feat(c/sedona-extension): Move FFI scalar kernel definitions to c/sedona-extension and write them in C

Cargo.toml

@@ -16,6 +16,7 @@
 # under the License.
 [workspace]
 members = [
+    "c/sedona-extension",
     "c/sedona-geoarrow-c",
     "c/sedona-geos",
     "c/sedona-proj",

c/sedona-extension/Cargo.toml

@@ -0,0 +1,39 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+[package]
+name = "sedona-extension"
+version.workspace = true
+authors.workspace = true
+license.workspace = true
+homepage.workspace = true
+repository.workspace = true
+description.workspace = true
+readme.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+
+[dependencies]
+arrow-array = { workspace = true, features = ["ffi"]}
+arrow-schema = { workspace = true, features = ["ffi"]}
+datafusion-common = { workspace = true }
+datafusion-expr = { workspace = true }
+libc = "0.2.178"
+sedona-common = { workspace = true }
+sedona-expr = { workspace = true }
+sedona-schema = { workspace = true }
+sedona-testing = { path = "../../rust/sedona-testing" }

c/sedona-extension/src/extension.rs

@@ -0,0 +1,122 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use std::{
+    ffi::c_int,
+    os::raw::{c_char, c_void},
+    ptr::null_mut,
+};
+
+use arrow_array::ffi::{FFI_ArrowArray, FFI_ArrowSchema};
+
+/// Raw FFI representation of the SedonaCScalarKernel
+///
+/// See the ImportedScalarKernel and ExportedScalarKernel for high-level
+/// APIs to import and export implementations using this struct.
+#[derive(Default)]
+#[repr(C)]
+pub struct SedonaCScalarKernel {
+    pub function_name:
+        Option<unsafe extern "C" fn(self_: *const SedonaCScalarKernel) -> *const c_char>,
+    pub new_impl: Option<
+        unsafe extern "C" fn(self_: *const SedonaCScalarKernel, out: *mut SedonaCScalarKernelImpl),
+    >,
+
+    pub release: Option<unsafe extern "C" fn(self_: *mut SedonaCScalarKernel)>,
+    pub private_data: *mut c_void,
+}
+
+unsafe impl Send for SedonaCScalarKernel {}
+unsafe impl Sync for SedonaCScalarKernel {}
+
+impl Drop for SedonaCScalarKernel {
+    fn drop(&mut self) {
+        if let Some(releaser) = self.release {
+            unsafe { releaser(self) }
+            self.release = None;
+            self.private_data = null_mut();
+        }
+    }
+}
+
+/// Raw FFI representation of the SedonaCScalarKernelImpl
+#[derive(Default)]
+#[repr(C)]
+pub struct SedonaCScalarKernelImpl {
+    pub init: Option<
+        unsafe extern "C" fn(
+            self_: *mut SedonaCScalarKernelImpl,
+            arg_types: *const *const FFI_ArrowSchema,
+            scalar_args: *mut *mut FFI_ArrowArray,
+            n_args: i64,
+            out: *mut FFI_ArrowSchema,
+        ) -> c_int,
+    >,
+
+    pub execute: Option<
+        unsafe extern "C" fn(
+            self_: *mut SedonaCScalarKernelImpl,
+            args: *mut *mut FFI_ArrowArray,
+            n_args: i64,
+            n_rows: i64,
+            out: *mut FFI_ArrowArray,
+        ) -> c_int,
+    >,
+
+    pub get_last_error:
+        Option<unsafe extern "C" fn(self_: *mut SedonaCScalarKernelImpl) -> *const c_char>,
+
+    pub release: Option<unsafe extern "C" fn(self_: *mut SedonaCScalarKernelImpl)>,
+
+    pub private_data: *mut c_void,
+}
+
+impl Drop for SedonaCScalarKernelImpl {
+    fn drop(&mut self) {
+        if let Some(releaser) = self.release {
+            unsafe { releaser(self) }
+            self.release = None;
+            self.private_data = null_mut();
+        }
+    }
+}
+
+/// Check if a schema is valid
+///
+/// The [FFI_ArrowSchema] doesn't have the ability to check for a NULL release callback,
+/// so we provide a mechanism to do so here.
+pub fn ffi_arrow_schema_is_valid(schema: *const FFI_ArrowSchema) -> bool {
+    let schema_internal = schema as *const c_void as *const ArrowSchemaInternal;
+    if let Some(schema_ref) = unsafe { schema_internal.as_ref() } {
+        schema_ref.release.is_some()
+    } else {
+        false
+    }
+}
+
+#[repr(C)]
+struct ArrowSchemaInternal {
+    format: *const c_char,
+    name: *const c_char,
+    metadata: *const c_char,
+    flags: i64,
+    n_children: i64,
+    children: *mut *mut ArrowSchemaInternal,
+    dictionary: *mut ArrowSchemaInternal,
+    release: Option<unsafe extern "C" fn(*mut ArrowSchemaInternal)>,
+    private_data: *mut c_void,
+}

c/sedona-extension/src/lib.rs

@@ -0,0 +1,19 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+pub(crate) mod extension;
+pub mod scalar_kernel;