Program Listing for File rvalue_ref.h

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

#ifndef TVM_FFI_RVALUE_REF_H_
#define TVM_FFI_RVALUE_REF_H_

#include <tvm/ffi/object.h>
#include <tvm/ffi/type_traits.h>

#include <string>
#include <utility>

namespace tvm {
namespace ffi {

template <typename TObjRef, typename = std::enable_if_t<std::is_base_of_v<ObjectRef, TObjRef>>>
class RValueRef {
 public:
  using ContainerType = typename TObjRef::ContainerType;
  explicit RValueRef(TObjRef&& data)
      : data_(details::ObjectUnsafe::ObjectPtrFromObjectRef<ContainerType>(std::move(data))) {}

  TObjRef operator*() && { return TObjRef(std::move(data_)); }

 private:
  mutable ObjectPtr<ContainerType> data_;

  template <typename, typename>
  friend struct TypeTraits;
};

template <typename TObjRef>
inline constexpr bool use_default_type_traits_v<RValueRef<TObjRef>> = false;

template <typename TObjRef>
struct TypeTraits<RValueRef<TObjRef>> : public TypeTraitsBase {
  static constexpr bool storage_enabled = false;

  TVM_FFI_INLINE static void CopyToAnyView(const RValueRef<TObjRef>& src, TVMFFIAny* result) {
    result->type_index = TypeIndex::kTVMFFIObjectRValueRef;
    result->zero_padding = 0;
    // store the address of the ObjectPtr, which allows us to move the value
    // and set the original ObjectPtr to nullptr
    result->v_ptr = &(src.data_);
  }

  TVM_FFI_INLINE static std::string GetMismatchTypeInfo(const TVMFFIAny* src) {
    if (src->type_index == TypeIndex::kTVMFFIObjectRValueRef) {
      ObjectPtr<Object>* rvalue_ref = reinterpret_cast<ObjectPtr<Object>*>(src->v_ptr);
      // object type does not match up, we need to try to convert the object
      // in this case we do not move the original rvalue ref since conversion creates a copy
      TVMFFIAny tmp_any;
      tmp_any.type_index = rvalue_ref->get()->type_index();
      tmp_any.zero_padding = 0;
      tmp_any.v_obj = reinterpret_cast<TVMFFIObject*>(rvalue_ref->get());
      return "RValueRef<" + TypeTraits<TObjRef>::GetMismatchTypeInfo(&tmp_any) + ">";
    } else {
      return TypeTraits<TObjRef>::GetMismatchTypeInfo(src);
    }
  }

  TVM_FFI_INLINE static std::optional<RValueRef<TObjRef>> TryCastFromAnyView(const TVMFFIAny* src) {
    // first try rvalue conversion
    if (src->type_index == TypeIndex::kTVMFFIObjectRValueRef) {
      ObjectPtr<Object>* rvalue_ref = reinterpret_cast<ObjectPtr<Object>*>(src->v_ptr);
      TVMFFIAny tmp_any;
      tmp_any.type_index = rvalue_ref->get()->type_index();
      tmp_any.zero_padding = 0;
      tmp_any.v_obj = reinterpret_cast<TVMFFIObject*>(rvalue_ref->get());
      // fast path, storage type matches, direct move the rvalue ref
      if (TypeTraits<TObjRef>::CheckAnyStrict(&tmp_any)) {
        return RValueRef<TObjRef>(
            details::ObjectUnsafe::ObjectRefFromObjectPtr<TObjRef>(std::move(*rvalue_ref)));
      }
      if (std::optional<TObjRef> opt = TypeTraits<TObjRef>::TryCastFromAnyView(&tmp_any)) {
        // object type does not match up, we need to try to convert the object
        // in this case we do not move the original rvalue ref since conversion creates a copy
        return RValueRef<TObjRef>(*std::move(opt));
      }
      return std::nullopt;
    }
    // try lvalue conversion
    if (std::optional<TObjRef> opt = TypeTraits<TObjRef>::TryCastFromAnyView(src)) {
      return RValueRef<TObjRef>(*std::move(opt));
    } else {
      return std::nullopt;
    }
  }

  TVM_FFI_INLINE static std::string TypeStr() {
    return "RValueRef<" + TypeTraits<TObjRef>::TypeStr() + ">";
  }
};
}  // namespace ffi
}  // namespace tvm

#endif  // TVM_FFI_RVALUE_REF_H_