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JSONlab
An open-source MATLAB/Octave JSON/UBJSON encoder and decoder
- Copyright (c) 2011-2013 Qianqian Fang <fangq at nmr.mgh.harvard.edu>
- License: BSD or GNU General Public License version 3 (GPL v3), see License*.txt
- Version: 0.9.8 (Optimus - alpha)
Table of Content:
- 1. Introduction
- 2. Installation
- 3. Using JSONlab
- 3.1. examples
- 5. Contribution and feedback
1. Introduction
JSON (JavaScript Object Notation) is a highly portable, human-readable and "fat-free" text format to represent complex and hierarchical data. It is as powerful as XML, but less verbose. JSON format is widely used for data-exchange in applications, and is essential for the wild success of Ajax and Web2.0.
UBJSON (Universal Binary JSON) is a binary JSON format, specifically optimized for compact file size and better performance while keeping the semantics as simple as the text-based JSON format. Using the UBJSON format allows to wrap complex binary data in a flexible and extensible structure, making it possible to process complex and large dataset without accuracy loss due to text conversions.
We envision that both JSON and its binary version will serve as part of the mainstream data-exchange formats for scientific research in the future. It will provide the flexibility and generality achieved by other popular general-purpose file specifications, such as HDF5, with significantly reduced complexity and enhanced performance.
JSONlab is a free and open-source implementation of a JSON/UBJSON encoder and a decoder in the native MATLAB language. It can be used to convert a MATLAB data structure (array, struct, cell, struct array and cell array) into JSON/UBJSON formatted strings, or to decode a JSON/UBJSON file into MATLAB data structure. JSONlab supports both MATLAB and GNU Octave (a free MATLAB clone).
2. Installation
The installation of JSONlab is no different than any other simple MATLAB toolbox. You only need to download/unzip the JSONlab package to a folder, and add the folder's path to MATLAB/Octave's path list by using the following command:
addpath('/path/to/jsonlab');
If you want to add this path permanently, you need to type "pathtool", browse to the iso2mesh folder and add it to the list, then click "Save".
Then, run "rehash" in MATLAB, and type "which loadjson", if you see an output, that means JSONlab is installed for MATLAB/Octave.
3. Using JSONlab
JSONlab provides two functions, loadjson.m -- a MATLAB->JSON decoder, and savejson.m -- a MATLAB->JSON encoder, for the text-based JSON, and two equivallent functions -- loadubjson and saveubjson for the binary JSON. The detailed help info for the four functions can be found below:
loadjson.m
data=loadjson(fname,opt)
or
data=loadjson(fname,'param1',value1,'param2',value2,...)
parse a JSON (JavaScript Object Notation) file or string
authors:Qianqian Fang (fangq<at> nmr.mgh.harvard.edu)
date: 2011/09/09
Nedialko Krouchev: http://www.mathworks.com/matlabcentral/fileexchange/25713
date: 2009/11/02
François Glineur: http://www.mathworks.com/matlabcentral/fileexchange/23393
date: 2009/03/22
Joel Feenstra:
http://www.mathworks.com/matlabcentral/fileexchange/20565
date: 2008/07/03
$Id: loadjson.m 394 2012-12-18 17:58:11Z fangq $
input:
fname: input file name, if fname contains "{}" or "[]", fname
will be interpreted as a JSON string
opt: 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.
output:
dat: a cell array, where {...} blocks are converted into cell arrays,
and [...] are converted to arrays
savejson.m
json=savejson(rootname,obj,filename)
or
json=savejson(rootname,obj,opt)
json=savejson(rootname,obj,'param1',value1,'param2',value2,...)
