jonkeane commented on a change in pull request #11225:
URL: https://github.com/apache/arrow/pull/11225#discussion_r717541592
##########
File path: r/src/altrep.cpp
##########
@@ -70,135 +69,125 @@ R_xlen_t Standard_Get_region<int>(SEXP data2, R_xlen_t i,
R_xlen_t n, int* buf)
return INTEGER_GET_REGION(data2, i, n, buf);
}
-// altrep R vector shadowing an Array.
+void DeleteArray(std::shared_ptr<Array>* ptr) { delete ptr; }
+using Pointer = cpp11::external_pointer<std::shared_ptr<Array>, DeleteArray>;
+
+// base class for all altrep vectors
+//
+// The altrep vector stores the Array as an external pointer in data1
+// Implementation classes AltrepVectorPrimitive<> and AltrepVectorString
+// also use data2
+struct AltrepVectorBase {
+ // store the Array as an external pointer in data1, mark as immutable
+ static SEXP Make(R_altrep_class_t class_t, const std::shared_ptr<Array>&
array) {
+ SEXP alt_ =
+ R_new_altrep(class_t, Pointer(new std::shared_ptr<Array>(array)),
R_NilValue);
+ MARK_NOT_MUTABLE(alt_);
+
+ return alt_;
+ }
+
+ // the Array that is being wrapped by the altrep object
+ static const std::shared_ptr<Array>& array(SEXP alt_) {
+ return *Pointer(R_altrep_data1(alt_));
+ }
+
+ // Is the vector materialized, i.e. does the data2 slot contain a
+ // standard R vector with the same data as the array.
+ static bool IsMaterialized(SEXP alt_) { return
!Rf_isNull(R_altrep_data2(alt_)); }
+
+ static R_xlen_t Length(SEXP alt_) { return array(alt_)->length(); }
+
+ static int No_NA(SEXP alt_) { return array(alt_)->null_count() == 0; }
+
+ static int Is_sorted(SEXP alt_) { return UNKNOWN_SORTEDNESS; }
+
+ // What gets printed on .Internal(inspect(<the altrep object>))
+ static Rboolean Inspect(SEXP alt_, int pre, int deep, int pvec,
+ void (*inspect_subtree)(SEXP, int, int, int)) {
+ const auto& array_ = array(alt_);
+ Rprintf("arrow::Array<%s, %d nulls> len=%d, Array=<%p>\n",
Review comment:
Oh, even better! Thanks for these. I'll move to using `.Internal()` that
way we don't need to worry about exporting `arrow:::is_altrep()` (and the
backwards compatibility of that in {arrowbench}
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