JSON formatting error using Boost JSON parser - c++

Question

I'm attempting to use Boost to read a JSON file from my Firefox configuration folder called sessionstore.js, where the information on the current/last Firefox session is saved for purposes of recovery. I've written a program based on the XML-based tutorial from the Boost website, simply swapping out the XML parts for the JSON parts, which can be seen below
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>
#include <boost/foreach.hpp>
#include <string>
#include <set>
#include <exception>
using boost::property_tree::ptree;
using namespace std;
const string FILENAME = "sessionstore.js";
const string WINDOW_TAG = "windows";
struct session_settings
{
void load (const string &FILENAME);
};
void session_settings::load (const string &FILENAME)
{
ptree pt;
read_json (FILENAME, pt);
}
int main()
{
try
{
session_settings Settings;
Settings.load(FILENAME);
}
catch (exception &e)
{
cout << "Error: " << e.what() << endl;
}
return 0;
}
The contents of the JSON file I'm trying to read are
{"windows":[{"tabs":[{"entries":[{"url":"about:home","title":"Mozilla Firefox Start Page","ID":5,"docshellID":11,"owner_b64":"NhAra3tiRRqhyKDUVsktxQAAAAAAAAAAwAAAAAAAAEYAAQAAAAAAAS8nfAAOr03buTZBMmukiq4HoizADOUR05MxABBLoP1AAAAAAAVhYm91dAAAAARob21l4NodcC97EdOM0ABgsPwUoweiLMAM5RHTkzEAEEug/UAAAAAADm1vei1zYWZlLWFib3V0AAAABGhvbWUAAAA=","docIdentifier":5},{"url":"http://www.google.co.uk/","title":"Google","ID":6,"docshellID":11,"docIdentifier":6,"children":[{"url":"about:blank","ID":7,"docshellID":12,"owner_b64":"NhAra3tiRRqhyKDUVsktxQAAAAAAAAAAwAAAAAAAAEYAAQAAAAAAAd6UctCANBHTk5kAEEug/UAHoizADOUR05MxABBLoP1AAAAAAv////8AAABQAQAAABhodHRwOi8vd3d3Lmdvb2dsZS5jby51ay8AAAAAAAAABAAAAAcAAAAQAAAAB/////8AAAAH/////wAAAAcAAAAQAAAAFwAAAAEAAAAXAAAAAQAAABcAAAABAAAAGAAAAAAAAAAY/////wAAABf/////AAAAF/////8AAAAX/////wEAAAAAAAAAAAABAAA=","docIdentifier":7,"scroll":"0,0"}],"formdata":{"#csi":"1","#hcache":"{\"BInSTfL-EtSt8QOl24nrCg\":[[69,{}],[14,{}],[60,{}],[81,{\"persisted\":true}],[42,{}],[43,{}],[83,{}],[95,{\"kfe\":{\"kfeHost\":\"clients1.google.co.uk\",\"kfeUrlPrefix\":\"/webpagethumbnail?r=2&f=2&s=300:585&query=&hl=en&gl=uk\",\"maxPrefetchConnections\":2,\"prefetch\":90,\"slowConnection\":false},\"logging\":{\"csiFraction\":0.05,\"gen204Fraction\":0.05},\"msgs\":{\"loading\":\"Still loading...