i<nlen; ++i) {

if (INT_MAX-reslen < ilen[i])

error(_("Join results in more than 2^31 rows (internal vecseq reached physical limit). Very likely misspecified join. Check for duplicate key values in i each of which join to the same group in x over and over again. If that's ok, try by=.EACHI to run j for each group to avoid the large allocation. Otherwise, please search for this error message in the FAQ, Wiki, Stack Overflow and data.table issue tracker for advice."));

reslen += ilen[i];

}

if (!isNull(clamp)) {

if (!isNumeric(clamp) || LENGTH(clamp)!=1)

error(_("clamp must be a double vector length 1")); // # nocov

double limit = REAL(clamp)[0];

if (limit<0)

error(_("clamp must be positive")); // # nocov

if (reslen>limit)

error(_("Join results in %d rows; more than %d = nrow(x)+nrow(i). Check for duplicate key values in i each of which join to the same group in x over and over again. If that's ok, try by=.EACHI to run j for each group to avoid the large allocation. If you are sure you wish to proceed, rerun with allow.cartesian=TRUE. Otherwise, please search for this error message in the FAQ, Wiki, Stack Overflow and data.table issue tracker for advice."), reslen, (int)limit);

}

SEXP ans = PROTECT(allocVector(INTSXP, reslen));

int *ians = INTEGER(ans);

int k = 0;

for (int i=0; i<nlen; ++i) {

int thisx = ix[i];

for (int j=0; j<ilen[i]; ++j) {

ians[k++] = thisx++;

}

}

UNPROTECT(1);

return(ans);

}