GH-43589: [Python] Add bindings for Buffer copy() method to other device

python/pyarrow/includes/libarrow.pxd

@@ -367,6 +367,9 @@ cdef extern from "arrow/api.h" namespace "arrow" nogil:
         const shared_ptr[CMemoryManager] memory_manager()
         CDeviceAllocationType device_type()
 
+        @staticmethod
+        CResult[shared_ptr[CBuffer]] Copy(shared_ptr[CBuffer] source, const shared_ptr[CMemoryManager]& to)
+
     CResult[shared_ptr[CBuffer]] SliceBufferSafe(
         const shared_ptr[CBuffer]& buffer, int64_t offset)
     CResult[shared_ptr[CBuffer]] SliceBufferSafe(

python/pyarrow/io.pxi

@@ -1446,6 +1446,41 @@ cdef class Buffer(_Weakrefable):
         """
         return _wrap_device_allocation_type(self.buffer.get().device_type())
 
+    def copy(self, destination):
+        """
+        Copy the buffer to the destination device.
+
+        The buffer contents will be copied into a new buffer allocated onto
+        the destination MemoryManager or Device. It will return the new Buffer.
+        This function supports cross-device copies.
+
+        Parameters
+        ----------
+        destination : pyarrow.MemoryManager or pyarrow.Device
+            Used to allocate the new buffer.
+
+        Returns
+        -------
+        Buffer
+        """
+        cdef:
+            shared_ptr[CBuffer] c_buffer
+            shared_ptr[CMemoryManager] c_memory_manager
+
+        if isinstance(destination, Device):
+            c_memory_manager = (<Device>destination).unwrap().get().default_memory_manager()
+        elif isinstance(destination, MemoryManager):
+            c_memory_manager = (<MemoryManager>destination).unwrap()
+        else:
+            raise TypeError(
+                "Argument 'destination' is incorrect type (expected pyarrow.Device or "
+                f"pyarrow.MemoryManager, got {type(destination)})"
+            )
+
+        with nogil:
+            c_buffer = GetResultValue(CBuffer.Copy(self.buffer, c_memory_manager))
+        return pyarrow_wrap_buffer(c_buffer)
+
     @property
     def parent(self):
         cdef shared_ptr[CBuffer] parent_buf = self.buffer.get().parent()

python/pyarrow/tests/test_cuda.py

@@ -119,6 +119,25 @@ def make_random_buffer(size, target='host'):
     raise ValueError('invalid target value')
 
 
+def test_copy_from_buffer():
+    arr, buf = make_random_buffer(128)
+    cudabuf = global_context.buffer_from_data(buf)
+
+    mm2 = global_context1.memory_manager
+    for dest in [mm2, mm2.device]:
+        buf2 = cudabuf.copy(dest)
+        assert buf2.device_type == pa.DeviceAllocationType.CUDA
+        assert buf2.copy(pa.default_cpu_memory_manager()).equals(buf)
+        cudabuf2 = cuda.CudaBuffer.from_buffer(buf2)
+        assert cudabuf2.size == cudabuf.size
+        assert not cudabuf2.is_cpu
+        assert cudabuf2.device_type == pa.DeviceAllocationType.CUDA
+
+        assert cudabuf2.copy_to_host().equals(buf)
+
+        assert cudabuf2.device == mm2.device
+
+
 @pytest.mark.parametrize("size", [0, 1, 1000])
 def test_context_device_buffer(size):
     # Creating device buffer from host buffer;

python/pyarrow/tests/test_io.py

@@ -710,6 +710,15 @@ def test_non_cpu_buffer(pickle_module):
     # Sliced buffers with same address
     assert buf_on_gpu_sliced.equals(cuda_buf[2:4])
 
+    # Testing copying buffer
+    mm = ctx.memory_manager
+    for dest in [mm, mm.device]:
+        buf2 = buf_on_gpu.copy(dest)
+        cuda_buf2 = cuda.CudaBuffer.from_buffer(buf2)
+        assert cuda_buf2.size == cuda_buf.size
+        assert cuda_buf2.to_pybytes() == b'testing'
+        assert buf2.device == mm.device
+
     # Buffers on different devices
     msg_device = "Device on which the data resides differs between buffers"
     with pytest.raises(ValueError, match=msg_device):