[ARROW-7767] [C++] Add a facility to create a Bitmap buffer from an data pointer with a specified sentinel

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: C++, R
• External issue URL: https://github.com/apache/arrow/issues/24004
• Assignee: Unassigned
• Reporter: Francois Saint-Jacques
• Created: 04/Feb/20 18:24
• Updated: 11/Jan/23 07:55

Description

This is a special case for R and other cases where the null value is represented by a sentinel. This would read the data pointer and return a null bitmap buffer where bits are activate for every row where the value is not the sentinel value. If no sentinel is encountered, return nullptr.

template <typename ArrowType, typename CType = ArrowType::c_type>
Result<std::shared_ptr<Buffer>> NullBitmapFromSentinelData(MemoryPool* pool, const CType* data, size_t n_values, CType sentinel_value);