Added buffer interoperability with arrow-rs

Cargo.toml

@@ -6,7 +6,7 @@ description = "Unofficial implementation of Apache Arrow spec in safe Rust"
 homepage = "https://github.com/jorgecarleitao/arrow2"
 repository = "https://github.com/jorgecarleitao/arrow2"
 authors = ["Jorge C. Leitao <[email protected]>", "Apache Arrow <[email protected]>"]
-keywords = [ "arrow", "analytics" ]
+keywords = ["arrow", "analytics"]
 edition = "2021"
 exclude = ["testing/"]
 
@@ -100,6 +100,9 @@ odbc-api = { version = "0.36", optional = true }
 # Faster hashing
 ahash = "0.8"
 
+# Support conversion to/from arrow-rs
+arrow-buffer = { version = "35.0.0", optional = true }
+
 [target.wasm32-unknown-unknown.dependencies]
 getrandom = { version = "0.2", features = ["js"] }
 
@@ -131,6 +134,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 [features]
 default = []
 full = [
+    "arrow",
     "io_odbc",
     "io_csv",
     "io_csv_async",
@@ -154,6 +158,7 @@ full = [
     # parses timezones used in timestamp conversions
     "chrono-tz",
 ]
+arrow = ["arrow-buffer"]
 io_odbc = ["odbc-api"]
 io_csv = ["io_csv_read", "io_csv_write"]
 io_csv_async = ["io_csv_read_async"]
@@ -195,7 +200,7 @@ io_avro_compression = [
 ]
 io_avro_async = ["avro-schema/async"]
 
-io_orc = [ "orc-format" ]
+io_orc = ["orc-format"]
 
 # serde+serde_json: its dependencies + error handling
 # serde_derive: there is some derive around

src/bitmap/immutable.rs

@@ -375,6 +375,22 @@ impl Bitmap {
     ) -> std::result::Result<Self, E> {
         Ok(MutableBitmap::try_from_trusted_len_iter_unchecked(iterator)?.into())
     }
+
+    /// Create a new [`Bitmap`] from an arrow [`NullBuffer`]
+    ///
+    /// [`NullBuffer`]: arrow_buffer::buffer::NullBuffer
+    #[cfg(feature = "arrow")]
+    pub fn from_null_buffer(value: arrow_buffer::buffer::NullBuffer) -> Self {
+        let offset = value.offset();
+        let length = value.len();
+        let unset_bits = value.null_count();
+        Self {
+            offset,
+            length,
+            unset_bits,
+            bytes: Arc::new(crate::buffer::to_bytes(value.buffer().clone())),
+        }
+    }
 }
 
 impl<'a> IntoIterator for &'a Bitmap {
@@ -394,3 +410,14 @@ impl IntoIterator for Bitmap {
         IntoIter::new(self)
     }
 }
+
+#[cfg(feature = "arrow")]
+impl From<Bitmap> for arrow_buffer::buffer::NullBuffer {
+    fn from(value: Bitmap) -> Self {
+        let null_count = value.unset_bits;
+        let buffer = crate::buffer::to_buffer(value.bytes);
+        let buffer = arrow_buffer::buffer::BooleanBuffer::new(buffer, value.offset, value.length);
+        // Safety: null count is accurate
+        unsafe { arrow_buffer::buffer::NullBuffer::new_unchecked(buffer, null_count) }
+    }
+}

src/buffer/immutable.rs

@@ -276,3 +276,17 @@ impl<T: Copy> IntoIterator for Buffer<T> {
         IntoIter::new(self)
     }
 }
+
+#[cfg(feature = "arrow")]
+impl<T: crate::types::NativeType> From<arrow_buffer::Buffer> for Buffer<T> {
+    fn from(value: arrow_buffer::Buffer) -> Self {
+        Self::from_bytes(crate::buffer::to_bytes(value))
+    }
+}
+
+#[cfg(feature = "arrow")]
+impl<T: crate::types::NativeType> From<Buffer<T>> for arrow_buffer::Buffer {
+    fn from(value: Buffer<T>) -> Self {
+        crate::buffer::to_buffer(value.data)
+    }
+}

src/buffer/mod.rs

@@ -5,7 +5,42 @@ mod iterator;
 
 use crate::ffi::InternalArrowArray;
 
