Export CGNS files. More...

#include <ReadCGNS.hpp>

Inheritance diagram for moab::ReadCGNS:

Collaboration diagram for moab::ReadCGNS:

Public Member Functions
ErrorCode	load_file (const char file_name, const EntityHandle file_set, const FileOptions &opts, const SubsetList subset_list=0, const Tag file_id_tag=0)
	Load mesh from a file.
ErrorCode	read_tag_values (const char file_name, const char tag_name, const FileOptions &opts, std::vector< int > &tag_values_out, const SubsetList *subset_list=0)
	Read tag values from a file.
	ReadCGNS (Interface *impl=NULL)
	Constructor.
virtual	~ReadCGNS ()
	Destructor.
Static Public Member Functions
static ReaderIface *	factory (Interface *)
	factory method
Private Member Functions
ErrorCode	create_elements (char sectionName, const Tag file_id_tag, const EntityType &ent_type, const int &verts_per_elem, long &section_offset, int elems_count, const std::vector< cgsize_t > &elemsConn)
ErrorCode	create_sets (char sectionName, const Tag file_id_tag, EntityType element_type, const Range &elements, const std::vector< int > &set_ids, int set_type)
ErrorCode	create_geometric_topology ()
ErrorCode	process_options (const FileOptions &opts)
	Process options passed into the reader.
Private Attributes
const char *	fileName
short	mesh_dim
ReadUtilIface *	readMeshIface
Interface *	mbImpl
	interface instance
Tag	globalId
Tag	boundary
Range	geomSets

Detailed Description

Export CGNS files.

Author:: Carlos Breviglieri, Carlos Junqueira Junior

Definition at line 20 of file ReadCGNS.hpp.

Constructor & Destructor Documentation

ReadCGNS::ReadCGNS ( Interface * impl = NULL )

Constructor.

Definition at line 34 of file ReadCGNS.cpp.

References mbImpl, moab::Interface::query_interface(), and readMeshIface.

Referenced by factory().

                                    : fileName( NULL ), mesh_dim( 0 ), mbImpl( impl ), globalId( 0 ), boundary( 0 )
{
    mbImpl->query_interface( readMeshIface );
}

ReadCGNS::~ReadCGNS ( ) [virtual]

Destructor.

Definition at line 39 of file ReadCGNS.cpp.

References mbImpl, readMeshIface, and moab::Interface::release_interface().

{
    if( readMeshIface )
    {
        mbImpl->release_interface( readMeshIface );
        readMeshIface = 0;
    }
}

Member Function Documentation

ErrorCode ReadCGNS::create_elements	(	char *	sectionName,
		const Tag *	file_id_tag,
		const EntityType &	ent_type,
		const int &	verts_per_elem,
		long &	section_offset,
		int	elems_count,
		const std::vector< cgsize_t > &	elemsConn
	)		`[private]`

Definition at line 471 of file ReadCGNS.cpp.

References cgsize_t, create_sets(), ErrorCode, fileName, moab::ReadUtilIface::get_element_connect(), MB_CHK_SET_ERR, MB_SUCCESS, readMeshIface, and moab::ReadUtilIface::update_adjacencies().

Referenced by load_file().

{
    ErrorCode result;

    // Create the element sequence; passes back a pointer to the internal storage for connectivity
    // and the starting entity handle
    EntityHandle* conn_array;
    EntityHandle handle = 0;

    result = readMeshIface->get_element_connect( elems_count, verts_per_elem, ent_type, 1, handle, conn_array );MB_CHK_SET_ERR( result, fileName << ": Trouble reading elements" );

    if( sizeof( EntityHandle ) == sizeof( cgsize_t ) )
    {
        memcpy( conn_array, &elemsConn[0], elemsConn.size() * sizeof( EntityHandle ) );
    }
    else
    {  // if CGNS is compiled without 64bit enabled
        std::vector< EntityHandle > elemsConnTwin( elemsConn.size(), 0 );
        for( int i = 0; i < elemsConn.size(); i++ )
        {
            elemsConnTwin[i] = static_cast< EntityHandle >( elemsConn[i] );
        }
        memcpy( conn_array, &elemsConnTwin[0], elemsConnTwin.size() * sizeof( EntityHandle ) );
    }

    // Notify MOAB of the new elements
    result = readMeshIface->update_adjacencies( handle, elems_count, verts_per_elem, conn_array );
    if( MB_SUCCESS != result ) return result;

