The onpload Conversion Process

The onpload conversion process is identical for both import or export operations. The onpload utility:

The custom-conversion function API uses ASCII strings as the canonical data type. The API functions present data as ASCII strings and expect data from the custom-conversion functions to be presented as ASCII strings. The API functions convert source data of different types to ASCII strings, and also convert ASCII string data from custom-conversion functions to destination data types.

Custom-conversion functions are loaded into the onpload executable through a shared library.

To integrate your custom-conversion functions into the onpload executable

Prepare the custom-conversion function table.
The onpload utility uses the entries in a function table to translate custom-function string names that are specified in the load or unload map. You must supply the function table and the custom-conversion functions.

To code the function table, use the following template for the file plcstcnv.c. You can copy this template from the $INFORMIXDIR/incl/hpl directory. Add as many entries into the functiontable array as needed.

The onpload utility searches the functiontable array for the string name of the custom-conversion function that the map specifies. The function pointer that is associated with the string name is retrieved and used as the custom-conversion function. In the following template for the file plcstcnv.c, ycf1 and ycf2 are the strings that ipload uses to find the custom functions your_conversion_func1 and your_conversion_func2, respectively. To add custom function string names to the onpload database, see Mapping Options.
```
/*
 * plcstcnv.c
 */
#include "pldriver.h"

extern int your_conversion_func1();
extern int your_conversion_func2();

struct functable functiontable[] =
{
    {"ycf1", your_conversion_func1},
    {"ycf2", your_conversion_func2},
    {0, 0}
};
/* end of plcstcnv.c */
```

Prepare your conversion functions. Use the template in the following example to code your conversion functions:

/*
 * your_custom_conversion.c
 */

/*
 * The argument list must be adhered to.
 */
int your_conversion_func1(outbuffer, buflen, value)
    char *outbuffer; /* where to put your output */
    int   buflen;    /* max size of buffer in bytes*/
    char *value;     /* input value */
{
    /* your processing here */
}

int your_conversion_func2(outbuffer, buflen, value)
    char *outbuffer; /* where to put your output */
    int   buflen;    /* max size of buffer */
    char *value;     /* input value */
{
/* your processing here */
}
/* end of your_custom_conversion.c */

Rebuild the onpload shared-library file ipldd09a.SOLIBSUFFIX, (where SOLIBSUFFIX is the shared-library suffix for your platform). Follow the instructions in Rebuilding the Shared-Library File.
The onpload utility uses the same library for both custom-conversion functions and custom drivers. When you rebuild the library, if there are custom drivers, you must link the custom-driver code as well as the custom-conversion functions.
Install the shared library in the appropriate path for your platform. For example, on Solaris the shared library should be installed in $INFORMIXDIR/lib or any configurable path that is specified by the HPL_DYNAMIC_LIB_PATH configuration parameter.