loadmsh.m

function [mesh] = loadmsh(name)
%LOADMSH load a *.MSH file for JIGSAW.
%
%   MESH = LOADMSH(NAME);
%
%   The following are optionally read from "NAME.MSH". Enti-
%   ties are loaded if they are present in the file:
%
%   .IF. MESH.MSHID == 'EUCLIDEAN-MESH':
%   -----------------------------------
%
%   MESH.POINT.COORD - [NPxND+1] array of point coordinates,
%       where ND is the number of spatial dimenions.
%       COORD(K,ND+1) is an ID tag for the K-TH point.
%
%   MESH.POINT.POWER - [NPx 1] array of vertex "weights",
%       associated with the dual "power" tessellation.
%
%   MESH.EDGE2.INDEX - [N2x 3] array of indexing for EDGE-2
%       elements, where INDEX(K,1:2) is an array of
%       "point-indices" associated with the K-TH edge, and
%       INDEX(K,3) is an ID tag for the K-TH edge.
%
%   MESH.TRIA3.INDEX - [N3x 4] array of indexing for TRIA-3
%       elements, where INDEX(K,1:3) is an array of
%       "point-indices" associated with the K-TH tria, and
%       INDEX(K,4) is an ID tag for the K-TH tria.
%
%   MESH.QUAD4.INDEX - [N4x 5] array of indexing for QUAD-4
%       elements, where INDEX(K,1:4) is an array of
%       "point-indices" associated with the K-TH quad, and
%       INDEX(K,5) is an ID tag for the K-TH quad.
%
%   MESH.TRIA4.INDEX - [M4x 5] array of indexing for TRIA-4
%       elements, where INDEX(K,1:4) is an array of
%       "point-indices" associated with the K-TH tria, and
%       INDEX(K,5) is an ID tag for the K-TH tria.
%
%   MESH.HEXA8.INDEX - [M8x 9] array of indexing for HEXA-8
%       elements, where INDEX(K,1:8) is an array of
%       "point-indices" associated with the K-TH hexa, and
%       INDEX(K,9) is an ID tag for the K-TH hexa.
%
%   MESH.WEDG6.INDEX - [M6x 7] array of indexing for WEDG-6
%       elements, where INDEX(K,1:6) is an array of
%       "point-indices" associated with the K-TH wedg, and
%       INDEX(K,7) is an ID tag for the K-TH wedg.
%
%   MESH.PYRA5.INDEX - [M5x 6] array of indexing for PYRA-5
%       elements, where INDEX(K,1:5) is an array of
%       "point-indices" associated with the K-TH pyra, and
%       INDEX(K,6) is an ID tag for the K-TH pyra.
%
%   MESH.BOUND.INDEX - [NBx 3] array of "boundary" indexing
%       in the domain, indicating how elements in the
%       geometry are associated with various enclosed areas
%       /volumes, herein known as "parts". INDEX(:,1) is an
%       array of "part" ID's, INDEX(:,2) is an array of
%       element numbering and INDEX(:,3) is an array of
%       element "tags", describing which element "kind" is
%       numbered via INDEX(:,2). Element tags are defined
%       via constants defined in GLOBALS.m.
%       In the default case, where BOUND is not specified,
%       all elements in the geometry are assumed to define
%       the boundaries of enclosed "parts".
%
%   MESH.VALUE - [NPxNV] array of "values" associated with
%       the vertices of the mesh.
%
%   MESH.SLOPE - [NPx 1] array of "slopes" associated with
%       the vertices of the mesh. Slope values define the
%       gradient-limits ||dh/dx|| used by the Eikonal solver
%       MARCHE.
%
%   .IF. MESH.MSHID == 'ELLIPSOID-MESH':
%   -----------------------------------
%
%   MESH.RADII - [ 3x 1] array of principle ellipsoid radii.
%
%   Additionally, entities described in the 'EUCLIDEAN-MESH'
%   data-type are optionally loaded.
%
%   .IF. MESH.MSHID == 'EUCLIDEAN-GRID':
%   .OR. MESH.MSHID == 'ELLIPSOID-GRID':
%   -----------------------------------
%
%   MESH.POINT.COORD - [NDx1] cell array of grid coordinates
%       where ND is the number of spatial dimenions. Each
%       array COORD{ID} should be a vector of grid coord.'s,
%       increasing or decreasing monotonically.
%
%   MESH.VALUE - [NMxNV] array of "values" associated with
%       the vertices of the grid, where NM is the product of
%       the dimensions of the grid. NV values are associated
%       with each vertex.
%
%   MESH.SLOPE - [NMx 1] array of "slopes" associated with
%       the vertices of the grid, where NM is the product of
%       the dimensions of the grid. Slope values define the
%       gradient-limits ||dh/dx|| used by the Eikonal solver
%       MARCHE.
%
%   See also JIGSAW, SAVEMSH
%

