viirya commented on code in PR #3685:
URL: https://github.com/apache/arrow-rs/pull/3685#discussion_r1101847348
##########
arrow/src/ffi.rs:
##########
@@ -24,68 +24,61 @@
//! The second interface maps native Rust types to the Rust-specific
implementation of Arrow such as `format` to `Datatype`,
//! `Buffer`, etc. This is handled by `ArrowArray`.
//!
+//!
+//! Export to FFI
+//!
//! ```rust
//! # use std::sync::Arc;
-//! # use arrow::array::{Int32Array, Array, ArrayData, export_array_into_raw,
make_array, make_array_from_raw};
-//! # use arrow::error::{Result, ArrowError};
+//! # use arrow::array::{Int32Array, Array, ArrayData, make_array};
+//! # use arrow::error::Result;
//! # use arrow::compute::kernels::arithmetic;
//! # use arrow::ffi::{ArrowArray, FFI_ArrowArray, FFI_ArrowSchema};
-//! # use std::convert::TryFrom;
//! # fn main() -> Result<()> {
//! // create an array natively
//! let array = Int32Array::from(vec![Some(1), None, Some(3)]);
+//! let data = array.into_data();
//!
-//! // export it
-//!
-//! let ffi_array = ArrowArray::try_new(array.data().clone())?;
-//! let (array_ptr, schema_ptr) = ArrowArray::into_raw(ffi_array);
-//!
-//! // consumed and used by something else...
+//! // Export it
+//! let out_array = FFI_ArrowArray::new(&data);
+//! let out_schema = FFI_ArrowSchema::try_from(data.data_type())?;
//!
//! // import it
-//! let array = unsafe { make_array_from_raw(array_ptr, schema_ptr)? };
+//! let array = ArrowArray::new(out_array, out_schema);
+//! let array = Int32Array::from(ArrayData::try_from(array)?);
//!
//! // perform some operation
-//! let array = array.as_any().downcast_ref::<Int32Array>().ok_or(
-//! ArrowError::ParseError("Expects an int32".to_string()),
-//! )?;
//! let array = arithmetic::add(&array, &array)?;
//!
//! // verify
//! assert_eq!(array, Int32Array::from(vec![Some(2), None, Some(6)]));
+//! #
+//! # Ok(())
+//! # }
+//! ```
//!
-//! // Simulate if raw pointers are provided by consumer
-//! let array = make_array(Int32Array::from(vec![Some(1), None,
Some(3)]).into_data());
-//!
-//! let out_array = Box::new(FFI_ArrowArray::empty());
-//! let out_schema = Box::new(FFI_ArrowSchema::empty());
-//! let out_array_ptr = Box::into_raw(out_array);
-//! let out_schema_ptr = Box::into_raw(out_schema);
-//!
-//! // export array into raw pointers from consumer
-//! unsafe { export_array_into_raw(array, out_array_ptr, out_schema_ptr)?; };
-//!
-//! // import it
-//! let array = unsafe { make_array_from_raw(out_array_ptr, out_schema_ptr)? };
-//!
-//! // perform some operation
-//! let array = array.as_any().downcast_ref::<Int32Array>().ok_or(
-//! ArrowError::ParseError("Expects an int32".to_string()),
-//! )?;
-//! let array = arithmetic::add(&array, &array)?;
+//! Import from FFI
//!
-//! // verify
-//! assert_eq!(array, Int32Array::from(vec![Some(2), None, Some(6)]));
+//! ```
+//! # use std::ptr::addr_of_mut;
+//! # use arrow::ffi::{ArrowArray, FFI_ArrowArray, FFI_ArrowSchema};
+//! # use arrow_array::{ArrayRef, make_array};
+//! # use arrow_schema::ArrowError;
+//! #
+//! /// A foreign data container that can export to C Data interface
+//! struct ForeignArray {};
//!
-//! // (drop/release)
-//! unsafe {
-//! Box::from_raw(out_array_ptr);
-//! Box::from_raw(out_schema_ptr);
-//! Arc::from_raw(array_ptr);
-//! Arc::from_raw(schema_ptr);
+//! impl ForeignArray {
+//! /// Export to C Data interface
+//! fn export(&self, array: *mut FFI_ArrowArray, schema: *mut
FFI_ArrowSchema) {
+//! // ...
+//! }
Review Comment:
Import? I assume that idea is to import from foreign array into C Data
Interface.
```suggestion
//! impl ForeignArray {
//! /// Import to C Data interface
//! fn import(&self, array: *mut FFI_ArrowArray, schema: *mut
FFI_ArrowSchema) {
//! // ...
//! }
```
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