renato2099 commented on code in PR #19079:
URL: https://github.com/apache/datafusion/pull/19079#discussion_r2595363784


##########
datafusion/ffi/src/proto/physical_extension_codec.rs:
##########
@@ -0,0 +1,701 @@
+// 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_void;
+use std::sync::Arc;
+
+use abi_stable::std_types::{RResult, RSlice, RStr, RVec};
+use abi_stable::StableAbi;
+use async_trait::async_trait;
+use datafusion_common::error::Result;
+use datafusion_execution::TaskContext;
+use datafusion_expr::{
+    AggregateUDF, AggregateUDFImpl, ScalarUDF, ScalarUDFImpl, WindowUDF, 
WindowUDFImpl,
+};
+use datafusion_physical_plan::ExecutionPlan;
+use datafusion_proto::physical_plan::PhysicalExtensionCodec;
+use tokio::runtime::Handle;
+
+use crate::execution::FFI_TaskContextProvider;
+use crate::execution_plan::FFI_ExecutionPlan;
+use crate::udaf::FFI_AggregateUDF;
+use crate::udf::FFI_ScalarUDF;
+use crate::udwf::FFI_WindowUDF;
+use crate::util::FFIResult;
+use crate::{df_result, rresult_return};
+
+/// A stable struct for sharing [`PhysicalExtensionCodec`] across FFI 
boundaries.
+#[repr(C)]
+#[derive(Debug, StableAbi)]
+#[allow(non_camel_case_types)]
+pub struct FFI_PhysicalExtensionCodec {
+    /// Decode bytes into an execution plan.
+    try_decode: unsafe extern "C" fn(
+        &Self,
+        buf: RSlice<u8>,
+        inputs: RVec<FFI_ExecutionPlan>,
+    ) -> FFIResult<FFI_ExecutionPlan>,
+
+    /// Encode an execution plan into bytes.
+    try_encode:
+        unsafe extern "C" fn(&Self, node: FFI_ExecutionPlan) -> 
FFIResult<RVec<u8>>,
+
+    /// Decode bytes into a user defined scalar function.
+    try_decode_udf: unsafe extern "C" fn(
+        &Self,
+        name: RStr,
+        buf: RSlice<u8>,
+    ) -> FFIResult<FFI_ScalarUDF>,
+
+    /// Encode a user defined scalar function into bytes.
+    try_encode_udf:
+        unsafe extern "C" fn(&Self, node: FFI_ScalarUDF) -> 
FFIResult<RVec<u8>>,
+
+    /// Decode bytes into a user defined aggregate function.
+    try_decode_udaf: unsafe extern "C" fn(
+        &Self,
+        name: RStr,
+        buf: RSlice<u8>,
+    ) -> FFIResult<FFI_AggregateUDF>,
+
+    /// Encode a user defined aggregate function into bytes.
+    try_encode_udaf:
+        unsafe extern "C" fn(&Self, node: FFI_AggregateUDF) -> 
FFIResult<RVec<u8>>,
+
+    /// Decode bytes into a user defined window function.
+    try_decode_udwf: unsafe extern "C" fn(
+        &Self,
+        name: RStr,
+        buf: RSlice<u8>,
+    ) -> FFIResult<FFI_WindowUDF>,
+
+    /// Encode a user defined window function into bytes.
+    try_encode_udwf:
+        unsafe extern "C" fn(&Self, node: FFI_WindowUDF) -> 
FFIResult<RVec<u8>>,
+
+    /// Access the current [`TaskContext`].
+    task_ctx_provider: FFI_TaskContextProvider,
+
+    /// Used to create a clone on the provider of the execution plan. This 
should
+    /// only need to be called by the receiver of the plan.
+    pub clone: unsafe extern "C" fn(plan: &Self) -> Self,
+
+    /// Release the memory of the private data when it is no longer being used.
+    pub release: unsafe extern "C" fn(arg: &mut Self),
+
+    /// Return the major DataFusion version number of this provider.
+    pub version: unsafe extern "C" fn() -> u64,
+
+    /// Internal data. This is only to be accessed by the provider of the plan.
+    /// A [`ForeignPhysicalExtensionCodec`] should never attempt to access 
this data.
+    pub private_data: *mut c_void,
+
+    /// Utility to identify when FFI objects are accessed locally through
+    /// the foreign interface.