convert a MATLAB object (cell, struct or array) into a JSON (JavaScript
Object Notation) string
author: Qianqian Fang (fangq<at> nmr.mgh.harvard.edu)
created on 2011/09/09
$Id: savejson.m 394 2012-12-18 17:58:11Z fangq $
input:
rootname: name of the root-object, if set to '', will use variable name
obj: a MATLAB object (array, cell, cell array, struct, struct array)
filename: a string for the file name to save the output JSON data
opt: a struct for additional options, use [] if all use default
opt can have the following fields (first in [.|.] is the default)
opt.FileName [''|string]: a file name to save the output JSON data
opt.FloatFormat ['%.10g'|string]: format to show each numeric element
of a 1D/2D array;
opt.ArrayIndent [1|0]: if 1, output explicit data array with
precedent indentation; if 0, no indentation
opt.ArrayToStruct[0|1]: when set to 0, savejson outputs 1D/2D
array in JSON array format; if sets to 1, an
array will be shown as a struct with fields
"_ArrayType_", "_ArraySize_" and "_ArrayData_"; for
sparse arrays, the non-zero elements will be
saved to _ArrayData_ field in triplet-format i.e.
(ix,iy,val) and "_ArrayIsSparse_" will be added
with a value of 1; for a complex array, the
_ArrayData_ array will include two columns
(4 for sparse) to record the real and imaginary
parts, and also "_ArrayIsComplex_":1 is added.
opt.ParseLogical [0|1]: if this is set to 1, logical array elem
will use true/false rather than 1/0.
opt.NoRowBracket [1|0]: if this is set to 1, arrays with a single
numerical element will be shown without a square
bracket, unless it is the root object; if 0, square
brackets are forced for any numerical arrays.
opt.ForceRootName [0|1]: when set to 1 and rootname is empty, savejson
will use the name of the passed obj variable as the
root object name; if obj is an expression and
does not have a name, 'root' will be used; if this
is set to 0 and rootname is empty, the root level
will be merged down to the lower level.
opt.Inf ['"$1_Inf_"'|string]: a customized regular expression pattern
to represent +/-Inf. The matched pattern is '([-+]*)Inf'
and $1 represents the sign. For those who want to use
1e999 to represent Inf, they can set opt.Inf to '$11e999'
opt.NaN ['"_NaN_"'|string]: a customized regular expression pattern
to represent NaN
opt.JSONP [''|string]: to generate a JSONP output (JSON with padding),
for example, if opt.JSON='foo', the JSON data is
wrapped inside a function call as 'foo(...);'
opt.UnpackHex [1|0]: conver the 0x[hex code] output by loadjson
back to the string form
opt can be replaced by a list of ('param',value) pairs. The param
string is equivallent to a field in opt.
output:
json: a string in the JSON format (see http://json.org)
examples:
a=struct('node',[1 9 10; 2 1 1.2], 'elem',[9 1;1 2;2 3],...
'face',[9 01 2; 1 2 3; NaN,Inf,-Inf], 'author','FangQ');
savejson('mesh',a)
savejson('',a,'ArrayIndent',0,'FloatFormat','\t%.5g')
loadubjson.m
data=loadubjson(fname,opt)
or
data=loadubjson(fname,'param1',value1,'param2',value2,...)
parse a JSON (JavaScript Object Notation) file or string
authors:Qianqian Fang (fangq<at> nmr.mgh.harvard.edu)
date: 2013/08/01
$Id: loadubjson.m 410 2013-08-24 03:33:18Z fangq $
input:
fname: input file name, if fname contains "{}" or "[]", fname
will be interpreted as a UBJSON string
opt: 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.
output:
dat: a cell array, where {...} blocks are converted into cell arrays,
and [...] are converted to arrays
saveubjson.m
json=saveubjson(rootname,obj,filename)
or
json=saveubjson(rootname,obj,opt)
json=saveubjson(rootname,obj,'param1',value1,'param2',value2,...)
convert a MATLAB object (cell, struct or array) into a Universal
Binary JSON (UBJSON) binary string
author: Qianqian Fang (fangq<at> nmr.mgh.harvard.edu)
created on 2013/08/17
$Id: saveubjson.m 410 2013-08-24 03:33:18Z fangq $
input:
rootname: name of the root-object, if set to '', will use variable name
obj: a MATLAB object (array, cell, cell array, struct, struct array)
filename: a string for the file name to save the output JSON data
opt: a struct for additional options, use [] if all use default
opt can have the following fields (first in [.|.] is the default)
opt.FileName [''|string]: a file name to save the output JSON data
opt.ArrayToStruct[0|1]: when set to 0, saveubjson outputs 1D/2D
array in JSON array format; if sets to 1, an
array will be shown as a struct with fields
"_ArrayType_", "_ArraySize_" and "_ArrayData_"; for
sparse arrays, the non-zero elements will be
saved to _ArrayData_ field in triplet-format i.e.
