restructure more

ThirdParty/assimp/code/AssetLib/Step/STEPFile.h

@@ -0,0 +1,925 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2025, assimp team
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+
+#ifndef INCLUDED_AI_STEPFILE_H
+#define INCLUDED_AI_STEPFILE_H
+
+#include <bitset>
+#include <map>
+#include <memory>
+#include <set>
+#include <typeinfo>
+#include <vector>
+
+#include "AssetLib/FBX/FBXDocument.h" //ObjectMap::value_type
+
+#include <assimp/DefaultLogger.hpp>
+
+#ifdef _MSC_VER
+#    pragma warning(push)
+#    pragma warning(disable : 4127 4456 4245 4512 )
+#endif // _MSC_VER
+
+#if _MSC_VER > 1500 || (defined __GNUC___)
+#    define ASSIMP_STEP_USE_UNORDERED_MULTIMAP
+#else
+#    define step_unordered_map map
+#    define step_unordered_multimap multimap
+#endif
+
+#ifdef ASSIMP_STEP_USE_UNORDERED_MULTIMAP
+#    include <unordered_map>
+#    if defined(_MSC_VER) && _MSC_VER <= 1600
+#        define step_unordered_map tr1::unordered_map
+#        define step_unordered_multimap tr1::unordered_multimap
+#    else
+#        define step_unordered_map unordered_map
+#        define step_unordered_multimap unordered_multimap
+#    endif
+#endif
+
+#include <assimp/LineSplitter.h>
+
+// uncomment this to have the loader evaluate all entities upon loading.
+// this is intended as stress test - by default, entities are evaluated
+// lazily and therefore not unless needed.
+
+namespace Assimp {
+
+// ********************************************************************************
+// before things get complicated, this is the basic outline:
+
+namespace STEP {
+
+namespace EXPRESS {
+
+// base data types known by EXPRESS schemata - any custom data types will derive one of those
+class DataType;
+class UNSET; /*: public DataType */
+class ISDERIVED; /*: public DataType */
+class ENUM; /*: public DataType */
+class ENTITY; /*: public DataType */
+class LIST; /*: public DataType */
+
+// a conversion schema is not exactly an EXPRESS schema, rather it
+// is a list of pointers to conversion functions to build up the
+// object tree from an input file.
+class ConversionSchema;
+} // namespace EXPRESS
+
+struct HeaderInfo;
+class Object;
+class LazyObject;
+class DB;
+
+typedef Object *(*ConvertObjectProc)(const DB &db, const EXPRESS::LIST &params);
+} // namespace STEP
+
+// ********************************************************************************
+
+namespace STEP {
+
+// -------------------------------------------------------------------------------
+/** Exception class used by the STEP loading & parsing code. It is typically
+ *  coupled with a line number.
+ */
+// -------------------------------------------------------------------------------
+struct SyntaxError : DeadlyImportError {
+    enum : uint64_t {
+        LINE_NOT_SPECIFIED = 0xfffffffffffffffLL
+    };
+
+    SyntaxError(const std::string &s, uint64_t line = LINE_NOT_SPECIFIED);
+};
+
+// -------------------------------------------------------------------------------
+/** Exception class used by the STEP loading & parsing code when a type
+ *  error (i.e. an entity expects a string but receives a bool) occurs.
+ *  It is typically coupled with both an entity id and a line number.
