unchecked view

arrow-array/src/builder/generic_bytes_view_builder.rs

@@ -116,6 +116,36 @@ impl<T: ByteViewType + ?Sized> GenericByteViewBuilder<T> {
  offset as u32
  }
 
+ /// Append a view of the given `block`, `offset` and `length`
+ ///
+ /// # Safety
+ /// (1) The block must have been added using [`Self::append_block`]
+ /// (2) The range `offset..offset+length` must be within the bounds of the block
+ /// (3) The data in the block must be valid of type `T`
+ pub unsafe fn append_view_unchecked(&mut self, block: u32, offset: u32, len: u32) {
+ let b = self.completed.get_unchecked(block as usize);
+ let start = offset as usize;
+ let end = start.saturating_add(len as usize);
+ let b = b.get_unchecked(start..end);
+
+ if len <= 12 {
+ let mut view_buffer = [0; 16];
+ view_buffer[0..4].copy_from_slice(&len.to_le_bytes());
+ view_buffer[4..4 + b.len()].copy_from_slice(b);
+ self.views_builder.append(u128::from_le_bytes(view_buffer));
+ } else {
+ let view = ByteView {
+ length: len,
+ prefix: u32::from_le_bytes(b[0..4].try_into().unwrap()),
+ buffer_index: block,
+ offset,
+ };
+ self.views_builder.append(view.into());
+ }
+
+ self.null_buffer_builder.append_non_null();
+ }
+
  /// Try to append a view of the given `block`, `offset` and `length`
  ///
  /// See [`Self::append_block`]
@@ -139,22 +169,9 @@ impl<T: ByteViewType + ?Sized> GenericByteViewBuilder<T> {
  ));
  }
 
- if len <= 12 {
- let mut view_buffer = [0; 16];
- view_buffer[0..4].copy_from_slice(&len.to_le_bytes());
- view_buffer[4..4 + b.len()].copy_from_slice(b);
- self.views_builder.append(u128::from_le_bytes(view_buffer));
- } else {
- let view = ByteView {
- length: len,
- prefix: u32::from_le_bytes(b[0..4].try_into().unwrap()),
- buffer_index: block,
- offset,
- };
- self.views_builder.append(view.into());
+ unsafe {
+ self.append_view_unchecked(block, offset, len);
  }
-
- self.null_buffer_builder.append_non_null();
  Ok(())
  }
 

arrow-cast/src/cast/dictionary.rs

@@ -129,12 +129,16 @@ fn view_from_dict_values<K: ArrowDictionaryKeyType, T: ByteViewType, V: ByteArra
  match i {
  Some(v) => {
  let idx = v.to_usize().unwrap();
- let offset = value_offsets[idx];
- let end = value_offsets[idx + 1];
- let length = end - offset;
- builder
- .try_append_view(0, offset.as_usize() as u32, length.as_usize() as u32)
- .unwrap();
+
+ // Safety
+ // (1) The index is within bounds as they are offsets
+ // (2) The append_view is safe 
+ unsafe {
+ let offset = value_offsets.get_unchecked(idx).as_usize();
+ let end = value_offsets.get_unchecked(idx + 1).as_usize();
+ let length = end - offset;
+ builder.append_view_unchecked(0, offset as u32, length as u32)
+ }
  }
  None => {
  builder.append_null();