Alignment/Geners/interface/GenericIO.hh - master - githubmirror/cmssw

Alignment/Geners/interface/GenericIO.hh
695 строк26 KB
Ivan Razumov
Add missing include
30 ноя 2023, 14:11
30 ноя 2023, 14:113d5c5ef
//
// Top-level API for serializing and deserializing arbitrary classes
//

#ifndef GENERS_GENERICIO_HH_
#define GENERS_GENERICIO_HH_

#include <memory>

#include "Alignment/Geners/interface/IOPointeeType.hh"
#include "Alignment/Geners/interface/binaryIO.hh"

#include "Alignment/Geners/interface/ArrayAdaptor.hh"
#include "Alignment/Geners/interface/ClearIfPointer.hh"
#include "Alignment/Geners/interface/StrippedType.hh"

namespace gs {
  /**
// Generic top-level function which can be used to write out
// almost anything. Intended mainly for use inside "write"
// methods of user-developed classes and templates. Returns
// "true" if the argument item is successfully written out.
*/
  template <class Stream, class Item>
  inline bool write_item(Stream &os, const Item &item, const bool writeClassId = true) {
    char *ps = nullptr;
    return process_const_item<GenericWriter>(item, os, ps, writeClassId);
  }

  /**
// A function for overwriting existing objects (which usually live
// on the stack). This function actually skips couple levels of
// indirection which would be generated by a call to "process_item".
*/
  template <class Stream, class Item>
  inline void restore_item(Stream &is, Item *item, const bool readClassId = true) {
    typedef std::vector<ClassId> State;
    assert(item);
    State state;
    const bool status = GenericReader<Stream, State, Item *, Int2Type<IOTraits<int>::ISPOINTER>>::process(
        item, is, &state, readClassId);
    if (is.fail())
      throw IOReadFailure("In gs::restore_item: input stream failure");
    if (!status)
      throw IOInvalidData("In gs::restore_item: invalid input stream data");
  }

  /**
// Function for returning objects on the heap. This function
// requires explicit specification of its first template
// parameter, the type of the item to read. This function
// either succeeds or throws an exception which inherits
// from std::exception.
*/
  template <class Item, class Stream>
  inline std::unique_ptr<Item> read_item(Stream &is, const bool readClassId = true) {
    typedef std::vector<ClassId> State;
    Item *item = nullptr;
    State state;
    const bool status = GenericReader<Stream, State, Item *, Int2Type<IOTraits<int>::ISNULLPOINTER>>::process(
        item, is, &state, readClassId);
    std::unique_ptr<Item> ptr(item);
    if (is.fail())
      throw IOReadFailure("In gs::read_item: input stream failure");
    if (!status || item == nullptr)
      throw IOInvalidData("In gs::read_item: invalid input stream data");
    return ptr;
  }

  /**
// Generic top-level function for writing arrays. Note that
// the length of the array is not written out and that the
// length must be known in advance in the scope from which
// the companion function, "read_array", is called. "true"
// is returned upon success, "false" on failure.
*/
  template <class Stream, class Item>
  inline bool write_array(Stream &os, Item *items, const std::size_t length) {
    char *ps = nullptr;
    return process_const_item<GenericWriter>(ArrayAdaptor<Item>(items, length), os, ps, false);
  }

  /**
// Function for deserializing arrays. The length of the array
// must be known in the scope from which this function is invoked.
*/
  template <class Stream, class Item>
  inline void read_array(Stream &is, Item *items, const std::size_t length) {
    typedef std::vector<ClassId> State;
    State state;
    ArrayAdaptor<Item> adap(items, length);
    const bool st = process_item<GenericReader>(adap, is, &state, false);
    if (is.fail())
      throw IOReadFailure("In gs::read_array: input stream failure");
    if (!st)
      throw IOInvalidData("In gs::read_array: invalid input stream data");
  }
}  // namespace gs

namespace gs {
  template <class Stream, class State, class Item, class Stage>
  struct GenericWriter2 : public GenericWriter<Stream, State, Item, Stage> {};

  template <class Stream, class State, class Item, class Stage>
  struct GenericReader2 : public GenericReader<Stream, State, Item, Stage> {};

