Some of 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.

# SEXP subsetDT(SEXP x, SEXP rows, SEXP cols);
# p_dtCsubsetDT = R_GetCCallable("data.table", "CsubsetDT");

## Details

For details how to use those see Writing R Extensions manual Linking to native routines in other packages section.

## 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(CsubsetDT, 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