loadjson.m

function [data, mmap] = loadjson(fname, varargin)
%
% data=loadjson(fname,opt)
%    or
% [data, mmap]=loadjson(fname,'param1',value1,'param2',value2,...)
%
% parse a JSON (JavaScript Object Notation) file or string and return a
% matlab data structure with optional memory-map (mmap) table
%
% 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 equivalent
%           to a field in opt. opt can have the following
%           fields (first in [.|.] is the default)
%
%           SimplifyCell [1|0]: 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.
%           UseMap [0|1]: if set to 1, loadjson uses a containers.Map to
%                         store map objects; otherwise use a struct object
%           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 [3|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
%           ObjectID [0|integer or list]: if set to a positive number,
%                         it returns the specified JSON object by index
%                         in a multi-JSON document; if set to a vector,
%                         it returns a list of specified objects.
%           JDataDecode [1|0]: if set to 1, call jdatadecode to decode
%                         JData structures defined in the JData
%                         Specification.
%           BuiltinJSON [0|1]: if set to 1, this function attempts to call
%                         jsondecode, if presents (MATLAB R2016b or Octave
%                         6) first. If jsondecode does not exist or failed,
%                         this function falls back to the jsonlab parser
%           MmapOnly [0|1]: if set to 1, this function only returns mmap
%           MMapInclude 'str1' or  {'str1','str2',..}: if provided, the
%                         returned mmap will be filtered by only keeping
%                         entries containing any one of the string patterns
%                         provided in a cell
%           MMapExclude 'str1' or  {'str1','str2',..}: if provided, the
%                         returned mmap will be filtered by removing
%                         entries containing any one of the string patterns
%                         provided in a cell
%
% output:
%      dat: a cell array, where {...} blocks are converted into cell arrays,
%           and [...] are converted to arrays
%      mmap: (optional) a cell array as memory-mapping table in the form of
%             {{jsonpath1,[start,length,<whitespace_pre>]},
%              {jsonpath2,[start,length,<whitespace_pre>]}, ...}
%           where jsonpath_i is a string in the JSONPath [1,2] format, and
%           "start" is an integer referring to the offset from the beginning
%           of the stream, and "length" is the JSON object string length.
%           An optional 3rd integer "whitespace_pre" may appear to record
%           the preceding whitespace length in case expansion of the data
%           record is needed when using the mmap.
%
%           The format of the mmap table returned from this function
%           follows the JSON-Mmap Specification Draft 1 [3] defined by the
%           NeuroJSON project, see https://neurojson.org/jsonmmap/draft1/
%
%           Memory-mapping table (mmap) is useful when fast reading/writing
%           specific data records inside a large JSON file without needing
%           to load/parse/overwrite the entire file.
%
%           The JSONPath keys used in mmap is largely compatible to the
%           upstream specification defined in [1], with a slight extension
%           to handle concatenated JSON files.
%
%           In the mmap jsonpath key, a '$' denotes the root object, a '.'
%           denotes a child of the preceding element; '.key' points to the
%           value segment of the child named "key" of the preceding
%           object; '[i]' denotes the (i+1)th member of the preceding
%           element, which must be an array. For example, a key
%
%           $.obj1.obj2[0].obj3
%
%           defines the memory-map of the "value" section in the below
%           hierarchy:
%             {
%                "obj1":{
%                    "obj2":[
%                       {"obj3":value},
%                       ...
%                    ],
%                    ...
%                 }
%             }
%           Please note that "value" can be any valid JSON value, including
%           an array, an object, a string or numerical value.
%
%           To handle concatenated JSON objects (including ndjson,
%           http://ndjson.org/), such as
%
%             {"root1": {"obj1": ...}}
%             ["root2", value1, value2, {"obj2": ...}]
%             {"root3": ...}
%
%           we use '$' or '$0' for the first root-object, and '$1' refers
%           to the 2nd root object (["root2",...]) and '$2' refers to the
%           3rd root object, and so on. Please note that this syntax is an
%           extension from the JSONPath documentation [1,2]
%
%           [1] https://goessner.net/articles/JsonPath/
%           [2] http://jsonpath.herokuapp.com/
%           [3] https://neurojson.org/jsonmmap/draft1/
%
% examples:
%      dat=loadjson('{"obj":{"string":"value","array":[1,2,3]}}')
%      dat=loadjson(['examples' filesep 'example1.json'])
%      [dat, mmap]=loadjson(['examples' filesep 'example1.json'],'SimplifyCell',0)
%
% 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(fname);
        catch
            string = urlread(['file://', fullfile(pwd, fname)]);
        end
    end
elseif (regexpi(fname, '^\s*(http|https|ftp|file)://'))
    string = urlread(fname);
else
    error('input file does not exist');
end

