The following sample external conversion routine converts C language 2-byte signed integers to and from ESL integers and floats. For simplicity, this routine handles only ESL floats and integers; it does not handle conversion to ESL strings. When requested to convert data to or from an ESL string, this routine writes an error message to the errorlog and returns a non-zero value indicating that the conversion failed.
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#include <io.h>
#include <windows.h>
#include <esllib.h>
#include <esltype.h>
char *pszBadArgument = "bad argument\n",
*pszNotImp = "this conversion not implemented\n",
*pszNull = "";
/* conversion function return codes: */
#define ERR_BADARG 1 /* bad argument */
#define ERR_NOTIMPLEMENTED 2 /* conversion not implemented */
#define ERR_NOMEM 3 /* creation of string failed */
int APIENTRY esl_cint ( pField, wType, wFieldLen,
wOpCode, pData, pArg)
char *pField; /* address of structure field */
unsigned int wFieldLen, /* length of structure field */
wOpCode; /* conversion opcode */
PEASELTYPE pData; /* source OR target data */
char *pArg; /* conversion routine argument...*/
/* ...if any, (from using clause) */
{
int retval = 0; /* indicates successful conversion */
switch (wOpCode)
{
case CONVERT_TO_EASEL: /* convert C integer to Easel type */
switch (wType)
{
/* Always include a case for EACH data type, and */
/* code to recognize and handle requests to execute */
/* conversions that are not implemented. */
case ESL_STRING: /* C integer to Easel string */
/* Write an error message and return an error */
/* code for conversions that are not implemented.*/
(void) write (2, pszNotImp, strlen (pszNotImp));
if (!(pData->hString = EslCreateString (0, pszNull)))
return (ERR_NOMEM);
return(ERR_NOTIMPLEMENTED);
case ESL_INTEGER: /* C integer variant to Easel integer */
if (wFieldLen == sizeof (int))
pData->Integer = (long) (*((int *) pField));
else
{
(void) write (2, pszNotImp, strlen (pszNotImp));
return(ERR_NOTIMPLEMENTED);
}
break;
case ESL_FLOAT: /* C integer variant to Easel float */
if (wFieldLen == sizeof (int))
pData->Float = (double) (*((int *) pField));
else
{
(void) write (2, pszNotImp, strlen (pszNotImp));
return(ERR_NOTIMPLEMENTED);
}
break;
default:
(void) write (2, pszBadArgument,
strlen (pszBadArgument));
return(ERR_BADARG);
break;
}
break;
case CONVERT_TO_EXTERNAL:
switch (wType)
{
/* Always include a case for EACH data type, and */
/* code to recognize and handle requests to execute */
/* conversions that are not implemented. */
case ESL_STRING: /* Easel string to C integer variant */
(void) write (2, pszNotImp, strlen (pszNotImp));
return(ERR_NOTIMPLEMENTED);
break;
case ESL_INTEGER: /* Easel integer to C integer variant */
if (wFieldLen == sizeof (int))
(*((int *) pField)) = (int) pData->Integer;
else
{
(void) write (2, pszNotImp, strlen (pszNotImp));
return(ERR_NOTIMPLEMENTED);
}
break;
case ESL_FLOAT: /* Easel float to C integer variant */
if (wFieldLen == sizeof (int))
*((int *) pField) = (int) pData->Float;
else
{
(void) write (2, pszNotImp, strlen (pszNotImp));
return(ERR_NOTIMPLEMENTED);
}
break;
default:
(void) write (2, pszBadArgument,
strlen (pszBadArgument));
return(ERR_BADARG);
break;
}
break;
default:
(void) write (2, pszBadArgument, strlen (pszBadArgument));
return(ERR_BADARG);
break;
}
return(retval);
}