  // The reader and writer templates should be specialized
  // (that is, their "process" function should be defined) using
  // the following processing stage types from "ProcessItem.hh":
  //
  // Int2Type<IOTraits<int>::ISPOD>                (+readIntoPtr)
  // InContainerHeader
  // InContainerFooter
  // InContainerSize
  // InPODArray
  // Int2Type<IOTraits<int>::ISWRITABLE>
  // Int2Type<IOTraits<int>::ISPOINTER>
  // Int2Type<IOTraits<int>::ISSHAREDPTR>
  // Int2Type<IOTraits<int>::ISPAIR>               (+readIntoPtr)
  // Int2Type<IOTraits<int>::ISSTRING>             (+readIntoPtr)
  //
  // In addition, the reader should be specialized for the following
  // types:
  //
  // InContainerCycle                              (process     only)
  // Int2Type<IOTraits<int>::ISSTDCONTAINER>       (readIntoPtr only)
  // Int2Type<IOTraits<int>::ISHEAPREADABLE>       (readIntoPtr only)
  // Int2Type<IOTraits<int>::ISPLACEREADABLE>      (readIntoPtr only)
  //
  // The resulting code is essentially one big compile-time state
  // machine with two main switching hubs: "process_item" function
  // from "ProcessItem.hh" and "process" function in GenericReader
  // template specialized for bare pointers.
  //

  //===================================================================
  //
  // Processing of a POD
  //
  //===================================================================
  template <class Stream, class State, class T>
  struct GenericWriter<Stream, State, T, Int2Type<IOTraits<int>::ISPOD>> {
    inline static bool process(const T &s, Stream &os, State *, const bool processClassId) {
      static const ClassId current(ClassId::makeId<T>());
      const bool status = processClassId ? current.write(os) : true;
      if (status)
        write_pod(os, s);
      return status && !os.fail();
    }
  };

  template <class Stream, class State, class T>
  struct GenericReader<Stream, State, T, Int2Type<IOTraits<int>::ISPOD>> {
    inline static bool readIntoPtr(T *&ptr, Stream &str, State *, const bool processClassId) {
      std::unique_ptr<T> myptr;
      if (ptr == nullptr)
        myptr = std::unique_ptr<T>(new T());
      if (processClassId) {
        static const ClassId current(ClassId::makeId<T>());
        ClassId id(str, 1);
        current.ensureSameName(id);
      }
      read_pod(str, ptr ? ptr : myptr.get());
      if (str.fail())
        return false;
      if (ptr == nullptr)
        ptr = myptr.release();
      return true;
    }

    inline static bool process(T &s, Stream &os, State *st, const bool processClassId) {
      T *ps = &s;
      return readIntoPtr(ps, os, st, processClassId);
    }
  };

  //===================================================================
  //
  // Processing of a container header
  //
  //===================================================================
  template <class Stream, class State, class Container>
  struct GenericWriter<Stream, State, Container, InContainerHeader> {
    inline static bool process(const Container &, Stream &os, State *, const bool processClassId) {
      typedef typename Container::value_type T;

      static const ClassId current(ClassId::makeId<Container>());
      bool status = processClassId ? current.write(os) : true;

      // Maybe we do not have to write out the container class id,
      // but we do have to write out the item class id -- unless the
      // container is just an array of pods. Otherwise we might not
      // be able to read the container items back.
      if (status && !(IOTraits<T>::IsPOD && IOTraits<Container>::IsContiguous)) {
        static const ClassId itemId(ClassId::makeId<T>());
        status = itemId.write(os);
      }
      return status;
    }
  };

  template <class Stream, class State, class Container>
  struct GenericReader<Stream, State, Container, InContainerHeader> {
    inline static bool process(Container &a, Stream &is, State *state, const bool processClassId) {
      typedef typename Container::value_type T;

      if (processClassId) {
        static const ClassId current(ClassId::makeId<Container>());
        ClassId id(is, 1);
        current.ensureSameName(id);
      }
      a.clear();
      if (!(IOTraits<T>::IsPOD && IOTraits<Container>::IsContiguous)) {
        ClassId id(is, 1);

        // Remember the class id of the contained items.
        // We need to do this even if the id is invalid because
        // the id will be popped back when the "InContainerFooter"
        // stage is processed.
        state->push_back(id);
      }
      return true;
    }
  };