%-----------------------------------------------------------
%   Darren Engwirda
%   github.com/dengwirda/jigsaw-matlab
%   30-May-2020
%   d.engwirda@gmail.com
%-----------------------------------------------------------
%

    mesh = [] ;

    try

    ffid = fopen(name,'r') ;

    real = '%f;' ;
    ints = '%i;' ;

    kind = 'EUCLIDEAN-MESH';

    if (ffid < +0)
    error(['File not found: ', name]) ;
    end

    nver = +0 ;
    ndim = +0 ;

    while (true)

    %-- read next line from file
        lstr = fgetl(ffid);

        if (ischar(lstr) )

        if (length(lstr) > +0 && lstr(1) ~= '#')

        %-- tokenise line about '=' character
            tstr = regexp(lower(lstr),'=','split');

            if (length(tstr) ~= +2)
                warning(['Invalid tag: ',lstr]);
                continue;
            end

            switch (strtrim(tstr{1}))
            case 'mshid'

        %-- read "MSHID" data

                stag = regexp(tstr{2},';','split');

                nver = str2double(stag{1}) ;

                if (isnan(nver))

                warning(['Invalid MSHID: ', lstr]);
                continue;

                end

                if (length(stag) >= +2)
                    kind = ...
                    strtrim(upper(stag{2}));
                end

            case 'ndims'

        %-- read "NDIMS" data

                ndim = str2double(tstr{2}) ;

            case 'radii'

        %-- read "RADII" data

                stag = regexp(tstr{2},';','split');

                if (length(stag) == +3)

                mesh.radii = [ ...
                    str2double(stag{1}), ...
                    str2double(stag{2}), ...
                    str2double(stag{3})  ...
                    ] ;

                if (any(isnan(mesh.radii)))

                warning(['Invalid RADII: ', lstr]);
                continue;

                end

                else

                warning(['Invalid RADII: ', lstr]);
                continue;

                end

            case 'point'

        %-- read "POINT" data

                nnum = str2double(tstr{2}) ;

                numr = nnum*(ndim+1);

               [data,have] = ...
            fscanf(ffid,[repmat(real,1,ndim),'%i'],numr);

                if (have ~= numr)

                warning('Invalid POINT! ') ;
                continue ;

                end

                if (ndim == +2)
                mesh.point.coord = [ ...
                    data(1:3:end), ...
                    data(2:3:end), ...
                    data(3:3:end)] ;
                end
                if (ndim == +3)
                mesh.point.coord = [ ...
                    data(1:4:end), ...
                    data(2:4:end), ...
                    data(3:4:end), ...
                    data(4:4:end)] ;
                end

            case 'seeds'

        %-- read "SEEDS" data

                nnum = str2double(tstr{2}) ;

                numr = nnum*(ndim+1);

               [data,have] = ...
            fscanf(ffid,[repmat(real,1,ndim),'%i'],numr);

                if (have ~= numr)

                warning('Invalid SEEDS! ') ;
                continue ;

                end

                if (ndim == +2)
                mesh.seeds.coord = [ ...
                    data(1:3:end), ...
                    data(2:3:end), ...
                    data(3:3:end)] ;
                end
                if (ndim == +3)
                mesh.seeds.coord = [ ...
                    data(1:4:end), ...
                    data(2:4:end), ...
                    data(3:4:end), ...
                    data(4:4:end)] ;
                end

            case 'coord'

        %-- read "COORD" data

                stag = regexp(tstr{2},';','split');

                idim = str2double(stag{1}) ;
                cnum = str2double(stag{2}) ;

                ndim = max(ndim,idim);

               [data,have] = ...
                    fscanf(ffid,'%f',cnum) ;

                if (have ~= cnum)

                warning('Invalid COORD! ') ;
                continue ;

                end

                mesh.point.coord{idim}= data  ;

            case 'edge2'

        %-- read "EDGE2" data

                nnum = str2double(tstr{2}) ;

                numr = nnum * 3;

               [data,have] = ...
            fscanf(ffid,[repmat(ints,1,2),'%i'],numr);

                if (have ~= numr)

                warning('Invalid EDGE2! ') ;
                continue ;

                end

                mesh.edge2.index = [ ...
                    data(1:3:end), ...
                    data(2:3:end), ...
                    data(3:3:end)] ;

                mesh.edge2.index(:,1:2) = ...
                mesh.edge2.index(:,1:2) + 1;

            case 'tria3'

        %-- read "TRIA3" data

                nnum = str2double(tstr{2}) ;

                numr = nnum * 4;

               [data,have] = ...
            fscanf(ffid,[repmat(ints,1,3),'%i'],numr);

                if (have ~= numr)

                warning('Invalid TRIA3! ') ;
                continue ;

                end

                mesh.tria3.index = [ ...
                    data(1:4:end), ...
                    data(2:4:end), ...
                    data(3:4:end), ...
                    data(4:4:end)] ;

                mesh.tria3.index(:,1:3) = ...
                mesh.tria3.index(:,1:3) + 1;

            case 'quad4'

        %-- read "QUAD4" data

                nnum = str2double(tstr{2}) ;

                numr = nnum * 5;

               [data,have] = ...
            fscanf(ffid,[repmat(ints,1,4),'%i'],numr);

                if (have ~= numr)

                warning('Invalid QUAD4! ') ;
                continue ;

                end

                mesh.quad4.index = [ ...
                    data(1:5:end), ...
                    data(2:5:end), ...
                    data(3:5:end), ...
                    data(4:5:end), ...
                    data(5:5:end)] ;

                mesh.quad4.index(:,1:4) = ...
                mesh.quad4.index(:,1:4) + 1;

            case 'tria4'

        %-- read "TRIA4" data

                nnum = str2double(tstr{2}) ;

                numr = nnum * 5;

               [data,have] = ...
            fscanf(ffid,[repmat(ints,1,4),'%i'],numr);

                if (have ~= numr)

                warning('Invalid TRIA4! ') ;
                continue ;

                end

                mesh.tria4.index = [ ...
                    data(1:5:end), ...
                    data(2:5:end), ...
                    data(3:5:end), ...
                    data(4:5:end), ...
                    data(5:5:end)] ;

                mesh.tria4.index(:,1:4) = ...
                mesh.tria4.index(:,1:4) + 1;

            case 'hexa8'

        %-- read "HEXA8" data

                nnum = str2double(tstr{2}) ;

                numr = nnum * 9;

               [data,have] = ...
            fscanf(ffid,[repmat(ints,1,8),'%i'],numr);

                if (have ~= numr)

                warning('Invalid HEXA8! ') ;
                continue ;

                end

                mesh.hexa8.index = [ ...
                    data(1:9:end), ...
                    data(2:9:end), ...
                    data(3:9:end), ...
                    data(4:9:end), ...
                    data(5:9:end), ...
                    data(6:9:end), ...
                    data(7:9:end), ...
                    data(8:9:end), ...
                    data(9:9:end)] ;

                mesh.hexa8.index(:,1:8) = ...
                mesh.hexa8.index(:,1:8) + 1;

            case 'wedg6'

        %-- read "WEDG6" data

                nnum = str2double(tstr{2}) ;

                numr = nnum * 7;

               [data,have] = ...
            fscanf(ffid,[repmat(ints,1,6),'%i'],numr);

                if (have ~= numr)

                warning('Invalid WEDG6! ') ;
                continue ;

                end

                mesh.wedg6.index = [ ...
                    data(1:7:end), ...
                    data(2:7:end), ...
                    data(3:7:end), ...
                    data(4:7:end), ...
                    data(5:7:end), ...
                    data(6:7:end), ...
                    data(7:7:end)] ;

                mesh.wedg6.index(:,1:6) = ...
                mesh.wedg6.index(:,1:6) + 1;

            case 'pyra5'

        %-- read "PYRA5" data

                nnum = str2double(tstr{2}) ;

                numr = nnum * 6;

               [data,have] = ...
            fscanf(ffid,[repmat(ints,1,5),'%i'],numr);

                if (have ~= numr)

                warning('Invalid PYRA5! ') ;
                continue ;

                end

                mesh.pyra5.index = [ ...
                    data(1:6:end), ...
                    data(2:6:end), ...
                    data(3:6:end), ...
                    data(4:6:end), ...
                    data(5:6:end), ...
                    data(6:6:end)] ;

                mesh.pyra5.index(:,1:5) = ...
                mesh.pyra5.index(:,1:5) + 1;

            case 'bound'

        %-- read "BOUND" data

                nnum = str2double(tstr{2}) ;

                numr = nnum * 3;