    // //////////////////////////////////
    // Create sets and tags

    Range elements( handle, handle + elems_count - 1 );

    // Store element IDs

    std::vector< int > id_list( elems_count );

    // Add 1 to offset id to 1-based numbering
    for( cgsize_t i = 0; i < elems_count; ++i )
        id_list[i] = i + 1 + section_offset;
    section_offset += elems_count;

    create_sets( sectionName, file_id_tag, ent_type, elements, id_list, 0 );

    return MB_SUCCESS;
}

ErrorCode moab::ReadCGNS::create_geometric_topology ( ) [private]

ErrorCode ReadCGNS::create_sets	(	char *	sectionName,
		const Tag *	file_id_tag,
		EntityType	element_type,
		const Range &	elements,
		const std::vector< int > &	set_ids,
		int	set_type
	)		`[private]`

Definition at line 525 of file ReadCGNS.cpp.

References moab::Interface::add_entities(), moab::Interface::create_meshset(), ErrorCode, fileName, globalId, MB_CHK_SET_ERR, MB_SUCCESS, MB_TAG_CREAT, MB_TAG_SPARSE, MB_TYPE_INTEGER, mbImpl, MESHSET_SET, moab::Interface::tag_get_handle(), and moab::Interface::tag_set_data().

Referenced by create_elements().

{
    ErrorCode result;

    result = mbImpl->tag_set_data( globalId, elements, &set_ids[0] );
    if( MB_SUCCESS != result ) return result;

    if( file_id_tag )
    {
        result = mbImpl->tag_set_data( *file_id_tag, elements, &set_ids[0] );
        if( MB_SUCCESS != result ) return result;
    }

    EntityHandle set_handle;

    Tag tag_handle;

    const char* setName = sectionName;

    mbImpl->tag_get_handle( setName, 1, MB_TYPE_INTEGER, tag_handle, MB_TAG_SPARSE | MB_TAG_CREAT );

    // Create set
    result = mbImpl->create_meshset( MESHSET_SET, set_handle );MB_CHK_SET_ERR( result, fileName << ": Trouble creating set" );

    //// Add dummy values to current set
    // std::vector<int> tags(set_ids.size(), 1);
    // result = mbImpl->tag_set_data(tag_handle, elements, &tags[0]);
    // if (MB_SUCCESS != result) return result;

    // Add them to the set
    result = mbImpl->add_entities( set_handle, elements );MB_CHK_SET_ERR( result, fileName << ": Trouble putting entities in set" );

    return MB_SUCCESS;
}

ReaderIface * ReadCGNS::factory ( Interface * iface ) [static]

factory method

Definition at line 29 of file ReadCGNS.cpp.

References ReadCGNS().

Referenced by moab::ReaderWriterSet::ReaderWriterSet().

{
    return new ReadCGNS( iface );
}

ErrorCode ReadCGNS::load_file	(	const char *	file_name,
		const EntityHandle *	file_set,
		const FileOptions &	opts,
		const SubsetList *	subset_list = `0`,
		const Tag *	file_id_tag = `0`
	)		`[virtual]`

Load mesh from a file.

Method all readers must provide to import a mesh.

Parameters:

file_name	The file to read.
file_set	Optional pointer to entity set representing file. If this is not NULL, reader may optionally tag the pointed-to set with format-specific meta-data.
subset_list	An optional struct pointer specifying the tags identifying entity sets to be read.
file_id_tag	If specified, reader should store for each entity it reads, a unique integer ID for this tag.

Author:: Jason Kraftcheck

Implements moab::ReaderIface.

Definition at line 57 of file ReadCGNS.cpp.

References cgsize_t, moab::Range::clear(), create_elements(), eps, ErrorCode, filename, fileName, geomSets, moab::ReadUtilIface::get_node_coords(), globalId, moab::Interface::globalId_tag(), MATERIAL_SET_TAG_NAME, MB_CHK_SET_ERR, MB_FILE_DOES_NOT_EXIST, MB_INDEX_OUT_OF_RANGE, MB_NOT_IMPLEMENTED, MB_SET_ERR, MB_START_ID, MB_SUCCESS, MB_UNSUPPORTED_OPERATION, MBEDGE, MBHEX, mbImpl, MBMAXTYPE, MBPRISM, MBPYRAMID, MBQUAD, MBTET, MBTRI, mesh_dim, moab::ReaderIface::IDTag::num_tag_values, process_options(), readMeshIface, size, moab::ReaderIface::SubsetList::tag_list, moab::ReaderIface::SubsetList::tag_list_length, moab::ReaderIface::IDTag::tag_name, moab::Interface::tag_set_data(), and moab::ReaderIface::IDTag::tag_values.