+    pub library_marker_id: extern "C" fn() -> usize,
+}
+
+unsafe impl Send for FFI_PhysicalExtensionCodec {}
+unsafe impl Sync for FFI_PhysicalExtensionCodec {}
+
+struct PhysicalExtensionCodecPrivateData {
+    provider: Arc<dyn PhysicalExtensionCodec>,
+    runtime: Option<Handle>,
+}
+
+impl FFI_PhysicalExtensionCodec {
+    fn inner(&self) -> &Arc<dyn PhysicalExtensionCodec> {
+        let private_data = self.private_data as *const 
PhysicalExtensionCodecPrivateData;
+        unsafe { &(*private_data).provider }
+    }
+
+    fn runtime(&self) -> &Option<Handle> {
+        let private_data = self.private_data as *const 
PhysicalExtensionCodecPrivateData;
+        unsafe { &(*private_data).runtime }
+    }
+}
+
+unsafe extern "C" fn try_decode_fn_wrapper(
+    codec: &FFI_PhysicalExtensionCodec,
+    buf: RSlice<u8>,
+    inputs: RVec<FFI_ExecutionPlan>,
+) -> FFIResult<FFI_ExecutionPlan> {
+    let task_ctx: Arc<TaskContext> =
+        rresult_return!((&codec.task_ctx_provider).try_into());
+    let codec = codec.inner();
+    let inputs = inputs
+        .into_iter()
+        .map(|plan| <Arc<dyn ExecutionPlan>>::try_from(&plan))
+        .collect::<Result<Vec<_>>>();
+    let inputs = rresult_return!(inputs);
+
+    let plan =
+        rresult_return!(codec.try_decode(buf.as_ref(), &inputs, 
task_ctx.as_ref()));
+
+    RResult::ROk(FFI_ExecutionPlan::new(plan, task_ctx, None))
+}
+
+unsafe extern "C" fn try_encode_fn_wrapper(
+    codec: &FFI_PhysicalExtensionCodec,
+    node: FFI_ExecutionPlan,
+) -> FFIResult<RVec<u8>> {
+    let codec = codec.inner();
+
+    let plan: Arc<dyn ExecutionPlan> = rresult_return!((&node).try_into());
+
+    let mut bytes = Vec::new();
+    rresult_return!(codec.try_encode(plan, &mut bytes));
+
+    RResult::ROk(bytes.into())
+}
+
+unsafe extern "C" fn try_decode_udf_fn_wrapper(
+    codec: &FFI_PhysicalExtensionCodec,
+    name: RStr,
+    buf: RSlice<u8>,
+) -> FFIResult<FFI_ScalarUDF> {
+    let codec = codec.inner();
+
+    let udf = rresult_return!(codec.try_decode_udf(name.as_str(), 
buf.as_ref()));
+    let udf = FFI_ScalarUDF::from(udf);
+
+    RResult::ROk(udf)
+}
+
+unsafe extern "C" fn try_encode_udf_fn_wrapper(
+    codec: &FFI_PhysicalExtensionCodec,
+    node: FFI_ScalarUDF,
+) -> FFIResult<RVec<u8>> {
+    let codec = codec.inner();
+    let node: Arc<dyn ScalarUDFImpl> = (&node).into();
+    let node = ScalarUDF::new_from_shared_impl(node);
+
+    let mut bytes = Vec::new();
+    rresult_return!(codec.try_encode_udf(&node, &mut bytes));
+
+    RResult::ROk(bytes.into())
+}
+
+unsafe extern "C" fn try_decode_udaf_fn_wrapper(
+    codec: &FFI_PhysicalExtensionCodec,
+    name: RStr,
+    buf: RSlice<u8>,
+) -> FFIResult<FFI_AggregateUDF> {
+    let codec_inner = codec.inner();
+    let udaf = rresult_return!(codec_inner.try_decode_udaf(name.into(), 
buf.as_ref()));
+    let udaf = FFI_AggregateUDF::from(udaf);
+
+    RResult::ROk(udaf)
+}
+
+unsafe extern "C" fn try_encode_udaf_fn_wrapper(
+    codec: &FFI_PhysicalExtensionCodec,
+    node: FFI_AggregateUDF,
+) -> FFIResult<RVec<u8>> {
+    let codec = codec.inner();
+    let udaf: Arc<dyn AggregateUDFImpl> = (&node).into();
+    let udaf = AggregateUDF::new_from_shared_impl(udaf);
+
+    let mut bytes = Vec::new();
+    rresult_return!(codec.try_encode_udaf(&udaf, &mut bytes));
+
+    RResult::ROk(bytes.into())
+}
+
+unsafe extern "C" fn try_decode_udwf_fn_wrapper(
+    codec: &FFI_PhysicalExtensionCodec,
+    name: RStr,
+    buf: RSlice<u8>,
+) -> FFIResult<FFI_WindowUDF> {
+    let codec = codec.inner();
+    let udwf = rresult_return!(codec.try_decode_udwf(name.into(), 
buf.as_ref()));
+    let udwf = FFI_WindowUDF::from(udwf);
+
+    RResult::ROk(udwf)
+}
+
+unsafe extern "C" fn try_encode_udwf_fn_wrapper(
+    codec: &FFI_PhysicalExtensionCodec,
+    node: FFI_WindowUDF,
+) -> FFIResult<RVec<u8>> {
+    let codec = codec.inner();
+    let udwf: Arc<dyn WindowUDFImpl> = (&node).into();
+    let udwf = WindowUDF::new_from_shared_impl(udwf);
+
+    let mut bytes = Vec::new();
+    rresult_return!(codec.try_encode_udwf(&udwf, &mut bytes));
+
+    RResult::ROk(bytes.into())
+}
+
+unsafe extern "C" fn release_fn_wrapper(provider: &mut 
FFI_PhysicalExtensionCodec) {
+    let private_data =
+        Box::from_raw(provider.private_data as *mut 
PhysicalExtensionCodecPrivateData);
+    drop(private_data);
+}
+
+unsafe extern "C" fn clone_fn_wrapper(
+    codec: &FFI_PhysicalExtensionCodec,
+) -> FFI_PhysicalExtensionCodec {
+    let old_codec = Arc::clone(codec.inner());
+    let runtime = codec.runtime().clone();
+
+    FFI_PhysicalExtensionCodec::new(old_codec, runtime, 
codec.task_ctx_provider.clone())
+}
+
+impl Drop for FFI_PhysicalExtensionCodec {
+    fn drop(&mut self) {
+        unsafe { (self.release)(self) }
+    }
+}
+
+impl FFI_PhysicalExtensionCodec {
+    /// Creates a new [`FFI_PhysicalExtensionCodec`].
