cyb70289 commented on a change in pull request #12574:
URL: https://github.com/apache/arrow/pull/12574#discussion_r820339520
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File path: cpp/src/arrow/csv/writer.cc
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@@ -572,33 +558,34 @@ class CSVWriterImpl : public ipc::RecordBatchWriter {
}
// Calculate cumulative offsets for each row (including delimiters).
// ',' * num_columns - 1(last column doesn't have ,) + eol
- int32_t delimiters_length =
+ const int32_t delimiters_length =
static_cast<int32_t>(batch.num_columns() - 1 + options_.eol.size());
- offsets_[0] += delimiters_length;
- for (int64_t row = 1; row < batch.num_rows(); row++) {
- offsets_[row] += offsets_[row - 1] + delimiters_length;
+ int64_t last_row_length = offsets_[0] + delimiters_length;
+ offsets_[0] = 0;
+ for (size_t row = 1; row < offsets_.size(); ++row) {
+ const int64_t this_row_length = offsets_[row] + delimiters_length;
+ offsets_[row] = offsets_[row - 1] + last_row_length;
+ last_row_length = this_row_length;
Review comment:
`offsets_[i]` was the length of row `i` before the conversion.
After the conversion, `offsets_[i]` is the start position of row `i` in
output buffer.
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