+ */
+// -------------------------------------------------------------------------------
+struct TypeError : DeadlyImportError {
+    enum : uint64_t {
+        ENTITY_NOT_SPECIFIED = 0xffffffffffffffffUL,
+        ENTITY_NOT_SPECIFIED_32 = 0x00000000ffffffff
+    };
+
+    TypeError(const std::string &s, uint64_t entity = ENTITY_NOT_SPECIFIED, uint64_t line = SyntaxError::LINE_NOT_SPECIFIED);
+};
+
+// hack to make a given member template-dependent
+template <typename T, typename T2>
+T2 &Couple(T2 &in) {
+    return in;
+}
+
+namespace EXPRESS {
+
+// -------------------------------------------------------------------------------
+//** Base class for all STEP data types */
+// -------------------------------------------------------------------------------
+class DataType {
+public:
+    typedef std::shared_ptr<const DataType> Out;
+
+public:
+    virtual ~DataType() = default;
+
+    template <typename T>
+    const T &To() const {
+        return dynamic_cast<const T &>(*this);
+    }
+
+    template <typename T>
+    T &To() {
+        return dynamic_cast<T &>(*this);
+    }
+
+    template <typename T>
+    const T *ToPtr() const {
+        return dynamic_cast<const T *>(this);
+    }
+
+    template <typename T>
+    T *ToPtr() {
+        return dynamic_cast<T *>(this);
+    }
+
+    // utilities to deal with SELECT entities, which currently lack automatic
+    // conversion support.
+    template <typename T>
+    const T &ResolveSelect(const DB &db) const {
+        return Couple<T>(db).MustGetObject(To<EXPRESS::ENTITY>())->template To<T>();
+    }
+
+    template <typename T>
+    const T *ResolveSelectPtr(const DB &db) const {
+        const EXPRESS::ENTITY *e = ToPtr<EXPRESS::ENTITY>();
+        return e ? Couple<T>(db).MustGetObject(*e)->template ToPtr<T>() : (const T *)nullptr;
+    }
+
+public:
+    /// @brief Parse a variable from a string and set 'inout' to the character behind the last consumed character.
+    ///
+    ///  An optional schema enables, if specified, automatic conversion of custom data types.
+    ///
+    /// @throw SyntaxError
+    static std::shared_ptr<const EXPRESS::DataType> Parse(const char *&inout, const char *end,
+            uint64_t line = SyntaxError::LINE_NOT_SPECIFIED, const EXPRESS::ConversionSchema *schema = nullptr);
+};
+
+typedef DataType SELECT;
+typedef DataType LOGICAL;
+
+// -------------------------------------------------------------------------------
+/// Sentinel class to represent explicitly unset (optional) fields ($)
+// -------------------------------------------------------------------------------
+class UNSET : public DataType {};
+
+// -------------------------------------------------------------------------------
+/// Sentinel class to represent explicitly derived fields (*)
+// -------------------------------------------------------------------------------
+class ISDERIVED : public DataType {};
+
+// -------------------------------------------------------------------------------
+/** Shared implementation for some of the primitive data type, i.e. int, float
+ */
+// -------------------------------------------------------------------------------
+template <typename T>
+class PrimitiveDataType : public DataType {
+public:
+    // This is the type that will cd ultimatively be used to
+    // expose this data type to the user.
+    typedef T Out;
+
+    PrimitiveDataType() = default;
+    PrimitiveDataType(const T &val) :
+            val(val) {}
+
+    PrimitiveDataType(const PrimitiveDataType &o) {
+        (*this) = o;
+    }
+
+    operator const T &() const {
+        return val;
+    }
+
+    PrimitiveDataType &operator=(const PrimitiveDataType &o) {
+        val = o.val;
+        return *this;
+    }
+
+protected:
+    T val;
+};
+
+typedef PrimitiveDataType<int64_t> INTEGER;
+typedef PrimitiveDataType<double> REAL;
+typedef PrimitiveDataType<double> NUMBER;
+typedef PrimitiveDataType<std::string> STRING;
+