+    pub fn new(
+        provider: Arc<dyn PhysicalExtensionCodec + Send>,
+        runtime: Option<Handle>,
+        task_ctx_provider: impl Into<FFI_TaskContextProvider>,
+    ) -> Self {
+        let task_ctx_provider = task_ctx_provider.into();
+        let private_data =
+            Box::new(PhysicalExtensionCodecPrivateData { provider, runtime });
+
+        Self {
+            try_decode: try_decode_fn_wrapper,
+            try_encode: try_encode_fn_wrapper,
+            try_decode_udf: try_decode_udf_fn_wrapper,
+            try_encode_udf: try_encode_udf_fn_wrapper,
+            try_decode_udaf: try_decode_udaf_fn_wrapper,
+            try_encode_udaf: try_encode_udaf_fn_wrapper,
+            try_decode_udwf: try_decode_udwf_fn_wrapper,
+            try_encode_udwf: try_encode_udwf_fn_wrapper,
+            task_ctx_provider,
+
+            clone: clone_fn_wrapper,
+            release: release_fn_wrapper,
+            version: crate::version,
+            private_data: Box::into_raw(private_data) as *mut c_void,
+            library_marker_id: crate::get_library_marker_id,
+        }
+    }
+}
+
+/// This wrapper struct exists on the receiver side of the FFI interface, so 
it has
+/// no guarantees about being able to access the data in `private_data`. Any 
functions
+/// defined on this struct must only use the stable functions provided in
+/// FFI_PhysicalExtensionCodec to interact with the foreign table provider.
+#[derive(Debug)]
+pub struct ForeignPhysicalExtensionCodec(pub FFI_PhysicalExtensionCodec);
+
+unsafe impl Send for ForeignPhysicalExtensionCodec {}
+unsafe impl Sync for ForeignPhysicalExtensionCodec {}
+
+impl From<&FFI_PhysicalExtensionCodec> for Arc<dyn PhysicalExtensionCodec> {
+    fn from(provider: &FFI_PhysicalExtensionCodec) -> Self {
+        if (provider.library_marker_id)() == crate::get_library_marker_id() {
+            Arc::clone(provider.inner())
+        } else {
+            Arc::new(ForeignPhysicalExtensionCodec(provider.clone()))
+        }
+    }
+}
+
+impl Clone for FFI_PhysicalExtensionCodec {
+    fn clone(&self) -> Self {
+        unsafe { (self.clone)(self) }
+    }
+}
+
+#[async_trait]
+impl PhysicalExtensionCodec for ForeignPhysicalExtensionCodec {
+    fn try_decode(
+        &self,
+        buf: &[u8],
+        inputs: &[Arc<dyn ExecutionPlan>],
+        _ctx: &TaskContext,
+    ) -> Result<Arc<dyn ExecutionPlan>> {
+        let task_ctx = (&self.0.task_ctx_provider).try_into()?;
+        let inputs = inputs
+            .iter()
+            .map(|plan| {
+                FFI_ExecutionPlan::new(Arc::clone(plan), 
Arc::clone(&task_ctx), None)
+            })
+            .collect();
+
+        let plan =
+            df_result!(unsafe { (self.0.try_decode)(&self.0, buf.into(), 
inputs) })?;
+        let plan: Arc<dyn ExecutionPlan> = (&plan).try_into()?;
+
+        Ok(plan)
+    }
+
+    fn try_encode(&self, node: Arc<dyn ExecutionPlan>, buf: &mut Vec<u8>) -> 
Result<()> {
+        let task_ctx = (&self.0.task_ctx_provider).try_into()?;
+        let plan = FFI_ExecutionPlan::new(node, task_ctx, None);
+        let bytes = df_result!(unsafe { (self.0.try_encode)(&self.0, plan) })?;
+
+        buf.extend(bytes);
+        Ok(())
+    }
+
+    fn try_decode_udf(&self, name: &str, buf: &[u8]) -> Result<Arc<ScalarUDF>> 
{
+        let udf = unsafe {
+            df_result!((self.0.try_decode_udf)(&self.0, name.into(), 
buf.into()))
+        }?;
+        let udf: Arc<dyn ScalarUDFImpl> = (&udf).into();
+
+        Ok(Arc::new(ScalarUDF::new_from_shared_impl(udf)))
+    }
+
+    fn try_encode_udf(&self, node: &ScalarUDF, buf: &mut Vec<u8>) -> 
Result<()> {
+        let node = FFI_ScalarUDF::from(Arc::new(node.clone()));
+        let bytes = df_result!(unsafe { (self.0.try_encode_udf)(&self.0, node) 
})?;
+
+        buf.extend(bytes);
+
+        Ok(())
+    }
+
+    fn try_decode_udaf(&self, name: &str, buf: &[u8]) -> 
Result<Arc<AggregateUDF>> {
+        let udaf = unsafe {
+            df_result!((self.0.try_decode_udaf)(&self.0, name.into(), 
buf.into()))
+        }?;
+        let udaf: Arc<dyn AggregateUDFImpl> = (&udaf).into();
+
+        Ok(Arc::new(AggregateUDF::new_from_shared_impl(udaf)))
+    }
+
+    fn try_encode_udaf(&self, node: &AggregateUDF, buf: &mut Vec<u8>) -> 
Result<()> {
+        let node = Arc::new(node.clone());
+        let node = FFI_AggregateUDF::from(node);
+        let bytes = df_result!(unsafe { (self.0.try_encode_udaf)(&self.0, 
node) })?;
+
+        buf.extend(bytes);
+
+        Ok(())
+    }
+
+    fn try_decode_udwf(&self, name: &str, buf: &[u8]) -> 
Result<Arc<WindowUDF>> {
+        let udwf = unsafe {
+            df_result!((self.0.try_decode_udwf)(&self.0, name.into(), 
buf.into()))
+        }?;
+        let udwf: Arc<dyn WindowUDFImpl> = (&udwf).into();
+
+        Ok(Arc::new(WindowUDF::new_from_shared_impl(udwf)))
