paleolimbot commented on code in PR #12323:
URL: https://github.com/apache/arrow/pull/12323#discussion_r848522035
##########
r/src/io.cpp:
##########
@@ -207,7 +209,209 @@ void io___BufferOutputStream__Write(
StopIfNotOk(stream->Write(RAW(bytes), bytes.size()));
}
-// TransformInputStream::TransformFunc wrapper
+// ------ RConnectionInputStream / RConnectionOutputStream
+
+class RConnectionFileInterface : public virtual arrow::io::FileInterface {
+ public:
+ explicit RConnectionFileInterface(cpp11::sexp connection_sexp)
+ : connection_sexp_(connection_sexp), closed_(false) {
+ check_closed();
+ }
+
+ arrow::Status Close() {
+ if (closed_) {
+ return arrow::Status::OK();
+ }
+
+ auto result = SafeCallIntoR<bool>([&]() {
+ cpp11::package("base")["close"](connection_sexp_);
+ return true;
+ });
+
+ RETURN_NOT_OK(result);
+ closed_ = true;
+ return arrow::Status::OK();
+ }
+
+ arrow::Result<int64_t> Tell() const {
+ if (closed()) {
+ return arrow::Status::IOError("R connection is closed");
+ }
+
+ cpp11::sexp result = cpp11::package("base")["seek"](connection_sexp_);
+ return cpp11::as_cpp<int64_t>(result);
+ }
+
+ bool closed() const { return closed_; }
+
+ protected:
+ cpp11::sexp connection_sexp_;
+
+ // Define the logic here because multiple inheritance makes it difficult
+ // for this base class, the InputStream and the RandomAccessFile
+ // interfaces to co-exist.
+ arrow::Result<int64_t> ReadBase(int64_t nbytes, void* out) {
+ if (closed()) {
+ return arrow::Status::IOError("R connection is closed");
+ }
+
+ return SafeCallIntoR<int64_t>([&] {
+ cpp11::function read_bin = cpp11::package("base")["readBin"];
+ cpp11::writable::raws ptype((R_xlen_t)0);
+ cpp11::integers n = cpp11::as_sexp<int>(nbytes);
+
+ cpp11::sexp result = read_bin(connection_sexp_, ptype, n);
+
+ int64_t result_size = cpp11::safe[Rf_xlength](result);
+ memcpy(out, cpp11::safe[RAW](result), result_size);
+ return result_size;
+ });
+ }
+
+ arrow::Result<std::shared_ptr<arrow::Buffer>> ReadBase(int64_t nbytes) {
+ arrow::BufferBuilder builder;
+ RETURN_NOT_OK(builder.Reserve(nbytes));
+
+ arrow::Result<int64_t> result;
+ RETURN_NOT_OK(result = ReadBase(nbytes, builder.mutable_data()));
+
+ builder.UnsafeAdvance(result.ValueOrDie());
+ return builder.Finish();
+ }
+
+ arrow::Status WriteBase(const void* data, int64_t nbytes) {
+ if (closed()) {
+ return arrow::Status::IOError("R connection is closed");
+ }
+
+ auto result = SafeCallIntoR<bool>([&]() {
Review Comment:
I couldn't figure out how to get a template specialization to return a
different type, but I implemented `Status SafeCallIntoRVoid() {}` that reads
much better.
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