json object to be created in run time

[Deepankar Gupta]

Hi
Please share the sample code to use {fmt} in json library. 

the number of mac address and  ip address given to me will be known during run time. I have to construct the json object during runtime.

I want to create json something like below.  The number of pids will be known during run time.


{
    "meta" : {},
    "data" : {
    "map-vtag" : "1234567890",
    "map" : {
        "pid1" : {
            "mac" : [ "00:00:00:00:00:01" ],
            "ipv4": [ "10.0.1.3/24" ]
            },
        "pid2" : {
            "mac" : [ "00:00:00:00:00:02" ]
            },
        "pid3" : {
            "mac" : [ "00:00:00:00:00:03" ]
            },
        "pid4" : {
            "mac" : [ "00:00:00:00:00:04" ]
            },
        "pid5" : {
            "mac" : [ "00:00:00:00:00:05" ]
            }
        }
    }

Thanks in Advance

Regards
Deepankar Gupta

[rogerz]

Use json_object_set() to insert new keys. 

I suggest you read the document on jansson site first. It is comprehensive and including many example.

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[Deepankar Gupta]

This is what i did to create array

fpJson = fopen("nMap.txt","w");
json_t *array = json_array();

 for(i=0;i<9;i++)
 {

    sprintf(index,"PID%d",i+1);
    if(strcmp(topo[i].ipAddress,"")!=0)
    {
         json =json_pack("{s : {s: [s], s: [s]}, }",
                index,
                    "mac", topo[i].macAddress,
                    "ipv4", topo[i].ipAddress
               );
    }
    else
    {

        json =json_pack("{s : {s: [s]}, }",
                index,
                    "mac", topo[i].macAddress
      );

    }
    json_array_append(array,json);
  }
  printf("json array size %d : \n",json_array_size(array));    // prints correct size of 9

//>> Now I want array to be packed

 char *str = "{s: {}, s: {s: s, s: o}}";

 jSon =json_pack(
        str,
        "meta",
        "data",
            "map-vtag", "123456",
            "map",
             json_array_get(array,0),
          );
 json_dumpf(jSon, fpJson,1);
 json_decref(jSon);


I am only able to get single only element from array packed, but not the whole array.  how should I do it ?



Regards
Deepankar

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[Petri Lehtinen]

Deepankar Gupta wrote:
> This is what i did to create array
>
> fpJson = fopen("nMap.txt","w");
> json_t *array = json_array();
>
> for(i=0;i<9;i++)
> {
>
> sprintf(index,"PID%d",i+1);
> if(strcmp(topo[i].ipAddress,"")!=0)
> {
> json =json_pack("{s : {s: [s], s: [s]}, }",
> index,
> "mac", topo[i].macAddress,
> "ipv4", topo[i].ipAddress
> );
> }
> else
> {
>
> json =json_pack("{s : {s: [s]}, }",
> index,
> "mac", topo[i].macAddress
> );
>
> }
> json_array_append(array,json);

You should use json_array_append_new() here to avoid a memory leak.
For details, see

http://www.digip.org/jansson/doc/2.4/apiref.html#reference-count

> }
> printf("json array size %d : \n",json_array_size(array)); // prints
> correct size of 9
>
> //>> Now I want array to be packed
>
> char *str = "{s: {}, s: {s: s, s: o}}";
>
> jSon =json_pack(
> str,
> "meta",
> "data",
> "map-vtag", "123456",
> "map",
> json_array_get(array,0),
> );
> json_dumpf(jSon, fpJson,1);
> json_decref(jSon);
>
>
> I am only able to get single only element from array packed, but not the whole
> array. how should I do it ?

Instead of calling json_array_get(), just pass the array itself. This
way it outputs the whole array and not just the first element.

Hope this helps.

Petri

[Deepankar Gupta]

Petri
As suggested, it worked perfectly as required. I had tried passing "array" directly before, but was not working. Only thing different I did was to use, as suggested by you, "json_array_append_new" instead of "json_array_append".


Petri thanks for the help once again.

Regards
Deepankar