+// -------------------------------------------------------------------------------
+/** Generic base class for all enumerated types */
+// -------------------------------------------------------------------------------
+class ENUMERATION : public STRING {
+public:
+    ENUMERATION(const std::string &val) :
+            STRING(val) {}
+};
+
+typedef ENUMERATION BOOLEAN;
+
+// -------------------------------------------------------------------------------
+/** This is just a reference to an entity/object somewhere else
+ */
+// -------------------------------------------------------------------------------
+class ENTITY : public PrimitiveDataType<uint64_t> {
+public:
+    ENTITY(uint64_t val) : PrimitiveDataType<uint64_t>(val) {}
+    ENTITY() : PrimitiveDataType<uint64_t>(TypeError::ENTITY_NOT_SPECIFIED) {}
+};
+
+// -------------------------------------------------------------------------------
+/** Wrap any STEP aggregate: LIST, SET, ... */
+// -------------------------------------------------------------------------------
+class LIST : public DataType {
+public:
+    // access a particular list index, throw std::range_error for wrong indices
+    std::shared_ptr<const DataType> operator[](size_t index) const {
+        return members[index];
+    }
+
+    size_t GetSize() const {
+        return members.size();
+    }
+
+public:
+    /** @see DaraType::Parse
+     */
+    static std::shared_ptr<const EXPRESS::LIST> Parse(const char *&inout, const char *end,
+            uint64_t line = SyntaxError::LINE_NOT_SPECIFIED,
+            const EXPRESS::ConversionSchema *schema = nullptr);
+
+private:
+    typedef std::vector<std::shared_ptr<const DataType>> MemberList;
+    MemberList members;
+};
+
+class BINARY : public PrimitiveDataType<uint32_t> {
+public:
+    BINARY(uint32_t val) : PrimitiveDataType<uint32_t>(val) {}
+    BINARY() : PrimitiveDataType<uint32_t>(TypeError::ENTITY_NOT_SPECIFIED_32) {}
+};
+
+// -------------------------------------------------------------------------------
+/* Not exactly a full EXPRESS schema but rather a list of conversion functions
+ * to extract valid C++ objects out of a STEP file. Those conversion functions
+ * may, however, perform further schema validations.
+ */
+// -------------------------------------------------------------------------------
+class ConversionSchema {
+public:
+    struct SchemaEntry {
+        SchemaEntry(const char *name, ConvertObjectProc func) : mName(name), mFunc(func) {}
+
+        const char *mName;
+        ConvertObjectProc mFunc;
+    };
+
+    typedef std::map<std::string, ConvertObjectProc> ConverterMap;
+
+    template <size_t N>
+    explicit ConversionSchema(const SchemaEntry (&schemas)[N]) {
+        *this = schemas;
+    }
+
+    ConversionSchema() = default;
+
+    ConvertObjectProc GetConverterProc(const std::string &name) const {
+        ConverterMap::const_iterator it = converters.find(name);
+        return it == converters.end() ? nullptr : (*it).second;
+    }
+
+    bool IsKnownToken(const std::string &name) const {
+        return converters.find(name) != converters.end();
+    }
+
+    const char *GetStaticStringForToken(const std::string &token) const {
+        ConverterMap::const_iterator it = converters.find(token);
+        return it == converters.end() ? nullptr : (*it).first.c_str();
+    }
+
+    template <size_t N>
+    const ConversionSchema &operator=(const SchemaEntry (&schemas)[N]) {
+        for (size_t i = 0; i < N; ++i) {
+            const SchemaEntry &schema = schemas[i];
+            converters[schema.mName] = schema.mFunc;
+        }
+        return *this;
+    }
+
+private:
+    ConverterMap converters;
+};
+} // namespace EXPRESS
+
+// ------------------------------------------------------------------------------
+/** Bundle all the relevant info from a STEP header, parts of which may later
+ *  be plainly dumped to the logfile, whereas others may help the caller pick an
+ *  appropriate loading strategy.