  //===================================================================
  //
  // Processing of a container footer
  //
  //===================================================================
  template <class Stream, class State, class Container>
  struct GenericWriter<Stream, State, Container, InContainerFooter> {
    inline static bool process(const Container &, Stream &, State *, bool) { return true; }
  };

  template <class Stream, class State, class Container>
  struct GenericReader<Stream, State, Container, InContainerFooter> {
    inline static bool process(Container &, Stream &, State *state, bool) {
      typedef typename Container::value_type T;
      if (!(IOTraits<T>::IsPOD && IOTraits<Container>::IsContiguous))
        state->pop_back();
      return true;
    }
  };

  //===================================================================
  //
  // Processing of container size
  //
  //===================================================================
  template <class Stream, class State, class Container>
  struct GenericWriter<Stream, State, Container, InContainerSize> {
    inline static bool process(const std::size_t &sz, Stream &os, State *, bool /* processClassId */) {
      write_pod(os, sz);
      return !os.fail();
    }
  };

  template <class Stream, class State, class Container>
  struct GenericReader<Stream, State, Container, InContainerSize> {
    inline static bool process(std::size_t &sz, Stream &is, State *, bool /* processClassId */) {
      read_pod(is, &sz);
      return !is.fail();
    }
  };

  //===================================================================
  //
  // Processing of data in contiguous POD containers
  //
  //===================================================================
  template <class Stream, class State, class ArrayLike>
  struct GenericWriter<Stream, State, ArrayLike, InPODArray> {
    inline static bool process(const ArrayLike &a, Stream &os, State *, bool) {
      const std::size_t len = a.size();
      write_pod(os, len);
      if (len)
        write_pod_array(os, &a[0], len);
      return !os.fail();
    }
  };

  template <class Stream, class State, class ArrayLike>
  struct GenericReader<Stream, State, ArrayLike, InPODArray> {
    inline static bool process(ArrayLike &a, Stream &s, State *, bool) {
      std::size_t len = 0;
      read_pod(s, &len);
      if (s.fail())
        return false;
      a.resize(len);
      if (!len)
        return true;
      read_pod_array(s, &a[0], len);
      return !s.fail();
    }
  };

  //===================================================================
  //
  // Processing of "writable" objects
  //
  //===================================================================
  template <class Stream, class State, class T>
  struct GenericWriter<Stream, State, T, Int2Type<IOTraits<int>::ISWRITABLE>> {
    inline static bool process(const T &s, Stream &os, State *, const bool processClassId) {
      return (processClassId ? s.classId().write(os) : true) && s.write(os) && !os.fail();
    }
  };

  template <class Stream, class State, class T>
  struct GenericReader<Stream, State, T, Int2Type<IOTraits<int>::ISWRITABLE>> {
    inline static bool process(T &s, Stream &is, State *st, const bool processClassId) {
      typedef IOTraits<T> M;
      T *ps = &s;
      return GenericReader<Stream, State, T, Int2Type<M::Signature &(M::ISPLACEREADABLE | M::ISHEAPREADABLE)>>::
          readIntoPtr(ps, is, st, processClassId);
    }
  };

  //===================================================================
  //
  // Processing of bare pointers.
  //
  // The writer simply dereferences the pointer.
  //
  // In the reader, we want to read stuff into the pointee object,
  // or want to create an item on the heap if the pointer value is 0.
  //
  //===================================================================
  template <class Stream, class State, class Ptr>
  struct GenericWriter<Stream, State, Ptr, Int2Type<IOTraits<int>::ISPOINTER>> {
    inline static bool process(const Ptr &ptr, Stream &os, State *s, const bool processClassId) {
      // Can't have pointers to pointers. This is a design
      // decision which simplifies things considerably.
      typedef typename IOPointeeType<Ptr>::type Pointee;
      typedef IOTraits<Pointee> M;
      static_assert((M::Signature & (M::ISPOINTER | M::ISSHAREDPTR)) == 0, "can not write pointers to pointers");

      // Can't have NULL pointers either. But this
      // can be checked at run time only.
      assert(ptr);
      return process_const_item<GenericWriter2>(*ptr, os, s, processClassId);
    }
  };

  template <class Stream, class State, class Ptr>
  struct GenericReader<Stream, State, Ptr, Int2Type<IOTraits<int>::ISPOINTER>> {
    inline static bool process(Ptr &ptr, Stream &str, State *s, const bool processClassId) {
      // We need to figure out the type of the pointee
      // and make a swich depending on that type.
      // Note that the pointee itself can not be a pointer.
      typedef typename IOPointeeType<Ptr>::type Pointee;
      typedef IOTraits<Pointee> M;
      static_assert((M::Signature & (M::ISPOINTER | M::ISSHAREDPTR)) == 0, "can not read pointers to pointers");