+    }
+
+    fn try_encode_udwf(&self, node: &WindowUDF, buf: &mut Vec<u8>) -> 
Result<()> {
+        let node = Arc::new(node.clone());
+        let node = FFI_WindowUDF::from(node);
+        let bytes = df_result!(unsafe { (self.0.try_encode_udwf)(&self.0, 
node) })?;
+
+        buf.extend(bytes);
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+pub(crate) mod tests {
+    use std::sync::Arc;
+
+    use arrow_schema::{DataType, Field, Schema};
+    use datafusion_common::exec_err;
+    use datafusion_execution::TaskContext;
+    use datafusion_expr::ptr_eq::arc_ptr_eq;
+    use datafusion_expr::{AggregateUDF, ScalarUDF, WindowUDF, WindowUDFImpl};
+    use datafusion_functions::math::abs::AbsFunc;
+    use datafusion_functions_aggregate::sum::Sum;
+    use datafusion_functions_window::rank::{Rank, RankType};
+    use datafusion_physical_plan::ExecutionPlan;
+    use datafusion_proto::physical_plan::PhysicalExtensionCodec;
+
+    use crate::execution_plan::tests::EmptyExec;
+    use crate::proto::physical_extension_codec::FFI_PhysicalExtensionCodec;
+
+    #[derive(Debug)]
+    pub(crate) struct TestExtensionCodec;
+
+    impl TestExtensionCodec {
+        pub(crate) const MAGIC_NUMBER: u8 = 127;
+    }
+
+    impl PhysicalExtensionCodec for TestExtensionCodec {
+        fn try_decode(
+            &self,
+            buf: &[u8],
+            _inputs: &[Arc<dyn ExecutionPlan>],
+            _ctx: &TaskContext,
+        ) -> datafusion_common::Result<Arc<dyn ExecutionPlan>> {
+            if buf[0] != Self::MAGIC_NUMBER {
+                return exec_err!(
+                    "TestExtensionCodec input buffer does not start with magic 
number"
+                );
+            }
+
+            if buf.len() != 2 || buf[1] != Self::MAGIC_NUMBER {
+                return exec_err!("TestExtensionCodec unable to decode udf");
+            }

Review Comment:
   I think it is just because of the way how the tests are setup , we could 
endup with a case with `[MAGIC_NUMBER, MAGIC_NUMBER]`, but I agree it could be 
simplified.
   @timsaucer feel free to correct me if I got it wrong 😅 



##########
datafusion/ffi/src/proto/logical_extension_codec.rs:
##########
@@ -0,0 +1,739 @@
+// 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_void;
+use std::sync::Arc;
+
+use abi_stable::std_types::{RResult, RSlice, RStr, RVec};
+use abi_stable::StableAbi;
+use arrow::datatypes::SchemaRef;
+use async_trait::async_trait;
+use datafusion_catalog::TableProvider;
+use datafusion_common::error::Result;
+use datafusion_common::{not_impl_err, TableReference};
+use datafusion_datasource::file_format::FileFormatFactory;
+use datafusion_execution::TaskContext;
+use datafusion_expr::{
+    AggregateUDF, AggregateUDFImpl, Extension, LogicalPlan, ScalarUDF, 
ScalarUDFImpl,
+    WindowUDF, WindowUDFImpl,
+};
+use datafusion_proto::logical_plan::LogicalExtensionCodec;
+use tokio::runtime::Handle;
+
+use crate::arrow_wrappers::WrappedSchema;
+use crate::execution::FFI_TaskContextProvider;
+use crate::table_provider::FFI_TableProvider;
+use crate::udaf::FFI_AggregateUDF;
+use crate::udf::FFI_ScalarUDF;
+use crate::udwf::FFI_WindowUDF;
+use crate::util::FFIResult;
+use crate::{df_result, rresult_return};
+
+/// A stable struct for sharing [`LogicalExtensionCodec`] across FFI 
boundaries.
+#[repr(C)]
+#[derive(Debug, StableAbi)]
+#[allow(non_camel_case_types)]
+pub struct FFI_LogicalExtensionCodec {
+    /// Decode bytes into a table provider.
+    try_decode_table_provider: unsafe extern "C" fn(
+        &Self,
+        buf: RSlice<u8>,
+        table_ref: RStr,
+        schema: WrappedSchema,
+    ) -> FFIResult<FFI_TableProvider>,
+
+    /// Encode a table provider into bytes.
+    try_encode_table_provider: unsafe extern "C" fn(
+        &Self,
+        table_ref: RStr,
+        node: FFI_TableProvider,
+    ) -> FFIResult<RVec<u8>>,
+
+    /// Decode bytes into a user defined scalar function.
+    try_decode_udf: unsafe extern "C" fn(
+        &Self,
+        name: RStr,
+        buf: RSlice<u8>,
+    ) -> FFIResult<FFI_ScalarUDF>,
+
+    /// Encode a user defined scalar function into bytes.
+    try_encode_udf:
+        unsafe extern "C" fn(&Self, node: FFI_ScalarUDF) -> 
FFIResult<RVec<u8>>,
+
+    /// Decode bytes into a user defined aggregate function.
+    try_decode_udaf: unsafe extern "C" fn(
+        &Self,
+        name: RStr,
+        buf: RSlice<u8>,
+    ) -> FFIResult<FFI_AggregateUDF>,
+
+    /// Encode a user defined aggregate function into bytes.
+    try_encode_udaf:
+        unsafe extern "C" fn(&Self, node: FFI_AggregateUDF) -> 
FFIResult<RVec<u8>>,
+
+    /// Decode bytes into a user defined window function.
+    try_decode_udwf: unsafe extern "C" fn(
+        &Self,
+        name: RStr,
+        buf: RSlice<u8>,
+    ) -> FFIResult<FFI_WindowUDF>,
+
+    /// Encode a user defined window function into bytes.
