CommonADIOS1IOHandler.cpp

/* Copyright 2017-2021 Fabian Koller, Axel Huebl
 *
 * This file is part of openPMD-api.
 *
 * openPMD-api is free software: you can redistribute it and/or modify
 * it under the terms of of either the GNU General Public License or
 * the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * openPMD-api is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License and the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License
 * and the GNU Lesser General Public License along with openPMD-api.
 * If not, see <http://www.gnu.org/licenses/>.
 */

#include "openPMD/IO/ADIOS/CommonADIOS1IOHandler.hpp"

#if openPMD_HAVE_ADIOS1

#include "openPMD/auxiliary/JSON_internal.hpp"
#include "openPMD/Error.hpp"
#include "openPMD/IO/ADIOS/ADIOS1IOHandlerImpl.hpp"
#include "openPMD/IO/ADIOS/ParallelADIOS1IOHandlerImpl.hpp"

#include <adios.h>
#include <algorithm>
#include <complex>
#include <cstring>
#include <iostream>
#include <map>
#include <memory>
#include <string>
#include <string>
#include <tuple>

namespace openPMD
{

#if openPMD_USE_VERIFY
#    define VERIFY(CONDITION, TEXT) { if(!(CONDITION)) throw std::runtime_error((TEXT)); }
#else
#    define VERIFY(CONDITION, TEXT) do{ (void)sizeof(CONDITION); } while( 0 )
#endif

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::close(int64_t fd)
{
    int status;
    status = adios_close(fd);
    VERIFY(status == err_no_error, "[ADIOS1] Internal error: Failed to close ADIOS file (open_write)");
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::close(ADIOS_FILE* f)
{
    int status;
    status = adios_read_close(f);
    VERIFY(status == err_no_error, "[ADIOS1] Internal error: Failed to close ADIOS file (open_read)");
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::flush_attribute(int64_t group, std::string const& name, Attribute const& att)
{
    auto dtype = att.dtype;
    // https://github.com/ComputationalRadiationPhysics/picongpu/pull/1756
    if( dtype == Datatype::BOOL )
        dtype = Datatype::UCHAR;

    int nelems = 0;
    switch( dtype )
    {
        using DT = Datatype;
        case DT::VEC_CHAR:
            nelems = att.get< std::vector< char > >().size();
            break;
        case DT::VEC_SHORT:
            nelems = att.get< std::vector< short > >().size();
            break;
        case DT::VEC_INT:
            nelems = att.get< std::vector< int > >().size();
            break;
        case DT::VEC_LONG:
            nelems = att.get< std::vector< long > >().size();
            break;
        case DT::VEC_LONGLONG:
            nelems = att.get< std::vector< long long > >().size();
            break;
        case DT::VEC_UCHAR:
            nelems = att.get< std::vector< unsigned char > >().size();
            break;
        case DT::VEC_USHORT:
            nelems = att.get< std::vector< unsigned short > >().size();
            break;
        case DT::VEC_UINT:
            nelems = att.get< std::vector< unsigned int > >().size();
            break;
        case DT::VEC_ULONG:
            nelems = att.get< std::vector< unsigned long > >().size();
            break;
        case DT::VEC_ULONGLONG:
            nelems = att.get< std::vector< unsigned long long > >().size();
            break;
        case DT::VEC_FLOAT:
            nelems = att.get< std::vector< float > >().size();
            break;
        case DT::VEC_DOUBLE:
            nelems = att.get< std::vector< double > >().size();
            break;
        case DT::VEC_LONG_DOUBLE:
            nelems = att.get< std::vector< long double > >().size();
            break;
        case DT::VEC_STRING:
            nelems = att.get< std::vector< std::string > >().size();
            break;
        case DT::ARR_DBL_7:
            nelems = 7;
            break;
        case DT::UNDEFINED:
            throw std::runtime_error("[ADIOS1] Unknown Attribute datatype (ADIOS1 Attribute flush)");
        default:
            nelems = 1;
    }

