Move type casting to c10/util/TypeCast.h (#28426)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28426
Type casting is used in copy, and will be used also in tensor iterator
in the next stacked diff. I move it to c10 to make it serve as an common
util for different things.
I also add two dynamic casting functions
- fetch_and_cast
- cast_and_store
fetch_and_cast fetch a value with dynamic type specified by a ScalarType
from a void pointer and cast it to a static type.
cast_and_store casts a static typed value into dynamic type specified
by a ScalarType, and store it into a void pointer.
Test Plan: Imported from OSS
Differential Revision: D18170996
Pulled By: ezyang
fbshipit-source-id: 41658afd5c0ab58c6b6c510424893d9a2a0c059e