\",\"mute\":\"Mute\",\"noPreview\":\"Preview not available\",\"sound\":\"Sound:\",\"soundOff\":\"off\",\"soundOn\":\"on\",\"unmute\":\"Unmute\"},\"pb\":{\"desiredHeight\":585,\"desiredWidth\":300,\"minHeight\":200,\"minWidth\":300},\"time\":{\"hoverClose\":300,\"hoverModeTimeout\":60,\"hoverOpen\":125,\"loading\":100,\"longHoverOpen\":725,\"prefetchOnLoad\":3000,\"timeout\":2500}}],[78,{}],[25,{\"m\":{\"bks\":true,\"blg\":true,\"dsc\":true,\"evn\":true,\"frm\":true,\"isch\":true,\"klg\":true,\"mbl\":true,\"nws\":true,\"plcs\":true,\"ppl\":true,\"prc\":true,\"pts\":true,\"rcp\":true,\"shop\":true,\"vid\":true},\"t\":null}],[64,{}],[105,{}],[22,{\"m_errors\":{\"32\":\"Sorry, no more results to show.\",\"default\":\"<font color=red>Error:</font> The server could not complete your request. Try again in 30 seconds.\"},\"m_tip\":\"Click for more information\"}],[77,{}],[84,{}],[99,{}],[29,{\"mcr\":5}],[92,{\"avgTtfc\":2000,\"fd\":1000,\"fl\":true,\"focus\":true,\"hpt\":250,\"kn\":true,\"mds\":\"clir,clue,dfn,evn,frim,klg,prc,rl,show,sp,sts,ww,mbl_he,mbl_hs,mbl_re,mbl_rs,mbl_sv,isch\",\"msg\":{\"dym\":\"Did you mean:\",\"gs\":\"Google Search\",\"kntt\":\"Use the up and down arrow keys to select each result. Press Enter to go to the selection.\",\"sif\":\"Search instead for\",\"srf\":\"Showing results for\"},\"odef\":true,\"ophe\":true,\"pq\":true,\"rpt\":41,\"tct\":\" ?\",\"tdur\":50}],[24,{}],[38,{}]]}"},"scroll":"0,0"}],"index":2,"hidden":false,"attributes":{"image":"http://www.google.co.uk/favicon.ico"},"storage":{"http://www.google.co.uk":{"web-v":"12_c9c918f0"}}}],"selected":1,"_closedTabs":[],"width":994,"height":688,"screenX":1650,"screenY":24,"sizemode":"normal","title":"Google"}],"selectedWindow":0,"_closedWindows":[{"tabs":[{"entries":[{"url":"about:home","title":"Mozilla Firefox Start Page","ID":0,"docshellID":5,"owner_b64":"NhAra3tiRRqhyKDUVsktxQAAAAAAAAAAwAAAAAAAAEYAAQAAAAAAAS8nfAAOr03buTZBMmukiq4HoizADOUR05MxABBLoP1AAAAAAAVhYm91dAAAAARob21l4NodcC97EdOM0ABgsPwUoweiLMAM5RHTkzEAEEug/UAAAAAADm1vei1zYWZlLWFib3V0AAAABGhvbWUAAAA="},{"url":"http://www.facebook.com/","title":"Welcome to Facebook - Log In, Sign Up or Learn More","ID":1,"docshellID":5,"docIdentifier":1,"formdata":{"//xhtml:div[#id='reg_form_box']/xhtml:table/xhtml:tbody/xhtml:tr[6]/xhtml:td[2]/xhtml:div/xhtml:div/xhtml:select":0,"//xhtml:div[#id='reg_form_box']/xhtml:table/xhtml:tbody/xhtml:tr[6]/xhtml:td[2]/xhtml:div/xhtml:div/xhtml:select[2]":0,"#sex":0,"#birthday_month":0,"#birthday_day":0,"#birthday_year":0},"scroll":"0,0"}],"index":2,"hidden":false,"attributes":{"image":"http://www.facebook.com/favicon.ico"}},{"entries":[{"url":"http://twitter.com/","title":"Twitter","ID":3,"docshellID":6,"docIdentifier":3,"children":[{"url":"http://api.twitter.com/receiver.html","ID":4,"docshellID":7,"referrer":"http://twitter.com/","docIdentifier":4,"scroll":"0,0"}],"formdata":{},"scroll":"0,0"}],"index":1,"hidden":false,"attributes":{"image":"http://twitter.com/phoenix/favicon.ico"}}],"selected":2,"_closedTabs":[],"width":994,"height":688,"screenX":1366,"screenY":307,"sizemode":"normal","cookies":[{"host":".facebook.com","value":"J4-69","path":"/","name":"lsd"},{"host":".facebook.com","value":"http%3A%2F%2Fwww.facebook.com%2F","path":"/","name":"reg_fb_gate"},{"host":".facebook.com","value":"http%3A%2F%2Fwww.facebook.com%2F","path":"/","name":"reg_fb_ref"},{"host":".facebook.com","value":"994x624","path":"/","name":"wd"},{"host":".twitter.com","value":"43838368","path":"/","name":"__utmc"},{"host":"twitter.com","value":"4bfz%2B%2BmebEkRkMWFCXm%2FCUOsvDoVeFTl","path":"/","name":"original_referer"},{"host":"scribe.twitter.com","value":"4bfz%2B%2BmebEkRkMWFCXm%2FCUOsvDoVeFTl","path":"/","name":"original_referer"},{"host":".twitter.com","value":"BAh7CToPY3JlYXRlZF9hdGwrCDoVZ%252F4vAToMY3NyZl9pZCIlODE2MGI1ZjJh%250AYmViNDMwODMxNDlkN2U5ZDg5Yjk4ZmU6B2lkIiU2N2I4YjdmNGExNWFkNzlk%250AODI0MDVjMGM1NmMzYjVhYSIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6%250ARmxhc2g6OkZsYXNoSGFzaHsABjoKQHVzZWR7AA%253D%253D--8b0d751e9774c5cfaa61fdec567cb782aa8757dd","path":"/","name":"_twitter_sess","httponly":true},{"host":".twitter.com","value":"43838368","path":"/","name":"__utmc"},{"host":"twitter.com","value":"4bfz%2B%2BmebEkRkMWFCXm%2FCUOsvDoVeFTl","path":"/","name":"original_referer"},{"host":"scribe.twitter.com","value":"4bfz%2B%2BmebEkRkMWFCXm%2FCUOsvDoVeFTl","path":"/","name":"original_referer"},{"host":".twitter.com","value":"BAh7CToPY3JlYXRlZF9hdGwrCDoVZ%252F4vAToMY3NyZl9pZCIlODE2MGI1ZjJh%250AYmViNDMwODMxNDlkN2U5ZDg5Yjk4ZmU6B2lkIiU2N2I4YjdmNGExNWFkNzlk%250AODI0MDVjMGM1NmMzYjVhYSIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6%250ARmxhc2g6OkZsYXNoSGFzaHsABjoKQHVzZWR7AA%253D%253D--8b0d751e9774c5cfaa61fdec567cb782aa8757dd","path":"/","name":"_twitter_sess","httponly":true}],"title":"Twitter"}],"session":{"state":"stopped","lastUpdate":1305658398727}}
and when I tried to load that with my program I got the error
Error: sessionstore.js(1): expected value
Since the file is formatted all on a single line, this meant the error could be anywhere in the file, so I ran it though a Javascript beautifier, keeping the default options, and pasted the results back into the original file and executed the program.