    auto values = auxiliary::allocatePtr(dtype, nelems);
    switch( att.dtype )
    {
        using DT = Datatype;
        case DT::CHAR:
        {
            auto ptr = reinterpret_cast< char* >(values.get());
            *ptr = att.get< char >();
            break;
        }
        case DT::UCHAR:
        {
            auto ptr = reinterpret_cast< unsigned char* >(values.get());
            *ptr = att.get< unsigned char >();
            break;
        }
        case DT::SHORT:
        {
            auto ptr = reinterpret_cast< short* >(values.get());
            *ptr = att.get< short >();
            break;
        }
        case DT::INT:
        {
            auto ptr = reinterpret_cast< int* >(values.get());
            *ptr = att.get< int >();
            break;
        }
        case DT::LONG:
        {
            auto ptr = reinterpret_cast< long* >(values.get());
            *ptr = att.get< long >();
            break;
        }
        case DT::LONGLONG:
        {
            auto ptr = reinterpret_cast< long long* >(values.get());
            *ptr = att.get< long long >();
            break;
        }
        case DT::USHORT:
        {
            auto ptr = reinterpret_cast< unsigned short* >(values.get());
            *ptr = att.get< unsigned short >();
            break;
        }
        case DT::UINT:
        {
            auto ptr = reinterpret_cast< unsigned int* >(values.get());
            *ptr = att.get< unsigned int >();
            break;
        }
        case DT::ULONG:
        {
            auto ptr = reinterpret_cast< unsigned long* >(values.get());
            *ptr = att.get< unsigned long >();
            break;
        }
        case DT::ULONGLONG:
        {
            auto ptr = reinterpret_cast< unsigned long long* >(values.get());
            *ptr = att.get< unsigned long long >();
            break;
        }
        case DT::FLOAT:
        {
            auto ptr = reinterpret_cast< float* >(values.get());
            *ptr = att.get< float >();
            break;
        }
        case DT::DOUBLE:
        {
            auto ptr = reinterpret_cast< double* >(values.get());
            *ptr = att.get< double >();
            break;
        }
        case DT::LONG_DOUBLE:
        {
            auto ptr = reinterpret_cast< long double* >(values.get());
            *ptr = att.get< long double >();
            break;
        }
        case DT::CFLOAT:
        {
            auto ptr = reinterpret_cast< std::complex< float >* >(values.get());
            *ptr = att.get< std::complex< float > >();
            break;
        }
        case DT::CDOUBLE:
        {
            auto ptr = reinterpret_cast< std::complex< double >* >(values.get());
            *ptr = att.get< std::complex< double > >();
            break;
        }
        case DT::CLONG_DOUBLE:
        {
            throw std::runtime_error("[ADIOS1] Unknown Attribute datatype (CLONG_DOUBLE)");
            break;
        }
        case DT::STRING:
        {
            auto const & v = att.get< std::string >();
            values = auxiliary::allocatePtr(Datatype::CHAR, v.length() + 1u);
            strcpy((char*)values.get(), v.c_str());
            break;
        }
        case DT::VEC_CHAR:
        {
            auto ptr = reinterpret_cast< char* >(values.get());
            auto const& vec = att.get< std::vector< char > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_SHORT:
        {
            auto ptr = reinterpret_cast< short* >(values.get());
            auto const& vec = att.get< std::vector< short > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_INT:
        {
            auto ptr = reinterpret_cast< int* >(values.get());
            auto const& vec = att.get< std::vector< int > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_LONG:
        {
            auto ptr = reinterpret_cast< long* >(values.get());
            auto const& vec = att.get< std::vector< long > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_LONGLONG:
        {
            auto ptr = reinterpret_cast< long long* >(values.get());
            auto const& vec = att.get< std::vector< long long > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_UCHAR:
        {
            auto ptr = reinterpret_cast< unsigned char* >(values.get());
            auto const& vec = att.get< std::vector< unsigned char > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_USHORT:
        {
            auto ptr = reinterpret_cast< unsigned short* >(values.get());
            auto const& vec = att.get< std::vector< unsigned short > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_UINT:
        {
            auto ptr = reinterpret_cast< unsigned int* >(values.get());
            auto const& vec = att.get< std::vector< unsigned int > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_ULONG:
        {
            auto ptr = reinterpret_cast< unsigned long* >(values.get());
            auto const& vec = att.get< std::vector< unsigned long > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_ULONGLONG:
        {
            auto ptr = reinterpret_cast< unsigned long long* >(values.get());
            auto const& vec = att.get< std::vector< unsigned long long > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_FLOAT:
        {
            auto ptr = reinterpret_cast< float* >(values.get());
            auto const& vec = att.get< std::vector< float > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_DOUBLE:
        {
            auto ptr = reinterpret_cast< double* >(values.get());
            auto const& vec = att.get< std::vector< double > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        case DT::VEC_LONG_DOUBLE:
        {
            auto ptr = reinterpret_cast< long double* >(values.get());
            auto const& vec = att.get< std::vector< long double > >();
            for( size_t i = 0; i < vec.size(); ++i )
                ptr[i] = vec[i];
            break;
        }
        /* not supported by ADIOS 1.13.1:
         *   https://github.com/ornladios/ADIOS/issues/212
         */
        case DT::VEC_CFLOAT:
        case DT::VEC_CDOUBLE:
        case DT::VEC_CLONG_DOUBLE:
        {
            throw std::runtime_error("[ADIOS1] Arrays of complex attributes are not supported");
            break;
        }
        case DT::VEC_STRING:
        {
            auto ptr = reinterpret_cast< char** >(values.get());
            auto const& vec = att.get< std::vector< std::string > >();
            for( size_t i = 0; i < vec.size(); ++i )
            {
                size_t size = vec[i].size() + 1;
                ptr[i] = new char[size];
                strncpy(ptr[i], vec[i].c_str(), size);
            }
            break;
        }
        case DT::ARR_DBL_7:
        {
            auto ptr = reinterpret_cast< double* >(values.get());
            auto const& arr = att.get< std::array< double, 7> >();
            for( size_t i = 0; i < 7; ++i )
                ptr[i] = arr[i];
            break;
        }
        case DT::BOOL:
        {
            auto ptr = reinterpret_cast< unsigned char* >(values.get());
            *ptr = static_cast< unsigned char >(att.get< bool >());
            break;
        }
        case DT::UNDEFINED:
            throw std::runtime_error("[ADIOS1] Unknown Attribute datatype (ADIOS1 Attribute flush)");
        default:
            throw std::runtime_error("[ADIOS1] Datatype not implemented in ADIOS IO");
    }

    int status;
    status = adios_define_attribute_byvalue(group,
                                            name.c_str(),
                                            "",
                                            getBP1DataType(att.dtype),
                                            nelems,
                                            values.get());
    VERIFY(status == err_no_error, "[ADIOS1] Internal error: Failed to define ADIOS attribute by value");

    if( att.dtype == Datatype::VEC_STRING )
    {
        auto ptr = reinterpret_cast< char** >(values.get());
        for( int i = 0; i < nelems; ++i )
            delete[] ptr[i];
    }
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::createFile(Writable* writable,
                                Parameter< Operation::CREATE_FILE > const& parameters)
{
    if( m_handler->m_backendAccess == Access::READ_ONLY )
        throw std::runtime_error("[ADIOS1] Creating a file in read-only mode is not possible.");

    if( !writable->written )
    {
        if( !auxiliary::directory_exists(m_handler->directory) )
        {
            bool success = auxiliary::create_directories(m_handler->directory);
            VERIFY(success, "[ADIOS1] Internal error: Failed to create directories during ADIOS file creation");
        }

        std::string name = m_handler->directory + parameters.name;
        if( !auxiliary::ends_with(name, ".bp") )
            name += ".bp";

        writable->written = true;
        writable->abstractFilePosition = std::make_shared< ADIOS1FilePosition >("/");

        m_filePaths[writable] = std::make_shared< std::string >(name);

        /* our control flow allows for more than one open file handle
         * if multiple files are opened with the same group, data might be lost */

        /* defer actually opening the file handle until the first Operation::WRITE_DATASET occurs */
        m_existsOnDisk[m_filePaths[writable]] = false;

        GetFileHandle(writable);
    }
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::createPath(Writable* writable,
                                Parameter< Operation::CREATE_PATH > const& parameters)
{
    if( m_handler->m_backendAccess == Access::READ_ONLY )
        throw std::runtime_error("[ADIOS1] Creating a path in a file opened as read only is not possible.");

    if( !writable->written )
    {
        /* Sanitize path */
        std::string path = parameters.path;
        if( auxiliary::starts_with(path, '/') )
            path = auxiliary::replace_first(path, "/", "");
        if( !auxiliary::ends_with(path, '/') )
            path += '/';

        /* ADIOS has no concept for explicitly creating paths.
         * They are implicitly created with the paths of variables/attributes. */

        writable->written = true;
        writable->abstractFilePosition = std::make_shared< ADIOS1FilePosition >(path);

        Writable* position;
        if( writable->parent )
            position = writable->parent;
        else
            position = writable; /* root does not have a parent but might still have to be written */
        auto res = m_filePaths.find(position);

        m_filePaths[writable] = res->second;
    }
}

static auxiliary::Option< std::string > datasetTransform(
    json::TracingJSON config )
{
    using ret_t = auxiliary::Option< std::string >;
    if( !config.json().contains( "dataset" ) )
    {
        return ret_t{};
    }
    config = config[ "dataset" ];
    if( !config.json().contains( "transform" ) )
    {
        return ret_t{};
    }
    config = config[ "transform" ];
    auto maybeRes = json::asStringDynamic( config.json() );
    if( maybeRes.has_value() )
    {
        return std::move( maybeRes.get() );
    }
    else
    {
        throw error::BackendConfigSchema(
            { "adios1", "dataset", "transform" },
            "Key must convertible to type string." );
    }
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::createDataset(Writable* writable,
                                   Parameter< Operation::CREATE_DATASET > const& parameters)
{
    if( m_handler->m_backendAccess == Access::READ_ONLY )
        throw std::runtime_error("[ADIOS1] Creating a dataset in a file opened as read only is not possible.");

    if( !writable->written )
    {
        /* ADIOS variable definitions require the file to be (re-)opened to take effect/not cause errors */
        auto res = m_filePaths.find(writable);
        if( res == m_filePaths.end() )
            res = m_filePaths.find(writable->parent);

        int64_t group = m_groups[res->second];

