[GitHub] [arrow-rs] tustvold opened a new issue, #1850: Add Vec-inspired APIs to BufferBuilder

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

tustvold opened a new issue, #1850:
URL: https://github.com/apache/arrow-rs/issues/1850

   **Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
   
   `BufferBuilder` is effectively a `Vec<T: ArrowNativeType>` that can be converted to `Buffer` without needing to copy. This is an incredibly useful abstraction for incrementally building and mutating data in place, prior to freezing it for hand-off to other systems.
   
   Unfortunately it is currently lacking some relatively minor functionality to enable this use-case. In particular access to the data that has been already written. The parquet crate currently rolls its own ScalarBuffer to work around this, but as described in #1849 it would be nice to avoid this duplication.
   
   **Describe the solution you'd like**
   
   Add the following APIs to `BufferBuilder`
   
   ```
   fn as_slice(&self) -> &[T] {
       unsafe { std::slice::from_raw_parts(self.buffer.as_ptr(), self.len) }
   }
   
   fn as_slice_mut(&mut self) -> &mut [T] {
       unsafe { std::slice::from_raw_parts_mut(self.buffer.as_ptr_mut(), self.len) }
   }
   
   fn truncate(&mut self, len: usize) {}
   
   fn extend_zeroed(&mut self, len: usize) {}
   ```
   
   **Describe alternatives you've considered**
   
   We could not do this
   
   **Additional context**
   
   * #1842 is necessary to provide these APIs safely
   * BufferBuilder should be moved to its own module to avoid others mutating its inner MutableArray (#1843)
   


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[GitHub] [arrow-rs] alamb closed issue #1850: Add Vec-inspired APIs to BufferBuilder

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

alamb closed issue #1850: Add Vec-inspired APIs to BufferBuilder
URL: https://github.com/apache/arrow-rs/issues/1850


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