assimp/code/BlenderDNA.inl

/*
Open Asset Import Library (assimp)
----------------------------------------------------------------------

Copyright (c) 2006-2018, assimp team


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  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
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  contributors may be used to endorse or promote products
  derived from this software without specific prior
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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*/

/** @file  BlenderDNA.inl
 *  @brief Blender `DNA` (file format specification embedded in
 *    blend file itself) loader.
 */
#ifndef INCLUDED_AI_BLEND_DNA_INL
#define INCLUDED_AI_BLEND_DNA_INL

#include <memory>
#include <assimp/TinyFormatter.h>

namespace Assimp {
namespace Blender {

//--------------------------------------------------------------------------------
const Field& Structure :: operator [] (const std::string& ss) const
{
    std::map<std::string, size_t>::const_iterator it = indices.find(ss);
    if (it == indices.end()) {
        throw Error((Formatter::format(),
            "BlendDNA: Did not find a field named `",ss,"` in structure `",name,"`"
            ));
    }

    return fields[(*it).second];
}

//--------------------------------------------------------------------------------
const Field* Structure :: Get (const std::string& ss) const
{
    std::map<std::string, size_t>::const_iterator it = indices.find(ss);
    return it == indices.end() ? NULL : &fields[(*it).second];
}

//--------------------------------------------------------------------------------
const Field& Structure :: operator [] (const size_t i) const
{
    if (i >= fields.size()) {
        throw Error((Formatter::format(),
            "BlendDNA: There is no field with index `",i,"` in structure `",name,"`"
            ));
    }

    return fields[i];
}

//--------------------------------------------------------------------------------
template <typename T> std::shared_ptr<ElemBase> Structure :: Allocate() const
{
    return std::shared_ptr<T>(new T());
}

//--------------------------------------------------------------------------------
template <typename T> void Structure :: Convert(
    std::shared_ptr<ElemBase> in,
    const FileDatabase& db) const
{
    Convert<T> (*static_cast<T*> ( in.get() ),db);
}

//--------------------------------------------------------------------------------
template <int error_policy, typename T, size_t M>
void Structure :: ReadFieldArray(T (& out)[M], const char* name, const FileDatabase& db) const
{
    const StreamReaderAny::pos old = db.reader->GetCurrentPos();
    try {
        const Field& f = (*this)[name];
        const Structure& s = db.dna[f.type];

        // is the input actually an array?
        if (!(f.flags & FieldFlag_Array)) {
            throw Error((Formatter::format(),"Field `",name,"` of structure `",
                this->name,"` ought to be an array of size ",M
                ));
        }

        db.reader->IncPtr(f.offset);

        // size conversions are always allowed, regardless of error_policy
        unsigned int i = 0;
        for(; i < std::min(f.array_sizes[0],M); ++i) {
            s.Convert(out[i],db);
        }
        for(; i < M; ++i) {
            _defaultInitializer<ErrorPolicy_Igno>()(out[i]);
        }
    }
    catch (const Error& e) {
        _defaultInitializer<error_policy>()(out,e.what());
    }

    // and recover the previous stream position
    db.reader->SetCurrentPos(old);

#ifndef ASSIMP_BUILD_BLENDER_NO_STATS
    ++db.stats().fields_read;
#endif
}

//--------------------------------------------------------------------------------
template <int error_policy, typename T, size_t M, size_t N>
void Structure :: ReadFieldArray2(T (& out)[M][N], const char* name, const FileDatabase& db) const
{
    const StreamReaderAny::pos old = db.reader->GetCurrentPos();
    try {
        const Field& f = (*this)[name];
        const Structure& s = db.dna[f.type];

        // is the input actually an array?
        if (!(f.flags & FieldFlag_Array)) {
            throw Error((Formatter::format(),"Field `",name,"` of structure `",
                this->name,"` ought to be an array of size ",M,"*",N
                ));
        }

        db.reader->IncPtr(f.offset);

        // size conversions are always allowed, regardless of error_policy
        unsigned int i = 0;
        for(; i < std::min(f.array_sizes[0],M); ++i) {
            unsigned int j = 0;
            for(; j < std::min(f.array_sizes[1],N); ++j) {
                s.Convert(out[i][j],db);
            }
            for(; j < N; ++j) {
                _defaultInitializer<ErrorPolicy_Igno>()(out[i][j]);
            }
        }
        for(; i < M; ++i) {
            _defaultInitializer<ErrorPolicy_Igno>()(out[i]);
        }
    }
    catch (const Error& e) {
        _defaultInitializer<error_policy>()(out,e.what());
    }