        /* Sanitize name */
        std::string name = parameters.name;
        if( auxiliary::starts_with(name, '/') )
            name = auxiliary::replace_first(name, "/", "");
        if( auxiliary::ends_with(name, '/') )
            name = auxiliary::replace_last(name, "/", "");

        std::string path = concrete_bp1_file_position(writable) + name;

        size_t ndims = parameters.extent.size();

        std::vector< std::string > chunkSize(ndims, "");
        std::vector< std::string > chunkOffset(ndims, "");
        int64_t id;
        for( size_t i = 0; i < ndims; ++i )
        {
            chunkSize[i] = "/tmp" + path + "_chunkSize" + std::to_string(i);
            id = adios_define_var(group, chunkSize[i].c_str(), "", adios_unsigned_long, "", "", "");
            VERIFY(id != 0, "[ADIOS1] Internal error: Failed to define ADIOS variable during Dataset creation");
            chunkOffset[i] = "/tmp" + path + "_chunkOffset" + std::to_string(i);
            id = adios_define_var(group, chunkOffset[i].c_str(), "", adios_unsigned_long, "", "", "");
            VERIFY(id != 0, "[ADIOS1] Internal error: Failed to define ADIOS variable during Dataset creation");
        }

        std::string chunkSizeParam = auxiliary::join(chunkSize, ",");
        std::string globalSize = getBP1Extent(parameters.extent);
        std::string chunkOffsetParam = auxiliary::join(chunkOffset, ",");
        id = adios_define_var(group,
                              path.c_str(),
                              "",
                              getBP1DataType(parameters.dtype),
                              chunkSizeParam.c_str(),
                              globalSize.c_str(),
                              chunkOffsetParam.c_str());
        VERIFY(id != 0, "[ADIOS1] Internal error: Failed to define ADIOS variable during Dataset creation");

        std::string transform = "";
        {
            json::TracingJSON options = json::parseOptions(
                parameters.options, /* considerFiles = */ false );
            if( options.json().contains( "adios1" ) )
            {
                options = options["adios1"];
                auto maybeTransform = datasetTransform( options );
                if( maybeTransform.has_value() )
                {
                    transform = maybeTransform.get();
                }

                parameters.warnUnusedParameters(
                    options,
                    "ADIOS1",
                    "Warning: parts of the backend configuration for "
                    "ADIOS1 dataset '" + name + "' remain unused:\n" );
            }
        }
        // Fallback: global option
        if( transform.empty() )
        {
            transform = m_defaultTransform;
        }

        if( !transform.empty() )
        {
            int status;
            status = adios_set_transform(id, transform.c_str());
            VERIFY(status == err_no_error, "[ADIOS1] Internal error: Failed to set ADIOS transform during Dataset creation");
        }

        writable->written = true;
        writable->abstractFilePosition = std::make_shared< ADIOS1FilePosition >(name);

        m_filePaths[writable] = res->second;
    }
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::extendDataset(Writable*,
                                   Parameter< Operation::EXTEND_DATASET > const&)
{
    throw std::runtime_error("[ADIOS1] Dataset extension not implemented in ADIOS backend");
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::openFile(Writable* writable,
                              Parameter< Operation::OPEN_FILE > const& parameters)
{
    if( !auxiliary::directory_exists(m_handler->directory) )
        throw no_such_file_error("[ADIOS1] Supplied directory is not valid: " + m_handler->directory);

    std::string name = m_handler->directory + parameters.name;
    if( !auxiliary::ends_with(name, ".bp") )
        name += ".bp";

    std::shared_ptr< std::string > filePath;
    auto it = std::find_if(m_filePaths.begin(), m_filePaths.end(),
                           [name](std::unordered_map< Writable*, std::shared_ptr< std::string > >::value_type const& entry){ return *entry.second == name; });
    if( it == m_filePaths.end() )
        filePath = std::make_shared< std::string >(name);
    else
        filePath = it->second;

    if( m_handler->m_backendAccess == Access::CREATE )
    {
        // called at Series::flush for iterations that has been flushed before
        // this is to make sure to point the Series.m_writer points to this iteration
        // so when call Series.flushAttribute(), the attributes can be flushed to the iteration level file.
        m_filePaths[writable] = filePath;
        writable->written = true;
        writable->abstractFilePosition = std::make_shared< ADIOS1FilePosition >("/");
        return;
     }
    /* close the handle that corresponds to the file we want to open */
    if( m_openWriteFileHandles.find(filePath) != m_openWriteFileHandles.end() )
    {
        close(m_openWriteFileHandles[filePath]);
        m_openWriteFileHandles.erase(filePath);
    }

    if( m_groups.find(filePath) == m_groups.end() )
        m_groups[filePath] =
            static_cast< ChildClass * >( this )->initialize_group(name);

    if( m_openReadFileHandles.find(filePath) == m_openReadFileHandles.end() )
    {
        ADIOS_FILE* f = static_cast< ChildClass * >( this )->open_read(name);
        m_openReadFileHandles[filePath] = f;
    }

    writable->written = true;
    writable->abstractFilePosition = std::make_shared< ADIOS1FilePosition >("/");

    m_filePaths[writable] = filePath;
    m_existsOnDisk[filePath] = true;
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::closeFile(
    Writable * writable,
    Parameter< Operation::CLOSE_FILE > const & )
{
    auto myFile = m_filePaths.find( writable );
    if( myFile == m_filePaths.end() )
    {
        return;
    }

    // finish write operations
    auto myGroup = m_groups.find( myFile->second );
    if( myGroup != m_groups.end() )
    {
        auto attributeWrites = m_attributeWrites.find( myGroup->second );
        if( this->m_handler->m_backendAccess != Access::READ_ONLY &&
            attributeWrites != m_attributeWrites.end() )
        {
            for( auto & att : attributeWrites->second )
            {
                flush_attribute( myGroup->second, att.first, att.second );
            }
            m_attributeWrites.erase( attributeWrites );
        }
        m_groups.erase( myGroup );
    }

    auto handle_write = m_openWriteFileHandles.find( myFile->second );
    if( handle_write != m_openWriteFileHandles.end() )
    {
        close( handle_write->second );
        m_openWriteFileHandles.erase( handle_write );
    }