{
    int num_material_sets        = 0;
    const int* material_set_list = 0;

    if( subset_list )
    {
        if( subset_list->tag_list_length > 1 && !strcmp( subset_list->tag_list[0].tag_name, MATERIAL_SET_TAG_NAME ) )
        {
            MB_SET_ERR( MB_UNSUPPORTED_OPERATION, "CGNS supports subset read only by material ID" );
        }
        material_set_list = subset_list->tag_list[0].tag_values;
        num_material_sets = subset_list->tag_list[0].num_tag_values;
    }

    ErrorCode result;

    geomSets.clear();
    globalId = mbImpl->globalId_tag();

    // Create set for more convenient check for material set ids
    std::set< int > blocks;
    for( const int* mat_set_end = material_set_list + num_material_sets; material_set_list != mat_set_end;
         ++material_set_list )
        blocks.insert( *material_set_list );

    // Map of ID->handle for nodes
    std::map< long, EntityHandle > node_id_map;

    // Save filename to member variable so we don't need to pass as an argument
    // to called functions
    fileName = filename;

    // Process options; see src/FileOptions.hpp for API for FileOptions class, and
    // doc/metadata_info.doc for a description of various options used by some of the readers in
    // MOAB
    result = process_options( opts );MB_CHK_SET_ERR( result, fileName << ": problem reading options" );

    // Open file
    int filePtr = 0;

    cg_open( filename, CG_MODE_READ, &filePtr );

    if( filePtr <= 0 )
    {
        MB_SET_ERR( MB_FILE_DOES_NOT_EXIST, fileName << ": fopen returned error" );
    }

    // Read number of verts, elements, sets
    long num_verts = 0, num_elems = 0, num_sets = 0;
    int num_bases = 0, num_zones = 0, num_sections = 0;

    char zoneName[128];
    cgsize_t size[3];

    mesh_dim = 3;  // Default to 3D

    // Read number of bases;
    cg_nbases( filePtr, &num_bases );

    if( num_bases > 1 )
    {
        MB_SET_ERR( MB_NOT_IMPLEMENTED, fileName << ": support for number of bases > 1 not implemented" );
    }

    for( int indexBase = 1; indexBase <= num_bases; ++indexBase )
    {
        // Get the number of zones/blocks in current base.
        cg_nzones( filePtr, indexBase, &num_zones );

        if( num_zones > 1 )
        {
            MB_SET_ERR( MB_NOT_IMPLEMENTED, fileName << ": support for number of zones > 1 not implemented" );
        }

        for( int indexZone = 1; indexZone <= num_zones; ++indexZone )
        {
            // Get zone name and size.
            cg_zone_read( filePtr, indexBase, indexZone, zoneName, size );

            // Read number of sections/Parts in current zone.
            cg_nsections( filePtr, indexBase, indexZone, &num_sections );

            num_verts = size[0];
            num_elems = size[1];
            num_sets  = num_sections;

            std::cout << "\nnumber of nodes = " << num_verts;
            std::cout << "\nnumber of elems = " << num_elems;
            std::cout << "\nnumber of parts = " << num_sets << std::endl;

            // //////////////////////////////////
            // Read Nodes

            // Allocate nodes; these are allocated in one shot, get contiguous handles starting with
            // start_handle, and the reader is passed back double*'s pointing to MOAB's native
            // storage for vertex coordinates for those verts
            std::vector< double* > coord_arrays;
            EntityHandle handle = 0;
            result              = readMeshIface->get_node_coords( 3, num_verts, MB_START_ID, handle, coord_arrays );MB_CHK_SET_ERR( result, fileName << ": Trouble reading vertices" );

            // Fill in vertex coordinate arrays
            cgsize_t beginPos = 1, endPos = num_verts;