-pub(crate) type Bytes<T> = foreign_vec::ForeignVec<InternalArrowArray, T>;
+pub(crate) enum BytesAllocator {
+    InternalArrowArray(InternalArrowArray),
+
+    #[cfg(feature = "arrow")]
+    Arrow(arrow_buffer::Buffer),
+}
+
+pub(crate) type Bytes<T> = foreign_vec::ForeignVec<BytesAllocator, T>;
+
+#[cfg(feature = "arrow")]
+pub(crate) fn to_buffer<T: crate::types::NativeType>(
+    value: std::sync::Arc<Bytes<T>>,
+) -> arrow_buffer::Buffer {
+    // This should never panic as ForeignVec pointer must be non-null
+    let ptr = std::ptr::NonNull::new(value.as_ptr() as _).unwrap();
+    let len = value.len() * std::mem::size_of::<T>();
+    // Safety: allocation is guaranteed to be valid for `len` bytes
+    unsafe { arrow_buffer::Buffer::from_custom_allocation(ptr, len, value) }
+}
+
+#[cfg(feature = "arrow")]
+pub(crate) fn to_bytes<T: crate::types::NativeType>(value: arrow_buffer::Buffer) -> Bytes<T> {
+    let ptr = value.as_ptr();
+    let align = ptr.align_offset(std::mem::align_of::<T>());
+    assert_eq!(align, 0, "not aligned");
+    let len = value.len() / std::mem::size_of::<T>();
+
+    // Valid as `NativeType: Pod` and checked alignment above
+    let ptr = value.as_ptr() as *const T;
+
+    let owner = crate::buffer::BytesAllocator::Arrow(value);
+
+    // Safety: slice is valid for len elements of T
+    unsafe { Bytes::from_foreign(ptr, len, owner) }
+}
+
 pub(super) use iterator::IntoIter;
 
 pub use immutable::Buffer;

src/ffi/array.rs

@@ -1,6 +1,7 @@
 //! Contains functionality to load an ArrayData from the C Data Interface
 use std::sync::Arc;
 
+use crate::buffer::BytesAllocator;
 use crate::{
     array::*,
     bitmap::{utils::bytes_for, Bitmap},
@@ -237,7 +238,7 @@ unsafe fn create_buffer<T: NativeType>(
 
     let len = buffer_len(array, data_type, index)?;
     let offset = buffer_offset(array, data_type, index);
-    let bytes = Bytes::from_foreign(ptr, len, owner);
+    let bytes = Bytes::from_foreign(ptr, len, BytesAllocator::InternalArrowArray(owner));
 
     Ok(Buffer::from_bytes(bytes).sliced(offset, len - offset))
 }
@@ -258,7 +259,7 @@ unsafe fn create_bitmap(
     let len: usize = array.length.try_into().expect("length to fit in `usize`");
     let offset: usize = array.offset.try_into().expect("Offset to fit in `usize`");
     let bytes_len = bytes_for(offset + len);
-    let bytes = Bytes::from_foreign(ptr, bytes_len, owner);
+    let bytes = Bytes::from_foreign(ptr, bytes_len, BytesAllocator::InternalArrowArray(owner));
 
     Ok(Bitmap::from_bytes(bytes, offset + len).sliced(offset, len))
 }

src/types/native.rs

@@ -1,5 +1,6 @@
 use std::convert::TryFrom;
 use std::ops::Neg;
+use std::panic::RefUnwindSafe;
 
 use bytemuck::{Pod, Zeroable};
 
@@ -14,6 +15,7 @@ pub trait NativeType:
     + Send
     + Sync
     + Sized
+    + RefUnwindSafe
     + std::fmt::Debug
     + std::fmt::Display
     + PartialEq