    // finish read operations
    auto handle_read = m_openReadFileHandles.find( myFile->second );
    if( handle_read != m_openReadFileHandles.end() )
    {
        auto scheduled = m_scheduledReads.find( handle_read->second );
        if( scheduled != m_scheduledReads.end() )
        {
            auto status = adios_perform_reads( scheduled->first, 1 );
            VERIFY(
                status == err_no_error,
                "[ADIOS1] Internal error: Failed to perform ADIOS reads during "
                "dataset reading" );

            for( auto & sel : scheduled->second )
                adios_selection_delete( sel );
            m_scheduledReads.erase( scheduled );
        }
        close( handle_read->second );
        m_openReadFileHandles.erase( handle_read );
    }
    m_existsOnDisk.erase( myFile->second );
    m_filePaths.erase( myFile );
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::availableChunks(
    Writable * writable,
    Parameter< Operation::AVAILABLE_CHUNKS > & params )
{
    ADIOS_FILE * f;
    f = m_openReadFileHandles.at( m_filePaths.at( writable ) );
    std::string name = concrete_bp1_file_position( writable );
    VERIFY(
        std::strcmp( f->path, m_filePaths.at( writable )->c_str() ) == 0,
        "[ADIOS1] Internal Error: Invalid ADIOS read file handle" );
    ADIOS_VARINFO * varinfo = adios_inq_var( f, name.c_str() );
    VERIFY(
        adios_errno == err_no_error,
        "[ADIOS1] Internal error: Failed to inquire ADIOS variable while "
        "querying available chunks." );
    int err = adios_inq_var_blockinfo( f, varinfo );
    VERIFY(
        err == 0,
        "[ADIOS1] Internal error: Failed to obtain ADIOS varinfo while "
        "querying available chunks." );
    int nblocks =
        varinfo->nblocks[ 0 ]; // we don't use steps, so index 0 is fine
    int ndim = varinfo->ndim;
    auto & table = *params.chunks;
    table.reserve( nblocks );
    for( int block = 0; block < nblocks; ++block )
    {
        ADIOS_VARBLOCK & varblock = varinfo->blockinfo[ block ];
        Offset offset( ndim );
        Extent extent( ndim );
        for( int i = 0; i < ndim; ++i )
        {
            offset[ i ] = varblock.start[ i ];
            extent[ i ] = varblock.count[ i ];
        }
        table.emplace_back( offset, extent, int( varblock.process_id ) );
    }
    adios_free_varinfo( varinfo );
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::openPath(
    Writable * writable,
    Parameter< Operation::OPEN_PATH > const & parameters )
{
    /* Sanitize path */
    std::string path = parameters.path;
    if( !path.empty() )
    {
        if( auxiliary::starts_with(path, '/') )
            path = auxiliary::replace_first(path, "/", "");
        if( !auxiliary::ends_with(path, '/') )
            path += '/';
    }

    writable->written = true;
    writable->abstractFilePosition = std::make_shared< ADIOS1FilePosition >(path);

    auto res = writable->parent ? m_filePaths.find(writable->parent) : m_filePaths.find(writable);

    m_filePaths[writable] = res->second;
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::openDataset(Writable* writable,
                                 Parameter< Operation::OPEN_DATASET >& parameters)
{
    ADIOS_FILE *f;
    auto res = m_filePaths.find(writable);
    if( res == m_filePaths.end() )
        res = m_filePaths.find(writable->parent);
    f = m_openReadFileHandles.at(res->second);

    /* Sanitize name */
    std::string name = parameters.name;
    if( auxiliary::starts_with(name, '/') )
        name = auxiliary::replace_first(name, "/", "");

    std::string datasetname = writable->abstractFilePosition
        ? concrete_bp1_file_position(writable)
        : concrete_bp1_file_position(writable) + name;

    ADIOS_VARINFO* vi;
    vi = adios_inq_var(f,
                       datasetname.c_str());
    std::string error_string("[ADIOS1] Internal error: ");
    error_string.append("Failed to inquire about ADIOS variable '")
                .append(datasetname)
                .append("' during dataset opening");
    VERIFY(adios_errno == err_no_error, error_string);
    VERIFY(vi != nullptr, error_string);

    Datatype dtype;

    // note the ill-named fixed-byte adios_... types
    // https://github.com/ornladios/ADIOS/issues/187
    switch( vi->type )
    {
        using DT = Datatype;
        case adios_byte:
            dtype = DT::CHAR;
            break;
        case adios_short:
            if( sizeof(short) == 2u )
                dtype = DT::SHORT;
            else if( sizeof(int) == 2u )
                dtype = DT::INT;
            else if( sizeof(long) == 2u )
                dtype = DT::LONG;
            else if( sizeof(long long) == 2u )
                dtype = DT::LONGLONG;
            else
                throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_short found.");
            break;
        case adios_integer:
            if( sizeof(short) == 4u )
                dtype = DT::SHORT;
            else if( sizeof(int) == 4u )
                dtype = DT::INT;
            else if( sizeof(long) == 4u )
                dtype = DT::LONG;
            else if( sizeof(long long) == 4u )
                dtype = DT::LONGLONG;
            else
                throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_integer found.");
            break;
        case adios_long:
            if( sizeof(short) == 8u )
                dtype = DT::SHORT;
            else if( sizeof(int) == 8u )
                dtype = DT::INT;
            else if( sizeof(long) == 8u )
                dtype = DT::LONG;
            else if( sizeof(long long) == 8u )
                dtype = DT::LONGLONG;
            else
                throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_long found.");
            break;
        case adios_unsigned_byte:
            dtype = DT::UCHAR;
            break;
        case adios_unsigned_short:
            if( sizeof(unsigned short) == 2u )
                dtype = DT::USHORT;
            else if( sizeof(unsigned int) == 2u )
                dtype = DT::UINT;
            else if( sizeof(unsigned long) == 2u )
                dtype = DT::ULONG;
            else if( sizeof(unsigned long long) == 2u )
                dtype = DT::ULONGLONG;
            else
                throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_unsigned_short found.");
            break;
        case adios_unsigned_integer:
            if( sizeof(unsigned short) == 4u )
                dtype = DT::USHORT;
            else if( sizeof(unsigned int) == 4u )
                dtype = DT::UINT;
            else if( sizeof(unsigned long) == 4u )
                dtype = DT::ULONG;
            else if( sizeof(unsigned long long) == 4u )
                dtype = DT::ULONGLONG;
            else
                throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_unsigned_integer found.");
            break;
        case adios_unsigned_long:
            if( sizeof(unsigned short) == 8u )
                dtype = DT::USHORT;
            else if( sizeof(unsigned int) == 8u )
                dtype = DT::UINT;
            else if( sizeof(unsigned long) == 8u )
                dtype = DT::ULONG;
            else if( sizeof(unsigned long long) == 8u )
                dtype = DT::ULONGLONG;
            else
                throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_unsigned_long found.");
            break;
        case adios_real:
            dtype = DT::FLOAT;
            break;
        case adios_double:
            dtype = DT::DOUBLE;
            break;
        case adios_long_double:
            dtype = DT::LONG_DOUBLE;
            break;
        case adios_complex:
            dtype = DT::CFLOAT;
            break;
        case adios_double_complex:
            dtype = DT::CDOUBLE;
            break;

        case adios_string:
        case adios_string_array:
        default:
            throw unsupported_data_error("[ADIOS1] Datatype not implemented for ADIOS dataset writing");
    }
    *parameters.dtype = dtype;

