pitrou commented on code in PR #13009:
URL: https://github.com/apache/arrow/pull/13009#discussion_r860704871
##########
cpp/src/arrow/stl_iterator.h:
##########
@@ -128,6 +131,199 @@ 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) {
+ UpdateComponents(*this);
+ }
+
+ // Value access
+ value_type operator*() const { return
*iterators_list_[current_chunk_index_]; }
+
+ value_type operator[](difference_type n) const {
+ auto chunk_location = GetChunkLocation(index_ + n);
+ return iterators_list_[chunk_location.chunk_index]
+ [chunk_location.index_in_chunk -
+
iterators_list_[chunk_location.chunk_index].index()];
+ }
+
+ int64_t index() const { return index_; }
+
+ // Forward / backward
+ ChunkedArrayIterator& operator++() {
+ ++index_;
+ if (iterators_list_[current_chunk_index_].index() ==
+
chunked_array_->chunk(static_cast<int>(current_chunk_index_))->length() - 1) {
+ iterators_list_[current_chunk_index_] -=
+ iterators_list_[current_chunk_index_].index();
+ current_chunk_index_++;
+ if
(!chunked_array_->chunk(static_cast<int>(current_chunk_index_))->length()) {
+ current_chunk_index_ = GetChunkLocation(index_).chunk_index;
+ }
+ iterators_list_[current_chunk_index_] -=
+ iterators_list_[current_chunk_index_].index();
+ } else {
+ iterators_list_[current_chunk_index_]++;
+ }
+ return *this;
+ }
+ ChunkedArrayIterator& operator--() {
+ --index_;
+ if (iterators_list_[current_chunk_index_].index()) {
+ iterators_list_[current_chunk_index_]--;
+ } else {
+ iterators_list_[current_chunk_index_] -=
+ iterators_list_[current_chunk_index_].index();
+ current_chunk_index_--;
+ if
(!chunked_array_->chunk(static_cast<int>(current_chunk_index_))->length()) {
+ current_chunk_index_ = GetChunkLocation(index_).chunk_index;
+ }
+ iterators_list_[current_chunk_index_] -=
+ iterators_list_[current_chunk_index_].index();
+ iterators_list_[current_chunk_index_] +=
+
chunked_array_->chunk(static_cast<int>(current_chunk_index_))->length() - 1;
+ }
+ return *this;
+ }
+
+ ChunkedArrayIterator operator++(int) {
+ ChunkedArrayIterator tmp(*this);
+ ++*this;
+ return tmp;
+ }
+ ChunkedArrayIterator operator--(int) {
+ ChunkedArrayIterator tmp(*this);
+ --*this;
+ return tmp;
+ }
+
+ // Arithmetic
+ difference_type operator-(const ChunkedArrayIterator& other) const {
+ return index_ - other.index_;
+ }
+ ChunkedArrayIterator operator+(difference_type n) const {
+ return ChunkedArrayIterator(*chunked_array_, index_ + n);
+ }
+ ChunkedArrayIterator operator-(difference_type n) const {
+ return ChunkedArrayIterator(*chunked_array_, index_ - n);
+ }
+ friend inline ChunkedArrayIterator operator+(difference_type diff,
+ const ChunkedArrayIterator&
other) {
+ return ChunkedArrayIterator(*other.chunked_array_, diff + other.index_);
+ }
+ friend inline ChunkedArrayIterator operator-(difference_type diff,
+ const ChunkedArrayIterator&
other) {
+ return ChunkedArrayIterator(*other.chunked_array_, diff - other.index_);
+ }
+ ChunkedArrayIterator& operator+=(difference_type n) {
+ bool in_current_chunk;
+ auto& current_iterator = iterators_list_[current_chunk_index_];
+ if (n >= 0) {
+ in_current_chunk =
+ n <
chunked_array_->chunk(static_cast<int>(current_chunk_index_))->length() -
+ current_iterator.index();
+ } else {
+ in_current_chunk = n > current_iterator.index();
+ }
+ if (in_current_chunk) {
+ index_ += n;
+ current_iterator += n;
+ return *this;
+ } else {
+ current_iterator -= current_iterator.index();
+ index_ += n;
+ UpdateComponents(*this, true);
+ return *this;
+ }
+ }
+ ChunkedArrayIterator& operator-=(difference_type n) {
+ (*this) += -n;
+ return *this;
+ }
+
+ // Comparisons
+ bool operator==(const ChunkedArrayIterator& other) const {
+ return index_ == other.index_;
+ }
+ bool operator!=(const ChunkedArrayIterator& other) const {
+ return index_ != other.index_;
+ }
+ bool operator<(const ChunkedArrayIterator& other) const {
+ return index_ < other.index_;
+ }
+ bool operator>(const ChunkedArrayIterator& other) const {
+ return index_ > other.index_;
+ }
+ bool operator<=(const ChunkedArrayIterator& other) const {
+ return index_ <= other.index_;
+ }
+ bool operator>=(const ChunkedArrayIterator& other) const {
+ return index_ >= other.index_;
+ }
+
+ private:
+ arrow::internal::ChunkLocation GetChunkLocation(int64_t index) const {
+ return chunked_array_->GetChunkResolver().Resolve(index);
+ }
+
+ void UpdateComponents(ChunkedArrayIterator<ArrayType>&
chunked_array_iterator,
+ bool update = false) {
+ if (!update) {
+ int64_t chunk_index = 0;
+ for (const auto& array :
chunked_array_iterator.chunked_array_->chunks()) {
+ chunked_array_iterator.iterators_list_.emplace_back(
+ *arrow::internal::checked_pointer_cast<ArrayType>(array));
+ auto chunk_length = array->length();
+ if (chunk_index) {
+ chunk_length += chunked_array_iterator.chunks_lengths_[chunk_index -
1];
+ }
+ chunked_array_iterator.chunks_lengths_.push_back(chunk_length);
+ chunk_index++;
+ }
+ }
+
+ chunked_array_iterator.current_chunk_index_ =
+ GetChunkLocation(chunked_array_iterator.index_).chunk_index;
+ auto& current_iterator =
+ chunked_array_iterator
+ .iterators_list_[chunked_array_iterator.current_chunk_index_];
+ current_iterator -= current_iterator.index() -
chunked_array_iterator.index_;
+ if (chunked_array_iterator.current_chunk_index_) {
+ current_iterator -=
+ chunked_array_iterator
+ .chunks_lengths_[chunked_array_iterator.current_chunk_index_ -
1];
+ }
+ }
+
+ const ChunkedArray* chunked_array_;
+ int64_t index_;
+ int64_t current_chunk_index_;
+ std::vector<int64_t> chunks_lengths_;
+ std::vector<ArrayIterator<ArrayType>> iterators_list_;
Review Comment:
I'm a bit surprised, are these members still needed? Ideally, everything can
be done using the ChunkResolver...
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