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

["Francois Saint-Jacques (Jira)" <ji...@apache.org>]

Francois Saint-Jacques created ARROW-7767:
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             Summary: [C++] Add a facility to create a Bitmap buffer from an data pointer with a specified sentinel
                 Key: ARROW-7767
                 URL: https://issues.apache.org/jira/browse/ARROW-7767
             Project: Apache Arrow
          Issue Type: Improvement
          Components: C++, R
            Reporter: Francois Saint-Jacques


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. 


{code:c++}
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>();
{code}




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