            // Read nodes coordinates.
            cg_coord_read( filePtr, indexBase, indexZone, "CoordinateX", RealDouble, &beginPos, &endPos,
                           coord_arrays[0] );
            cg_coord_read( filePtr, indexBase, indexZone, "CoordinateY", RealDouble, &beginPos, &endPos,
                           coord_arrays[1] );
            cg_coord_read( filePtr, indexBase, indexZone, "CoordinateZ", RealDouble, &beginPos, &endPos,
                           coord_arrays[2] );

            // CGNS seems to always include the Z component, even if the mesh is 2D.
            // Check if Z is zero and determine mesh dimension.
            // Also create the node_id_map data.
            double sumZcoord = 0.0;
            double eps       = 1.0e-12;
            for( long i = 0; i < num_verts; ++i, ++handle )
            {
                int index = i + 1;

                node_id_map.insert( std::pair< long, EntityHandle >( index, handle ) ).second;

                sumZcoord += *( coord_arrays[2] + i );
            }
            if( std::abs( sumZcoord ) <= eps ) mesh_dim = 2;

            // Create reverse map from handle to id
            std::vector< int > ids( num_verts );
            std::vector< int >::iterator id_iter = ids.begin();
            std::vector< EntityHandle > handles( num_verts );
            std::vector< EntityHandle >::iterator h_iter = handles.begin();
            for( std::map< long, EntityHandle >::iterator i = node_id_map.begin(); i != node_id_map.end();
                 ++i, ++id_iter, ++h_iter )
            {
                *id_iter = i->first;
                *h_iter  = i->second;
            }
            // Store IDs in tags
            result = mbImpl->tag_set_data( globalId, &handles[0], num_verts, &ids[0] );
            if( MB_SUCCESS != result ) return result;
            if( file_id_tag )
            {
                result = mbImpl->tag_set_data( *file_id_tag, &handles[0], num_verts, &ids[0] );
                if( MB_SUCCESS != result ) return result;
            }
            ids.clear();
            handles.clear();

            // //////////////////////////////////
            // Read elements data

            EntityType ent_type;

            long section_offset = 0;

            // Define which mesh parts are volume families.
            // Mesh parts with volumeID[X] = 0 are boundary parts.
            std::vector< int > volumeID( num_sections, 0 );

            for( int section = 0; section < num_sections; ++section )
            {
                ElementType_t elemsType;
                int iparent_flag, nbndry;
                char sectionName[128];
                int verts_per_elem;

                int cgSection = section + 1;

                cg_section_read( filePtr, indexBase, indexZone, cgSection, sectionName, &elemsType, &beginPos, &endPos,
                                 &nbndry, &iparent_flag );

                size_t section_size = endPos - beginPos + 1;

                // Read element description in current section

                switch( elemsType )
                {
                    case BAR_2:
                        ent_type       = MBEDGE;
                        verts_per_elem = 2;
                        break;
                    case TRI_3:
                        ent_type       = MBTRI;
                        verts_per_elem = 3;
                        if( mesh_dim == 2 ) volumeID[section] = 1;
                        break;
                    case QUAD_4:
                        ent_type       = MBQUAD;
                        verts_per_elem = 4;
                        if( mesh_dim == 2 ) volumeID[section] = 1;
                        break;
                    case TETRA_4:
                        ent_type       = MBTET;
                        verts_per_elem = 4;
                        if( mesh_dim == 3 ) volumeID[section] = 1;
                        break;
                    case PYRA_5:
                        ent_type       = MBPYRAMID;
                        verts_per_elem = 5;
                        if( mesh_dim == 3 ) volumeID[section] = 1;
                        break;
                    case PENTA_6:
                        ent_type       = MBPRISM;
                        verts_per_elem = 6;
                        if( mesh_dim == 3 ) volumeID[section] = 1;
                        break;
                    case HEXA_8:
                        ent_type       = MBHEX;
                        verts_per_elem = 8;
                        if( mesh_dim == 3 ) volumeID[section] = 1;
                        break;
                    case MIXED:
                        ent_type       = MBMAXTYPE;
                        verts_per_elem = 0;
                        break;
                    default:
                        MB_SET_ERR( MB_INDEX_OUT_OF_RANGE, fileName << ": Trouble determining element type" );
                }

                if( elemsType == TETRA_4 || elemsType == PYRA_5 || elemsType == PENTA_6 || elemsType == HEXA_8 ||
                    elemsType == TRI_3 || elemsType == QUAD_4 || ( ( elemsType == BAR_2 ) && mesh_dim == 2 ) )
                {
                    // Read connectivity into conn_array directly

                    cgsize_t iparentdata;
                    cgsize_t connDataSize;