+ */
+// ------------------------------------------------------------------------------
+struct HeaderInfo {
+    std::string timestamp;
+    std::string app;
+    std::string fileSchema;
+};
+
+// ------------------------------------------------------------------------------
+/** Base class for all concrete object instances
+ */
+// ------------------------------------------------------------------------------
+class Object {
+public:
+    Object(const char *classname = "unknown") : id(0), classname(classname) {}
+
+    virtual ~Object() = default;
+
+    // utilities to simplify casting to concrete types
+    template <typename T>
+    const T &To() const {
+        return dynamic_cast<const T &>(*this);
+    }
+
+    template <typename T>
+    T &To() {
+        return dynamic_cast<T &>(*this);
+    }
+
+    template <typename T>
+    const T *ToPtr() const {
+        return dynamic_cast<const T *>(this);
+    }
+
+    template <typename T>
+    T *ToPtr() {
+        return dynamic_cast<T *>(this);
+    }
+
+    uint64_t GetID() const {
+        return id;
+    }
+
+    std::string GetClassName() const {
+        return classname;
+    }
+
+    void SetID(uint64_t newval) {
+        id = newval;
+    }
+
+private:
+    uint64_t id;
+    const char *const classname;
+};
+
+template <typename T>
+size_t GenericFill(const STEP::DB &db, const EXPRESS::LIST &params, T *in);
+// (intentionally undefined)
+
+// ------------------------------------------------------------------------------
+/** CRTP shared base class for use by concrete entity implementation classes */
+// ------------------------------------------------------------------------------
+template <typename TDerived, size_t arg_count>
+struct ObjectHelper : virtual Object {
+    ObjectHelper() : aux_is_derived(0) {}
+
+    static Object *Construct(const STEP::DB &db, const EXPRESS::LIST &params) {
+        // make sure we don't leak if Fill() throws an exception
+        std::unique_ptr<TDerived> impl(new TDerived());
+
+        // GenericFill<T> is undefined so we need to have a specialization
+        static_cast<void>(GenericFill<TDerived>(db, params, &*impl));
+
+        return impl.release();
+    }
+
+    // note that this member always exists multiple times within the hierarchy
+    // of an individual object, so any access to it must be disambiguated.
+    std::bitset<arg_count> aux_is_derived;
+};
+
+// ------------------------------------------------------------------------------
+/** Class template used to represent OPTIONAL data members in the converted schema */
+// ------------------------------------------------------------------------------
+template <typename T>
+struct Maybe {
+    Maybe() : have() {}
+
+    explicit Maybe(const T &ptr) : ptr(ptr), have(true) {}
+
+    void flag_invalid() {
+        have = false;
+    }
+
+    void flag_valid() {
+        have = true;
+    }
+
+    bool operator!() const {
+        return !have;
+    }
+
+    operator bool() const {
+        return have;
+    }
+
+    operator const T &() const {
+        return Get();
+    }
+
+    const T &Get() const {
+        ai_assert(have);
+        return ptr;
+    }
+
+    Maybe &operator=(const T &_ptr) {
+        ptr = _ptr;
+        have = true;
+        return *this;
+    }
+
+private:
+    template <typename T2>
+    friend struct InternGenericConvert;
+
+    operator T &() {
+        return ptr;
+    }
+
+    T ptr;
+    bool have;
+};
+
+// ------------------------------------------------------------------------------
+/** A LazyObject is created when needed. Before this happens, we just keep
+ *  the text line that contains the object definition.
+ */
+// -------------------------------------------------------------------------------
+class LazyObject {
+    friend class DB;
+
+public:
+    LazyObject(DB &db, uint64_t id, uint64_t line, const char *type, const char *args);
+    ~LazyObject();
+
+    Object &operator*() {
+        if (!obj) {
+            LazyInit();
+            ai_assert(obj);
+        }
+        return *obj;
+    }
+
+    const Object &operator*() const {
+        if (!obj) {
+            LazyInit();
+            ai_assert(obj);
+        }
+        return *obj;
+    }
+
+    template <typename T>
+    const T &To() const {
+        return dynamic_cast<const T &>(**this);
+    }
+
+    template <typename T>
+    T &To() {
+        return dynamic_cast<T &>(**this);
+    }
+
+    template <typename T>
+    const T *ToPtr() const {
+        return dynamic_cast<const T *>(&**this);
+    }
+
+    template <typename T>
+    T *ToPtr() {
