pitrou commented on a change in pull request #12574:
URL: https://github.com/apache/arrow/pull/12574#discussion_r821645141
##########
File path: cpp/src/arrow/csv/writer.cc
##########
@@ -571,34 +556,39 @@ class CSVWriterImpl : public ipc::RecordBatchWriter {
column_populators_[col]->UpdateRowLengths(*batch.column(col),
offsets_.data()));
}
// Calculate cumulative offsets for each row (including delimiters).
- // ',' * num_columns - 1(last column doesn't have ,) + eol
- int32_t delimiters_length =
+ // - before conversion: offsets_[i] = length of i-th row
Review comment:
```suggestion
// - before conversion: offsets_[i] = length of (i-1)th row
```
##########
File path: cpp/src/arrow/csv/writer.cc
##########
@@ -571,34 +556,39 @@ class CSVWriterImpl : public ipc::RecordBatchWriter {
column_populators_[col]->UpdateRowLengths(*batch.column(col),
offsets_.data()));
}
// Calculate cumulative offsets for each row (including delimiters).
- // ',' * num_columns - 1(last column doesn't have ,) + eol
- int32_t delimiters_length =
+ // - before conversion: offsets_[i] = length of i-th row
+ // - after conversion: offsets_[i] = offset to the starting of i-th row
buffer
+ // - offsets_[0] = 0
+ // - offsets_[i] = offsets_[i-1] + len(i-1-th row) + len(delimiters)
+ // Delimiters: ',' * num_columns - 1(last column doesn't have ,) + eol
Review comment:
```suggestion
// Delimiters: ',' * (num_columns - 1) + eol
```
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