JSON support

[n-isaka]

I tried to implement the JSON function.
This function like a environment function with jansson.

DISPLAY JSON-NAME : Specify the name of JSON structure.
DISPLAY JSON-KEY : Register period separated key names.
ACCEPT JSON-VALUE: Gets the value specified by JSON-KEY from JSON-NAME data.

Look at this branch: feature/JSON_support

COBOL sample:

      ******************************************************************
      *  opensource COBOL JSON support
      ******************************************************************
       IDENTIFICATION              DIVISION.
      ******************************************************************
       PROGRAM-ID.                 JSON.
       AUTHOR.                     n-isaka.
       DATE-WRITTEN.               2019-06-13.
      ******************************************************************
       ENVIRONMENT                 DIVISION.
      ******************************************************************
       CONFIGURATION               SECTION.
       SPECIAL-NAMES.
      ******************************************************************
       INPUT-OUTPUT                SECTION.
       FILE-CONTROL.
      ******************************************************************
       DATA                        DIVISION.
      ******************************************************************
       FILE                        SECTION.
      ******************************************************************
       WORKING-STORAGE             SECTION.
       01  JSON-STR                PIC  X(255).
       01  J-KEY                   PIC  X(255).
       01  J-VALUE                 PIC  X(255).
      ******************************************************************
       PROCEDURE                   DIVISION.
      ******************************************************************
       MAIN-RTN.

      *    *** １つ目のJSONを登録
           STRING '{'                             DELIMITED BY SIZE
                     '"key1" : "value1",'         DELIMITED BY SIZE
                     '"key2" : 2,'                DELIMITED BY SIZE
                     '"key3" : {'                 DELIMITED BY SIZE
                        '"key3-1" : "value3-1",'  DELIMITED BY SIZE
                        '"key3-2" : "value3-2"'   DELIMITED BY SIZE
                     '},'                         DELIMITED BY SIZE
                     '"key4" : ['                 DELIMITED BY SIZE
                        '"value4-1",'             DELIMITED BY SIZE
                        '"value4-2",'             DELIMITED BY SIZE
                        '"value4-3"'              DELIMITED BY SIZE
                     ']'                          DELIMITED BY SIZE
                  '}'                             DELIMITED BY SIZE
                  INTO JSON-STR.

           DISPLAY "JSON"          UPON JSON-NAME.
           DISPLAY JSON-STR        UPON JSON-VALUE.

      *    *** ２つ目のJSONを登録
           MOVE SPACE              TO JSON-STR.
           STRING '{'                             DELIMITED BY SIZE
                     '"key10" : "value10"'        DELIMITED BY SIZE
                  '}'                             DELIMITED BY SIZE
                  INTO JSON-STR.

           DISPLAY "JSON2"         UPON JSON-NAME.
           DISPLAY JSON-STR        UPON JSON-VALUE.

      *    *** １つ目のJSONを選択
           DISPLAY "JSON"          UPON JSON-NAME.

      *    *** １つ目のJSONからKEYでデータを取得
      *    *** 配列は対応
           MOVE "key4[1]"          TO J-KEY.
           MOVE SPACE              TO J-VALUE.
           DISPLAY J-KEY           UPON JSON-KEY.
           ACCEPT  J-VALUE         FROM JSON-VALUE.
           DISPLAY J-KEY ":" J-VALUE.
      *    key4[1] : value4-2

      *    *** 数値型も対応
           MOVE "key2"             TO J-KEY.
           MOVE SPACE              TO J-VALUE.
           DISPLAY J-KEY           UPON JSON-KEY.
           ACCEPT  J-VALUE         FROM JSON-VALUE.
           DISPLAY J-KEY ":" J-VALUE.
      *    key2 : 2

      *    *** 入れ子も対応
           MOVE "key3.key3-2"      TO J-KEY.
           MOVE SPACE              TO J-VALUE.
           DISPLAY J-KEY           UPON JSON-KEY.
           ACCEPT  J-VALUE         FROM JSON-VALUE.
           DISPLAY J-KEY ":" J-VALUE.
      *    key3.key3-2 : value3-2

      *    *** ２つ目のJSONを選択
           DISPLAY "JSON2"         UPON JSON-NAME.

      *    *** ２つ目のJSONから値を取得
           MOVE "key10"            TO J-KEY.
           MOVE SPACE              TO J-VALUE.
           DISPLAY J-KEY           UPON JSON-KEY.
           ACCEPT  J-VALUE         FROM JSON-VALUE.
           DISPLAY J-KEY ":" J-VALUE.
      *    key10 : value10

      *    *** この時1個目のJSONからは値がとれない
           MOVE "key3.key3-2"      TO J-KEY.
           MOVE SPACE              TO J-VALUE.
           DISPLAY J-KEY           UPON JSON-KEY.
           ACCEPT  J-VALUE         FROM JSON-VALUE.
           DISPLAY J-KEY ":" J-VALUE.
      *    key3.key3-2 : 

       MAIN-EXT.
           STOP RUN.