+    try_encode_udwf:
+        unsafe extern "C" fn(&Self, node: FFI_WindowUDF) -> 
FFIResult<RVec<u8>>,
+
+    task_ctx_provider: FFI_TaskContextProvider,
+
+    /// Used to create a clone on the provider of the execution plan. This 
should
+    /// only need to be called by the receiver of the plan.
+    pub clone: unsafe extern "C" fn(plan: &Self) -> Self,
+
+    /// Release the memory of the private data when it is no longer being used.
+    pub release: unsafe extern "C" fn(arg: &mut Self),
+
+    /// Return the major DataFusion version number of this provider.
+    pub version: unsafe extern "C" fn() -> u64,
+
+    /// Internal data. This is only to be accessed by the provider of the plan.
+    /// A [`ForeignLogicalExtensionCodec`] should never attempt to access this 
data.
+    pub private_data: *mut c_void,
+
+    /// Utility to identify when FFI objects are accessed locally through
+    /// the foreign interface.
+    pub library_marker_id: extern "C" fn() -> usize,
+}
+
+unsafe impl Send for FFI_LogicalExtensionCodec {}
+unsafe impl Sync for FFI_LogicalExtensionCodec {}
+
+struct LogicalExtensionCodecPrivateData {
+    provider: Arc<dyn LogicalExtensionCodec>,
+    runtime: Option<Handle>,
+}
+
+impl FFI_LogicalExtensionCodec {
+    fn inner(&self) -> &Arc<dyn LogicalExtensionCodec> {
+        let private_data = self.private_data as *const 
LogicalExtensionCodecPrivateData;
+        unsafe { &(*private_data).provider }
+    }
+
+    fn runtime(&self) -> &Option<Handle> {
+        let private_data = self.private_data as *const 
LogicalExtensionCodecPrivateData;
+        unsafe { &(*private_data).runtime }
+    }
+
+    fn task_ctx(&self) -> Result<Arc<TaskContext>> {
+        (&self.task_ctx_provider).try_into()
+    }
+}
+
+unsafe extern "C" fn try_decode_table_provider_fn_wrapper(
+    codec: &FFI_LogicalExtensionCodec,
+    buf: RSlice<u8>,
+    table_ref: RStr,
+    schema: WrappedSchema,
+) -> FFIResult<FFI_TableProvider> {
+    let ctx = rresult_return!(codec.task_ctx());
+    let runtime = codec.runtime().clone();
+    let codec = codec.inner();
+    let table_ref = TableReference::from(table_ref.as_str());
+    let schema: SchemaRef = schema.into();
+
+    let table_provider = rresult_return!(codec.try_decode_table_provider(
+        buf.as_ref(),
+        &table_ref,
+        schema,
+        ctx.as_ref()
+    ));
+
+    RResult::ROk(FFI_TableProvider::new(table_provider, true, runtime))
+}
+
+unsafe extern "C" fn try_encode_table_provider_fn_wrapper(
+    codec: &FFI_LogicalExtensionCodec,
+    table_ref: RStr,
+    node: FFI_TableProvider,
+) -> FFIResult<RVec<u8>> {
+    let table_ref = TableReference::from(table_ref.as_str());
+    let table_provider: Arc<dyn TableProvider> = (&node).into();
+    let codec = codec.inner();
+
+    let mut bytes = Vec::new();
+    rresult_return!(codec.try_encode_table_provider(
+        &table_ref,
+        table_provider,
+        &mut bytes
+    ));
+
+    RResult::ROk(bytes.into())
+}
+
+unsafe extern "C" fn try_decode_udf_fn_wrapper(
+    codec: &FFI_LogicalExtensionCodec,
+    name: RStr,
+    buf: RSlice<u8>,
+) -> FFIResult<FFI_ScalarUDF> {
+    let codec = codec.inner();
+
+    let udf = rresult_return!(codec.try_decode_udf(name.as_str(), 
buf.as_ref()));
+    let udf = FFI_ScalarUDF::from(udf);
+
+    RResult::ROk(udf)
+}
+
+unsafe extern "C" fn try_encode_udf_fn_wrapper(
+    codec: &FFI_LogicalExtensionCodec,
+    node: FFI_ScalarUDF,
+) -> FFIResult<RVec<u8>> {
+    let codec = codec.inner();
+    let node: Arc<dyn ScalarUDFImpl> = (&node).into();
+    let node = ScalarUDF::new_from_shared_impl(node);
+
+    let mut bytes = Vec::new();
+    rresult_return!(codec.try_encode_udf(&node, &mut bytes));
+
+    RResult::ROk(bytes.into())
+}
+
+unsafe extern "C" fn try_decode_udaf_fn_wrapper(
+    codec: &FFI_LogicalExtensionCodec,
+    name: RStr,
+    buf: RSlice<u8>,
+) -> FFIResult<FFI_AggregateUDF> {
+    let codec_inner = codec.inner();
+    let udaf = rresult_return!(codec_inner.try_decode_udaf(name.into(), 
buf.as_ref()));
+    let udaf = FFI_AggregateUDF::from(udaf);
+
+    RResult::ROk(udaf)
+}
+
+unsafe extern "C" fn try_encode_udaf_fn_wrapper(
+    codec: &FFI_LogicalExtensionCodec,
+    node: FFI_AggregateUDF,
+) -> FFIResult<RVec<u8>> {
+    let codec = codec.inner();
+    let udaf: Arc<dyn AggregateUDFImpl> = (&node).into();
+    let udaf = AggregateUDF::new_from_shared_impl(udaf);
+
+    let mut bytes = Vec::new();
+    rresult_return!(codec.try_encode_udaf(&udaf, &mut bytes));
+
+    RResult::ROk(bytes.into())
+}
+
+unsafe extern "C" fn try_decode_udwf_fn_wrapper(
+    codec: &FFI_LogicalExtensionCodec,
+    name: RStr,
+    buf: RSlice<u8>,
+) -> FFIResult<FFI_WindowUDF> {
+    let codec = codec.inner();
+    let udwf = rresult_return!(codec.try_decode_udwf(name.into(), 
buf.as_ref()));
+    let udwf = FFI_WindowUDF::from(udwf);
