emilk commented on code in PR #6901:
URL: https://github.com/apache/arrow-rs/pull/6901#discussion_r1890437471
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arrow-buffer/src/buffer/scalar.rs:
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@@ -64,14 +64,41 @@ impl<T: ArrowNativeType> ScalarBuffer<T> {
///
/// * `offset` or `len` would result in overflow
/// * `buffer` is not aligned to a multiple of `std::mem::align_of::<T>`
- /// * `bytes` is not large enough for the requested slice
+ /// * `buffer` is not large enough for the requested slice
pub fn new(buffer: Buffer, offset: usize, len: usize) -> Self {
let size = std::mem::size_of::<T>();
let byte_offset = offset.checked_mul(size).expect("offset overflow");
let byte_len = len.checked_mul(size).expect("length overflow");
buffer.slice_with_length(byte_offset, byte_len).into()
}
+ /// Create a new [`ScalarBuffer`] from a [`Buffer`], and an `offset`
+ /// and `length` in units of `T`
+ ///
+ /// # Safety
+ ///
+ /// This method will be safe UNLESS any of the following:
+ ///
+ /// * `offset` or `len` would result in overflow
+ /// * `buffer` is not aligned to a multiple of `std::mem::align_of::<T>`
+ /// * `buffer` is not large enough for the requested slice
+ pub unsafe fn new_unchecked(buffer: Buffer, offset: usize, len: usize) ->
Self {
+ let size = std::mem::size_of::<T>();
+ let byte_offset = offset * size;
+ let byte_len = len * size;
+ unsafe {
+ buffer
+ .slice_with_length_unchecked(byte_offset, byte_len)
+ .into()
+ }
+ }
+
+ /// The length of the scalar buffer, in units of `T`.
+ #[inline]
+ pub fn len_in_elements(&self) -> usize {
Review Comment:
This is so the user can do their own range checking easily, and also so that
the docstring for `slice_unchecked` has something to refer to.
We should maybe call this function `len`, but I went with the more explicit,
since `len` usually means "number of bytes" in other contexts.
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