[GitMensch]

I highly suggest to not implement it that way and add the IBM extension GENERATE JSON instead. See patch for adding GENERATE JSON to GnuCOBOL.

If this project would update to the newer (L)GPL versions then it could integrate any changes that were proposed and/or integrated into GnuCOBOL under (C) Free Software Foundation (the old OpenCOBOL Copyrights were transferred to the FSF under the updated license).

[n-isaka]

Thank you for the suggestion. I will look at it.

We will discuss licensing within the team.

[n-isaka]

I understood that IBM extensions are intuitive operations that correspond to COBOL data types.

However, I think that I may be able to use my approach to process JSON irregular data format.

I would like to think a little more.

In addition, we are discussing about license.

[GitMensch]

I understood that IBM extensions are intuitive operations that correspond to COBOL data types.

Especially: it is a "common" extension (adopted by at least MicroFocus and likely also others) you may find in existing sources.

However, I think that I may be able to use my approach to process JSON irregular data format.

Please elaborate on this.

In addition, we are discussing about license.

I totally agree that this is off-topic for this issue, it may be tracked with a different one.

[n-isaka]

I understand IBM extensions are used as follows:

       WORKING-STORAGE             SECTION.
       01  EMP-REC-VARS.
         03  EMP-NO                PIC S9(04) VALUE ZERO.
         03  EMP-NAME              PIC  X(20) .
         03  EMP-SALARY            PIC S9(04) VALUE ZERO.

{
   "EMP-REC-VARS" : {
      "EMP-NO" : 0001,
      "EMP-NAME" : "HOKKAI TARO         ",
      "EMP-SALARY" : 0400
   }
}

IBM extensions insert such JSON data into COBOL data type.

But, JSON data is flexible, they have not a data or additional data.

{
   "EMP-REC-VARS" : {
      "EMP-NO" : 0001,
      "EMP-NAME" : "HOKKAI TARO         ",

      "EMP-AGE" : 32
   }
}

In such cases, the IBM extension will be "ON EXCEPTION".

I think I can use that JSON data, because my function can be given a KEY dynamically.
So, I want to implement functions for example "GET_KEYS", "GET_ARRAYS_SIZE".

[n-isaka]

I just updated the branch, feature/JSON_support.

Each function is called by CALL, COBOL Programs hold a JSON object in POINTER type.

I think that new functions is more usefull for using flexible JSON data.
Because, Users can reach any object by using functions also GET_KEY, GET_ARRLEN, GET_TYPE.

COBOL sample:

      ******************************************************************
       IDENTIFICATION              DIVISION.
      ******************************************************************
       PROGRAM-ID.                 JSON7.
       AUTHOR.                     n-isaka.
       DATE-WRITTEN.               2019-07-11.
      ******************************************************************
       ENVIRONMENT                 DIVISION.
      ******************************************************************
       CONFIGURATION               SECTION.
       SPECIAL-NAMES.
      ******************************************************************
       INPUT-OUTPUT                SECTION.
       FILE-CONTROL.
      ******************************************************************
       DATA                        DIVISION.
      ******************************************************************
       FILE                        SECTION.
      ******************************************************************
       WORKING-STORAGE             SECTION.
       01  JSON-STR                PIC  X(255).
       01  J-KEY                   PIC  X(30).
       01  J-VALUE                 PIC  X(30).
       01  J-VALUE-INT             PIC  9(05).
       
      *MAIN
       01  STATUS1                 PIC  9(8) COMP-5.
       01  STATUS2                 PIC  9(8) COMP-5.
       01  J-KEY-NUM               PIC  9(2).
       01  JSON-ROOT               USAGE POINTER.
       01  J-POINTER               USAGE POINTER.
       01  I-POINTER               USAGE POINTER.

      *SUB
       01  STATUS3                 PIC  9(8) COMP-5.
       01  STATUS4                 PIC  9(8) COMP-5.
       01  J-KEY-NUM2              PIC  9(2).
       01  J-LENGTH                PIC  9(2).
       01  J-POINTER2              USAGE POINTER.
       01  I-POINTER2              USAGE POINTER.

      ******************************************************************
       LINKAGE                     SECTION.
      ******************************************************************
       PROCEDURE                   DIVISION.
      ******************************************************************
       MAIN-RTN.

           STRING '{'                             DELIMITED BY SIZE
                     '"key1" : "value1",'         DELIMITED BY SIZE
                     '"key2" : 2,'                DELIMITED BY SIZE
                     '"key3" : {'                 DELIMITED BY SIZE
                        '"key3-1" : "value3-1",'  DELIMITED BY SIZE
                        '"key3-2" : "value3-2"'   DELIMITED BY SIZE
                     '},'                         DELIMITED BY SIZE
                     '"key4" : ['                 DELIMITED BY SIZE
                        '"value4-1",'             DELIMITED BY SIZE
                        '"value4-2",'             DELIMITED BY SIZE
                        '"value4-3"'              DELIMITED BY SIZE
                     ']'                          DELIMITED BY SIZE
                  '}'                             DELIMITED BY SIZE
                  INTO JSON-STR.