+
+    RResult::ROk(udwf)
+}
+
+unsafe extern "C" fn try_encode_udwf_fn_wrapper(
+    codec: &FFI_LogicalExtensionCodec,
+    node: FFI_WindowUDF,
+) -> FFIResult<RVec<u8>> {
+    let codec = codec.inner();
+    let udwf: Arc<dyn WindowUDFImpl> = (&node).into();
+    let udwf = WindowUDF::new_from_shared_impl(udwf);
+
+    let mut bytes = Vec::new();
+    rresult_return!(codec.try_encode_udwf(&udwf, &mut bytes));
+
+    RResult::ROk(bytes.into())
+}
+
+unsafe extern "C" fn release_fn_wrapper(provider: &mut 
FFI_LogicalExtensionCodec) {
+    let private_data =
+        Box::from_raw(provider.private_data as *mut 
LogicalExtensionCodecPrivateData);
+    drop(private_data);
+}
+
+unsafe extern "C" fn clone_fn_wrapper(
+    codec: &FFI_LogicalExtensionCodec,
+) -> FFI_LogicalExtensionCodec {
+    let old_codec = Arc::clone(codec.inner());
+    let runtime = codec.runtime().clone();
+
+    FFI_LogicalExtensionCodec::new(old_codec, runtime, 
codec.task_ctx_provider.clone())
+}
+
+impl Drop for FFI_LogicalExtensionCodec {
+    fn drop(&mut self) {
+        unsafe { (self.release)(self) }
+    }
+}
+
+impl FFI_LogicalExtensionCodec {
+    /// Creates a new [`FFI_LogicalExtensionCodec`].
+    pub fn new(
+        provider: Arc<dyn LogicalExtensionCodec + Send>,
+        runtime: Option<Handle>,
+        task_ctx_provider: impl Into<FFI_TaskContextProvider>,
+    ) -> Self {
+        let task_ctx_provider = task_ctx_provider.into();
+        let private_data =
+            Box::new(LogicalExtensionCodecPrivateData { provider, runtime });
+
+        Self {
+            try_decode_table_provider: try_decode_table_provider_fn_wrapper,
+            try_encode_table_provider: try_encode_table_provider_fn_wrapper,
+            try_decode_udf: try_decode_udf_fn_wrapper,
+            try_encode_udf: try_encode_udf_fn_wrapper,
+            try_decode_udaf: try_decode_udaf_fn_wrapper,
+            try_encode_udaf: try_encode_udaf_fn_wrapper,
+            try_decode_udwf: try_decode_udwf_fn_wrapper,
+            try_encode_udwf: try_encode_udwf_fn_wrapper,
+            task_ctx_provider,
+
+            clone: clone_fn_wrapper,
+            release: release_fn_wrapper,
+            version: crate::version,
+            private_data: Box::into_raw(private_data) as *mut c_void,
+            library_marker_id: crate::get_library_marker_id,
+        }
+    }
+}
+
+/// This wrapper struct exists on the receiver side of the FFI interface, so 
it has
+/// no guarantees about being able to access the data in `private_data`. Any 
functions
+/// defined on this struct must only use the stable functions provided in
+/// FFI_LogicalExtensionCodec to interact with the foreign table provider.
+#[derive(Debug)]
+pub struct ForeignLogicalExtensionCodec(pub FFI_LogicalExtensionCodec);
+
+unsafe impl Send for ForeignLogicalExtensionCodec {}
+unsafe impl Sync for ForeignLogicalExtensionCodec {}
+
+impl From<&FFI_LogicalExtensionCodec> for Arc<dyn LogicalExtensionCodec> {
+    fn from(provider: &FFI_LogicalExtensionCodec) -> Self {
+        if (provider.library_marker_id)() == crate::get_library_marker_id() {
+            Arc::clone(provider.inner())
+        } else {
+            Arc::new(ForeignLogicalExtensionCodec(provider.clone()))
+        }
+    }
+}
+
+impl Clone for FFI_LogicalExtensionCodec {
+    fn clone(&self) -> Self {
+        unsafe { (self.clone)(self) }
+    }
+}
+
+#[async_trait]
+impl LogicalExtensionCodec for ForeignLogicalExtensionCodec {
+    fn try_decode(
+        &self,
+        _buf: &[u8],
+        _inputs: &[LogicalPlan],
+        _ctx: &TaskContext,
+    ) -> Result<Extension> {
+        not_impl_err!("FFI does not support decode of Extensions")
+    }
+
+    fn try_encode(&self, _node: &Extension, _buf: &mut Vec<u8>) -> Result<()> {
+        not_impl_err!("FFI does not support encode of Extensions")
+    }
+
+    fn try_decode_table_provider(
+        &self,
+        buf: &[u8],
+        table_ref: &TableReference,
+        schema: SchemaRef,
+        _ctx: &TaskContext,
+    ) -> Result<Arc<dyn TableProvider>> {
+        let table_ref = table_ref.to_string();
+        let schema: WrappedSchema = schema.into();
+
+        let ffi_table_provider = unsafe {
+            df_result!((self.0.try_decode_table_provider)(
+                &self.0,
+                buf.into(),
+                table_ref.as_str().into(),
+                schema
+            ))
+        }?;
+
+        Ok((&ffi_table_provider).into())
+    }
+
+    fn try_encode_table_provider(
+        &self,
+        table_ref: &TableReference,
+        node: Arc<dyn TableProvider>,
+        buf: &mut Vec<u8>,
+    ) -> Result<()> {
+        let table_ref = table_ref.to_string();
+        let node = FFI_TableProvider::new(node, true, None);
+
+        let bytes = df_result!(unsafe {
+            (self.0.try_encode_table_provider)(&self.0, 