      return GenericReader<
          Stream,
          State,
          Pointee,
          Int2Type<M::Signature &(M::ISPOD | M::ISSTDCONTAINER | M::ISHEAPREADABLE | M::ISPLACEREADABLE | M::ISPAIR |
                                  M::ISTUPLE | M::ISEXTERNAL | M::ISSTRING)>>::readIntoPtr(ptr, str, s, processClassId);
    }
  };

  template <class Stream, class State, class Ptr>
  struct GenericReader<Stream, State, Ptr, Int2Type<IOTraits<int>::ISNULLPOINTER>> {
    inline static bool process(Ptr &ptr, Stream &str, State *s, const bool processClassId) {
      // We need to figure out the type of the pointee
      // and make a swich depending on that type.
      // Note that the pointee itself can not be a pointer.
      typedef typename IOPointeeType<Ptr>::type Pointee;
      typedef IOTraits<Pointee> M;
      static_assert((M::Signature & (M::ISNULLPOINTER | M::ISSHAREDPTR)) == 0, "can not read pointers to pointers");

      return GenericReader<
          Stream,
          State,
          Pointee,
          Int2Type<M::Signature &(M::ISPOD | M::ISSTDCONTAINER | M::ISPUREHEAPREADABLE | M::ISPLACEREADABLE | M::ISPAIR |
                                  M::ISTUPLE | M::ISEXTERNAL | M::ISSTRING)>>::readIntoPtr(ptr, str, s, processClassId);
    }
  };

  //===================================================================
  //
  // Processing of shared pointers -- similar logic to pointers.
  // For the reader, handling of the shared pointer is reduced
  // to handling of a normal pointer with 0 value.
  //
  //===================================================================
  template <class Stream, class State, class Ptr>
  struct GenericWriter<Stream, State, Ptr, Int2Type<IOTraits<int>::ISSHAREDPTR>> {
    inline static bool process(const Ptr &ptr, Stream &os, State *s, const bool processClassId) {
      typedef typename Ptr::element_type Pointee;
      typedef IOTraits<Pointee> M;
      static_assert((M::Signature & (M::ISPOINTER | M::ISSHAREDPTR)) == 0, "can not write pointers to pointers");
      assert(ptr.get());
      return process_const_item<GenericWriter2>(*ptr, os, s, processClassId);
    }
  };

  template <class Stream, class State, class ShPtr>
  struct GenericReader<Stream, State, ShPtr, Int2Type<IOTraits<int>::ISSHAREDPTR>> {
    inline static bool process(ShPtr &a, Stream &str, State *s, const bool processClassId) {
      typedef typename ShPtr::element_type Pointee;
      typedef IOTraits<Pointee> M;
      static_assert((M::Signature & (M::ISPOINTER | M::ISSHAREDPTR)) == 0, "can not read pointers to pointers");
      Pointee *ptr = 0;
      const bool status = GenericReader<Stream, State, Pointee *, Int2Type<IOTraits<int>::ISNULLPOINTER>>::process(
          ptr, str, s, processClassId);
      if (status) {
        assert(ptr);
        a = std::shared_ptr<Pointee>(ptr);
        return true;
      } else {
        delete ptr;
        return false;
      }
    }
  };

  //===================================================================
  //
  // Processing of std::pair
  //
  //===================================================================
  template <class Stream, class State, class T>
  struct GenericWriter<Stream, State, T, Int2Type<IOTraits<int>::ISPAIR>> {
    inline static bool process(const T &s, Stream &os, State *st, const bool processClassId) {
      // Here is a little problem: in this scope "GenericWriter"
      // means GenericWriter<Stream, State, T,
      //                     Int2Type<IOTraits<int>::ISPAIR> >
      // However, we want to use the whole template, unspecialized.
      // This is why "GenericWriter2" is introduced: a copy of
      // "GenericWriter" via public inheritance.
      static const ClassId current(ClassId::makeId<T>());
      return (processClassId ? current.write(os) : true) &&
             process_const_item<GenericWriter2>(s.first, os, st, false) &&
             process_const_item<GenericWriter2>(s.second, os, st, false);
    }
  };