           CALL "CBL_JSON_PARSE" USING  JSON-STR,
                                        JSON-ROOT
                                 GIVING STATUS1.

           CALL "CBL_JSON_GET_KEY_START" USING  JSON-ROOT,
                                                I-POINTER
                                         GIVING STATUS1.

           MOVE 0 TO STATUS1.
           MOVE 1 TO J-KEY-NUM.

           PERFORM UNTIL J-KEY-NUM >= 99
               CALL "CBL_JSON_GET_KEY_NEXT" 
                                  USING JSON-ROOT,
                                        I-POINTER,
                                        J-KEY
                                  GIVING STATUS1
               IF STATUS1 = 10 THEN
                  EXIT PERFORM
               END-IF
               DISPLAY J-KEY
               CALL "CBL_JSON_GET_OBJECT" USING JSON-ROOT,
                                                J-KEY,
                                                J-POINTER
                                          GIVING STATUS2
               CALL "CBL_JSON_GET_TYPE" USING J-POINTER
                                        GIVING STATUS2

               EVALUATE STATUS2
                   WHEN 0
                        PERFORM JSON-OBJECT
                   WHEN 1
                        PERFORM JSON-ARRAY
                   WHEN 2
                        CALL "CBL_JSON_GET_VALUE" USING  J-POINTER,
                                                         J-VALUE
                                                  GIVING STATUS2
                        DISPLAY "STRING:" J-VALUE
                   WHEN 3
                        CALL "CBL_JSON_GET_VALUE" USING  J-POINTER,
                                                         J-VALUE-INT
                                                  GIVING STATUS2
                        DISPLAY "INTEGER:" J-VALUE-INT
               END-EVALUATE

               ADD 1 TO J-KEY-NUM
           END-PERFORM.

       MAIN-EXT.
           STOP RUN.


       JSON-OBJECT SECTION.
           CALL "CBL_JSON_GET_KEY_START" USING  J-POINTER,
                                                I-POINTER2
                                         GIVING STATUS3.

           MOVE 0 TO STATUS3.
           MOVE 1 TO J-KEY-NUM.

           PERFORM UNTIL J-KEY-NUM2 >= 99
               CALL "CBL_JSON_GET_KEY_NEXT" 
                                  USING J-POINTER,
                                        I-POINTER2,
                                        J-KEY
                                  GIVING STATUS3
               IF STATUS3 = 10 THEN
                  EXIT PERFORM
               END-IF
               DISPLAY J-KEY
               CALL "CBL_JSON_GET_OBJECT" USING J-POINTER,
                                                J-KEY,
                                                J-POINTER2
                                          GIVING STATUS4

               CALL "CBL_JSON_GET_VALUE" USING  J-POINTER2,
                                                J-VALUE
                                         GIVING STATUS4
               DISPLAY "CHILD:" J-VALUE

               ADD 1 TO J-KEY-NUM2
           END-PERFORM.


       JSON-OBJECT-EXT.
           EXIT SECTION.

       JSON-ARRAY SECTION.
           CALL "CBL_JSON_GET_ARRLEN" USING  J-POINTER
                                      GIVING J-LENGTH.

           MOVE 0 TO STATUS3.
           
           DISPLAY "LENGTH:" J-LENGTH.

           PERFORM VARYING J-KEY-NUM FROM 0 BY 1
                                     UNTIL J-KEY-NUM >= J-LENGTH

               CALL "CBL_JSON_GET_OBJECT_A" USING J-POINTER,
                                                J-KEY-NUM,
                                                J-POINTER2
                                          GIVING STATUS4

               CALL "CBL_JSON_GET_VALUE" USING  J-POINTER2,
                                                J-VALUE
                                         GIVING STATUS4

               DISPLAY "INDEX[" J-KEY-NUM "]:" J-VALUE

           END-PERFORM.

       JSON-ARRAY-EXT.
           EXIT SECTION.

[GitMensch]

In such cases, the IBM extension will be "ON EXCEPTION".

Looking at https://www.microfocus.com/documentation/visual-cobol/vc60/DevHub/GUID-BC279EEA-6FE7-4F79-AB8B-062A709E4B34.html it wouldn't.
It would populate every matching item, would leave items with no name matching as-is (=COBOL name, but no JSON match) and for items that are only in JSON that have no match in COBOL would set JSON-RETURN to a nonzero value. Exceptions will only occur if there is no match at all or if the datatypes don't match.

The biggest point to consider the IBM extension: it is already wide adapted, so will ease porting scenarios (and also has a good chance to be added to COBOL 20xx+ [the next standard after the current round]).