The formatted JSON is
{
"windows": [{
"tabs": [{
"entries": [{
"url": "about:home",
"title": "Mozilla Firefox Start Page",
"ID": 5,
"docshellID": 11,
"owner_b64": "NhAra3tiRRqhyKDUVsktxQAAAAAAAAAAwAAAAAAAAEYAAQAAAAAAAS8nfAAOr03buTZBMmukiq4HoizADOUR05MxABBLoP1AAAAAAAVhYm91dAAAAARob21l4NodcC97EdOM0ABgsPwUoweiLMAM5RHTkzEAEEug/UAAAAAADm1vei1zYWZlLWFib3V0AAAABGhvbWUAAAA=",
"docIdentifier": 5
}, {
"url": "http://www.google.co.uk/",
"title": "Google",
"ID": 6,
"docshellID": 11,
"docIdentifier": 6,
"children": [{
"url": "about:blank",
"ID": 7,
"docshellID": 12,
"owner_b64": "NhAra3tiRRqhyKDUVsktxQAAAAAAAAAAwAAAAAAAAEYAAQAAAAAAAd6UctCANBHTk5kAEEug/UAHoizADOUR05MxABBLoP1AAAAAAv////8AAABQAQAAABhodHRwOi8vd3d3Lmdvb2dsZS5jby51ay8AAAAAAAAABAAAAAcAAAAQAAAAB/////8AAAAH/////wAAAAcAAAAQAAAAFwAAAAEAAAAXAAAAAQAAABcAAAABAAAAGAAAAAAAAAAY/////wAAABf/////AAAAF/////8AAAAX/////wEAAAAAAAAAAAABAAA=",
"docIdentifier": 7,
"scroll": "0,0"
}],
"formdata": {
"#csi": "1",
"#hcache": "{\"BInSTfL-EtSt8QOl24nrCg\":[[69,{}],[14,{}],[60,{}],[81,{\"persisted\":true}],[42,{}],[43,{}],[83,{}],[95,{\"kfe\":{\"kfeHost\":\"clients1.google.co.uk\",\"kfeUrlPrefix\":\"/webpagethumbnail?r=2&f=2&s=300:585&query=&hl=en&gl=uk\",\"maxPrefetchConnections\":2,\"prefetch\":90,\"slowConnection\":false},\"logging\":{\"csiFraction\":0.05,\"gen204Fraction\":0.05},\"msgs\":{\"loading\":\"Still loading...\",\"mute\":\"Mute\",\"noPreview\":\"Preview not available\",\"sound\":\"Sound:\",\"soundOff\":\"off\",\"soundOn\":\"on\",\"unmute\":\"Unmute\"},\"pb\":{\"desiredHeight\":585,\"desiredWidth\":300,\"minHeight\":200,\"minWidth\":300},\"time\":{\"hoverClose\":300,\"hoverModeTimeout\":60,\"hoverOpen\":125,\"loading\":100,\"longHoverOpen\":725,\"prefetchOnLoad\":3000,\"timeout\":2500}}],[78,{}],[25,{\"m\":{\"bks\":true,\"blg\":true,\"dsc\":true,\"evn\":true,\"frm\":true,\"isch\":true,\"klg\":true,\"mbl\":true,\"nws\":true,\"plcs\":true,\"ppl\":true,\"prc\":true,\"pts\":true,\"rcp\":true,\"shop\":true,\"vid\":true},\"t\":null}],[64,{}],[105,{}],[22,{\"m_errors\":{\"32\":\"Sorry, no more results to show.\",\"default\":\"<font color=red>Error:</font> The server could not complete your request. Try again in 30 seconds.\"},\"m_tip\":\"Click for more information\"}],[77,{}],[84,{}],[99,{}],[29,{\"mcr\":5}],[92,{\"avgTtfc\":2000,\"fd\":1000,\"fl\":true,\"focus\":true,\"hpt\":250,\"kn\":true,\"mds\":\"clir,clue,dfn,evn,frim,klg,prc,rl,show,sp,sts,ww,mbl_he,mbl_hs,mbl_re,mbl_rs,mbl_sv,isch\",\"msg\":{\"dym\":\"Did you mean:\",\"gs\":\"Google Search\",\"kntt\":\"Use the up and down arrow keys to select each result. Press Enter to go to the selection.\",\"sif\":\"Search instead for\",\"srf\":\"Showing results for\"},\"odef\":true,\"ophe\":true,\"pq\":true,\"rpt\":41,\"tct\":\" ?\",\"tdur\":50}],[24,{}],[38,{}]]}"
},
"scroll": "0,0"
}],
"index": 2,
"hidden": false,
"attributes": {
"image": "http://www.google.co.uk/favicon.ico"
},
"storage": {
"http://www.google.co.uk": {
"web-v": "12_c9c918f0"
}
}
}],
