loadjson.m

function data = loadjson(fname,varargin)
%
% data=loadjson(fname,opt)
%    or
% data=loadjson(fname,'param1',value1,'param2',value2,...)
%
% parse a JSON (JavaScript Object Notation) file or string
%
% authors:Qianqian Fang (q.fang <at> neu.edu)
% created on 2011/09/09, including previous works from 
%
%         Nedialko Krouchev: http://www.mathworks.com/matlabcentral/fileexchange/25713
%            created on 2009/11/02
%         François Glineur: http://www.mathworks.com/matlabcentral/fileexchange/23393
%            created on  2009/03/22
%         Joel Feenstra:
%         http://www.mathworks.com/matlabcentral/fileexchange/20565
%            created on 2008/07/03
%
% input:
%      fname: input file name; if fname contains "{}" or "[]", fname
%             will be interpreted as a JSON string
%      opt: (optional) a struct to store parsing options, opt can be replaced by 
%           a list of ('param',value) pairs - the param string is equivallent
%           to a field in opt. opt can have the following 
%           fields (first in [.|.] is the default)
%
%           SimplifyCell [0|1]: if set to 1, loadjson will call cell2mat
%                         for each element of the JSON data, and group 
%                         arrays based on the cell2mat rules.
%           FastArrayParser [1|0 or integer]: if set to 1, use a
%                         speed-optimized array parser when loading an 
%                         array object. The fast array parser may 
%                         collapse block arrays into a single large
%                         array similar to rules defined in cell2mat; 0 to 
%                         use a legacy parser; if set to a larger-than-1
%                         value, this option will specify the minimum
%                         dimension to enable the fast array parser. For
%                         example, if the input is a 3D array, setting
%                         FastArrayParser to 1 will return a 3D array;
%                         setting to 2 will return a cell array of 2D
%                         arrays; setting to 3 will return to a 2D cell
%                         array of 1D vectors; setting to 4 will return a
%                         3D cell array.
%           ShowProgress [0|1]: if set to 1, loadjson displays a progress bar.
%           ParseStringArray [0|1]: if set to 0, loadjson converts "string arrays" 
%                         (introduced in MATLAB R2016b) to char arrays; if set to 1,
%                         loadjson skips this conversion.
%           FormatVersion [2|float]: set the JSONLab format version; since
%                         v2.0, JSONLab uses JData specification Draft 1
%                         for output format, it is incompatible with all
%                         previous releases; if old output is desired,
%                         please set FormatVersion to 1.9 or earlier.
%           Encoding ['']: json file encoding. Support all encodings of
%                         fopen() function
%           JDataDecode [1|0]: if set to 1, call jdatadecode to decode
%                        JData structures defined in the JData
%                        Specification.
%
% output:
%      dat: a cell array, where {...} blocks are converted into cell arrays,
%           and [...] are converted to arrays
%
% examples:
%      dat=loadjson('{"obj":{"string":"value","array":[1,2,3]}}')
%      dat=loadjson(['examples' filesep 'example1.json'])
%      dat=loadjson(['examples' filesep 'example1.json'],'SimplifyCell',1)
%
% license:
%     BSD or GPL version 3, see LICENSE_{BSD,GPLv3}.txt files for details 
%
% -- this function is part of JSONLab toolbox (http://iso2mesh.sf.net/cgi-bin/index.cgi?jsonlab)
%

    opt=varargin2struct(varargin{:});
    
    if(regexp(fname,'^\s*(?:\[.*\])|(?:\{.*\})\s*$','once'))
       string=fname;
    elseif(exist(fname,'file'))
       try
           encoding = jsonopt('Encoding','',opt);
           if(isempty(encoding))
               string = fileread(fname);
           else
               fid = fopen(fname,'r','n',encoding);
               string = fread(fid,'*char')';
               fclose(fid);
           end
       catch
           try
               string = urlread(['file://',fname]);
           catch
               string = urlread(['file://',fullfile(pwd,fname)]);
           end
       end
    else
       error('input file does not exist');
    end

    pos = 1; inputlen = length(string); inputstr = string;
    arraytokenidx=find(inputstr=='[' | inputstr==']');
    arraytoken=inputstr(arraytokenidx);