+        return dynamic_cast<T *>(&**this);
+    }
+
+    Object *operator->() {
+        return &**this;
+    }
+
+    const Object *operator->() const {
+        return &**this;
+    }
+
+    bool operator==(const std::string &atype) const {
+        return type == atype;
+    }
+
+    bool operator!=(const std::string &atype) const {
+        return type != atype;
+    }
+
+    uint64_t GetID() const {
+        return id;
+    }
+
+private:
+    void LazyInit() const;
+
+private:
+    mutable uint64_t id;
+    const char *const type;
+    DB &db;
+    mutable const char *args;
+    mutable Object *obj;
+};
+
+template <typename T>
+inline bool operator == (const std::shared_ptr<LazyObject> &lo, T whatever) {
+    return *lo == whatever; // XXX use std::forward if we have 0x
+}
+
+template <typename T>
+inline bool operator == (const std::pair<uint64_t, std::shared_ptr<LazyObject>> &lo, T whatever) {
+    return *(lo.second) == whatever; // XXX use std::forward if we have 0x
+}
+
+// ------------------------------------------------------------------------------
+/** Class template used to represent lazily evaluated object references in the converted schema */
+// ------------------------------------------------------------------------------
+template <typename T>
+struct Lazy {
+    typedef Lazy Out;
+    Lazy(const LazyObject *obj = nullptr) : obj(obj) {}
+
+    operator const T *() const {
+        if (obj == nullptr) {
+            throw TypeError("Obj type is nullptr.");
+        }
+        return obj->ToPtr<T>();
+    }
+
+    operator const T &() const {
+        if (obj == nullptr) {
+            throw TypeError("Obj type is nullptr.");
+        }
+        return obj->To<T>();
+    }
+
+    const T &operator*() const {
+        if (obj == nullptr) {
+            throw TypeError("Obj type is nullptr.");
+        }
+        return obj->To<T>();
+    }
+
+    const T *operator->() const {
+        if (obj == nullptr) {
+            throw TypeError("Obj type is nullptr.");
+        }
+        return &obj->To<T>();
+    }
+
+    const LazyObject *obj;
+};
+
+// ------------------------------------------------------------------------------
+/** Class template used to represent LIST and SET data members in the converted schema */
+// ------------------------------------------------------------------------------
+template <typename T, uint64_t min_cnt, uint64_t max_cnt = 0uL>
+struct ListOf : public std::vector<typename T::Out> {
+    typedef typename T::Out OutScalar;
+    typedef ListOf Out;
+
+    ListOf() {
+        static_assert(min_cnt <= max_cnt || !max_cnt, "min_cnt <= max_cnt || !max_cnt");
+    }
+};
+
+// ------------------------------------------------------------------------------
+template <typename TOut>
+struct PickBaseType {
+    typedef EXPRESS::PrimitiveDataType<TOut> Type;
+};
+
+template <typename TOut>
+struct PickBaseType<Lazy<TOut>> {
+    typedef EXPRESS::ENTITY Type;
+};
+
+template <>
+struct PickBaseType<std::shared_ptr<const EXPRESS::DataType>>;
+
+// ------------------------------------------------------------------------------
+template <typename T>
+struct InternGenericConvert {
+    void operator()(T &out, const std::shared_ptr<const EXPRESS::DataType> &in, const STEP::DB & /*db*/) {
+        try {
+            out = dynamic_cast<const typename PickBaseType<T>::Type &>(*in);
+        } catch (std::bad_cast &) {
+            throw TypeError("type error reading literal field");
+        }
+    }
+};
+
+template <>
+struct InternGenericConvert<std::shared_ptr<const EXPRESS::DataType>> {
+    void operator()(std::shared_ptr<const EXPRESS::DataType> &out, const std::shared_ptr<const EXPRESS::DataType> &in, const STEP::DB & /*db*/) {
+        out = in;
+    }
+};
+
+template <typename T>
+struct InternGenericConvert<Maybe<T>> {
+    void operator()(Maybe<T> &out, const std::shared_ptr<const EXPRESS::DataType> &in, const STEP::DB &db) {
+        GenericConvert((T &)out, in, db);
+        out.flag_valid();
+    }
+};
+
+#if _MSC_VER > 1920
+#pragma warning(push)
+#pragma warning(disable : 4127)
+#endif // _WIN32
+
+template <typename T, uint64_t min_cnt, uint64_t max_cnt>
+struct InternGenericConvertList {
+    void operator()(ListOf<T, min_cnt, max_cnt> &out, const std::shared_ptr<const EXPRESS::DataType> &inp_base, const STEP::DB &db) {
+
+        const EXPRESS::LIST *inp = dynamic_cast<const EXPRESS::LIST *>(inp_base.get());
+        if (!inp) {
+            throw TypeError("type error reading aggregate");
+        }
+
+        // XXX is this really how the EXPRESS notation ([?:3],[1:3]) is intended?