               [data,have] = ...
            fscanf(ffid,[repmat(ints,1,2),'%i'],numr);

                if (have ~= numr)

                warning('Invalid BOUND! ') ;
                continue ;

                end

                mesh.bound.index = [ ...
                    data(1:3:end), ...
                    data(2:3:end), ...
                    data(3:3:end)] ;

                mesh.bound.index(:,2:2) = ...
                mesh.bound.index(:,2:2) + 1;

            case 'value'

        %-- read "VALUE" data

                stag = regexp(tstr{2},';','split');

                if (length(stag) == +2)

                nnum = str2double(stag{1}) ;
                vnum = str2double(stag{2}) ;

                else

                warning(['Invalid VALUE: ', lstr]);
                continue;

                end

                numr = nnum * (vnum+0) ;

                fstr = repmat(real,1,vnum) ;

               [data,have] = fscanf( ...
                  ffid,fstr(1:end-1),numr) ;

                if (have ~= numr)

                warning(['Invalid VALUE: ', lstr]);
                continue ;

                end

                mesh.value = zeros(nnum, vnum);

                for vpos = +1 : vnum

                    mesh.value(:,vpos) = ...
                       data(vpos:vnum:end) ;

                end

            case 'power'

        %-- read "POWER" data

                stag = regexp(tstr{2},';','split');

                if (length(stag) == +2)

                nnum = str2double(stag{1}) ;
                pnum = str2double(stag{2}) ;

                else

                warning(['Invalid POWER: ', lstr]);
                continue;

                end

                numr = nnum * (pnum+0) ;

                fstr = repmat(real,1,pnum) ;

               [data,have] = fscanf( ...
                  ffid,fstr(1:end-1),numr) ;

                if (have ~= numr)

                warning(['Invalid POWER: ', lstr]);
                continue ;

                end

                mesh.point.power = ...
                    zeros(nnum, pnum) ;

                for ppos = +1 : pnum

                    mesh.point.power(:,ppos) = ...
                       data(ppos:pnum:end) ;

                end

            case 'slope'

        %-- read "SLOPE" data

                stag = regexp(tstr{2},';','split');

                if (length(stag) == +2)

                nnum = str2double(stag{1}) ;
                vnum = str2double(stag{2}) ;

                else

                warning(['Invalid SLOPE: ', lstr]);
                continue;

                end

                numr = nnum * (vnum+0) ;

                fstr = repmat(real,1,vnum) ;

               [data,have] = fscanf( ...
                  ffid,fstr(1:end-1),numr) ;

                if (have ~= numr)

                warning(['Invalid SLOPE: ', lstr]);
                continue ;

                end

                mesh.slope = ...
                    zeros(nnum, vnum) ;

                for ppos = +1 : vnum

                    mesh.slope(:,ppos) = ...
                       data(ppos:vnum:end) ;

                end



            end

        end

        else
    %-- if(~ischar(lstr)) //i.e. end-of-file
            break;
        end

    end

    mesh.mshID = kind ;
    mesh.fileV = nver ;

    if (ndim > +0)
        switch (lower(mesh.mshID))
            case{'euclidean-grid', ...
                 'ellipsoid-grid'}
                if (inspect(mesh,'value') && ...
                    inspect(mesh,'point') )

                if     (ndim == +2)

            %-- reshape data to 2-dim. array
                mesh.value = reshape( ...
                    mesh.value, ...
                length(mesh.point.coord{2}), ...
                length(mesh.point.coord{1}), ...
                    [] ) ;

                elseif (ndim == +3)

            %-- reshape data to 3-dim. array
                mesh.value = reshape( ...
                    mesh.value, ...
                length(mesh.point.coord{2}), ...
                length(mesh.point.coord{1}), ...
                length(mesh.point.coord{3}), ...
                    [] ) ;

                end

                end

                if (inspect(mesh,'slope') && ...
                    inspect(mesh,'point') )

                if     (ndim == +2)

            %-- reshape data to 2-dim. array
                mesh.slope = reshape( ...
                    mesh.slope, ...
                length(mesh.point.coord{2}), ...
                length(mesh.point.coord{1}), ...
                    [] ) ;

                elseif (ndim == +3)

            %-- reshape data to 3-dim. array
                mesh.slope = reshape( ...
                    mesh.slope, ...
                length(mesh.point.coord{2}), ...
                length(mesh.point.coord{1}), ...
                length(mesh.point.coord{3}), ...
                    [] ) ;

                end

                end
        end
    end

    fclose(ffid) ;

    catch err

%-- ensure that we close the file regardless!
    if (ffid>-1)
    fclose(ffid) ;
    end

    rethrow(err) ;

    end

end