    // and recover the previous stream position
    db.reader->SetCurrentPos(old);

#ifndef ASSIMP_BUILD_BLENDER_NO_STATS
    ++db.stats().fields_read;
#endif
}

//--------------------------------------------------------------------------------
template <int error_policy, template <typename> class TOUT, typename T>
bool Structure :: ReadFieldPtr(TOUT<T>& out, const char* name, const FileDatabase& db,
    bool non_recursive /*= false*/) const
{
    const StreamReaderAny::pos old = db.reader->GetCurrentPos();
    Pointer ptrval;
    const Field* f;
    try {
        f = &(*this)[name];

        // sanity check, should never happen if the genblenddna script is right
        if (!(f->flags & FieldFlag_Pointer)) {
            throw Error((Formatter::format(),"Field `",name,"` of structure `",
                this->name,"` ought to be a pointer"));
        }

        db.reader->IncPtr(f->offset);
        Convert(ptrval,db);
        // actually it is meaningless on which Structure the Convert is called
        // because the `Pointer` argument triggers a special implementation.
    }
    catch (const Error& e) {
        _defaultInitializer<error_policy>()(out,e.what());

        out.reset();
        return false;
    }

    // resolve the pointer and load the corresponding structure
    const bool res = ResolvePointer(out,ptrval,db,*f, non_recursive);

    if(!non_recursive) {
        // and recover the previous stream position
        db.reader->SetCurrentPos(old);
    }

#ifndef ASSIMP_BUILD_BLENDER_NO_STATS
    ++db.stats().fields_read;
#endif

    return res;
}

//--------------------------------------------------------------------------------
template <int error_policy, template <typename> class TOUT, typename T, size_t N>
bool Structure :: ReadFieldPtr(TOUT<T> (&out)[N], const char* name,
    const FileDatabase& db) const
{
    // XXX see if we can reduce this to call to the 'normal' ReadFieldPtr
    const StreamReaderAny::pos old = db.reader->GetCurrentPos();
    Pointer ptrval[N];
    const Field* f;
    try {
        f = &(*this)[name];

        // sanity check, should never happen if the genblenddna script is right
        if ((FieldFlag_Pointer|FieldFlag_Pointer) != (f->flags & (FieldFlag_Pointer|FieldFlag_Pointer))) {
            throw Error((Formatter::format(),"Field `",name,"` of structure `",
                this->name,"` ought to be a pointer AND an array"));
        }

        db.reader->IncPtr(f->offset);

        size_t i = 0;
        for(; i < std::min(f->array_sizes[0],N); ++i) {
            Convert(ptrval[i],db);
        }
        for(; i < N; ++i) {
            _defaultInitializer<ErrorPolicy_Igno>()(ptrval[i]);
        }

        // actually it is meaningless on which Structure the Convert is called
        // because the `Pointer` argument triggers a special implementation.
    }
    catch (const Error& e) {
        _defaultInitializer<error_policy>()(out,e.what());
        for(size_t i = 0; i < N; ++i) {
            out[i].reset();
        }
        return false;
    }

    bool res = true;
    for(size_t i = 0; i < N; ++i) {
        // resolve the pointer and load the corresponding structure
        res = ResolvePointer(out[i],ptrval[i],db,*f) && res;
    }

    // and recover the previous stream position
    db.reader->SetCurrentPos(old);

#ifndef ASSIMP_BUILD_BLENDER_NO_STATS
    ++db.stats().fields_read;
#endif
    return res;
}

//--------------------------------------------------------------------------------
template <int error_policy, typename T>
void Structure :: ReadField(T& out, const char* name, const FileDatabase& db) const
{
    const StreamReaderAny::pos old = db.reader->GetCurrentPos();
    try {
        const Field& f = (*this)[name];
        // find the structure definition pertaining to this field
        const Structure& s = db.dna[f.type];

        db.reader->IncPtr(f.offset);
        s.Convert(out,db);
    }
    catch (const Error& e) {
        _defaultInitializer<error_policy>()(out,e.what());
    }

    // and recover the previous stream position
    db.reader->SetCurrentPos(old);

#ifndef ASSIMP_BUILD_BLENDER_NO_STATS
    ++db.stats().fields_read;
#endif
}


//--------------------------------------------------------------------------------
// field parsing for raw untyped data (like CustomDataLayer.data)
template <int error_policy>
bool Structure::ReadCustomDataPtr(std::shared_ptr<ElemBase>&out, int cdtype, const char* name, const FileDatabase& db) const {

	const StreamReaderAny::pos old = db.reader->GetCurrentPos();