(ix,iy,val) and "_ArrayIsSparse_" will be added
with a value of 1; for a complex array, the
_ArrayData_ array will include two columns
(4 for sparse) to record the real and imaginary
parts, and also "_ArrayIsComplex_":1 is added.
opt.ParseLogical [1|0]: if this is set to 1, logical array elem
will use true/false rather than 1/0.
opt.NoRowBracket [1|0]: if this is set to 1, arrays with a single
numerical element will be shown without a square
bracket, unless it is the root object; if 0, square
brackets are forced for any numerical arrays.
opt.ForceRootName [0|1]: when set to 1 and rootname is empty, saveubjson
will use the name of the passed obj variable as the
root object name; if obj is an expression and
does not have a name, 'root' will be used; if this
is set to 0 and rootname is empty, the root level
will be merged down to the lower level.
opt.JSONP [''|string]: to generate a JSONP output (JSON with padding),
for example, if opt.JSON='foo', the JSON data is
wrapped inside a function call as 'foo(...);'
opt.UnpackHex [1|0]: conver the 0x[hex code] output by loadjson
back to the string form
opt can be replaced by a list of ('param',value) pairs. The param
string is equivallent to a field in opt.
output:
json: a string in the JSON format (see http://json.org)
examples:
a=struct('node',[1 9 10; 2 1 1.2], 'elem',[9 1;1 2;2 3],...
'face',[9 01 2; 1 2 3; NaN,Inf,-Inf], 'author','FangQ');
saveubjson('mesh',a)
saveubjson('',a,'ArrayIndent',0,'FloatFormat','\t%.5g')
3.1. examples
Under the "examples" folder, you can find several scripts to demonstrate the basic utilities of JSONlab. Running the "demo_jsonlab_basic.m" script, you will see the conversions from MATLAB data structure to JSON text and backward. In "jsonlab_selftest.m", we load complex JSON files downloaded from the Internet and validate the loadjson/savejson functions for regression testing purposes. Similarly, a "demo_ubjson_basic.m" script is provided to test the saveubjson and loadubjson pairs for various matlab data structures.
Please run these examples and understand how JSONlab works before you use it to process your data.
4. Known Issues and TODOs
JSONlab has several known limitations. We are striving to make it more general and robust. Hopefully at some future releases, the limitations become less.
Here are the known issues:
- Any high-dimensional cell-array will be converted to a 1D array;
- When processing names containing multi-byte characters, Octave and MATLAB can give different field-names; you can use feature('DefaultCharacterSet','latin1') in MATLAB to get consistant results
- Can not handle classes.
5. Contribution and feedback
JSONlab is an open-source project. This means you can not only use it and modify it as you wish, but also you can contribute your changes back to JSONlab so that everyone else can enjoy the improvement. For anyone who want to contribute, please download JSONlab source code from it's subversion repository by using the following command:
svn checkout svn://svn.code.sf.net/p/iso2mesh/code/trunk/jsonlab jsonlab
You can make changes to the files as needed. Once you are satisfied with your changes, and ready to share it with others, please cd the root directory of JSONlab, and type
svn diff > yourname_featurename.patch
You then email the .patch file to JSONlab's maintainer, Qianqian Fang, at the email address shown in the beginning of this file. Qianqian will review the changes and commit it to the subversion if they are satisfactory.
We appreciate any suggestions and feedbacks from you. Please use iso2mesh's mailing list to report any questions you may have with JSONlab:
http://groups.google.com/group/iso2mesh-users?hl=en&pli=1
(Subscription to the mailing list is needed in order to post messages).