table_ref.as_str().into(), node)
+        })?;
+
+        buf.extend(bytes);
+
+        Ok(())
+    }
+
+    fn try_decode_file_format(
+        &self,
+        _buf: &[u8],
+        _ctx: &TaskContext,
+    ) -> Result<Arc<dyn FileFormatFactory>> {
+        not_impl_err!("FFI does not support decode_file_format")
+    }
+
+    fn try_encode_file_format(
+        &self,
+        _buf: &mut Vec<u8>,
+        _node: Arc<dyn FileFormatFactory>,
+    ) -> Result<()> {
+        not_impl_err!("FFI does not support encode_file_format")
+    }
+
+    fn try_decode_udf(&self, name: &str, buf: &[u8]) -> Result<Arc<ScalarUDF>> 
{
+        let udf = unsafe {
+            df_result!((self.0.try_decode_udf)(&self.0, name.into(), 
buf.into()))
+        }?;
+        let udf: Arc<dyn ScalarUDFImpl> = (&udf).into();
+
+        Ok(Arc::new(ScalarUDF::new_from_shared_impl(udf)))
+    }
+
+    fn try_encode_udf(&self, node: &ScalarUDF, buf: &mut Vec<u8>) -> 
Result<()> {
+        let node = FFI_ScalarUDF::from(Arc::new(node.clone()));
+        let bytes = df_result!(unsafe { (self.0.try_encode_udf)(&self.0, node) 
})?;
+
+        buf.extend(bytes);
+
+        Ok(())
+    }
+
+    fn try_decode_udaf(&self, name: &str, buf: &[u8]) -> 
Result<Arc<AggregateUDF>> {
+        let udaf = unsafe {
+            df_result!((self.0.try_decode_udaf)(&self.0, name.into(), 
buf.into()))
+        }?;
+        let udaf: Arc<dyn AggregateUDFImpl> = (&udaf).into();
+
+        Ok(Arc::new(AggregateUDF::new_from_shared_impl(udaf)))
+    }
+
+    fn try_encode_udaf(&self, node: &AggregateUDF, buf: &mut Vec<u8>) -> 
Result<()> {
+        let node = Arc::new(node.clone());
+        let node = FFI_AggregateUDF::from(node);
+        let bytes = df_result!(unsafe { (self.0.try_encode_udaf)(&self.0, 
node) })?;
+
+        buf.extend(bytes);
+
+        Ok(())
+    }
+
+    fn try_decode_udwf(&self, name: &str, buf: &[u8]) -> 
Result<Arc<WindowUDF>> {
+        let udwf = unsafe {
+            df_result!((self.0.try_decode_udwf)(&self.0, name.into(), 
buf.into()))
+        }?;
+        let udwf: Arc<dyn WindowUDFImpl> = (&udwf).into();
+
+        Ok(Arc::new(WindowUDF::new_from_shared_impl(udwf)))
+    }
+
+    fn try_encode_udwf(&self, node: &WindowUDF, buf: &mut Vec<u8>) -> 
Result<()> {
+        let node = Arc::new(node.clone());
+        let node = FFI_WindowUDF::from(node);
+        let bytes = df_result!(unsafe { (self.0.try_encode_udwf)(&self.0, 
node) })?;
+
+        buf.extend(bytes);
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::sync::Arc;
+
+    use arrow::array::record_batch;
+    use arrow_schema::{DataType, Field, Schema, SchemaRef};
+    use datafusion_catalog::{MemTable, TableProvider};
+    use datafusion_common::{exec_err, TableReference};
+    use datafusion_datasource::file_format::FileFormatFactory;
+    use datafusion_execution::TaskContext;
+    use datafusion_expr::ptr_eq::arc_ptr_eq;
+    use datafusion_expr::{AggregateUDF, Extension, LogicalPlan, ScalarUDF, 
WindowUDF};
+    use datafusion_functions::math::abs::AbsFunc;
+    use datafusion_functions_aggregate::sum::Sum;
+    use datafusion_functions_window::rank::{Rank, RankType};
+    use datafusion_proto::logical_plan::LogicalExtensionCodec;
+    use datafusion_proto::physical_plan::PhysicalExtensionCodec;
+
+    use crate::proto::logical_extension_codec::FFI_LogicalExtensionCodec;
+    use crate::proto::physical_extension_codec::tests::TestExtensionCodec;
+
+    fn create_test_table() -> MemTable {
+        let schema = Arc::new(Schema::new(vec![Field::new("a", 
DataType::Int32, true)]));
+        let rb = record_batch!(("a", Int32, [1, 2, 3]))
+            .expect("should be able to create a record batch");
+        MemTable::try_new(schema, vec![vec![rb]])
+            .expect("should be able to create an in memory table")
+    }
+
+    impl LogicalExtensionCodec for TestExtensionCodec {
+        fn try_decode(
+            &self,
+            _buf: &[u8],
+            _inputs: &[LogicalPlan],
+            _ctx: &TaskContext,
+        ) -> datafusion_common::Result<Extension> {
+            unimplemented!()
+        }
+
+        fn try_encode(
+            &self,
+            _node: &Extension,
+            _buf: &mut Vec<u8>,
+        ) -> datafusion_common::Result<()> {
+            unimplemented!()
+        }
+
+        fn try_decode_table_provider(
+            &self,
+            buf: &[u8],
+            _table_ref: &TableReference,
+            schema: SchemaRef,
+            _ctx: &TaskContext,
+        ) -> datafusion_common::Result<Arc<dyn TableProvider>> {
+            if buf[0] != Self::MAGIC_NUMBER {
+                return exec_err!(
+                    "TestExtensionCodec input buffer does not start with magic 
number"
+                );
+            }
+
+            if schema != create_test_table().schema() {