    Extent e;
    e.resize(vi->ndim);
    for( int i = 0; i < vi->ndim; ++i )
        e[i] = vi->dims[i];
    *parameters.extent = e;

    writable->written = true;
    if( !writable->abstractFilePosition )
    {
        writable->abstractFilePosition
            = std::make_shared< ADIOS1FilePosition >(name);
    }

    m_openReadFileHandles[res->second] = f;
    m_filePaths[writable] = res->second;
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::deleteFile(Writable* writable,
                                Parameter< Operation::DELETE_FILE > const& parameters)
{
    if( m_handler->m_backendAccess == Access::READ_ONLY )
        throw std::runtime_error("[ADIOS1] Deleting a file opened as read only is not possible.");

    if( writable->written )
    {
        auto path = m_filePaths.at(writable);
        if( m_openReadFileHandles.find(path) != m_openReadFileHandles.end() )
        {
            close(m_openReadFileHandles.at(path));
            m_openReadFileHandles.erase(path);
        }
        if( m_openWriteFileHandles.find(path) != m_openWriteFileHandles.end() )
        {
            close(m_openWriteFileHandles.at(path));
            m_openWriteFileHandles.erase(path);
        }

        std::string name = m_handler->directory + parameters.name;
        if( !auxiliary::ends_with(name, ".bp") )
            name += ".bp";

        if( !auxiliary::file_exists(name) )
            throw std::runtime_error("[ADIOS1] File does not exist: " + name);

        auxiliary::remove_file(name);

        writable->written = false;
        writable->abstractFilePosition.reset();

        m_filePaths.erase(writable);
    }
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::deletePath(Writable*,
                                Parameter< Operation::DELETE_PATH > const&)
{
    throw std::runtime_error("[ADIOS1] Path deletion not implemented in ADIOS backend");
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::deleteDataset(Writable*,
                                   Parameter< Operation::DELETE_DATASET > const&)
{
    throw std::runtime_error("[ADIOS1] Dataset deletion not implemented in ADIOS backend");
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::deleteAttribute(Writable*,
                                     Parameter< Operation::DELETE_ATT > const&)
{
    throw std::runtime_error("[ADIOS1] Attribute deletion not implemented in ADIOS backend");
}

template< typename ChildClass >
int64_t CommonADIOS1IOHandlerImpl< ChildClass >::GetFileHandle(Writable* writable)
{
    auto res = m_filePaths.find(writable);
    if( res == m_filePaths.end() )
        res = m_filePaths.find(writable->parent);
    int64_t fd;

    if( m_openWriteFileHandles.find(res->second) == m_openWriteFileHandles.end() )
    {
        std::string  name  = *(res->second);
        m_groups[m_filePaths[writable]] =
            static_cast< ChildClass * >( this )->initialize_group(name);

        fd = static_cast< ChildClass * >( this )->open_write(writable);
        m_openWriteFileHandles[res->second] = fd;
    } else
        fd = m_openWriteFileHandles.at(res->second);

    return fd;
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::writeDataset(Writable* writable,
                                  Parameter< Operation::WRITE_DATASET > const& parameters)
{
    if( m_handler->m_backendAccess == Access::READ_ONLY )
        throw std::runtime_error("[ADIOS1] Writing into a dataset in a file opened as read-only is not possible.");

    int64_t fd = GetFileHandle(writable);

    std::string name = concrete_bp1_file_position(writable);

    size_t ndims = parameters.extent.size();

    std::string chunkSize;
    std::string chunkOffset;
    int status;
    for( size_t i = 0; i < ndims; ++i )
    {
        chunkSize = "/tmp" + name + "_chunkSize" + std::to_string(i);
        status = adios_write(fd, chunkSize.c_str(), &parameters.extent[i]);
        VERIFY(status == err_no_error, "[ADIOS1] Internal error: Failed to write ADIOS variable during Dataset writing");
        chunkOffset = "/tmp" + name + "_chunkOffset" + std::to_string(i);
        status = adios_write(fd, chunkOffset.c_str(), &parameters.offset[i]);
        VERIFY(status == err_no_error, "[ADIOS1] Internal error: Failed to write ADIOS variable during Dataset writing");
    }

    status = adios_write(fd,
                         name.c_str(),
                         parameters.data.get());
    VERIFY(status == err_no_error, "[ADIOS1] Internal error: Failed to write ADIOS variable during Dataset writing");
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::writeAttribute(Writable* writable,
                                    Parameter< Operation::WRITE_ATT > const& parameters)
{
    if( m_handler->m_backendAccess == Access::READ_ONLY )
        throw std::runtime_error("[ADIOS1] Writing an attribute in a file opened as read only is not possible.");

    std::string name = concrete_bp1_file_position(writable);
    if( !auxiliary::ends_with(name, '/') )
        name += '/';
    name += parameters.name;

    auto res = m_filePaths.find(writable);
    if( res == m_filePaths.end() )
        res = m_filePaths.find(writable->parent);
    GetFileHandle(writable);

    int64_t group = m_groups[res->second];

    auto& attributes = m_attributeWrites[group];
    attributes.erase(name);
    attributes.emplace(name, parameters.resource);
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::readDataset(Writable* writable,
                                 Parameter< Operation::READ_DATASET >& parameters)
{
    switch( parameters.dtype )
    {
        using DT = Datatype;
        case DT::DOUBLE:
        case DT::FLOAT:
        case DT::CDOUBLE:
        case DT::CFLOAT:
        case DT::SHORT:
        case DT::INT:
        case DT::LONG:
        case DT::LONGLONG:
        case DT::USHORT:
        case DT::UINT:
        case DT::ULONG:
        case DT::ULONGLONG:
        case DT::CHAR:
        case DT::UCHAR:
        case DT::BOOL:
            break;
        case DT::UNDEFINED:
            throw std::runtime_error("[ADIOS1] Unknown Attribute datatype (ADIOS1 Dataset read)");
        default:
            throw std::runtime_error("[ADIOS1] Datatype not implemented in ADIOS1 IO");
    }

    ADIOS_FILE* f;
    f = m_openReadFileHandles.at(m_filePaths.at(writable));
    VERIFY(std::strcmp(f->path, m_filePaths.at(writable)->c_str()) == 0,
           "[ADIOS1] Internal Error: Invalid ADIOS read file handle");

    ADIOS_SELECTION* sel;
    sel = adios_selection_boundingbox(parameters.extent.size(),
                                      parameters.offset.data(),
                                      parameters.extent.data());
    VERIFY(sel != nullptr, "[ADIOS1] Internal error: Failed to select ADIOS bounding box during dataset reading");
    VERIFY(adios_errno == err_no_error, "[ADIOS1] Internal error: Failed to select ADIOS bounding box during dataset reading");

    std::string varname = concrete_bp1_file_position(writable);
    void* data = parameters.data.get();

    int status;
    status = adios_schedule_read(f,
                                 sel,
                                 varname.c_str(),
                                 0,
                                 1,
                                 data);
    VERIFY(status == err_no_error, "[ADIOS1] Internal error: Failed to schedule ADIOS read during dataset reading");
    VERIFY(adios_errno == err_no_error, "[ADIOS1] Internal error: Failed to schedule ADIOS read during dataset reading");

    m_scheduledReads[f].push_back(sel);
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::readAttribute(Writable* writable,
                                   Parameter< Operation::READ_ATT >& parameters)
{
    if( !writable->written )
        throw std::runtime_error("[ADIOS1] Internal error: Writable not marked written during attribute reading");