  template <class Stream, class State, class T>
  struct GenericReader<Stream, State, T, Int2Type<IOTraits<int>::ISPAIR>> {
    inline static bool readIntoPtr(T *&ptr, Stream &str, State *s, const bool processClassId) {
      std::unique_ptr<T> myptr;
      if (ptr == 0) {
        myptr = std::unique_ptr<T>(new T());
        clearIfPointer(myptr.get()->first);
        clearIfPointer(myptr.get()->second);
      }
      std::vector<std::vector<ClassId>> itemIds;
      if (processClassId) {
        static const ClassId current(ClassId::makeId<T>());
        ClassId pairId(str, 1);
        current.ensureSameName(pairId);
        pairId.templateParameters(&itemIds);
        assert(itemIds.size() == 2U);
      } else {
        assert(!s->empty());
        s->back().templateParameters(&itemIds);
        if (itemIds.size() != 2U) {
          std::string err(
              "In gs::GenericReader::readIntoPtr: "
              "bad class id for std::pair on the "
              "class id stack: ");
          err += s->back().id();
          throw IOInvalidData(err);
        }
      }
      if (!(process_item<GenericReader2>((ptr ? ptr : myptr.get())->first, str, &itemIds[0], false) &&
            process_item<GenericReader2>((ptr ? ptr : myptr.get())->second, str, &itemIds[1], false)))
        return false;
      if (ptr == 0)
        ptr = myptr.release();
      return true;
    }

    inline static bool process(T &s, Stream &os, State *st, const bool processClassId) {
      T *ps = &s;
      return readIntoPtr(ps, os, st, processClassId);
    }
  };

  //===================================================================
  //
  // Processing of std::string
  //
  //===================================================================
  template <class Stream, class State>
  struct GenericWriter<Stream, State, std::string, Int2Type<IOTraits<int>::ISSTRING>> {
    inline static bool process(const std::string &s, Stream &os, State *, const bool processClassId) {
      static const ClassId current(ClassId::makeId<std::string>());
      const bool status = processClassId ? current.write(os) : true;
      if (status)
        write_string<char>(os, s);
      return status && !os.fail();
    }
  };

  template <class Stream, class State>
  struct GenericReader<Stream, State, std::string, Int2Type<IOTraits<int>::ISSTRING>> {
    inline static bool readIntoPtr(std::string *&ptr, Stream &is, State *, const bool processClassId) {
      std::unique_ptr<std::string> myptr;
      if (ptr == nullptr)
        myptr = std::make_unique<std::string>();
      if (processClassId) {
        static const ClassId current(ClassId::makeId<std::string>());
        ClassId id(is, 1);
        current.ensureSameName(id);
      }
      read_string<char>(is, ptr ? ptr : myptr.get());
      if (is.fail())
        return false;
      if (ptr == nullptr)
        ptr = myptr.release();
      return true;
    }

    inline static bool process(std::string &s, Stream &is, State *st, const bool processClassId) {
      std::string *ptr = &s;
      return readIntoPtr(ptr, is, st, processClassId);
    }
  };

  //===================================================================
  //
  // Processing of container readout
  //
  //===================================================================
  template <class Stream, class State, class Container>
  struct GenericReader<Stream, State, Container, InContainerCycle> {
  private:
    typedef typename Container::value_type item_type;
    typedef IOTraits<item_type> M;

    // Item is a simple pointer
    inline static bool process2(Container &obj, Stream &is, State *st, const std::size_t itemN, Int2Type<1>) {
      item_type ptr = 0;
      const bool status =
          GenericReader<Stream, State, item_type, Int2Type<IOTraits<int>::ISNULLPOINTER>>::process(ptr, is, st, true);
      if (status) {
        assert(ptr);
        InsertContainerItem<Container>::insert(obj, ptr, itemN);
      } else
        delete ptr;
      return status;
    }

    // Item is a shared pointer
    inline static bool process2(Container &obj, Stream &is, State *st, const std::size_t itemN, Int2Type<2>) {
      typedef typename item_type::element_type Pointee;
      Pointee *ptr = 0;
      const bool status =
          GenericReader<Stream, State, Pointee *, Int2Type<IOTraits<int>::ISNULLPOINTER>>::process(ptr, is, st, true);
      if (status) {
        assert(ptr);
        std::shared_ptr<Pointee> sptr(ptr);
        InsertContainerItem<Container>::insert(obj, sptr, itemN);
      } else
        delete ptr;
      return status;
    }