+        const size_t len = inp->GetSize();
+        if (0 != max_cnt && len > max_cnt) {
+            ASSIMP_LOG_WARN("too many aggregate elements");
+        } else if (len < min_cnt) {
+            ASSIMP_LOG_WARN("too few aggregate elements");
+        }
+
+        out.reserve(inp->GetSize());
+        for (size_t i = 0; i < inp->GetSize(); ++i) {
+
+            out.push_back(typename ListOf<T, min_cnt, max_cnt>::OutScalar());
+            try {
+                GenericConvert(out.back(), (*inp)[i], db);
+            } catch (const TypeError &t) {
+                throw TypeError(t.what() + std::string(" of aggregate"));
+            }
+        }
+    }
+};
+
+template <typename T>
+struct InternGenericConvert<Lazy<T>> {
+    void operator()(Lazy<T> &out, const std::shared_ptr<const EXPRESS::DataType> &in_base, const STEP::DB &db) {
+        const EXPRESS::ENTITY *in = dynamic_cast<const EXPRESS::ENTITY *>(in_base.get());
+        if (!in) {
+            throw TypeError("type error reading entity");
+        }
+        out = Couple<T>(db).GetObject(*in);
+    }
+};
+
+template <typename T1>
+inline void GenericConvert(T1 &a, const std::shared_ptr<const EXPRESS::DataType> &b, const STEP::DB &db) {
+    return InternGenericConvert<T1>()(a, b, db);
+}
+
+template <typename T1, uint64_t N1, uint64_t N2>
+inline void GenericConvert(ListOf<T1, N1, N2> &a, const std::shared_ptr<const EXPRESS::DataType> &b, const STEP::DB &db) {
+    return InternGenericConvertList<T1, N1, N2>()(a, b, db);
+}
+
+// ------------------------------------------------------------------------------
+/** Lightweight manager class that holds the map of all objects in a
+ *  STEP file. DB's are exclusively maintained by the functions in
+ *  STEPFileReader.h
+ */
+// -------------------------------------------------------------------------------
+class DB {
+    friend DB *ReadFileHeader(std::shared_ptr<IOStream> stream);
+    friend void ReadFile(DB &db, const EXPRESS::ConversionSchema &scheme,
+            const char *const *types_to_track, size_t len,
+            const char *const *inverse_indices_to_track, size_t len2);
+
+    friend class LazyObject;
+
+public:
+    // objects indexed by ID - this can grow pretty large (i.e some hundred million
+    // entries), so use raw pointers to avoid *any* overhead.
+    typedef std::map<uint64_t, const LazyObject *> ObjectMap;
+
+    // objects indexed by their declarative type, but only for those that we truly want
+    typedef std::set<const LazyObject *> ObjectSet;
+    typedef std::map<std::string, ObjectSet> ObjectMapByType;
+
+    // list of types for which to keep inverse indices for all references
+    // that the respective objects keep.
+    // the list keeps pointers to strings in static storage
+    typedef std::set<const char *> InverseWhitelist;
+
+    // references - for each object id the ids of all objects which reference it
+    // this is used to simulate STEP inverse indices for selected types.