+                return exec_err!("Incorrect test table schema");
+            }
+
+            if buf.len() != 2 || buf[1] != Self::MAGIC_NUMBER {
+                return exec_err!("TestExtensionCodec unable to decode table 
provider");
+            }
+
+            Ok(Arc::new(create_test_table()) as Arc<dyn TableProvider>)
+        }
+
+        fn try_encode_table_provider(
+            &self,
+            _table_ref: &TableReference,
+            node: Arc<dyn TableProvider>,
+            buf: &mut Vec<u8>,
+        ) -> datafusion_common::Result<()> {
+            buf.push(Self::MAGIC_NUMBER);
+
+            if !node.as_any().is::<MemTable>() {
+                return exec_err!("TestExtensionCodec only expects Abs UDF");
+            };
+
+            if node.schema() != create_test_table().schema() {
+                return exec_err!("Unexpected schema for encoding.");
+            }
+
+            buf.push(Self::MAGIC_NUMBER);
+
+            Ok(())
+        }
+
+        fn try_decode_file_format(
+            &self,
+            _buf: &[u8],
+            _ctx: &TaskContext,
+        ) -> datafusion_common::Result<Arc<dyn FileFormatFactory>> {
+            unimplemented!()
+        }
+
+        fn try_encode_file_format(
+            &self,
+            _buf: &mut Vec<u8>,
+            _node: Arc<dyn FileFormatFactory>,
+        ) -> datafusion_common::Result<()> {
+            unimplemented!()
+        }
+
+        fn try_decode_udf(
+            &self,
+            name: &str,
+            buf: &[u8],
+        ) -> datafusion_common::Result<Arc<ScalarUDF>> {
+            PhysicalExtensionCodec::try_decode_udf(self, name, buf)
+        }
+
+        fn try_encode_udf(
+            &self,
+            node: &ScalarUDF,
+            buf: &mut Vec<u8>,
+        ) -> datafusion_common::Result<()> {
+            PhysicalExtensionCodec::try_encode_udf(self, node, buf)
+        }
+
+        fn try_decode_udaf(
+            &self,
+            name: &str,
+            buf: &[u8],
+        ) -> datafusion_common::Result<Arc<AggregateUDF>> {
+            PhysicalExtensionCodec::try_decode_udaf(self, name, buf)
+        }
+
+        fn try_encode_udaf(
+            &self,
+            node: &AggregateUDF,
+            buf: &mut Vec<u8>,
+        ) -> datafusion_common::Result<()> {
+            PhysicalExtensionCodec::try_encode_udaf(self, node, buf)
+        }
+
+        fn try_decode_udwf(
+            &self,
+            name: &str,
+            buf: &[u8],
+        ) -> datafusion_common::Result<Arc<WindowUDF>> {
+            PhysicalExtensionCodec::try_decode_udwf(self, name, buf)
+        }
+
+        fn try_encode_udwf(
+            &self,
+            node: &WindowUDF,
+            buf: &mut Vec<u8>,
+        ) -> datafusion_common::Result<()> {
+            PhysicalExtensionCodec::try_encode_udwf(self, node, buf)
+        }
+    }
+
+    #[test]
+    fn roundtrip_ffi_logical_extension_codec_table_provider(
+    ) -> datafusion_common::Result<()> {
+        let codec = Arc::new(TestExtensionCodec {});
+        let (ctx, task_ctx_provider) = 
crate::util::tests::test_session_and_ctx();
+
+        let mut ffi_codec =
+            FFI_LogicalExtensionCodec::new(codec, None, task_ctx_provider);
+        ffi_codec.library_marker_id = crate::mock_foreign_marker_id;
+        let foreign_codec: Arc<dyn LogicalExtensionCodec> = 
(&ffi_codec).into();
+
+        let table = Arc::new(create_test_table()) as Arc<dyn TableProvider>;
+        let mut bytes = Vec::new();
+        foreign_codec.try_encode_table_provider(&"my_table".into(), table, 
&mut bytes)?;
+
+        let returned_table = foreign_codec.try_decode_table_provider(
+            &bytes,
+            &"my_table".into(),
+            create_test_table().schema(),
+            ctx.task_ctx().as_ref(),
+        )?;
+
+        assert!(returned_table.as_any().is::<MemTable>());
+
+        Ok(())
+    }
+
+    #[test]
+    fn roundtrip_ffi_logical_extension_codec_udf() -> 
datafusion_common::Result<()> {
+        let codec = Arc::new(TestExtensionCodec {});
+        let (_ctx, task_ctx_provider) = 
crate::util::tests::test_session_and_ctx();
+
+        let mut ffi_codec =
+            FFI_LogicalExtensionCodec::new(codec, None, task_ctx_provider);
+        ffi_codec.library_marker_id = crate::mock_foreign_marker_id;
+        let foreign_codec: Arc<dyn LogicalExtensionCodec> = 
(&ffi_codec).into();
+
+        let udf = Arc::new(ScalarUDF::from(AbsFunc::new()));
+        let mut bytes = Vec::new();
+        foreign_codec.try_encode_udf(udf.as_ref(), &mut bytes)?;

Review Comment:
   I am wondering if having a unit test that shows error handling (or expected 
behavior) when trying the round trip but the data we are reading is 
corrupted/incomplete somehow. That was at least it is clear for the consumers 
what the intent would be



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