                    // Get number of entries on the connectivity list for this section
                    cg_ElementDataSize( filePtr, indexBase, indexZone, cgSection, &connDataSize );

                    // Need a temporary vector to later cast to conn_array.
                    std::vector< cgsize_t > elemNodes( connDataSize );

                    cg_elements_read( filePtr, indexBase, indexZone, cgSection, &elemNodes[0], &iparentdata );

                    // //////////////////////////////////
                    // Create elements, sets and tags

                    create_elements( sectionName, file_id_tag, ent_type, verts_per_elem, section_offset, section_size,
                                     elemNodes );
                }  // Homogeneous mesh type
                else if( elemsType == MIXED )
                {
                    // We must first sort all elements connectivities into continuous vectors

                    cgsize_t connDataSize;
                    cgsize_t iparentdata;

                    cg_ElementDataSize( filePtr, indexBase, indexZone, cgSection, &connDataSize );

                    std::vector< cgsize_t > elemNodes( connDataSize );

                    cg_elements_read( filePtr, indexBase, indexZone, cgSection, &elemNodes[0], &iparentdata );

                    std::vector< cgsize_t > elemsConn_EDGE;
                    std::vector< cgsize_t > elemsConn_TRI, elemsConn_QUAD;
                    std::vector< cgsize_t > elemsConn_TET, elemsConn_PYRA, elemsConn_PRISM, elemsConn_HEX;
                    cgsize_t count_EDGE, count_TRI, count_QUAD;
                    cgsize_t count_TET, count_PYRA, count_PRISM, count_HEX;

                    // First, get elements count for current section

                    count_EDGE = count_TRI = count_QUAD = 0;
                    count_TET = count_PYRA = count_PRISM = count_HEX = 0;

                    int connIndex = 0;
                    for( int i = beginPos; i <= endPos; i++ )
                    {
                        elemsType = ElementType_t( elemNodes[connIndex] );

                        // Get current cell node count.
                        cg_npe( elemsType, &verts_per_elem );

                        switch( elemsType )
                        {
                            case BAR_2:
                                count_EDGE += 1;
                                break;
                            case TRI_3:
                                count_TRI += 1;
                                break;
                            case QUAD_4:
                                count_QUAD += 1;
                                break;
                            case TETRA_4:
                                count_TET += 1;
                                break;
                            case PYRA_5:
                                count_PYRA += 1;
                                break;
                            case PENTA_6:
                                count_PRISM += 1;
                                break;
                            case HEXA_8:
                                count_HEX += 1;
                                break;
                            default:
                                MB_SET_ERR( MB_INDEX_OUT_OF_RANGE, fileName << ": Trouble determining element type" );
                        }

                        connIndex += ( verts_per_elem + 1 );  // Add one to skip next element descriptor
                    }

                    if( count_EDGE > 0 ) elemsConn_EDGE.resize( count_EDGE * 2 );
                    if( count_TRI > 0 ) elemsConn_TRI.resize( count_TRI * 3 );
                    if( count_QUAD > 0 ) elemsConn_QUAD.resize( count_QUAD * 4 );
                    if( count_TET > 0 ) elemsConn_TET.resize( count_TET * 4 );
                    if( count_PYRA > 0 ) elemsConn_PYRA.resize( count_PYRA * 5 );
                    if( count_PRISM > 0 ) elemsConn_PRISM.resize( count_PRISM * 6 );
                    if( count_HEX > 0 ) elemsConn_HEX.resize( count_HEX * 8 );

                    // Grab mixed section elements connectivity

                    int idx_edge, idx_tri, idx_quad;
                    int idx_tet, idx_pyra, idx_prism, idx_hex;
                    idx_edge = idx_tri = idx_quad = 0;
                    idx_tet = idx_pyra = idx_prism = idx_hex = 0;

                    connIndex = 0;
                    for( int i = beginPos; i <= endPos; i++ )
                    {
                        elemsType = ElementType_t( elemNodes[connIndex] );

                        // Get current cell node count.
                        cg_npe( elemsType, &verts_per_elem );