    ADIOS_FILE* f;
    f = m_openReadFileHandles.at(m_filePaths.at(writable));

    std::string attrname = concrete_bp1_file_position(writable);
    if( !auxiliary::ends_with(attrname, '/') )
        attrname += "/";
    attrname += parameters.name;

    ADIOS_DATATYPES datatype = adios_unknown;
    int size = 0;
    void* data = nullptr;

    int status;
    status = adios_get_attr(f,
                            attrname.c_str(),
                            &datatype,
                            &size,
                            &data);
    VERIFY(status == 0, "[ADIOS1] Internal error: Failed to get ADIOS1 attribute during attribute read");
    VERIFY(datatype != adios_unknown, "[ADIOS1] Internal error: Read unknown ADIOS1 datatype during attribute read");
    VERIFY(size != 0, "[ADIOS1] Internal error: ADIOS1 read 0-size attribute");

    // size is returned in number of allocated bytes
    // note the ill-named fixed-byte adios_... types
    // https://github.com/ornladios/ADIOS/issues/187
    switch( datatype )
    {
        case adios_byte:
            break;
        case adios_short:
            size /= 2;
            break;
        case adios_integer:
            size /= 4;
            break;
        case adios_long:
            size /= 8;
            break;
        case adios_unsigned_byte:
            break;
        case adios_unsigned_short:
            size /= 2;
            break;
        case adios_unsigned_integer:
            size /= 4;
            break;
        case adios_unsigned_long:
            size /= 8;
            break;
        case adios_real:
            size /= 4;
            break;
        case adios_double:
            size /= 8;
            break;
        case adios_long_double:
            size /= sizeof(long double);
            break;
        case adios_complex:
            size /= 8;
            break;
        case adios_double_complex:
            size /= 16;
            break;
        case adios_string:
            break;
        case adios_string_array:
            size /= sizeof(char*);
            break;

        default:
            throw unsupported_data_error(
                    "[ADIOS1] readAttribute: Unsupported ADIOS1 attribute datatype '" +
                    std::to_string(datatype) + "' in size check");
    }

