Update exchange API to be capsule following new convention

This PR updates the exchange API to be capsule following the new convention.
Note that the exchange API python recommendation is not yet updated on the array-api
side and so far there hasn't yet been downstream implementation, so this change
should be safe in generally.

Author: tqchen

include/dlpack/dlpack.h

@@ -19,7 +19,7 @@
 #define DLPACK_MAJOR_VERSION 1
 
 /*! \brief The current minor version of dlpack */
-#define DLPACK_MINOR_VERSION 2
+#define DLPACK_MINOR_VERSION 3
 
 /*! \brief DLPACK_DLL prefix for windows */
 #ifdef _WIN32
@@ -375,7 +375,7 @@ typedef struct DLManagedTensorVersioned {
 } DLManagedTensorVersioned;
 
 //----------------------------------------------------------------------
-// DLPack `__c_dlpack_exchange_api__` fast exchange protocol definitions
+// DLPack `__dlpack_c_exchange_api__` fast exchange protocol definitions
 //----------------------------------------------------------------------
 /*!
  * \brief Request a producer library to create a new tensor.
@@ -391,7 +391,7 @@ typedef struct DLManagedTensorVersioned {
  * \param error_ctx Context for `SetError`.
  * \param SetError The function to set the error.
  * \return The owning DLManagedTensorVersioned* or NULL on failure.
- *         SetError is called exactly when NULL is returned (the implementor
+ *         SetError is called exactly when NULL is returned (the implementer
  *         must ensure this).
  * \note - As a C function, must not thrown C++ exceptions.
  *       - Error propagation via SetError to avoid any direct need
@@ -432,11 +432,11 @@ typedef int (*DLPackManagedTensorFromPyObjectNoSync)(                 //
  * \brief Exports a PyObject* Tensor/NDArray to a provided DLTensor.
  *
  * This function provides a faster interface for temporary, non-owning, exchange.
- * The producer (implementor) still owns the memory of data, strides, shape.
+ * The producer (implementer) still owns the memory of data, strides, shape.
  * The liveness of the DLTensor and the data it views is only guaranteed until
  * control is returned.
  *
- * This function currently assumes that the producer (implementor) can fill
+ * This function currently assumes that the producer (implementer) can fill
  * in the DLTensor shape and strides without the need for temporary allocations.
  *
  * This function does not perform any stream synchronization. The consumer should query
@@ -488,7 +488,7 @@ typedef int (*DLPackCurrentWorkStream)(                         //
  * \brief Imports a DLManagedTensorVersioned to a PyObject* Tensor/NDArray.
  *
  * Convert an owning DLManagedTensorVersioned* to the Python tensor of the
- * producer (implementor) library with the correct type.
+ * producer (implementer) library with the correct type.
  *
  * This function does not perform any stream synchronization.
  *
@@ -532,16 +532,17 @@ typedef struct DLPackExchangeAPIHeader {
  * \brief Framework-specific function pointers table for DLPack exchange.
  *
  * Additionally to `__dlpack__()` we define a C function table sharable by
- * Python implementations via `__c_dlpack_exchange_api__`.
- * This attribute must be set on the type as a Python integer compatible
- * with `PyLong_FromVoidPtr`/`PyLong_AsVoidPtr`.
+ *
+ * Python implementations via `__dlpack_c_exchange_api__`.
+ * This attribute must be set on the type as a Python PyCapsule
+ * with name "dlpack_exchange_api".
  *
  * A consumer library may use a pattern such as:
  *
  * \code
  *
- * PyObject *api_obj = type(tensor_obj).__c_dlpack_exchange_api__;  // as C-code
- * MyDLPackExchangeAPI *api = PyLong_AsVoidPtr(api_obj);
+ * PyObject *api_obj = type(tensor_obj).__dlpack_c_exchange_api__;  // as C-code
+ * MyDLPackExchangeAPI *api = PyCapsule_GetPointer(api_obj, "dlpack_exchange_api");
  * if (api == NULL && PyErr_Occurred()) { goto handle_error; }
  *
  * \endcode