function [dims, maxlevel, count] = nestbracket2dim(str,brackets)
%
% [dims, maxlevel, count] = nestbracket2dim(str,brackets)
%
% Extracting the dimension vector of a JSON string formatted array
% by analyzing the pairs of opening/closing bracket tokenss; this function
% only returns valid dimension information when the array is an N-D array
%
% authors:Qianqian Fang (q.fang <at> neu.edu)
%
% input:
% str: a string-formatted JSON array using square-brackets for enclosing
% elements and comma as separators between elements
% brackets: (optional), a string of length 2, with the first character
% being the opening token and the 2nd being the closing token.
% if not given, brackets is set to '[]' to find matching square-brackets;
% for example, '{}' looks for a matching closing curly-bracket in
% the string key(pos(startpos,:end))
%
% output:
% dims: the speculated dimension vector with the length matching the maximum
% depth of the embedded bracket pairs. When the input string encodes an
% N-D array, the dims vector contains all integers; however, returning
% an all-integer dims vector does not mean the array is rectangular.
% maxlevel: return the depth of the enclosed brackets in the string, i.e. the
% length of the dims vector.
% count: the relative depth from the level 0 - scanning from the left
% to right of the string, an opening token increases the level by 1
% and a closing token decreases the level by 1; a zero indicates
% the positions of a matching bracket of the same level.
%
% example:
% str='[[ [1,2,3], [4,2,1]], [ [10,1,0], [2,5,10]] ]'; % an N-D array
% [dim,dep]=nestbracket2dim(str)
% str='[[ [1,2,3], [4,2,1]], [ [10,1,0], [2,5]] ]'; % an invalid N-D array
% [dim,dep]=nestbracket2dim(str)
% 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(nargin<2)
brackets='[]';
end
str=str(str==brackets(1) | str==brackets(2) | str==',');
count=cumsum(str==brackets(1)) - cumsum(str==brackets(2));
maxlevel=max(count);
dims=histc(count,1:maxlevel);
dims(1:end-1)=dims(1:end-1)*0.5;
dims(2:end)=dims(2:end)./dims(1:end-1);
dims=fliplr(dims);