                        switch( elemsType )
                        {
                            case BAR_2:
                                for( int j = 0; j < 2; ++j )
                                    elemsConn_EDGE[idx_edge + j] = elemNodes[connIndex + j + 1];
                                idx_edge += 2;
                                break;
                            case TRI_3:
                                for( int j = 0; j < 3; ++j )
                                    elemsConn_TRI[idx_tri + j] = elemNodes[connIndex + j + 1];
                                idx_tri += 3;
                                break;
                            case QUAD_4:
                                for( int j = 0; j < 4; ++j )
                                    elemsConn_QUAD[idx_quad + j] = elemNodes[connIndex + j + 1];
                                idx_quad += 4;
                                break;
                            case TETRA_4:
                                for( int j = 0; j < 4; ++j )
                                    elemsConn_TET[idx_tet + j] = elemNodes[connIndex + j + 1];
                                idx_tet += 4;
                                break;
                            case PYRA_5:
                                for( int j = 0; j < 5; ++j )
                                    elemsConn_PYRA[idx_pyra + j] = elemNodes[connIndex + j + 1];
                                idx_pyra += 5;
                                break;
                            case PENTA_6:
                                for( int j = 0; j < 6; ++j )
                                    elemsConn_PRISM[idx_prism + j] = elemNodes[connIndex + j + 1];
                                idx_prism += 6;
                                break;
                            case HEXA_8:
                                for( int j = 0; j < 8; ++j )
                                    elemsConn_HEX[idx_hex + j] = elemNodes[connIndex + j + 1];
                                idx_hex += 8;
                                break;
                            default:
                                MB_SET_ERR( MB_INDEX_OUT_OF_RANGE, fileName << ": Trouble determining element type" );
                        }

                        connIndex += ( verts_per_elem + 1 );  // Add one to skip next element descriptor
                    }

                    // //////////////////////////////////
                    // Create elements, sets and tags

                    if( count_EDGE > 0 )
                        create_elements( sectionName, file_id_tag, MBEDGE, 2, section_offset, count_EDGE,
                                         elemsConn_EDGE );

                    if( count_TRI > 0 )
                        create_elements( sectionName, file_id_tag, MBTRI, 3, section_offset, count_TRI, elemsConn_TRI );

                    if( count_QUAD > 0 )
                        create_elements( sectionName, file_id_tag, MBQUAD, 4, section_offset, count_QUAD,
                                         elemsConn_QUAD );

                    if( count_TET > 0 )
                        create_elements( sectionName, file_id_tag, MBTET, 4, section_offset, count_TET, elemsConn_TET );

                    if( count_PYRA > 0 )
                        create_elements( sectionName, file_id_tag, MBPYRAMID, 5, section_offset, count_PYRA,
                                         elemsConn_PYRA );

                    if( count_PRISM > 0 )
                        create_elements( sectionName, file_id_tag, MBPRISM, 6, section_offset, count_PRISM,
                                         elemsConn_PRISM );

                    if( count_HEX > 0 )
                        create_elements( sectionName, file_id_tag, MBHEX, 8, section_offset, count_HEX, elemsConn_HEX );
                }  // Mixed mesh type
            }      // num_sections

            cg_close( filePtr );

            return result;
        }  // indexZone for
    }      // indexBase for

    return MB_SUCCESS;
}

ErrorCode ReadCGNS::process_options ( const FileOptions & opts ) [private]

Process options passed into the reader.

Parameters:

opts	Options passed into this read

Definition at line 565 of file ReadCGNS.cpp.

References moab::FileOptions::mark_all_seen(), and MB_SUCCESS.

Referenced by load_file().

{
    // Mark all options seen, to avoid compile warning on unused variable
    opts.mark_all_seen();

    return MB_SUCCESS;
}

ErrorCode ReadCGNS::read_tag_values	(	const char *	file_name,
		const char *	tag_name,
		const FileOptions &	opts,
		std::vector< int > &	tag_values_out,
		const SubsetList *	subset_list = `0`
	)		`[virtual]`

Read tag values from a file.

Read the list if all integer tag values from the file for a tag that is a single integer value per entity.

Parameters:

file_name	The file to read.
tag_name	The tag for which to read values
tag_values_out	Output: The list of tag values.
subset_list	An array of tag name and value sets specifying the subset of the file to read. If multiple tags are specified, the sets that match all tags (intersection) should be read.
subset_list_length	The length of the 'subset_list' array.