"selected": 1,
"_closedTabs": [],
"width": 994,
"height": 688,
"screenX": 1650,
"screenY": 24,
"sizemode": "normal",
"title": "Google"
}],
"selectedWindow": 0,
"_closedWindows": [{
"tabs": [{
"entries": [{
"url": "about:home",
"title": "Mozilla Firefox Start Page",
"ID": 0,
"docshellID": 5,
"owner_b64": "NhAra3tiRRqhyKDUVsktxQAAAAAAAAAAwAAAAAAAAEYAAQAAAAAAAS8nfAAOr03buTZBMmukiq4HoizADOUR05MxABBLoP1AAAAAAAVhYm91dAAAAARob21l4NodcC97EdOM0ABgsPwUoweiLMAM5RHTkzEAEEug/UAAAAAADm1vei1zYWZlLWFib3V0AAAABGhvbWUAAAA="
}, {
"url": "http://www.facebook.com/",
"title": "Welcome to Facebook - Log In, Sign Up or Learn More",
"ID": 1,
"docshellID": 5,
"docIdentifier": 1,
"formdata": {
"//xhtml:div[#id='reg_form_box']/xhtml:table/xhtml:tbody/xhtml:tr[6]/xhtml:td[2]/xhtml:div/xhtml:div/xhtml:select": 0,
"//xhtml:div[#id='reg_form_box']/xhtml:table/xhtml:tbody/xhtml:tr[6]/xhtml:td[2]/xhtml:div/xhtml:div/xhtml:select[2]": 0,
"#sex": 0,
"#birthday_month": 0,
"#birthday_day": 0,
"#birthday_year": 0
},
"scroll": "0,0"
}],
"index": 2,
"hidden": false,
"attributes": {
"image": "http://www.facebook.com/favicon.ico"
}
}, {
"entries": [{
"url": "http://twitter.com/",
"title": "Twitter",
"ID": 3,
"docshellID": 6,
"docIdentifier": 3,
"children": [{
"url": "http://api.twitter.com/receiver.html",
"ID": 4,
"docshellID": 7,
"referrer": "http://twitter.com/",
"docIdentifier": 4,
"scroll": "0,0"
}],
"formdata": {},
"scroll": "0,0"
}],
"index": 1,
"hidden": false,
"attributes": {
"image": "http://twitter.com/phoenix/favicon.ico"
}
}],
"selected": 2,
"_closedTabs": [],
"width": 994,
"height": 688,
"screenX": 1366,
"screenY": 307,
"sizemode": "normal",
"cookies": [{
"host": ".facebook.com",
"value": "J4-69",
"path": "/",
"name": "lsd"
}, {
"host": ".facebook.com",
"value": "http%3A%2F%2Fwww.facebook.com%2F",
"path": "/",
"name": "reg_fb_gate"
}, {
"host": ".facebook.com",
"value": "http%3A%2F%2Fwww.facebook.com%2F",
"path": "/",
"name": "reg_fb_ref"
}, {
"host": ".facebook.com",
"value": "994x624",
"path": "/",
"name": "wd"
}, {
"host": ".twitter.com",
"value": "43838368",
"path": "/",
"name": "__utmc"
}, {
"host": "twitter.com",
"value": "4bfz%2B%2BmebEkRkMWFCXm%2FCUOsvDoVeFTl",
"path": "/",
"name": "original_referer"
}, {
"host": "scribe.twitter.com",
"value": "4bfz%2B%2BmebEkRkMWFCXm%2FCUOsvDoVeFTl",
"path": "/",
"name": "original_referer"
}, {
"host": ".twitter.com",
"value": "BAh7CToPY3JlYXRlZF9hdGwrCDoVZ%252F4vAToMY3NyZl9pZCIlODE2MGI1ZjJh%250AYmViNDMwODMxNDlkN2U5ZDg5Yjk4ZmU6B2lkIiU2N2I4YjdmNGExNWFkNzlk%250AODI0MDVjMGM1NmMzYjVhYSIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6%250ARmxhc2g6OkZsYXNoSGFzaHsABjoKQHVzZWR7AA%253D%253D--8b0d751e9774c5cfaa61fdec567cb782aa8757dd",
"path": "/",
"name": "_twitter_sess",
"httponly": true
}, {
"host": ".twitter.com",
"value": "43838368",
"path": "/",
"name": "__utmc"
}, {
"host": "twitter.com",
"value": "4bfz%2B%2BmebEkRkMWFCXm%2FCUOsvDoVeFTl",
"path": "/",
"name": "original_referer"
}, {
"host": "scribe.twitter.com",
