Static method of _Memory to create from external allocation

Method takes USMRef, number of bytes and queue reference.

If USMRef is bound to context in the queue and USM type comes
back not 'unknown', appropriate MemoryUSM* object is created
which assumes ownership of this memory.

Optional `memory_owner` keyword argument may be specified to set
the recorded reference object to something other than None (signaling
that _Memory is responsible for memory deallocation).

This can be used to create MemoryUSM* Python object from natively
allocated memory, populate it, but leave deallocation to the caller.
It could also be set to a PyCapsule object that carries a custom deleter.

Author: oleksandr-pavlyk

dpctl/memory/_memory.pxd

@@ -55,6 +55,12 @@ cdef public class _Memory [object Py_MemoryObject, type Py_MemoryType]:
         DPCTLSyclUSMRef p, SyclContext ctx)
     @staticmethod
     cdef public bytes get_pointer_type(DPCTLSyclUSMRef p, SyclContext ctx)
+    @staticmethod
+    cdef public object create_from_usm_pointer_size_qref(
+        DPCTLSyclUSMRef USMRef,
+        Py_ssize_t nbytes,
+        DPCTLSyclQueueRef QRef,
+        object memory_owner=*)
 
 
 cdef public class MemoryUSMShared(_Memory) [object PyMemoryUSMSharedObject,

dpctl/memory/_memory.pyx

@@ -39,9 +39,11 @@ from dpctl._backend cimport (  # noqa: E211
     DPCTLQueue_Copy,
     DPCTLQueue_Create,
     DPCTLQueue_Delete,
+    DPCTLQueue_GetContext,
     DPCTLQueue_Memcpy,
     DPCTLSyclContextRef,
     DPCTLSyclDeviceRef,
+    DPCTLSyclUSMRef,
     DPCTLUSM_GetPointerDevice,
     DPCTLUSM_GetPointerType,
 )
@@ -431,6 +433,43 @@ cdef class _Memory:
 
         return <bytes>usm_type
 
+    @staticmethod
+    cdef object create_from_usm_pointer_size_qref(
+        DPCTLSyclUSMRef USMRef, Py_ssize_t nbytes, DPCTLSyclQueueRef QRef, object memory_owner=None):
+        """
+        """
+        cdef const char *usm_type
+        cdef DPCTLSyclContextRef CRef = NULL
+        cdef DPCTLSyclQueueRef QRef_copy = NULL
+        cdef _Memory _mem
+        cdef object mem_ty
+        if nbytes <= 0:
+            raise ValueError("Number of bytes must must be positive")
+        if (QRef is NULL):
+            raise TypeError("Argument DPCTLSyclQueueRef is NULL")
+        CRef = DPCTLQueue_GetContext(QRef)
+        if (CRef is NULL):
+            raise ValueError("Could not retrieve context from QRef")
+        usm_type = DPCTLUSM_GetPointerType(USMRef, CRef)
+        if usm_type == b"shared":
+            mem_ty = MemoryUSMShared
+        elif usm_type == b"device":
+            mem_ty = MemoryUSMDevice
+        elif usm_type == b"host":
+            mem_ty = MemoryUSMHost
+        else:
+            raise ValueError("Argument pointer is not bound to context in the given queue")
+        res = _Memory.__new__(_Memory)
+        _mem = <_Memory> res
+        _mem._cinit_empty()
+        _mem.memory_ptr = USMRef
+        _mem.nbytes = nbytes
+        QRef_copy = DPCTLQueue_Copy(QRef)
+        _mem.queue = SyclQueue._create(QRef_copy)
+        _mem.refobj = memory_owner
+        return mem_ty(res)
+
+
 
 cdef class MemoryUSMShared(_Memory):
     """