	Pointer ptrval;
	const Field* f;
	try	{
		f = &(*this)[name];

		// sanity check, should never happen if the genblenddna script is right
		if (!(f->flags & FieldFlag_Pointer)) {
			throw Error((Formatter::format(), "Field `", name, "` of structure `",
				this->name, "` ought to be a pointer"));
		}

		db.reader->IncPtr(f->offset);
		Convert(ptrval, db);
		// actually it is meaningless on which Structure the Convert is called
		// because the `Pointer` argument triggers a special implementation.
	}
	catch (const Error& e) {
		_defaultInitializer<error_policy>()(out, e.what());
		out.reset();
	}

	bool readOk = true;
	if (ptrval.val)	{
		// get block for ptr
		const FileBlockHead* block = LocateFileBlockForAddress(ptrval, db);
		db.reader->SetCurrentPos(block->start + static_cast<size_t>((ptrval.val - block->address.val)));
		// read block->num instances of given type to out
		readOk = readCustomData(out, cdtype, block->num, db);
	}

	// and recover the previous stream position
	db.reader->SetCurrentPos(old);

#ifndef ASSIMP_BUILD_BLENDER_NO_STATS
	++db.stats().fields_read;
#endif

	return readOk;
}

//--------------------------------------------------------------------------------
template <int error_policy, template <typename> class TOUT, typename T>
bool Structure::ReadFieldPtrVector(vector<TOUT<T>>&out, const char* name, const FileDatabase& db) const {
	out.clear();

	const StreamReaderAny::pos old = db.reader->GetCurrentPos();

	Pointer ptrval;
	const Field* f;
	try	{
		f = &(*this)[name];

		// sanity check, should never happen if the genblenddna script is right
		if (!(f->flags & FieldFlag_Pointer)) {
			throw Error((Formatter::format(), "Field `", name, "` of structure `",
				this->name, "` ought to be a pointer"));
		}

		db.reader->IncPtr(f->offset);
		Convert(ptrval, db);
		// actually it is meaningless on which Structure the Convert is called
		// because the `Pointer` argument triggers a special implementation.
	}
	catch (const Error& e) {
		_defaultInitializer<error_policy>()(out, e.what());
		out.clear();
		return false;
	}


	if (ptrval.val)	{
		// find the file block the pointer is pointing to
		const FileBlockHead* block = LocateFileBlockForAddress(ptrval, db);
		db.reader->SetCurrentPos(block->start + static_cast<size_t>((ptrval.val - block->address.val)));
		// FIXME: basically, this could cause problems with 64 bit pointers on 32 bit systems.
		// I really ought to improve StreamReader to work with 64 bit indices exclusively.

		const Structure& s = db.dna[f->type];
		for (size_t i = 0; i < block->num; ++i)	{
			TOUT<T> p(new T);
			s.Convert(*p, db);
			out.push_back(p);
		}
	}

	db.reader->SetCurrentPos(old);

#ifndef ASSIMP_BUILD_BLENDER_NO_STATS
	++db.stats().fields_read;
#endif

	return true;
}


//--------------------------------------------------------------------------------
template <template <typename> class TOUT, typename T>
bool Structure :: ResolvePointer(TOUT<T>& out, const Pointer & ptrval, const FileDatabase& db,
    const Field& f,
    bool non_recursive /*= false*/) const
{
    out.reset(); // ensure null pointers work
    if (!ptrval.val) {
        return false;
    }
    const Structure& s = db.dna[f.type];
    // find the file block the pointer is pointing to
    const FileBlockHead* block = LocateFileBlockForAddress(ptrval,db);

    // also determine the target type from the block header
    // and check if it matches the type which we expect.
    const Structure& ss = db.dna[block->dna_index];
    if (ss != s) {
        throw Error((Formatter::format(),"Expected target to be of type `",s.name,
            "` but seemingly it is a `",ss.name,"` instead"
            ));
    }

    // try to retrieve the object from the cache
    db.cache(out).get(s,out,ptrval);
    if (out) {
        return true;
    }

    // seek to this location, but save the previous stream pointer.
    const StreamReaderAny::pos pold = db.reader->GetCurrentPos();
    db.reader->SetCurrentPos(block->start+ static_cast<size_t>((ptrval.val - block->address.val) ));
    // FIXME: basically, this could cause problems with 64 bit pointers on 32 bit systems.
    // I really ought to improve StreamReader to work with 64 bit indices exclusively.