if (jsonopt('BuiltinJSON', 0, opt) && exist('jsondecode', 'builtin'))
    try
        newstring = regexprep(string, '[\r\n]', '');
        newdata = jsondecode(newstring);
        newdata = jdatadecode(newdata, 'Base64', 1, 'Recursive', 1, varargin{:});
        data = newdata;
        return
    catch
        warning('built-in jsondecode function failed to parse the file, fallback to loadjson');
    end
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;
opt.simplifycell = jsonopt('SimplifyCell', 1, opt);
opt.simplifycellarray = jsonopt('SimplifyCellArray', opt.simplifycell, opt);
opt.formatversion = jsonopt('FormatVersion', 3, opt);
opt.fastarrayparser = jsonopt('FastArrayParser', 1, opt);
opt.parsestringarray = jsonopt('ParseStringArray', 0, opt);
opt.usemap = jsonopt('UseMap', 0, opt);
opt.arraydepth_ = 1;
opt.mmaponly = jsonopt('MmapOnly', 0, opt);

if (jsonopt('ShowProgress', 0, opt) == 1)
    opt.progressbar_ = waitbar(0, 'loading ...');
end

objid = jsonopt('ObjectID', 0, opt);
maxobjid = max(objid);
if (maxobjid == 0)
    maxobjid = inf;
end
opt.jsonpath_ = '$';
if (nargout > 1 || opt.mmaponly)
    mmap = {};
end
jsoncount = 1;
while pos <= inputlen
    [cc, pos, w1] = next_char(inputstr, pos);
    switch (cc)
        case '{'
            if (nargout > 1 || opt.mmaponly)
                mmap{end + 1} = {opt.jsonpath_, [pos, 0, w1]};
                [data{jsoncount}, pos, index_esc, newmmap] = parse_object(inputstr, pos, esc, index_esc, opt);
                if (pos < 0)
                    opt.usemap = 1;
                    [data{jsoncount}, pos, index_esc, newmmap] = parse_object(inputstr, -pos, esc, index_esc, opt);
                end
                mmap{end}{2}(2) = pos - mmap{end}{2}(1);
                mmap = [mmap(:); newmmap(:)];
            else
                [data{jsoncount}, pos, index_esc] = parse_object(inputstr, pos, esc, index_esc, opt);
                if (pos < 0)
                    opt.usemap = 1;
                    [data{jsoncount}, pos, index_esc] = parse_object(inputstr, -pos, esc, index_esc, opt);
                end
            end
        case '['
            if (nargout > 1 || opt.mmaponly)
                mmap{end + 1} = {opt.jsonpath_, [pos, 0, w1]};
                [data{jsoncount}, pos, index_esc, newmmap] = parse_array(inputstr, pos, esc, index_esc, opt);
                mmap{end}{2}(2) = pos - mmap{end}{2}(1);
                mmap = [mmap(:); newmmap(:)];
            else
                [data{jsoncount}, pos, index_esc] = parse_array(inputstr, pos, esc, index_esc, opt);
            end
        otherwise
            pos = error_pos('Outer level structure must be an object or an array', inputstr, pos);
    end
    if (jsoncount >= maxobjid)
        break
    end
    opt.jsonpath_ = sprintf('$%d', jsoncount);
    jsoncount = jsoncount + 1;
end % while

if (length(objid) > 1 || min(objid) > 1)
    data = data(objid(objid <= length(data)));
end

jsoncount = length(data);
if (jsoncount == 1 && iscell(data))
    data = data{1};
end
if (nargout > 1 || opt.mmaponly)
    mmap = mmap';
    mmap = filterjsonmmap(mmap, jsonopt('MMapExclude', {}, opt), 0);
    mmap = filterjsonmmap(mmap, jsonopt('MMapInclude', {}, opt), 1);
    mmap = cellfun(@(x) {x{1}, x{2}(1:(2 + int8(length(x{2}) >= 3 && (x{2}(3) > 0))))}, mmap, 'UniformOutput', false);
end
if (jsonopt('JDataDecode', 1, varargin{:}) == 1)
    try
        data = jdatadecode(data, 'Base64', 1, 'Recursive', 1, varargin{:});
    catch ME
        warning(['Failed to decode embedded JData annotations, '...
                 'return raw JSON data\n\njdatadecode error: %s\n%s\nCall stack:\n%s\n'], ...
                ME.identifier, ME.message, char(savejson('', ME.stack)));
    end
end
if (opt.mmaponly)
    data = mmap;
end
if (isfield(opt, 'progressbar_'))
    close(opt.progressbar_);
end

