Even faster version of cSplit....

cSplit.R

cSplit <- function(indt, splitCols, sep = ",", direction = "wide", fixed = TRUE, 
                   drop = TRUE, stripWhite = TRUE, type.convert = TRUE) {
  require(stringi)
  require(splitstackshape)
  
  Trim <- function(invec) {
    `dim<-`(stri_trim_both(invec), dim(invec))
  }
  
  padNAcols <- function(inmat, colsneeded) {
    colsNeeded <- colsneeded - ncol(inmat)
    if (colsNeeded == 0) {
      inmat
    } else {
      cbind(inmat, matrix(NA, nrow = nrow(inmat), ncol = colsNeeded))
    } 
  }
  
  if (!is.data.table(indt)) 
    indt <- as.data.table(indt)
  else indt <- copy(indt)
  if (is.numeric(splitCols)) 
    splitCols <- splitstackshape:::Names(indt, splitCols)
  
  if (length(sep) == 1) 
    sep <- rep(sep, length(splitCols))
  if (length(sep) != length(splitCols)) {
    stop("Verify you have entered the correct number of sep")
  }
  
  switch(
    direction,
    wide = {
      X <- lapply(seq_along(splitCols), function(x) {
        temp1 <- stri_split_fixed(indt[[splitCols[x]]], sep[x], 
                                  simplify = TRUE, omit_empty = TRUE)
        if (isTRUE(stripWhite)) temp1 <- Trim(temp1)
        temp1 <- as.data.table(temp1)
        setnames(temp1, paste(splitCols[x], splitstackshape:::.pad(
          sequence(ncol(temp1))), sep = "_"))
        if (isTRUE(type.convert)) temp1 <- temp1[, lapply(.SD, type.convert)]
        temp1
      })
      out <- cbind(indt, do.call(cbind, X))
      if (isTRUE(drop)) out[, (splitCols) := NULL][]
    },
    long = {
      Y <- lapply(seq_along(splitCols), function(x) {
        temp1 <- stri_split_fixed(indt[[splitCols[x]]], sep[x],
                                  simplify = TRUE, omit_empty = TRUE)
      })
      
      Ncols <- max(vapply(Y, ncol, 1L))
      
      Y <- lapply(Y, function(x) {
        out <- c(t(padNAcols(x, Ncols)))
        if (isTRUE(stripWhite)) out <- stri_trim_both(out)
        out
      })
      
      YDT <- as.data.table(Y)
      setnames(YDT, paste0(splitCols, "_new"))
      
      if (isTRUE(type.convert)) YDT <- YDT[, lapply(.SD, type.convert)]
      
      out <- cbind(expandRows(indt, Ncols, count.is.col = FALSE), YDT)
      if (isTRUE(drop)) out[, (splitCols) := NULL][]
    })
}

To do:

[X] Add the direction = "long" setting.
[ ] Remind self of what the makeEqual setting did. *Seems to be irrelevant--no need to pad empty columns, is there? Needed for direction = "long" when splitting multiple columns at once.