feat: add metadata bridge for Python CUDA export

Add a private metadata-only bridge on PyVortex arrays so the optional CUDA extension can reconstruct arrays through its own local Vortex session instead of passing Rust ArrayRef values across Python extension modules.

The CUDA extension now parses the metadata tree, calls local array plugins for deserialization, and exports bufferless arrays through the Arrow C Device capsule path. The capsule ownership code handles live and consumed capsule names and releases Arrow resources on error paths. Physical buffer handoff remains a follow-up.

Signed-off-by: "Alexander Droste" <alexander.droste@protonmail.com>

Signed-off-by: Alexander Droste <alexander.droste@protonmail.com>

Author: 0ax1

Cargo.lock

@@ -543,14 +543,14 @@ fn released_device_array(device_id: i64) -> ArrowDeviceArray {
 }
 
 /// Release an Arrow C schema if it is live.
-fn release_schema(schema: &mut FFI_ArrowSchema) {
+pub fn release_schema(schema: &mut FFI_ArrowSchema) {
     if let Some(release) = schema.release {
         unsafe { release(schema) };
     }
 }
 
 /// Release an Arrow device array if it is live.
-fn release_device_array(array: &mut ArrowDeviceArray) {
+pub fn release_device_array(array: &mut ArrowDeviceArray) {
     if let Some(release) = array.array.release {
         unsafe { release(&raw mut array.array) };
     }

vortex-cuda/src/arrow/mod.rs

@@ -27,5 +27,7 @@ default = ["extension-module"]
 extension-module = []
 
 [dependencies]
+arrow-schema = { workspace = true }
 pyo3 = { workspace = true, features = ["abi3", "abi3-py311"] }
+vortex = { workspace = true }
 vortex-cuda = { workspace = true }

vortex-python-cuda/Cargo.toml

@@ -4,8 +4,9 @@ name = "vortex-data-cuda"
 dynamic = ["version", "description", "authors"]
 requires-python = ">= 3.11"
 # The CUDA extension package must exactly match the base package version because the two extensions
-# exchange Vortex IPC buffers. Keep this in sync with the workspace package version; release
-# automation may rewrite it when publishing a non-workspace version.
+# exchange private Vortex vtable metadata. Future buffer-handoff support will extend this private
+# bridge. Keep this in sync with the workspace package version; release automation may rewrite it
+# when publishing a non-workspace version.
 dependencies = ["vortex-data==0.1.0"]
 classifiers = [
     "Development Status :: 4 - Beta",

vortex-python-cuda/pyproject.toml

@@ -1,6 +1,10 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright the Vortex contributors
 
-from ._lib import cuda_available  # pyright: ignore[reportMissingModuleSource]
+from ._lib import (  # pyright: ignore[reportMissingModuleSource]
+    cuda_available,
+    debug_array_metadata_dtype,
+    export_device_array,
+)
 
-__all__ = ["cuda_available"]
+__all__ = ["cuda_available", "debug_array_metadata_dtype", "export_device_array"]

vortex-python-cuda/python/vortex_cuda/__init__.py

@@ -2,3 +2,7 @@
 #  SPDX-FileCopyrightText: Copyright the Vortex contributors
 
 def cuda_available() -> bool: ...
+def debug_array_metadata_dtype(array: object) -> str: ...
+def export_device_array(
+    array: object, requested_schema: object | None = None, **kwargs: object
+) -> tuple[object, object]: ...