[GitHub] [arrow-nanoarrow] paleolimbot opened a new issue, #4: Implement bitmap helpers

[GitBox <gi...@apache.org>]

paleolimbot opened a new issue, #4:
URL: https://github.com/apache/arrow-nanoarrow/issues/4

   Dealing with bitmaps is hard and we should provide some tools to do the finicky hard-to-get-right math:
   
   - `ArrowBitmapIsNull(const void* bitmap, int64_t i)`
   - `ArrowBitmapSetNull(void* bitmap, int64_t i, char value)`
   - `ArrowBitmapCountNull(const void* bitmap, int64_t bitmap_size_bits)`
   
   I think we also need a builder dedicated to bitmaps since building them up incrementally (without allocating if there are no null) is much of the use case. Something like
   
   ```
   struct ArrowBitmapBuilder { struct ArrowBuffer buffer; int64_t n_values; uint8_t pending_values[64]; int8_t pending_values_offset; }
   ArrowBitmapBuilderAppendInt8(struct ArrowBitmapBuilder* bitmap_builder, const int8_t* values, int64_t n_values);
   ArrowBitmapBuilderAppendInt32(struct ArrowBitmapBuilder* bitmap_builder, const int32_t* values, int64_t n_values);
   ArrowBitmapBuilderReset(struct ArrowBitmapBuilder* bitmap_builder);
   ```
   
   (because char and int arrays are common ways that these things are stored)


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[GitHub] [arrow-nanoarrow] paleolimbot closed issue #4: Implement bitmap helpers

[GitBox <gi...@apache.org>]

paleolimbot closed issue #4: Implement bitmap helpers
URL: https://github.com/apache/arrow-nanoarrow/issues/4


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