    // Item is heap-readable
    inline static bool process2(Container &obj, Stream &is, State *st, const std::size_t itemN, Int2Type<3>) {
      // No class id -- this is a member of a container
      assert(!st->empty());
      item_type *ptr = item_type::read(st->back(), is);
      if (ptr) {
        InsertContainerItem<Container>::insert(obj, *ptr, itemN);
        delete ptr;
      }
      return ptr;
    }

    // Item is not a pointer and not heap-readable.
    // Assume that it has a default constructor.
    inline static bool process2(Container &obj, Stream &is, State *st, const std::size_t itemN, Int2Type<4>) {
      typedef typename StrippedType<item_type>::type NCType;
      NCType item;
      NCType *pitem = &item;
      bool status =
          GenericReader<Stream, State, NCType *, Int2Type<IOTraits<int>::ISPOINTER>>::process(pitem, is, st, false);
      if (status)
        InsertContainerItem<Container>::insert(obj, item, itemN);
      return status;
    }

  public:
    inline static bool process(Container &obj, Stream &is, State *st, const std::size_t itemN) {
      // By default, we will assume that container starts empty.
      // Here, we need to produce a new item. There are 3 options:
      //   1) make it on the stack, insert a copy into the container
      //   2) make it on the heap, insert a copy, delete original
      //   3) the container contains pointers to begin with, so
      //      we make it on the stack and add a pointer to the container
      return process2(obj,
                      is,
                      st,
                      itemN,
                      Int2Type<M::IsPointer * 1 + M::IsSharedPtr * 2 + M::IsHeapReadable * 3 +
                               !(M::IsPointer || M::IsSharedPtr || M::IsHeapReadable) * 4>());
    }
  };

  //===================================================================
  //
  // Reading things when a pointer is given
  //
  //===================================================================
  template <class Stream, class State, class T>
  struct GenericReader<Stream, State, T, Int2Type<IOTraits<int>::ISSTDCONTAINER>> {
    inline static bool readIntoPtr(T *&ptr, Stream &str, State *s, const bool processClassId) {
      if (ptr)
        return process_item<GenericReader2>(*ptr, str, s, processClassId);
      else {
        std::unique_ptr<T> myptr(new T());
        if (!process_item<GenericReader2>(*myptr, str, s, processClassId))
          return false;
        ptr = myptr.release();
        return true;
      }
    }
  };

  template <class Stream, class State, class T>
  struct GenericReader<Stream, State, T, Int2Type<IOTraits<int>::ISHEAPREADABLE>> {
    inline static bool readIntoPtr(T *&ptr, Stream &str, State *s, const bool processClassId) {
      T *readback = 0;
      if (processClassId) {
        ClassId id(str, 1);
        readback = T::read(id, str);
      } else {
        assert(!s->empty());
        readback = T::read(s->back(), str);
      }
      if (readback) {
        if (ptr) {
          try {
            // We will assume here that the "read"
            // operation takes precedence over constness
            *const_cast<typename StrippedType<T>::type *>(ptr) = *readback;
          } catch (...) {
            delete readback;
            throw;
          }
          delete readback;
        } else
          ptr = readback;
      }
      return readback;
    }
  };

  template <class Stream, class State, class T>
  struct GenericReader<Stream, State, T, Int2Type<IOTraits<int>::ISPUREHEAPREADABLE>> {
    inline static bool readIntoPtr(T *&ptr, Stream &str, State *s, const bool processClassId) {
      T *readback = nullptr;
      if (processClassId) {
        ClassId id(str, 1);
        readback = T::read(id, str);
      } else {
        assert(!s->empty());
        readback = T::read(s->back(), str);
      }
      if (readback) {
        assert(!ptr);
        ptr = readback;
      }
      return readback;
    }
  };

  template <class Stream, class State, class T>
  struct GenericReader<Stream, State, T, Int2Type<IOTraits<int>::ISPLACEREADABLE>> {
    inline static bool readIntoPtr(T *&ptr, Stream &str, State *s, const bool processClassId) {
      std::unique_ptr<T> myptr;
      if (ptr == 0)
        myptr = std::unique_ptr<T>(new T());
      if (processClassId) {
        ClassId id(str, 1);
        T::restore(id, str, ptr ? ptr : myptr.get());
      } else {
        assert(!s->empty());
        T::restore(s->back(), str, ptr ? ptr : myptr.get());
      }
      if (ptr == 0)
        ptr = myptr.release();
      return ptr;
    }
  };
}  // namespace gs

#endif  // GENERS_GENERICIO_HH_