data.table exported C routines

Some of the internally used C routines are now exported. This interface should be considered experimental. List of exported C routines and their signatures are provided below in the usage section.

Usage

# SEXP DT_subsetDT(SEXP x, SEXP rows, SEXP cols);
# p_DT_subsetDT = R_GetCCallable("data.table", "DT_subsetDT");

Details

Details on how to use these can be found in the Writing R Extensions manual Linking to native routines in other packages section. An example use with Rcpp:

  dt = data.table::as.data.table(iris)
  Rcpp::cppFunction("SEXP mysub2(SEXP x, SEXP rows, SEXP cols) { return DT_subsetDT(x,rows,cols); }",
    include="#include <datatableAPI.h>",
    depends="data.table")
  mysub2(dt, 1:4, 1:4)

Note

Be aware C routines are likely to have less input validation than their corresponding R interface. For example one should not expect DT[-5L] will be equal to .Call(DT_subsetDT, DT, -5L, seq_along(DT)) because translation of i=-5L to seq_len(nrow(DT))[-5L] might be happening on R level. Moreover checks that i argument is in range of 1:nrow(DT), missingness, etc. might be happening on R level too.

References

https://cran.r-project.org/doc/manuals/r-release/R-exts.html