tests/it/bitmap/immutable.rs

@@ -39,3 +39,29 @@ fn debug() {
 
     assert_eq!(format!("{b:?}"), "[0b111110__, 0b_______1]");
 }
+
+#[test]
+#[cfg(feature = "arrow")]
+fn from_arrow() {
+    use arrow_buffer::buffer::{BooleanBuffer, NullBuffer};
+    let buffer = arrow_buffer::Buffer::from_iter(vec![true, true, true, false, false, false, true]);
+    let bools = BooleanBuffer::new(buffer, 0, 7);
+    let nulls = NullBuffer::new(bools);
+    assert_eq!(nulls.null_count(), 3);
+
+    let bitmap = Bitmap::from_null_buffer(nulls.clone());
+    assert_eq!(nulls.null_count(), bitmap.unset_bits());
+    assert_eq!(nulls.len(), bitmap.len());
+    let back = NullBuffer::from(bitmap);
+    assert_eq!(nulls, back);
+
+    let nulls = nulls.slice(1, 3);
+    assert_eq!(nulls.null_count(), 1);
+    assert_eq!(nulls.len(), 3);
+
+    let bitmap = Bitmap::from_null_buffer(nulls.clone());
+    assert_eq!(nulls.null_count(), bitmap.unset_bits());
+    assert_eq!(nulls.len(), bitmap.len());
+    let back = NullBuffer::from(bitmap);
+    assert_eq!(nulls, back);
+}

tests/it/buffer/immutable.rs

@@ -43,3 +43,67 @@ fn from_vec() {
     assert_eq!(buffer.len(), 3);
     assert_eq!(buffer.as_slice(), &[0, 1, 2]);
 }
+
+#[test]
+#[cfg(feature = "arrow")]
+fn from_arrow() {
+    let buffer = arrow_buffer::Buffer::from_vec(vec![1_i32, 2_i32, 3_i32]);
+    let b = Buffer::<i32>::from(buffer.clone());
+    assert_eq!(b.len(), 3);
+    assert_eq!(b.as_slice(), &[1, 2, 3]);
+    let back = arrow_buffer::Buffer::from(b);
+    assert_eq!(back, buffer);
+
+    let buffer = buffer.slice(4);
+    let b = Buffer::<i32>::from(buffer.clone());
+    assert_eq!(b.len(), 2);
+    assert_eq!(b.as_slice(), &[2, 3]);
+    let back = arrow_buffer::Buffer::from(b);
+    assert_eq!(back, buffer);
+
+    let buffer = arrow_buffer::Buffer::from_vec(vec![1_i64, 2_i64]);
+    let b = Buffer::<i32>::from(buffer.clone());
+    assert_eq!(b.len(), 4);
+    assert_eq!(b.as_slice(), &[1, 0, 2, 0]);
+    let back = arrow_buffer::Buffer::from(b);
+    assert_eq!(back, buffer);
+
+    let buffer = buffer.slice(4);
+    let b = Buffer::<i32>::from(buffer.clone());
+    assert_eq!(b.len(), 3);
+    assert_eq!(b.as_slice(), &[0, 2, 0]);
+    let back = arrow_buffer::Buffer::from(b);
+    assert_eq!(back, buffer);
+}
+
+#[test]
+#[cfg(feature = "arrow")]
+fn from_arrow_vec() {
+    // Zero-copy vec conversion in arrow-rs
+    let buffer = arrow_buffer::Buffer::from_vec(vec![1_i32, 2_i32, 3_i32]);
+    let back: Vec<i32> = buffer.into_vec().unwrap();
+
+    // Zero-copy vec conversion in arrow2
+    let buffer = Buffer::<i32>::from(back);
+    let back: Vec<i32> = buffer.into_mut().unwrap_right();
+
+    let buffer = arrow_buffer::Buffer::from_vec(back);
+    let buffer = Buffer::<i32>::from(buffer);
+
+    // But not possible after conversion between buffer representations
+    let _ = buffer.into_mut().unwrap_left();
+
+    let buffer = Buffer::<i32>::from(vec![1_i32]);
+    let buffer = arrow_buffer::Buffer::from(buffer);
+
+    // But not possible after conversion between buffer representations
+    let _ = buffer.into_vec::<i32>().unwrap_err();
+}
+
+#[test]
+#[cfg(feature = "arrow")]
+#[should_panic(expected = "not aligned")]
+fn from_arrow_misaligned() {
+    let buffer = arrow_buffer::Buffer::from_vec(vec![1_i32, 2_i32, 3_i32]).slice(1);
+    let _ = Buffer::<i32>::from(buffer);
+}