AlvinJ15 commented on code in PR #13009:
URL: https://github.com/apache/arrow/pull/13009#discussion_r865035604
##########
cpp/src/arrow/stl_iterator.h:
##########
@@ -128,6 +132,153 @@ class ArrayIterator {
int64_t index_;
};
+template <typename ArrayType,
+ typename ValueAccessor = detail::DefaultValueAccessor<ArrayType>>
+class ChunkedArrayIterator {
+ public:
+ using value_type = arrow::util::optional<typename ValueAccessor::ValueType>;
+ using difference_type = int64_t;
+ using pointer = value_type*;
+ using reference = value_type&;
+ using iterator_category = std::random_access_iterator_tag;
+
+ // Some algorithms need to default-construct an iterator
+ ChunkedArrayIterator() : chunked_array_(NULLPTR), index_(0),
current_chunk_index_(0) {}
+
+ explicit ChunkedArrayIterator(const ChunkedArray& chunked_array, int64_t
index = 0)
+ : chunked_array_(&chunked_array), index_(index) {
+ auto chunk_location = GetChunkLocation(this->index_);
+ if (chunked_array.length()) {
+ current_array_iterator_ = ArrayIterator<ArrayType>(
+ *arrow::internal::checked_pointer_cast<ArrayType>(
+
chunked_array_->chunk(static_cast<int>(chunk_location.chunk_index))),
+ index_);
+ } else {
+ current_array_iterator_ = {};
+ }
+
+ this->current_chunk_index_ = chunk_location.chunk_index;
+ current_array_iterator_ -= this->index() - chunk_location.index_in_chunk;
+ }
+
+ // Value access
+ value_type operator*() const { return *current_array_iterator_; }
+
+ value_type operator[](difference_type n) const {
+ auto chunk_location = GetChunkLocation(index_ + n);
+ if (current_chunk_index_ == chunk_location.chunk_index) {
Review Comment:
The `arrow::internal::checked_pointer_cast<ArrayType>` when creating an
ArrayIterator, is less expensive than `int64_t` comparissons and a arithmetic
operation?
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