# Compiling JSON UDFs in a Separate Library

Although the JSON UDFs can be included in the CONNECT library module, there are cases when you may need to have them in a separate library.

This is when CONNECT is compiled embedded, or if you want to test or use these UDFs with other MariaDB versions not including them.

To make it, you need to have access to the most recent MariaDB source code. Then, make a project containing these files:

1. jsonudf.cpp
2. json.cpp
3. value.cpp
4. osutil.c
5. plugutil.cpp
6. maputil.cpp
7. jsonutil.cpp

`jsonutil.cpp` is not distributed with the source code, you will have to make it from the following:

```cpp
#include "my_global.h"
#include "mysqld.h"
#include "plugin.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>

#include "global.h"

extern "C" int GetTraceValue(void) { return 0; }
uint GetJsonGrpSize(void) { return 100; }

/***********************************************************************/
/*  These replace missing function of the (not used) DTVAL class.      */
/***********************************************************************/
typedef struct _datpar   *PDTP;
PDTP MakeDateFormat(PGLOBAL, PSZ, bool, bool, int) { return NULL; }
int ExtractDate(char*, PDTP, int, int val[6]) { return 0; }


#ifdef __WIN__
my_bool CloseFileHandle(HANDLE h)
{
	return !CloseHandle(h);
} /* end of CloseFileHandle */

#else  /* UNIX */
my_bool CloseFileHandle(HANDLE h)
{
	return (close(h)) ? TRUE : FALSE;
}  /* end of CloseFileHandle */

int GetLastError()
{
	return errno;
}  /* end of GetLastError */

#endif  // UNIX

/***********************************************************************/
/*  Program for sub-allocating one item in a storage area.             */
/*  Note: This function is equivalent to PlugSubAlloc except that in   */
/*  case of insufficient memory, it returns NULL instead of doing a    */
/*  long jump. The caller must test the return value for error.        */
/***********************************************************************/
void *PlgDBSubAlloc(PGLOBAL g, void *memp, size_t size)
{
  PPOOLHEADER pph;                        // Points on area header.

  if (!memp)  	//  Allocation is to be done in the Sarea
    memp = g->Sarea;

  size = ((size + 7) / 8) * 8;  /* Round up size to multiple of 8 */
  pph = (PPOOLHEADER)memp;

  if ((uint)size > pph->FreeBlk) { /* Not enough memory left in pool */
    sprintf(g->Message,
     "Not enough memory in Work area for request of %d (used=%d free=%d)",
			(int)size, pph->To_Free, pph->FreeBlk);
    return NULL;
  } // endif size

  // Do the suballocation the simplest way
  memp = MakePtr(memp, pph->To_Free);   // Points to sub_allocated block
  pph->To_Free += size;                 // New offset of pool free block
  pph->FreeBlk -= size;                 // New size   of pool free block

  return (memp);
} // end of PlgDBSubAlloc
```

You can create the file by copy/paste from the above.

Set all the additional include directories to the MariaDB include directories used in plugin compiling plus the reference of the storage/connect directories, and compile like any other UDF giving any name to the made library module (I used `jsonudf.dll` on Windows).

Then you can create the functions using this name as the soname parameter.

There are some restrictions when using the UDFs this way:

* The [connect\_json\_grp\_size](https://mariadb.com/docs/server/server-usage/storage-engines/connect-system-variables#connect_json_grp_size) variable cannot be accessed. The group size is set and retrieved using the [jsonset\_grp\_size](https://mariadb.com/docs/server/server-usage/storage-engines/connect-table-types/connect-json-table-type#jsonset_grp_size) and [jsonget\_grp\_size](https://mariadb.com/docs/server/server-usage/storage-engines/connect-table-types/connect-json-table-type#jsonget_grp_size) functions (previously 100).
* In case of error, warnings are replaced by messages sent to stderr.
* No trace.

<sub>*This page is licensed: CC BY-SA / Gnu FDL*</sub>

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