    // continue conversion after allocating the required storage
    size_t num = block->size / ss.size;
    T* o = _allocate(out,num);

    // cache the object before we convert it to avoid cyclic recursion.
    db.cache(out).set(s,out,ptrval);

    // if the non_recursive flag is set, we don't do anything but leave
    // the cursor at the correct position to resolve the object.
    if (!non_recursive) {
        for (size_t i = 0; i < num; ++i,++o) {
            s.Convert(*o,db);
        }

        db.reader->SetCurrentPos(pold);
    }

#ifndef ASSIMP_BUILD_BLENDER_NO_STATS
    if(out) {
        ++db.stats().pointers_resolved;
    }
#endif
    return false;
}


//--------------------------------------------------------------------------------
inline bool Structure :: ResolvePointer( std::shared_ptr< FileOffset >& out, const Pointer & ptrval,
    const FileDatabase& db,
    const Field&,
    bool) const
{
    // Currently used exclusively by PackedFile::data to represent
    // a simple offset into the mapped BLEND file.
    out.reset();
    if (!ptrval.val) {
        return false;
    }

    // find the file block the pointer is pointing to
    const FileBlockHead* block = LocateFileBlockForAddress(ptrval,db);

    out =  std::shared_ptr< FileOffset > (new FileOffset());
    out->val = block->start+ static_cast<size_t>((ptrval.val - block->address.val) );
    return false;
}

//--------------------------------------------------------------------------------
template <template <typename> class TOUT, typename T>
bool Structure :: ResolvePointer(vector< TOUT<T> >& out, const Pointer & ptrval,
    const FileDatabase& db,
    const Field& f,
    bool) const
{
    // This is a function overload, not a template specialization. According to
    // the partial ordering rules, it should be selected by the compiler
    // for array-of-pointer inputs, i.e. Object::mats.

    out.reset();
    if (!ptrval.val) {
        return false;
    }

    // find the file block the pointer is pointing to
    const FileBlockHead* block = LocateFileBlockForAddress(ptrval,db);
    const size_t num = block->size / (db.i64bit?8:4);

    // keep the old stream position
    const StreamReaderAny::pos pold = db.reader->GetCurrentPos();
    db.reader->SetCurrentPos(block->start+ static_cast<size_t>((ptrval.val - block->address.val) ));

    bool res = false;
    // allocate raw storage for the array
    out.resize(num);
    for (size_t i = 0; i< num; ++i) {
        Pointer val;
        Convert(val,db);

        // and resolve the pointees
        res = ResolvePointer(out[i],val,db,f) && res;
    }

    db.reader->SetCurrentPos(pold);
    return res;
}

//--------------------------------------------------------------------------------
template <> bool Structure :: ResolvePointer<std::shared_ptr,ElemBase>(std::shared_ptr<ElemBase>& out,
    const Pointer & ptrval,
    const FileDatabase& db,
    const Field&,
    bool
) const
{
    // Special case when the data type needs to be determined at runtime.
    // Less secure than in the `strongly-typed` case.

    out.reset();
    if (!ptrval.val) {
        return false;
    }

    // find the file block the pointer is pointing to
    const FileBlockHead* block = LocateFileBlockForAddress(ptrval,db);

    // determine the target type from the block header
    const Structure& s = db.dna[block->dna_index];

    // try to retrieve the object from the cache
    db.cache(out).get(s,out,ptrval);
    if (out) {
        return true;
    }

    // seek to this location, but save the previous stream pointer.
    const StreamReaderAny::pos pold = db.reader->GetCurrentPos();
    db.reader->SetCurrentPos(block->start+ static_cast<size_t>((ptrval.val - block->address.val) ));
    // FIXME: basically, this could cause problems with 64 bit pointers on 32 bit systems.
    // I really ought to improve StreamReader to work with 64 bit indices exclusively.

