westonpace commented on a change in pull request #9095:
URL: https://github.com/apache/arrow/pull/9095#discussion_r555194653
##########
File path: cpp/src/arrow/util/iterator.h
##########
@@ -186,6 +194,109 @@ class Iterator : public
util::EqualityComparable<Iterator<T>> {
Result<T> (*next_)(void*) = NULLPTR;
};
+template <typename T>
+struct TransformFlow {
+ using YieldValueType = T;
+
+ TransformFlow(YieldValueType value, bool ready_for_next)
+ : finished_(false),
+ ready_for_next_(ready_for_next),
+ status_(),
+ yield_value_(std::move(value)) {}
+ TransformFlow(bool finished, bool ready_for_next)
+ : finished_(finished), ready_for_next_(ready_for_next), status_(),
yield_value_() {}
+ TransformFlow(Status s) // NOLINT runtime/explicit
+ : finished_(true), ready_for_next_(false), status_(s), yield_value_() {}
+
+ bool HasValue() const { return yield_value_.has_value(); }
+ bool Finished() const { return finished_; }
+ Status status() const { return status_; }
+ bool Ok() const { return status_.ok(); }
+ bool ReadyForNext() const { return ready_for_next_; }
+ T Value() const { return *yield_value_; }
+
+ bool finished_;
+ bool ready_for_next_;
Review comment:
done
##########
File path: cpp/src/arrow/util/iterator.h
##########
@@ -186,6 +194,109 @@ class Iterator : public
util::EqualityComparable<Iterator<T>> {
Result<T> (*next_)(void*) = NULLPTR;
};
+template <typename T>
+struct TransformFlow {
+ using YieldValueType = T;
+
+ TransformFlow(YieldValueType value, bool ready_for_next)
+ : finished_(false),
+ ready_for_next_(ready_for_next),
+ status_(),
+ yield_value_(std::move(value)) {}
+ TransformFlow(bool finished, bool ready_for_next)
+ : finished_(finished), ready_for_next_(ready_for_next), status_(),
yield_value_() {}
+ TransformFlow(Status s) // NOLINT runtime/explicit
+ : finished_(true), ready_for_next_(false), status_(s), yield_value_() {}
+
+ bool HasValue() const { return yield_value_.has_value(); }
+ bool Finished() const { return finished_; }
+ Status status() const { return status_; }
+ bool Ok() const { return status_.ok(); }
+ bool ReadyForNext() const { return ready_for_next_; }
+ T Value() const { return *yield_value_; }
+
+ bool finished_;
+ bool ready_for_next_;
+ Status status_;
+ util::optional<YieldValueType> yield_value_;
+};
+
+struct TransformFinish {
+ template <typename T>
+ operator TransformFlow<T>() && { // NOLINT explicit
+ return TransformFlow<T>(true, true);
+ }
+};
+
+struct TransformSkip {
+ template <typename T>
+ operator TransformFlow<T>() && { // NOLINT explicit
+ return TransformFlow<T>(false, true);
+ }
+};
+
+template <typename T>
+TransformFlow<T> TransformYield(T value = {}, bool ready_for_next = true) {
+ return TransformFlow<T>(std::move(value), ready_for_next);
+}
+
+template <typename T, typename V>
+using Transformer = std::function<TransformFlow<V>(T)>;
+
+template <typename T, typename V>
+class TransformIterator {
+ public:
+ explicit TransformIterator(Iterator<T> it, Transformer<T, V> transformer)
+ : it_(std::move(it)),
+ transformer_(std::move(transformer)),
+ last_value_(),
+ finished_() {}
+
+ util::optional<Result<V>> Pump() {
+ while (!finished_ && last_value_.has_value()) {
+ TransformFlow<V> next = transformer_(*last_value_);
+ if (next.ReadyForNext()) {
+ last_value_.reset();
+ }
+ if (next.Finished()) {
+ finished_ = true;
+ }
+ if (!next.Ok()) {
+ return next.status();
+ }
+ if (next.HasValue()) {
+ return next.Value();
+ }
+ }
+ if (finished_) {
+ return IterationTraits<V>::End();
+ }
+ return util::optional<V>();
+ }
+
+ Result<V> Next() {
+ while (!finished_) {
+ util::optional<Result<V>> next = Pump();
+ if (next.has_value()) {
+ return *next;
+ }
+ ARROW_ASSIGN_OR_RAISE(last_value_, it_.Next());
+ }
+ return IterationTraits<V>::End();
+ }
+
+ private:
+ Iterator<T> it_;
+ Transformer<T, V> transformer_;
+ util::optional<T> last_value_;
+ bool finished_;
Review comment:
done
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