+    typedef std::step_unordered_multimap<uint64_t, uint64_t> RefMap;
+    typedef std::pair<RefMap::const_iterator, RefMap::const_iterator> RefMapRange;
+
+private:
+    DB(const std::shared_ptr<StreamReaderLE> &reader) :
+            reader(reader), splitter(*reader, true, true), evaluated_count(), schema(nullptr) {}
+
+public:
+    ~DB() {
+        for (ObjectMap::value_type &o : objects) {
+            delete o.second;
+        }
+    }
+
+    uint64_t GetObjectCount() const {
+        return objects.size();
+    }
+
+    uint64_t GetEvaluatedObjectCount() const {
+        return evaluated_count;
+    }
+
+    const HeaderInfo &GetHeader() const {
+        return header;
+    }
+
+    const EXPRESS::ConversionSchema &GetSchema() const {
+        return *schema;
+    }
+
+    const ObjectMap &GetObjects() const {
+        return objects;
+    }
+
+    const ObjectMapByType &GetObjectsByType() const {
+        return objects_bytype;
+    }
+
+    const RefMap &GetRefs() const {
+        return refs;
+    }
+
+    bool KeepInverseIndicesForType(const char *const type) const {
+        return inv_whitelist.find(type) != inv_whitelist.end();
+    }
+
+    // get the yet unevaluated object record with a given id
+    const LazyObject *GetObject(uint64_t id) const {
+        const ObjectMap::const_iterator it = objects.find(id);
+        if (it != objects.end()) {
+            return (*it).second;
+        }
+        return nullptr;
+    }
+
+    // get an arbitrary object out of the soup with the only restriction being its type.
+    const LazyObject *GetObject(const std::string &type) const {
+        const ObjectMapByType::const_iterator it = objects_bytype.find(type);
+        if (it != objects_bytype.end() && (*it).second.size()) {
+            return *(*it).second.begin();
+        }
+        return nullptr;
+    }
+
+    // same, but raise an exception if the object doesn't exist and return a reference
+    const LazyObject &MustGetObject(uint64_t id) const {
+        const LazyObject *o = GetObject(id);
+        if (!o) {
+            throw TypeError("requested entity is not present", id);
+        }
+        return *o;
+    }
+
+    const LazyObject &MustGetObject(const std::string &type) const {
+        const LazyObject *o = GetObject(type);
+        if (!o) {
+            throw TypeError("requested entity of type " + type + "is not present");
+        }
+        return *o;
+    }
+
+#ifdef ASSIMP_IFC_TEST
+
+    // evaluate *all* entities in the file. this is a power test for the loader
+    void EvaluateAll() {
+        for (ObjectMap::value_type &e : objects) {
+            **e.second;
+        }
+        ai_assert(evaluated_count == objects.size());
+    }
+
+#endif
+
+private:
+    // full access only offered to close friends - they should
+    // use the provided getters rather than messing around with
+    // the members directly.
+    LineSplitter &GetSplitter() {
+        return splitter;
+    }
+
+    void InternInsert(const LazyObject *lz) {
+        objects[lz->GetID()] = lz;
+
+        const ObjectMapByType::iterator it = objects_bytype.find(lz->type);
+        if (it != objects_bytype.end()) {
+            (*it).second.insert(lz);
+        }
+    }
+
+    void SetSchema(const EXPRESS::ConversionSchema &_schema) {
+        schema = &_schema;
+    }
+
+    void SetTypesToTrack(const char *const *types, size_t N) {
+        for (size_t i = 0; i < N; ++i) {
+            objects_bytype[types[i]] = ObjectSet();
+        }
+    }
+
+    void SetInverseIndicesToTrack(const char *const *types, size_t N) {
+        for (size_t i = 0; i < N; ++i) {
+            const char *const sz = schema->GetStaticStringForToken(types[i]);
+            ai_assert(sz);
+            inv_whitelist.insert(sz);
+        }
+    }
+
+    HeaderInfo &GetHeader() {
+        return header;
+    }
+
+    void MarkRef(uint64_t who, uint64_t by_whom) {
+        refs.insert(std::make_pair(who, by_whom));
+    }
+
+private:
+    HeaderInfo header;
+    ObjectMap objects;
+    ObjectMapByType objects_bytype;
+    RefMap refs;
+    InverseWhitelist inv_whitelist;
+    std::shared_ptr<StreamReaderLE> reader;
+    LineSplitter splitter;
+    uint64_t evaluated_count;
+    const EXPRESS::ConversionSchema *schema;
+};
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif // _MSC_VER
+
+} // namespace STEP
+} // namespace Assimp
+
+#endif // INCLUDED_AI_STEPFILE_H