    // continue conversion after allocating the required storage
    DNA::FactoryPair builders = db.dna.GetBlobToStructureConverter(s,db);
    if (!builders.first) {
        // this might happen if DNA::RegisterConverters hasn't been called so far
        // or if the target type is not contained in `our` DNA.
        out.reset();
        ASSIMP_LOG_WARN_F( "Failed to find a converter for the `",s.name,"` structure" );
        return false;
    }

    // allocate the object hull
    out = (s.*builders.first)();

    // cache the object immediately to prevent infinite recursion in a
    // circular list with a single element (i.e. a self-referencing element).
    db.cache(out).set(s,out,ptrval);

    // and do the actual conversion
    (s.*builders.second)(out,db);
    db.reader->SetCurrentPos(pold);

    // store a pointer to the name string of the actual type
    // in the object itself. This allows the conversion code
    // to perform additional type checking.
    out->dna_type = s.name.c_str();


#ifndef ASSIMP_BUILD_BLENDER_NO_STATS
    ++db.stats().pointers_resolved;
#endif
    return false;
}

//--------------------------------------------------------------------------------
const FileBlockHead* Structure :: LocateFileBlockForAddress(const Pointer & ptrval, const FileDatabase& db) const
{
    // the file blocks appear in list sorted by
    // with ascending base addresses so we can run a
    // binary search to locate the pointer quickly.

    // NOTE: Blender seems to distinguish between side-by-side
    // data (stored in the same data block) and far pointers,
    // which are only used for structures starting with an ID.
    // We don't need to make this distinction, our algorithm
    // works regardless where the data is stored.
    vector<FileBlockHead>::const_iterator it = std::lower_bound(db.entries.begin(),db.entries.end(),ptrval);
    if (it == db.entries.end()) {
        // this is crucial, pointers may not be invalid.
        // this is either a corrupted file or an attempted attack.
        throw DeadlyImportError((Formatter::format(),"Failure resolving pointer 0x",
            std::hex,ptrval.val,", no file block falls into this address range"
            ));
    }
    if (ptrval.val >= (*it).address.val + (*it).size) {
        throw DeadlyImportError((Formatter::format(),"Failure resolving pointer 0x",
            std::hex,ptrval.val,", nearest file block starting at 0x",
            (*it).address.val," ends at 0x",
            (*it).address.val + (*it).size
            ));
    }
    return &*it;
}

// ------------------------------------------------------------------------------------------------
// NOTE: The MSVC debugger keeps showing up this annoying `a cast to a smaller data type has
// caused a loss of data`-warning. Avoid this warning by a masking with an appropriate bitmask.

template <typename T> struct signless;
template <> struct signless<char> {typedef unsigned char type;};
template <> struct signless<short> {typedef unsigned short type;};
template <> struct signless<int> {typedef unsigned int type;};
template <> struct signless<unsigned char> { typedef unsigned char type; };
template <typename T>
struct static_cast_silent {
    template <typename V>
    T operator()(V in) {
        return static_cast<T>(in & static_cast<typename signless<T>::type>(-1));
    }
};

template <> struct static_cast_silent<float> {
    template <typename V> float  operator()(V in) {
        return static_cast<float> (in);
    }
};

template <> struct static_cast_silent<double> {
    template <typename V> double operator()(V in) {
        return static_cast<double>(in);
    }
};

// ------------------------------------------------------------------------------------------------
template <typename T> inline void ConvertDispatcher(T& out, const Structure& in,const FileDatabase& db)
{
    if (in.name == "int") {
        out = static_cast_silent<T>()(db.reader->GetU4());
    }
    else if (in.name == "short") {
        out = static_cast_silent<T>()(db.reader->GetU2());
    }
    else if (in.name == "char") {
        out = static_cast_silent<T>()(db.reader->GetU1());
    }
    else if (in.name == "float") {
        out = static_cast<T>(db.reader->GetF4());
    }
    else if (in.name == "double") {
        out = static_cast<T>(db.reader->GetF8());
    }
    else {
        throw DeadlyImportError("Unknown source for conversion to primitive data type: "+in.name);
    }
}

// ------------------------------------------------------------------------------------------------
template <> inline void Structure :: Convert<int>    (int& dest,const FileDatabase& db) const
{
    ConvertDispatcher(dest,*this,db);
}

// ------------------------------------------------------------------------------------------------
template<> inline void Structure :: Convert<short>  (short& dest,const FileDatabase& db) const
{
    // automatic rescaling from short to float and vice versa (seems to be used by normals)
    if (name == "float") {
        float f = db.reader->GetF4();
        if ( f > 1.0f )
            f = 1.0f;
        dest = static_cast<short>( f * 32767.f);
        //db.reader->IncPtr(-4);
        return;
    }
    else if (name == "double") {
        dest = static_cast<short>(db.reader->GetF8() * 32767.);
        //db.reader->IncPtr(-8);
        return;
    }
    ConvertDispatcher(dest,*this,db);
}