"value": "4bfz%2B%2BmebEkRkMWFCXm%2FCUOsvDoVeFTl",
"path": "/",
"name": "original_referer"
}, {
"host": ".twitter.com",
"value": "BAh7CToPY3JlYXRlZF9hdGwrCDoVZ%252F4vAToMY3NyZl9pZCIlODE2MGI1ZjJh%250AYmViNDMwODMxNDlkN2U5ZDg5Yjk4ZmU6B2lkIiU2N2I4YjdmNGExNWFkNzlk%250AODI0MDVjMGM1NmMzYjVhYSIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6%250ARmxhc2g6OkZsYXNoSGFzaHsABjoKQHVzZWR7AA%253D%253D--8b0d751e9774c5cfaa61fdec567cb782aa8757dd",
"path": "/",
"name": "_twitter_sess",
"httponly": true
}],
"title": "Twitter"
}],
"session": {
"state": "stopped",
"lastUpdate": 1305658398727
}
}
The error
Error: sessionstore.js(179): expected value
now identifies the fault as being on the third-last line, the one that reads "lastUpdate": 1305658398727. From what I've read about the JSON format, this sounds to me like a comma or bracket is missing from this line, but this is a file that has been produced my Mozilla to work with Firefox, and I don't believe that they would make a mistake like that, so I am lead to believe that there is a problem with the JSON parser in Boost. Can anyone please confirm if this is the case, or if I'm the one doing something wrong?

Answer 1

I think the problem is this value is bigger than an int or a double. I don't know what data type uses BOOST JSON for reading numbers. To test this, just change the number to be a string and parse it again. In the standard, numbers are not limited, but you have to select a data type to represent them, and maybe they selected double, clearly not enough for this number. I'll take a look to see if you can configure the type used for numbers.
EDIT:
Looking again at the implementation, the "number" rule is implemented using Spirit as follows:
number
= strict_real_p
| int_p
;
Looking at Spirit strict_real_p uses double as the underlying type, and int_p actually uses an int.
The bad news is that, for what I see in the code, this is not configurable, so you have to change the JSON to be interpreted.

Answer 2

After receiving answers from Diego Sevilla and c-smile, I did a bit of Googling to figure out how I would incorporate their suggestions into Boost, since changing the JSON file unfortunately isn't an option in my case, and I came across this ticket on the Boost bug tracker that describes my exact problem. It has since been fixed and released with Boost 1.45. I, however, am using version 1.42 from the Ubuntu repositories, so will need to install the newer version manually.

Answer 3

As Diego said that is because 1305658398727 does not fit into neither strict_real_p nor int_p production.
I suspect you will need either other JSON parser or to modify Spirit definitions by yourself.
Either like this:
number
= strict_real_p
| int_p
| int64_p
;
or just as:
number
= real_p;
Ideally date/time in JSON should be presented by strings in ISO format. In this case you will not have such problems. I suspect that data there is just a number of milliseconds since 1970-01-01 (JavaScript Date.valueOf())