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function json = jsonset(fname, mmap, varargin)
%
% json=jsonset(fname,mmap,'$.jsonpath1',newval1,'$.jsonpath2','newval2',...)
%
% Fast writing of JSON data records to stream or disk using memory-map
% (mmap) returned by loadjson/loadbj and JSONPath-like keys
%
% authors:Qianqian Fang (q.fang <at> neu.edu)
% initially created on 2022/02/02
%
% input:
% fname: a JSON/BJData/UBJSON string or stream, or a file name
% mmap: memory-map returned by loadjson/loadbj of the same data
% important: mmap must be produced from the same file/string,
% otherwise calling this function may cause data corruption
% '$.jsonpath1,2,3,...': a series of strings in the form of JSONPath
% as the key to each of the record to be written
%
% output:
% json: the modified JSON string or, in the case fname is a filename,
% the cell string made of jsonpaths that are successfully
% written
%
% examples:
% % create test data
% d.arr={[1,2],'a',struct('c',2)}; d.obj=struct('k','test')
% % convert to json string
% str=savejson('',d,'compact',1)
% % parse and return mmap
% [dat, mmap]=loadjson(str);
% % display mmap entries
% savejson('',mmap)
% % replace value using mmap
% json=jsonset(str,mmap,'$.arr[2].c','5')
% % save same json string to file (must set savebinary 1)
% savejson('',d,'filename','file.json','compact',1,'savebinary',1);
% % fast write to file
% json=jsonset('file.json',mmap,'$.arr[2].c','5')
%
% 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)
%
if (regexp(fname, '^\s*(?:\[.*\])|(?:\{.*\})\s*$', 'once'))
inputstr = fname;
else
if (~exist('memmapfile', 'file'))
fid = fopen(fname, 'r+b');
end
end
mmap = [mmap{:}];
keylist = mmap(1:2:end);
opt = struct;
for i = 1:2:length(varargin)
if (isempty(regexp(varargin{i}, '^\$', 'once')))
opt.(encodevarname(varargin{i})) = varargin{i + 1};
end
end
json = {};
for i = 1:2:length(varargin)
if (regexp(varargin{i}, '^\$'))
[tf, loc] = ismember(varargin{i}, keylist);
if (tf)
bmap = mmap{loc * 2};
if (ischar(varargin{i + 1}))
val = varargin{i + 1};
else
val = savejson('', varargin{i + 1}, 'compact', 1);
end
if (length(val) <= bmap(2))
val = [val repmat(' ', [1, bmap(2) - length(val)])];
if (exist('inputstr', 'var'))
inputstr(bmap(1):bmap(1) + bmap(2) - 1) = val;
else
if (exist('memmapfile', 'file'))
rec = {'uint8', [1 bmap(2)], 'x'};
fmap = memmapfile(fname, 'writable', true, 'offset', bmap(1) - 1, 'format', rec, 'repeat', 1);
fmap.Data.x = uint8(val);
else
fseek(fid, bmap(1) - 1, 'bof');
fwrite(fid, val);
end
json{end + 1} = {varargin{i}, val};
end
end
end
end
end
if (exist('fid', 'var') && fid >= 0)
fclose(fid);
end
if (exist('inputstr', 'var'))
json = inputstr;
end
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