// ------------------------------------------------------------------------------------------------
template <> inline void Structure :: Convert<char>   (char& dest,const FileDatabase& db) const
{
    // automatic rescaling from char to float and vice versa (seems useful for RGB colors)
    if (name == "float") {
        dest = static_cast<char>(db.reader->GetF4() * 255.f);
        return;
    }
    else if (name == "double") {
        dest = static_cast<char>(db.reader->GetF8() * 255.f);
        return;
    }
    ConvertDispatcher(dest,*this,db);
}

// ------------------------------------------------------------------------------------------------
template <> inline void Structure::Convert<unsigned char>(unsigned char& dest, const FileDatabase& db) const
{
	// automatic rescaling from char to float and vice versa (seems useful for RGB colors)
	if (name == "float") {
		dest = static_cast<unsigned char>(db.reader->GetF4() * 255.f);
		return;
	}
	else if (name == "double") {
		dest = static_cast<unsigned char>(db.reader->GetF8() * 255.f);
		return;
	}
	ConvertDispatcher(dest, *this, db);
}


// ------------------------------------------------------------------------------------------------
template <> inline void Structure :: Convert<float>  (float& dest,const FileDatabase& db) const
{
    // automatic rescaling from char to float and vice versa (seems useful for RGB colors)
    if (name == "char") {
        dest = db.reader->GetI1() / 255.f;
        return;
    }
    // automatic rescaling from short to float and vice versa (used by normals)
    else if (name == "short") {
        dest = db.reader->GetI2() / 32767.f;
        return;
    }
    ConvertDispatcher(dest,*this,db);
}

// ------------------------------------------------------------------------------------------------
template <> inline void Structure :: Convert<double> (double& dest,const FileDatabase& db) const
{
    if (name == "char") {
        dest = db.reader->GetI1() / 255.;
        return;
    }
    else if (name == "short") {
        dest = db.reader->GetI2() / 32767.;
        return;
    }
    ConvertDispatcher(dest,*this,db);
}

// ------------------------------------------------------------------------------------------------
template <> inline void Structure :: Convert<Pointer> (Pointer& dest,const FileDatabase& db) const
{
    if (db.i64bit) {
        dest.val = db.reader->GetU8();
        //db.reader->IncPtr(-8);
        return;
    }
    dest.val = db.reader->GetU4();
    //db.reader->IncPtr(-4);
}

//--------------------------------------------------------------------------------
const Structure& DNA :: operator [] (const std::string& ss) const
{
    std::map<std::string, size_t>::const_iterator it = indices.find(ss);
    if (it == indices.end()) {
        throw Error((Formatter::format(),
            "BlendDNA: Did not find a structure named `",ss,"`"
            ));
    }

    return structures[(*it).second];
}

//--------------------------------------------------------------------------------
const Structure* DNA :: Get (const std::string& ss) const
{
    std::map<std::string, size_t>::const_iterator it = indices.find(ss);
    return it == indices.end() ? NULL : &structures[(*it).second];
}

//--------------------------------------------------------------------------------
const Structure& DNA :: operator [] (const size_t i) const
{
    if (i >= structures.size()) {
        throw Error((Formatter::format(),
            "BlendDNA: There is no structure with index `",i,"`"
            ));
    }

    return structures[i];
}

//--------------------------------------------------------------------------------
template <template <typename> class TOUT> template <typename T> void ObjectCache<TOUT> :: get (
    const Structure& s,
    TOUT<T>& out,
    const Pointer& ptr
) const {

    if(s.cache_idx == static_cast<size_t>(-1)) {
        s.cache_idx = db.next_cache_idx++;
        caches.resize(db.next_cache_idx);
        return;
    }

    typename StructureCache::const_iterator it = caches[s.cache_idx].find(ptr);
    if (it != caches[s.cache_idx].end()) {
        out = std::static_pointer_cast<T>( (*it).second );

#ifndef ASSIMP_BUILD_BLENDER_NO_STATS
        ++db.stats().cache_hits;
#endif
    }
    // otherwise, out remains untouched
}


//--------------------------------------------------------------------------------
template <template <typename> class TOUT> template <typename T> void ObjectCache<TOUT> :: set (
    const Structure& s,
    const TOUT<T>& out,
    const Pointer& ptr
) {
    if(s.cache_idx == static_cast<size_t>(-1)) {
        s.cache_idx = db.next_cache_idx++;
        caches.resize(db.next_cache_idx);
    }
    caches[s.cache_idx][ptr] = std::static_pointer_cast<ElemBase>( out );

#ifndef ASSIMP_BUILD_BLENDER_NO_STATS
    ++db.stats().cached_objects;
#endif
}

}}
#endif