    % String delimiters and escape chars identified to improve speed:
    esc = find(inputstr=='"' | inputstr=='\' ); % comparable to: regexp(inputstr, '["\\]');
    index_esc = 1;

    opt.arraytoken_=arraytoken;
    opt.arraytokenidx_=arraytokenidx;

    if(jsonopt('ShowProgress',0,opt)==1)
        opt.progressbar_=waitbar(0,'loading ...');
    end
    jsoncount=1;
    while pos <= inputlen
        [cc,pos]=next_char(inputstr, pos);
        switch(cc)
            case '{'
                [data{jsoncount},pos,index_esc] = parse_object(inputstr, pos, esc, index_esc,opt);
            case '['
                [data{jsoncount},pos,index_esc] = parse_array(inputstr, pos, esc, index_esc,opt);
            otherwise
                pos=error_pos('Outer level structure must be an object or an array',inputstr,pos);
        end
        jsoncount=jsoncount+1;
    end % while

    jsoncount=length(data);
    if(jsoncount==1 && iscell(data))
        data=data{1};
    end

    if(jsonopt('JDataDecode',1,varargin{:})==1)
        data=jdatadecode(data,'Base64',1,'Recursive',1,varargin{:});
    end
    
    if(isfield(opt,'progressbar_'))
        close(opt.progressbar_);
    end
end

%%-------------------------------------------------------------------------
%% helper functions
%%-------------------------------------------------------------------------

function [object, pos,index_esc] = parse_array(inputstr, pos, esc, index_esc, varargin) % JSON array is written in row-major order
    pos=parse_char(inputstr, pos, '[');
    object = cell(0, 1);
    arraydepth=jsonopt('arraydepth_',1,varargin{:});
    pbar=-1;
    if(isfield(varargin{1},'progressbar_'))
        pbar=varargin{1}.progressbar_;
    end
    format=jsonopt('FormatVersion',2,varargin{:});
    [cc,pos]=next_char(inputstr,pos);
    
    if cc ~= ']'
        try
            if(jsonopt('FastArrayParser',1,varargin{:})>=1 && arraydepth>=jsonopt('FastArrayParser',1,varargin{:}))
                [endpos, maxlevel]=fast_match_bracket(varargin{1}.arraytoken_,varargin{1}.arraytokenidx_,pos);
                if(~isempty(endpos))
                    arraystr=['[' inputstr(pos:endpos)];
                    arraystr=sscanf_prep(arraystr);
                    if(isempty(find(arraystr=='"', 1)))
                        % handle 1D array first
                        if(maxlevel==1)
                            astr=arraystr(2:end-1);
                            astr(astr==' ')='';
                            [obj, count, errmsg, nextidx]=sscanf(astr,'%f,',[1,inf]);
                            if(nextidx>=length(astr)-1)
                                    object=obj;
                                    pos=endpos;
                                    pos=parse_char(inputstr, pos, ']');
                                    return;
                            end
                        end

                        % next handle 2D array, these are most common ones
                        if(maxlevel==2 && ~isempty(regexp(arraystr(2:end),'^\s*\[','once')))
                            rowstart=find(arraystr(2:end)=='[',1)+1;
                            if(rowstart)
                                [obj, nextidx]=parse2darray(inputstr,pos+rowstart,arraystr);
                                if(nextidx>=length(arraystr)-1)
                                    object=obj;
                                    if(format>1.9)
                                        object=object.';
                                    end
                                    pos=endpos;
                                    pos=parse_char(inputstr, pos, ']');
                                    if(pbar>0)
                                        waitbar(pos/length(inStr),pbar,'loading ...');
                                    end
                                    return;
                                end
                            end
                        end

                        % for N-D packed array in a nested array construct, 
                        % in the future can replace 1d and 2d cases
                        if(maxlevel>2 && ~isempty(regexp(arraystr(2:end),'^\s*\[\s*\[','once')))
                            astr=arraystr;
                            dims=nestbracket2dim(astr);
                            if(any(dims==0) || all(mod(dims(:),1) == 0)) % all dimensions are integers - this can be problematic
                                astr=arraystr;
                                astr(astr=='[')='';
                                astr(astr==']')='';
                                astr=regexprep(astr,'\s*,',',');
                                astr=regexprep(astr,'\s*$','');
                                [obj, count, errmsg, nextidx]=sscanf(astr,'%f,',inf);
                                if(nextidx>=length(astr)-1)
                                        object=reshape(obj,dims);
                                        if(format>1.9)
                                            object=permute(object,ndims(object):-1:1);
                                        end
                                        pos=endpos;
                                        pos=parse_char(inputstr, pos, ']');
                                        if(pbar>0)
                                            waitbar(pos/length(inStr),pbar,'loading ...');
                                        end
                                        return;
                                end
                            end
                        end
                    end
                end
            end
            if(isempty(regexp(arraystr,':','once')))
                arraystr=regexprep(arraystr,'\[','{');
                arraystr=regexprep(arraystr,'\]','}');
                if(jsonopt('ParseStringArray',0,varargin{:})==0)
                    arraystr=regexprep(arraystr,'\"','''');
                end
                object=eval(arraystr);
                if(iscell(object))
                    object=cellfun(@unescapejsonstring,object,'UniformOutput',false);
                end
                pos=endpos;
            end
        catch
        end
        if(isempty(endpos) || pos~=endpos)
            while 1
                newopt=varargin2struct(varargin{:},'arraydepth_',arraydepth+1);
                [val, pos,index_esc] = parse_value(inputstr, pos, esc, index_esc,newopt);
                object{end+1} = val;
                [cc,pos]=next_char(inputstr,pos);
                if cc == ']'
                    break;
                end
                pos=parse_char(inputstr, pos, ',');
            end
        end
    end