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

function [object, pos, index_esc, mmap] = parse_array(inputstr, pos, esc, index_esc, varargin) % JSON array is written in row-major order
if (nargout > 3)
    mmap = {};
    origpath = varargin{1}.jsonpath_;
end
pos = parse_char(inputstr, pos, '[');
object = cell(0, 1);
arraydepth = varargin{1}.arraydepth_;
pbar = -1;
if (isfield(varargin{1}, 'progressbar_'))
    pbar = varargin{1}.progressbar_;
end
format = varargin{1}.formatversion;
[cc, pos] = next_char(inputstr, pos);
endpos = [];

if cc ~= ']'
    try
        if ((varargin{1}.fastarrayparser) >= 1 && arraydepth >= varargin{1}.fastarrayparser)
            [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

                    % for N-D packed array in a nested array construct,
                    if (maxlevel >= 2 && ~isempty(regexp(arraystr(2:end), '^\s*\[', 'once')))
                        [dims, isndarray] = nestbracket2dim(arraystr);
                        rowstart = find(arraystr(2:end) == '[', 1) + 1;
                        if (rowstart && isndarray)
                            [obj, nextidx] = parsendarray(arraystr, dims);
                            if (nextidx >= length(arraystr) - 1)
                                object = obj;
                                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(inputstr), pbar, 'loading ...');
                                end
                                return
                            end
                        end
                    end
                end
            end
        end
        if (isempty(regexp(arraystr, ':', 'once')) && isempty(regexp(arraystr, '\(', 'once')))
            arraystr = regexprep(arraystr, '\[', '{');
            arraystr = regexprep(arraystr, '\]', '}');
            if (varargin{1}.parsestringarray == 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)
        w2 = 0;
        while 1
            varargin{1}.arraydepth_ = arraydepth + 1;
            if (nargout > 3)
                varargin{1}.jsonpath_ = [origpath sprintf('[%d]', length(object))];
                mmap{end + 1} = {varargin{1}.jsonpath_, [pos, 0, w2]};
                [val, pos, index_esc, newmmap] = parse_value(inputstr, pos, esc, index_esc, varargin{:});
                mmap{end}{2}(2) = pos - mmap{end}{2}(1);
                mmap = [mmap(:); newmmap(:)];
            else
                [val, pos, index_esc] = parse_value(inputstr, pos, esc, index_esc, varargin{:});
            end
            object{end + 1} = val;
            [cc, pos] = next_char(inputstr, pos);
            if cc == ']'
                break
            end
            [pos, w1, w2] = parse_char(inputstr, pos, ',');
        end
    end
end

if (varargin{1}.simplifycell)
    if (iscell(object) && ~isempty(object) && (all(cellfun(@isnumeric, object)) || all(cellfun(@isstruct, object))))
        if (all(cellfun(@(e) isequal(size(object{1}), size(e)), object(2:end))))
            try
                oldobj = object;
                if (iscell(object) && length(object) > 1 && ndims(object{1}) >= 2)
                    catdim = size(object{1});
                    catdim = ndims(object{1}) - (catdim(end) == 1) + 1;
                    object = cat(catdim, object{:});
                    object = permute(object, ndims(object):-1:1);
                else
                    object = cell2mat(object.').';
                end
                if (iscell(oldobj) && isstruct(object) && numel(object) > 1 && varargin{1}.simplifycellarray == 0)
                    object = oldobj;
                end
            catch
            end
        end
    end
    if (~iscell(object) && size(object, 1) > 1 && ndims(object) == 2)
        object = object.';
    end
end
pos = parse_char(inputstr, pos, ']');

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

function [pos, w1, w2] = parse_char(inputstr, pos, c)
w1 = pos;
w2 = 0;
pos = skip_whitespace(pos, inputstr);
w1 = pos - w1;
if pos > length(inputstr) || inputstr(pos) ~= c
    pos = error_pos(sprintf('Expected %c at position %%d', c), inputstr, pos);
else
    pos = pos + 1;
    w2 = pos;
    pos = skip_whitespace(pos, inputstr);
    w2 = pos - w2;
end
%% -------------------------------------------------------------------------

function [c, pos, w1] = next_char(inputstr, pos)
w1 = pos;
pos = skip_whitespace(pos, inputstr);
w1 = pos - w1;
if pos > length(inputstr)
    c = [];
else
    c = inputstr(pos);
end