    Datatype dtype;
    Attribute a(0);
    if( size == 1 )
    {
        switch( datatype )
        {
            using DT = Datatype;
            case adios_byte:
                dtype = DT::CHAR;
                a = Attribute(*reinterpret_cast< char* >(data));
                break;
            case adios_short:
                if( sizeof(short) == 2u )
                {
                    dtype = DT::SHORT;
                    a = Attribute(*reinterpret_cast< short* >(data));
                }
                else if( sizeof(int) == 2u )
                {
                    dtype = DT::INT;
                    a = Attribute(*reinterpret_cast< int* >(data));
                }
                else if( sizeof(long) == 2u )
                {
                    dtype = DT::LONG;
                    a = Attribute(*reinterpret_cast< long* >(data));
                }
                else if( sizeof(long long) == 2u )
                {
                    dtype = DT::LONGLONG;
                    a = Attribute(*reinterpret_cast< long long* >(data));
                }
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_short found.");
                break;
            case adios_integer:
                if( sizeof(short) == 4u )
                {
                    dtype = DT::SHORT;
                    a = Attribute(*reinterpret_cast< short* >(data));
                }
                else if( sizeof(int) == 4u )
                {
                    dtype = DT::INT;
                    a = Attribute(*reinterpret_cast< int* >(data));
                }
                else if( sizeof(long) == 4u )
                {
                    dtype = DT::LONG;
                    a = Attribute(*reinterpret_cast< long* >(data));
                }
                else if( sizeof(long long) == 4u )
                {
                    dtype = DT::LONGLONG;
                    a = Attribute(*reinterpret_cast< long long* >(data));
                }
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_integer found.");
                break;
            case adios_long:
                if( sizeof(short) == 8u )
                {
                    dtype = DT::SHORT;
                    a = Attribute(*reinterpret_cast< short* >(data));
                }
                else if( sizeof(int) == 8u )
                {
                    dtype = DT::INT;
                    a = Attribute(*reinterpret_cast< int* >(data));
                }
                else if( sizeof(long) == 8u )
                {
                    dtype = DT::LONG;
                    a = Attribute(*reinterpret_cast< long* >(data));
                }
                else if( sizeof(long long) == 8u )
                {
                    dtype = DT::LONGLONG;
                    a = Attribute(*reinterpret_cast< long long* >(data));
                }
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_long found.");
                break;
            case adios_unsigned_byte:
                dtype = DT::UCHAR;
                a = Attribute(*reinterpret_cast< unsigned char* >(data));
                break;
            case adios_unsigned_short:
                if( sizeof(unsigned short) == 2u )
                {
                    dtype = DT::USHORT;
                    a = Attribute(*reinterpret_cast< unsigned short* >(data));
                }
                else if( sizeof(unsigned int) == 2u )
                {
                    dtype = DT::UINT;
                    a = Attribute(*reinterpret_cast< unsigned int* >(data));
                }
                else if( sizeof(unsigned long) == 2u )
                {
                    dtype = DT::ULONG;
                    a = Attribute(*reinterpret_cast< unsigned long* >(data));
                }
                else if( sizeof(unsigned long long) == 2u )
                {
                    dtype = DT::ULONGLONG;
                    a = Attribute(*reinterpret_cast< unsigned long long* >(data));
                }
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_unsigned_short found.");
                break;
            case adios_unsigned_integer:
                if( sizeof(unsigned short) == 4u )
                {
                    dtype = DT::USHORT;
                    a = Attribute(*reinterpret_cast< unsigned short* >(data));
                }
                else if( sizeof(unsigned int) == 4u )
                {
                    dtype = DT::UINT;
                    a = Attribute(*reinterpret_cast< unsigned int* >(data));
                }
                else if( sizeof(unsigned long) == 4u )
                {
                    dtype = DT::ULONG;
                    a = Attribute(*reinterpret_cast< unsigned long* >(data));
                }
                else if( sizeof(unsigned long long) == 4u )
                {
                    dtype = DT::ULONGLONG;
                    a = Attribute(*reinterpret_cast< unsigned long long* >(data));
                }
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_unsigned_integer found.");
                break;
            case adios_unsigned_long:
                if( sizeof(unsigned short) == 8u )
                {
                    dtype = DT::USHORT;
                    a = Attribute(*reinterpret_cast< unsigned short* >(data));
                }
                else if( sizeof(unsigned int) == 8u )
                {
                    dtype = DT::UINT;
                    a = Attribute(*reinterpret_cast< unsigned int* >(data));
                }
                else if( sizeof(unsigned long) == 8u )
                {
                    dtype = DT::ULONG;
                    a = Attribute(*reinterpret_cast< unsigned long* >(data));
                }
                else if( sizeof(unsigned long long) == 8u )
                {
                    dtype = DT::ULONGLONG;
                    a = Attribute(*reinterpret_cast< unsigned long long* >(data));
                }
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_unsigned_long found.");
                break;
            case adios_real:
                dtype = DT::FLOAT;
                a = Attribute(*reinterpret_cast< float* >(data));
                break;
            case adios_double:
                dtype = DT::DOUBLE;
                a = Attribute(*reinterpret_cast< double* >(data));
                break;
            case adios_long_double:
                dtype = DT::LONG_DOUBLE;
                a = Attribute(*reinterpret_cast< long double* >(data));
                break;
            case adios_complex:
                dtype = DT::CFLOAT;
                a = Attribute(*reinterpret_cast< std::complex<float>* >(data));
                break;
            case adios_double_complex:
                dtype = DT::CDOUBLE;
                a = Attribute(*reinterpret_cast< std::complex<double>* >(data));
                break;
            case adios_string:
            {
                dtype = DT::STRING;
                auto c = reinterpret_cast< char* >(data);
                a = Attribute(auxiliary::strip(std::string(c, std::strlen(c)), {'\0'}));
                break;
            }
            case adios_string_array:
            {
                dtype = DT::VEC_STRING;
                auto c = reinterpret_cast< char** >(data);
                std::vector< std::string > vs;
                vs.resize(size);
                for( int i = 0; i < size; ++i )
                {
                    vs[i] = auxiliary::strip(std::string(c[i], std::strlen(c[i])), {'\0'});
                    /** @todo pointer should be freed, but this causes memory corruption */
                    //free(c[i]);
                }
                a = Attribute(vs);
                break;
            }
            default:
                throw unsupported_data_error(
                    "[ADIOS1] readAttribute: Unsupported ADIOS1 attribute datatype '" +
                    std::to_string(datatype) + "' in scalar branch");
        }
    }
    else
    {
        switch( datatype )
        {
            using DT = Datatype;
            case adios_byte:
            {
                dtype = DT::VEC_CHAR;
                auto c = reinterpret_cast< char* >(data);
                std::vector< char > vc;
                vc.resize(size);
                for( int i = 0; i < size; ++i )
                    vc[i] = c[i];
                a = Attribute(vc);
                break;
            }
            case adios_short:
            {
                if( sizeof(short) == 2u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< short >(data, size), DT::VEC_SHORT);
                else if( sizeof(int) == 2u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< int >(data, size), DT::VEC_INT);
                else if( sizeof(long) == 2u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< long >(data, size), DT::VEC_LONG);
                else if( sizeof(long long) == 2u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< long long >(data, size), DT::VEC_LONGLONG);
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_short found.");
                break;
            }
            case adios_integer:
            {
                if( sizeof(short) == 4u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< short >(data, size), DT::VEC_SHORT);
                else if( sizeof(int) == 4u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< int >(data, size), DT::VEC_INT);
                else if( sizeof(long) == 4u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< long >(data, size), DT::VEC_LONG);
                else if( sizeof(long long) == 4u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< long long >(data, size), DT::VEC_LONGLONG);
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_integer found.");
                break;
            }
            case adios_long:
            {
                if( sizeof(short) == 8u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< short >(data, size), DT::VEC_SHORT);
                else if( sizeof(int) == 8u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< int >(data, size), DT::VEC_INT);
                else if( sizeof(long) == 8u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< long >(data, size), DT::VEC_LONG);
                else if( sizeof(long long) == 8u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< long long >(data, size), DT::VEC_LONGLONG);
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_long found.");
                break;
            }
            case adios_unsigned_byte:
            {
                dtype = DT::VEC_UCHAR;
                auto uc = reinterpret_cast< unsigned char* >(data);
                std::vector< unsigned char > vuc;
                vuc.resize(size);
                for( int i = 0; i < size; ++i )
                    vuc[i] = uc[i];
                a = Attribute(vuc);
                break;
            }
            case adios_unsigned_short:
            {
                if( sizeof(unsigned short) == 2u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned short >(data, size), DT::VEC_USHORT);
                else if( sizeof(unsigned int) == 2u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned int >(data, size), DT::VEC_UINT);
                else if( sizeof(unsigned long) == 2u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned long >(data, size), DT::VEC_ULONG);
                else if( sizeof(unsigned long long) == 2u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned long long >(data, size), DT::VEC_ULONGLONG);
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_unsigned_short found.");
                break;
            }
            case adios_unsigned_integer:
            {
                if( sizeof(unsigned short) == 4u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned short >(data, size), DT::VEC_USHORT);
                else if( sizeof(unsigned int) == 4u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned int >(data, size), DT::VEC_UINT);
                else if( sizeof(unsigned long) == 4u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned long >(data, size), DT::VEC_ULONG);
                else if( sizeof(unsigned long long) == 4u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned long long >(data, size), DT::VEC_ULONGLONG);
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_unsigned_integer found.");
                break;
            }
            case adios_unsigned_long:
            {
                if( sizeof(unsigned short) == 8u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned short >(data, size), DT::VEC_USHORT);
                else if( sizeof(unsigned int) == 8u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned int >(data, size), DT::VEC_UINT);
                else if( sizeof(unsigned long) == 8u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned long >(data, size), DT::VEC_ULONG);
                else if( sizeof(unsigned long long) == 8u )
                    std::tie(a, dtype) = std::make_tuple(readVectorAttributeInternal< unsigned long long >(data, size), DT::VEC_ULONGLONG);
                else
                    throw unsupported_data_error("[ADIOS1] No native equivalent for Datatype adios_unsigned_long found.");
                break;
            }
            case adios_real:
            {
                dtype = DT::VEC_FLOAT;
                auto f4 = reinterpret_cast< float* >(data);
                std::vector< float > vf;
                vf.resize(size);
                for( int i = 0; i < size; ++i )
                    vf[i] = f4[i];
                a = Attribute(vf);
                break;
            }
            case adios_double:
            {
                dtype = DT::VEC_DOUBLE;
                auto d8 = reinterpret_cast< double* >(data);
                std::vector< double > vd;
                vd.resize(size);
                for( int i = 0; i < size; ++i )
                    vd[i] = d8[i];
                a = Attribute(vd);
                break;
            }
            case adios_long_double:
            {
                dtype = DT::VEC_LONG_DOUBLE;
                auto ld = reinterpret_cast< long double* >(data);
                std::vector< long double > vld;
                vld.resize(size);
                for( int i = 0; i < size; ++i )
                    vld[i] = ld[i];
                a = Attribute(vld);
                break;
            }
            /* not supported by ADIOS 1.13.1: VEC_CFLOAT, VEC_CDOUBLE, VEC_CLONG_DOUBLE
             *   https://github.com/ornladios/ADIOS/issues/212
             */
            case adios_string:
            {
                dtype = DT::STRING;
                a = Attribute(auxiliary::strip(std::string(reinterpret_cast< char* >(data), size), {'\0'}));
                break;
            }
            case adios_string_array:
            {
                dtype = DT::VEC_STRING;
                auto c = reinterpret_cast< char** >(data);
                std::vector< std::string > vs;
                vs.resize(size);
                for( int i = 0; i < size; ++i )
                {
                    vs[i] = auxiliary::strip(std::string(c[i], std::strlen(c[i])), {'\0'});
                    /** @todo pointer should be freed, but this causes memory corruption */
                    //free(c[i]);
                }
                a = Attribute(vs);
                break;
            }

            default:
                throw unsupported_data_error(
                    "[ADIOS1] readAttribute: Unsupported ADIOS1 attribute datatype '" +
                    std::to_string(datatype) + "' in vector branch");
        }
    }

    free(data);

