src/support/utilities.h

/*
 * Copyright 2016 WebAssembly Community Group participants
 *
 * Licensed 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 wasm_support_utilities_h
#define wasm_support_utilities_h

#include "compiler-support.h"

#include <cassert>
#include <cstdint>
#include <cstring>
#include <memory>
#include <iostream>
#include <type_traits>

#include "support/bits.h"

namespace wasm {

// Type punning needs to be done through this function to avoid undefined
// behavior: unions and reinterpret_cast aren't valid approaches.
template <class Destination, class Source>
inline Destination bit_cast(const Source& source) {
  static_assert(sizeof(Destination) == sizeof(Source),
                "bit_cast needs to be between types of the same size");
  static_assert(std::is_pod<Destination>::value, "non-POD bit_cast undefined");
  static_assert(std::is_pod<Source>::value, "non-POD bit_cast undefined");
  Destination destination;
  std::memcpy(&destination, &source, sizeof(destination));
  return destination;
}

inline size_t alignAddr(size_t address, size_t alignment) {
  assert(alignment && IsPowerOf2((uint32_t)alignment) &&
         "Alignment is not a power of two!");

  assert(address + alignment - 1 >= address);

  return ((address + alignment - 1) & ~(alignment - 1));
}

template<typename T, typename... Args>
std::unique_ptr<T> make_unique(Args&&... args)
{
    return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
}

// Helper for non-asserting failures.
// Used to collapse code like:
//   if (foo() && !bar()) {
//     Fatal() << "Error: foo and not bar!";
//   }
// Into:
//   FatalIf(foo() && !bar()) << "foo and not bar!";
class FatalIf {
  bool condition;
 public:
  FatalIf(bool condition) : condition(condition) {
    if (condition) {
      std::cerr << "Fatal: ";
    }
  }
  template<typename T>
  FatalIf &operator<<(T arg) {
    if (condition) {
      std::cerr << arg;
    }
    return *this;
  }
  ~FatalIf() {
    if (condition) {
      std::cerr << "\n";
      exit(1);
    }
  }
};

// For fatal errors which could arise from input (i.e. not assertion failures)
class Fatal : public FatalIf {
 public:
  Fatal() : FatalIf(true) { }
  WASM_NORETURN ~Fatal() {
    std::cerr << "\n";
    exit(1);
  }
};

}  // namespace wasm

#endif   // wasm_support_utilities_h