    if(jsonopt('SimplifyCell',0,varargin{:})==1)
      try
        oldobj=object;
        object=cell2mat(object')';
        if(iscell(oldobj) && isstruct(object) && numel(object)>1 && jsonopt('SimplifyCellArray',1,varargin{:})==0)
            object=oldobj;
        elseif(size(object,1)>1 && ismatrix(object))
            object=object';
        end
      catch
      end
    end
    pos=parse_char(inputstr, pos, ']');

    if(pbar>0)
        waitbar(pos/length(inputstr),pbar,'loading ...');
    end
end
%%-------------------------------------------------------------------------

function pos=parse_char(inputstr, pos, c)
    pos=skip_whitespace(pos, inputstr);
    if pos > length(inputstr) || inputstr(pos) ~= c
        pos=error_pos(sprintf('Expected %c at position %%d', c),inputstr,pos);
    else
        pos = pos + 1;
        pos=skip_whitespace(pos, inputstr);
    end
end
%%-------------------------------------------------------------------------

function [c, pos] = next_char(inputstr, pos)
    pos=skip_whitespace(pos, inputstr);
    if pos > length(inputstr)
        c = [];
    else
        c = inputstr(pos);
    end
end

%%-------------------------------------------------------------------------
function [str, pos,index_esc] = parseStr(inputstr, pos, esc, index_esc, varargin)
    if inputstr(pos) ~= '"'
        pos=error_pos('String starting with " expected at position %d',inputstr,pos);
    else
        pos = pos + 1;
    end
    str = '';
    while pos <= length(inputstr)
        while index_esc <= length(esc) && esc(index_esc) < pos
            index_esc = index_esc + 1;
        end
        if index_esc > length(esc)
            str = [str inputstr(pos:end)];
            pos = length(inputstr) + 1;
            break;
        else
            str = [str inputstr(pos:esc(index_esc)-1)];
            pos = esc(index_esc);
        end
        nstr = length(str);
        switch inputstr(pos)
            case '"'
                pos = pos + 1;
                if(~isempty(str))
                    if(strcmp(str,'_Inf_'))
                        str=Inf;
                    elseif(strcmp(str,'-_Inf_'))
                        str=-Inf;
                    elseif(strcmp(str,'_NaN_'))
                        str=NaN;
                    end
                end
                return;
            case '\'
                if pos+1 > length(inputstr)
                    pos=error_pos('End of file reached right after escape character',inputstr,pos);
                end
                pos = pos + 1;
                switch inputstr(pos)
                    case {'"' '\' '/'}
                        str(nstr+1) = inputstr(pos);
                        pos = pos + 1;
                    case {'b' 'f' 'n' 'r' 't'}
                        str(nstr+1) = sprintf(['\' inputstr(pos)]);
                        pos = pos + 1;
                    case 'u'
                        if pos+4 > length(inputstr)
                            pos=error_pos('End of file reached in escaped unicode character',inputstr,pos);
                        end
                        str(nstr+(1:6)) = inputstr(pos-1:pos+4);
                        pos = pos + 5;
                end
            otherwise % should never happen
                str(nstr+1) = inputstr(pos);
                keyboard;
                pos = pos + 1;
        end
    end
    str=unescapejsonstring(str);
    pos=error_pos('End of file while expecting end of inputstr',inputstr,pos);
end
%%-------------------------------------------------------------------------

function [num, pos] = parse_number(inputstr, pos, varargin)
    currstr=inputstr(pos:min(pos+30,end));
    [num, one, err, delta] = sscanf(currstr, '%f', 1);
    if ~isempty(err)
        pos=error_pos('Error reading number at position %d',inputstr,pos);
    end
    pos = pos + delta-1;
end
%%-------------------------------------------------------------------------

function [val, pos,index_esc] = parse_value(inputstr, pos, esc, index_esc, varargin)
    len=length(inputstr);
    if(isfield(varargin{1},'progressbar_'))
        waitbar(pos/len,varargin{1}.progressbar_,'loading ...');
    end