    *parameters.dtype = dtype;
    *parameters.resource = a.getResource();
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::listPaths(Writable* writable,
                               Parameter< Operation::LIST_PATHS >& parameters)
{
    if( !writable->written )
        throw std::runtime_error("[ADIOS1] Internal error: Writable not marked written during path listing");

    ADIOS_FILE* f;
    f = m_openReadFileHandles.at(m_filePaths.at(writable));

    std::string name = concrete_bp1_file_position(writable);

    std::unordered_set< std::string > paths;
    std::unordered_set< std::string > variables;
    for( int i = 0; i < f->nvars; ++i )
    {
        char* str = f->var_namelist[i];
        std::string s(str, std::strlen(str));
        if( auxiliary::starts_with(s, name) )
        {
            /* remove the writable's path from the name */
            s = auxiliary::replace_first(s, name, "");
            variables.emplace(s);
            if( std::any_of(s.begin(), s.end(), [](char c) { return c == '/'; }) )
            {
                /* there are more path levels after the current writable */
                s = s.substr(0, s.find_first_of('/'));
                paths.emplace(s);
            }
        }
    }
    for( int i = 0; i < f->nattrs; ++i )
    {
        char* str = f->attr_namelist[i];
        std::string s(str, std::strlen(str));
        if( auxiliary::starts_with(s, name) )
        {
            /* remove the writable's path from the name */
            s = auxiliary::replace_first(s, name, "");
            if( std::any_of(s.begin(), s.end(), [](char c) { return c == '/'; }) )
            {
                /* remove the attribute name */
                s = s.substr(0, s.find_last_of('/'));
                if( !std::any_of(variables.begin(),
                                 variables.end(),
                                 [&s](std::string const& var){ return auxiliary::starts_with(var, s); }))
                {
                    /* this is either a group or a constant scalar */
                    s = s.substr(0, s.find_first_of('/'));
                    paths.emplace(s);
                }
            }
        }
    }

    *parameters.paths = std::vector< std::string >(paths.begin(), paths.end());
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::listDatasets(Writable* writable,
                                  Parameter< Operation::LIST_DATASETS >& parameters)
{
    if( !writable->written )
        throw std::runtime_error("[ADIOS1] Internal error: Writable not marked written during dataset listing");

    ADIOS_FILE* f;
    f = m_openReadFileHandles.at(m_filePaths.at(writable));

    std::string name = concrete_bp1_file_position(writable);

    std::unordered_set< std::string > paths;
    for( int i = 0; i < f->nvars; ++i )
    {
        char* str = f->var_namelist[i];
        std::string s(str, std::strlen(str));
        if( auxiliary::starts_with(s, name) )
        {
            /* remove the writable's path from the name */
            s = auxiliary::replace_first(s, name, "");
            if( std::none_of(s.begin(), s.end(), [](char c) { return c == '/'; }) )
            {
                /* this is a dataset of the writable */
                paths.emplace(s);
            }
        }
    }

    *parameters.datasets = std::vector< std::string >(paths.begin(), paths.end());
}

template< typename ChildClass >
void
CommonADIOS1IOHandlerImpl< ChildClass >::listAttributes(Writable* writable,
                                    Parameter< Operation::LIST_ATTS >& parameters)
{
    if( !writable->written )
        throw std::runtime_error("[ADIOS1] Internal error: Writable not marked written during attribute listing");

    ADIOS_FILE* f;
    f = m_openReadFileHandles.at(m_filePaths.at(writable));

    std::string name = concrete_bp1_file_position(writable);

    if( !auxiliary::ends_with(name, '/') )
    {
        /* writable is a dataset and corresponds to an ADIOS variable */
        ADIOS_VARINFO* info;
        info = adios_inq_var(f,
                             name.c_str());
        VERIFY(adios_errno == err_no_error, "[ADIOS1] Internal error: Failed to inquire ADIOS variable during attribute listing");
        VERIFY(info != nullptr, "[ADIOS1] Internal error: Failed to inquire ADIOS variable during attribute listing");

        name += '/';
        parameters.attributes->reserve(info->nattrs);
        for( int i = 0; i < info->nattrs; ++i )
        {
            char* c = f->attr_namelist[info->attr_ids[i]];
            parameters.attributes->push_back(auxiliary::replace_first(std::string(c, std::strlen(c)), name, ""));
        }

        adios_free_varinfo(info);
    } else
    {
        /* there is no ADIOS variable associated with the writable */
        std::unordered_set< std::string > attributes;
        for( int i = 0; i < f->nattrs; ++i )
        {
            char* str = f->attr_namelist[i];
            std::string s(str, std::strlen(str));
            if( auxiliary::starts_with(s, name) )
            {
                /* remove the writable's path from the name */
                s = auxiliary::replace_first(s, name, "");
                if( std::none_of(s.begin(), s.end(), [](char c) { return c == '/'; }) )
                {
                    /* this is an attribute of the writable */
                    attributes.insert(s);
                }
            }
        }
        *parameters.attributes = std::vector< std::string >(attributes.begin(), attributes.end());
    }
}

template< typename ChildClass >
void CommonADIOS1IOHandlerImpl< ChildClass >::initJson(
    json::TracingJSON config )
{
    if( !config.json().contains( "adios1" ) )
    {
        return;
    }
    auto maybeTransform = datasetTransform( config[ "adios1" ] );
    if( maybeTransform.has_value() )
    {
        m_defaultTransform = std::move( maybeTransform.get() );
    }
    auto shadow = config.invertShadow();
    if( shadow.size() > 0 )
    {
        switch( config.originallySpecifiedAs )
        {
        case json::SupportedLanguages::JSON:
            std::cerr << "Warning: parts of the JSON configuration for ADIOS1 "
                         "remain unused:\n"
                      << shadow << std::endl;
            break;
        case json::SupportedLanguages::TOML:
        {
            auto asToml = json::jsonToToml( shadow );
            std::cerr << "Warning: parts of the JSON configuration for ADIOS1 "
                         "remain unused:\n"
                      << asToml << std::endl;
            break;
        }
        }
    }
}

template class CommonADIOS1IOHandlerImpl< ADIOS1IOHandlerImpl >;
#if openPMD_HAVE_MPI
template class CommonADIOS1IOHandlerImpl< ParallelADIOS1IOHandlerImpl >;
#endif // openPMD_HAVE_MPI

} // namespace openPMD
#endif // openPMD_HAVE_ADIOS1