New xlsb_sheets() function

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: readxlsb
 Type: Package
 Title: Read 'Excel' Binary (.xlsb) Workbooks
-Version: 0.1.4
+Version: 0.2.0
 Date: 2020-09-29
 Authors@R: person("Michael", "Allen", role = c("aut", "cre"), email = "michael@velofrog.com")
 Depends: R (>= 3.3.0)
@@ -22,4 +22,4 @@ Suggests:
     rmarkdown
 VignetteBuilder:
     knitr
-RoxygenNote: 7.0.1
+RoxygenNote: 7.1.2

NAMESPACE

@@ -1,6 +1,7 @@
 # Generated by roxygen2: do not edit by hand
 
 export(read_xlsb)
+export(xlsb_sheets)
 importFrom(Rcpp,evalCpp)
 importFrom(utils,unzip)
 useDynLib(readxlsb, .registration = TRUE)

R/parse_xlsb.R

@@ -0,0 +1,18 @@
+## Backend function for superior modularity
+parse_xlsb <- function(path) {
+  ## Parameter checks
+  stop_if_not_defined(path, "path missing")
+
+  xlsb_env = new.env()
+
+  xlsb_contents = unzip(zipfile = path, list = TRUE)
+  idx = which(grepl("xl/workbook.bin", xlsb_contents$Name))
+  if (length(idx) == 0) stop("Failed to find xl/workbook.bin in file")
+  cn = unz(path, filename = xlsb_contents[idx, "Name"], open = "rb")
+  xlsb_env$stream = readBin(cn, "raw", xlsb_contents[idx, "Length"])
+  close(cn)
+
+  ## Parse workbook.bin
+  ParseWorkbook(xlsb_env)
+  xlsb_env
+}

R/read_xlsb.R

@@ -63,21 +63,8 @@ read_xlsb = function(path, sheet = NULL, range = NULL, col_names = TRUE, col_typ
                      na = "", trim_ws = TRUE, skip = 0, ...) {
 
   ## Parameter checks
-  stop_if_not_defined(path, "path missing")
   if (!is.numeric(skip) || (skip < 0)) stop("Expecting non-negative value for skip")
-
-  ## Store intermediate objects in an environment
-  xlsb_env = new.env()
-
-  xlsb_contents = unzip(zipfile = path, list = TRUE)
-  idx = which(grepl("xl/workbook.bin", xlsb_contents$Name))
-  if (length(idx) == 0) stop("Failed to find xl/workbook.bin in file")
-  cn = unz(path, filename = xlsb_contents[idx, "Name"], open = "rb")
-  xlsb_env$stream = readBin(cn, "raw", xlsb_contents[idx, "Length"])
-  close(cn)
-
-  ## Parse workbook.bin
-  ParseWorkbook(xlsb_env)
+  xlsb_env <- parse_xlsb(path)
 
   ## Use workbook.bin.rels XML file to extract Type and Target fields
   idx = which(grepl("xl/_rels/workbook.bin.rels", xlsb_contents$Name))

R/xlsb_sheets.R

@@ -0,0 +1,12 @@
+#' List all sheets in a .xlsb workbook
+#'
+#' Analogous to the \code{excel_sheets} function from \code{readxl}. Efficiently gets the sheet names without needing to read any surplus data.
+#' @usage xlsb_sheets(path)
+#' @param path Path to the xlsb workbook
+#' @examples
+#' xlsb_sheets(path = system.file("extdata", "TestBook.xlsb", package = "readxlsb"))
+#'
+#' @export
+xlsb_sheets = function(path) {
+  parse_xlsb(path)$sheets$Name
+}

src/RcppExports.cpp

@@ -5,6 +5,11 @@
 
 using namespace Rcpp;
 
+#ifdef RCPP_USE_GLOBAL_ROSTREAM
+Rcpp::Rostream<true>&  Rcpp::Rcout = Rcpp::Rcpp_cout_get();
+Rcpp::Rostream<false>& Rcpp::Rcerr = Rcpp::Rcpp_cerr_get();
+#endif
+
 // ParseWorkbook
 void ParseWorkbook(Rcpp::Environment xlsb_env);
 RcppExport SEXP _readxlsb_ParseWorkbook(SEXP xlsb_envSEXP) {