%% -------------------------------------------------------------------------
function [str, pos, index_esc, mmap] = parseStr(inputstr, pos, esc, index_esc, varargin)
if (nargout > 3)
    mmap = {};
end
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);
%% -------------------------------------------------------------------------

function [num, pos] = parse_number(inputstr, pos, varargin)
currstr = inputstr(pos:min(pos + 30, end));
[num, tmp, 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;
%% -------------------------------------------------------------------------

function varargout = parse_value(inputstr, pos, esc, index_esc, varargin)
len = length(inputstr);
if (isfield(varargin{1}, 'progressbar_'))
    waitbar(pos / len, varargin{1}.progressbar_, 'loading ...');
end
varargout{3} = index_esc;
if (nargout > 3)
    varargout{4} = {};
end
switch (inputstr(pos))
    case '"'
        [varargout{1:nargout}] = parseStr(inputstr, pos, esc, index_esc, varargin{:});
        return
    case '['
        [varargout{1:nargout}] = parse_array(inputstr, pos, esc, index_esc, varargin{:});
        return
    case '{'
        [varargout{1:nargout}] = parse_object(inputstr, pos, esc, index_esc, varargin{:});
        if (varargout{2} < 0)
            varargin{1}.usemap = 1;
            [varargout{1:nargout}] = parse_object(inputstr, -varargout{2}, esc, index_esc, varargin{:});
        end
        return
    case {'-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'}
        [varargout{1:2}] = parse_number(inputstr, pos, varargin{:});
        return
    case 't'
        if pos + 3 <= len && strcmpi(inputstr(pos:pos + 3), 'true')
            varargout{1} = true;
            varargout{2} = pos + 4;
            return
        end
    case 'f'
        if pos + 4 <= len && strcmpi(inputstr(pos:pos + 4), 'false')
            varargout{1} = false;
            varargout{2} = pos + 5;
            return
        end
    case 'n'
        if pos + 3 <= len && strcmpi(inputstr(pos:pos + 3), 'null')
            varargout{1} = [];
            varargout{2} = pos + 4;
            return
        end
end
varargout{2} = error_pos('Value expected at position %d', inputstr, pos);

%% -------------------------------------------------------------------------
function [object, pos, index_esc, mmap] = parse_object(inputstr, pos, esc, index_esc, varargin)
oldpos = pos;
oldindex_esc = index_esc;
if (nargout > 3)
    mmap = {};
    origpath = varargin{1}.jsonpath_;
end
pos = parse_char(inputstr, pos, '{');
usemap = varargin{1}.usemap;
if (usemap)
    object = containers.Map();
else
    object = [];
end
[cc, pos] = next_char(inputstr, pos);
if cc ~= '}'
    while 1
        [str, pos, index_esc] = parseStr(inputstr, pos, esc, index_esc, varargin{:});
        if (length(str) > 63)
            pos = -oldpos;
            index_esc = oldindex_esc;
            object = [];
            return
        end
        if isempty(str) && ~usemap
            str = 'x0x0_'; % empty name is valid in JSON, decodevarname('x0x0_') restores '\0'
        end
        [pos, w1, w2] = parse_char(inputstr, pos, ':');
        if (nargout > 3)
            varargin{1}.jsonpath_ = [origpath, '.', str];
            mmap{end + 1} = {varargin{1}.jsonpath_, [pos, 0, w2]};
            [val, pos, index_esc, newmmap] = parse_value(inputstr, pos, esc, index_esc, varargin{:});
            mmap{end}{2}(2) = pos - mmap{end}{2}(1);
            mmap = [mmap(:); newmmap(:)];
        else
            [val, pos, index_esc] = parse_value(inputstr, pos, esc, index_esc, varargin{:});
        end
        if (usemap)
            object(str) = val;
        else
            str = encodevarname(str, varargin{:});
            if (length(str) > 63)
                pos = -oldpos;
                index_esc = oldindex_esc;
                object = [];
                return
            end
            object.(str) = val;
        end
        [cc, pos] = next_char(inputstr, pos);
        if cc == '}'
            break
        end
        pos = parse_char(inputstr, pos, ',');
    end
end
pos = parse_char(inputstr, pos, '}');

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

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('JSONLAB:JSON:InvalidFormat', msg);

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

function newpos = skip_whitespace(pos, inputstr)
newpos = pos;
while newpos <= length(inputstr) && isspace(inputstr(newpos))
    newpos = newpos + 1;
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) || isempty(find(str == '\', 1)))
    return
end
newstr = sprintf(str);
newstr = regexprep(newstr, '\\u([0-9A-Fa-f]{4})', '${char(base2dec($1,16))}');

%% -------------------------------------------------------------------------
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')) = ' ';

%% -------------------------------------------------------------------------
function [obj, nextidx] = parsendarray(arraystr, dims)
astr = arraystr;
astr(astr == '[') = ' ';
astr(astr == ']') = ' ';
astr(astr == ',') = ' ';
[obj, count, errmsg, nextidx] = sscanf(astr, '%f', inf);
if (nextidx >= length(astr) - 1)
    obj = reshape(obj, dims);
    nextidx = length(arraystr) + 1;
end