    switch(inputstr(pos))
        case '"'
            [val, pos,index_esc] = parseStr(inputstr, pos, esc, index_esc,varargin{:});
            return;
        case '['
            [val, pos,index_esc] = parse_array(inputstr, pos, esc, index_esc, varargin{:});
            return;
        case '{'
            [val, pos,index_esc] = parse_object(inputstr, pos, esc, index_esc, varargin{:});
            return;
        case {'-','0','1','2','3','4','5','6','7','8','9'}
            [val, pos] = parse_number(inputstr, pos, varargin{:});
            return;
        case 't'
            if pos+3 <= len && strcmpi(inputstr(pos:pos+3), 'true')
                val = true;
                pos = pos + 4;
                return;
            end
        case 'f'
            if pos+4 <= len && strcmpi(inputstr(pos:pos+4), 'false')
                val = false;
                pos = pos + 5;
                return;
            end
        case 'n'
            if pos+3 <= len && strcmpi(inputstr(pos:pos+3), 'null')
                val = [];
                pos = pos + 4;
                return;
            end
    end
    pos=error_pos('Value expected at position %d',inputstr,pos);
end

%%-------------------------------------------------------------------------
function [object, pos, index_esc] = parse_object(inputstr, pos, esc, index_esc, varargin)
    pos=parse_char(inputstr, pos, '{');
    object = [];
    [cc,pos]=next_char(inputstr,pos);
    if cc ~= '}'
        while 1
            [str, pos, index_esc] = parseStr(inputstr, pos, esc, index_esc, varargin{:});
            if isempty(str)
                pos=error_pos('Name of value at position %d cannot be empty',inputstr,pos);
            end
            pos=parse_char(inputstr, pos, ':');
            [val, pos,index_esc] = parse_value(inputstr, pos, esc, index_esc, varargin{:});
            object.(encodevarname(str,varargin{:}))=val;
            [cc,pos]=next_char(inputstr,pos);
            if cc == '}'
                break;
            end
            pos=parse_char(inputstr, pos, ',');
        end
    end
    pos=parse_char(inputstr, pos, '}');
end

%%-------------------------------------------------------------------------

function pos=error_pos(msg, inputstr, pos)
    poShow = max(min([pos-15 pos-1 pos pos+20],length(inputstr)),1);
    if poShow(3) == poShow(2)
        poShow(3:4) = poShow(2)+[0 -1];  % display nothing after
    end
    msg = [sprintf(msg, pos) ': ' ...
    inputstr(poShow(1):poShow(2)) '<error>' inputstr(poShow(3):poShow(4)) ];
    error( ['JSONparser:invalidFormat: ' msg] );
end

%%-------------------------------------------------------------------------

function newpos=skip_whitespace(pos, inputstr)
    newpos=pos;
    while newpos <= length(inputstr) && isspace(inputstr(newpos))
        newpos = newpos + 1;
    end
end

%%-------------------------------------------------------------------------
function newstr=unescapejsonstring(str)
    newstr=str;
    if(iscell(str))
        try
            newstr=cell2mat(cellfun(@(x) cell2mat(x),str(:),'un',0));
        catch
        end
    end
    if(~ischar(str))
        return;
    end
    escapechars={'\\','\"','\/','\a','\b','\f','\n','\r','\t','\v'};
    for i=1:length(escapechars);
        newstr=regexprep(newstr,regexprep(escapechars{i},'\\','\\\\'), escapechars{i});
    end
    newstr=regexprep(newstr,'\\u([0-9A-Fa-f]{4})', '${char(base2dec($1,16))}');
end

%%-------------------------------------------------------------------------
function arraystr=sscanf_prep(str)
    arraystr=str;
    if(regexp(str,'"','once'))
        arraystr=regexprep(arraystr,'"_NaN_"','NaN');
        arraystr=regexprep(arraystr,'"([-+]*)_Inf_"','$1Inf');
    end
    arraystr(arraystr==sprintf('\n'))=[];
    arraystr(arraystr==sprintf('\r'))=[];
end

%%-------------------------------------------------------------------------
function [obj, nextidx,nextdim]=parse2darray(inputstr,startpos,arraystr)
    rowend=match_bracket(inputstr,startpos);
    rowstr=sscanf_prep(inputstr(startpos-1:rowend));
    [vec1, nextdim, errmsg, nextidx]=sscanf(rowstr,'%f,',[1 inf]);
    if(nargin==2)
        obj=nextdim;
        return;
    end
    astr=arraystr;
    astr(astr=='[')='';
    astr(astr==']')='';
    astr=regexprep(deblank(astr),'\s+,',',');
    [obj, count, errmsg, nextidx]=sscanf(astr,'%f,',inf);
    if(nextidx>=length(astr)-1)
            obj=reshape(obj,nextdim,numel(obj)/nextdim);
            nextidx=length(arraystr)+1;
    end
end