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NAME

mg_init, mg_ehand, mg_uhand - initialize MGF entity handlers

SYNOPSIS

#include "parser.h"

void mg_init( void )

int mg_defuhand( int argc, char **argv )

extern int (*mg_ehand[MG_NENTITIES])( int argc, char **argv )

extern int (*mg_uhand)( int argc, char **argv )

extern unsigned mg_nunknown

DESCRIPTION

The parser dispatch table, mg_ehand is initially set to all NULL pointers, and it is the duty of the calling program to assign entity handler functions to each of the supported entity positions in the array. The entities are given in the include file "parser.h" as the following: 

#define MG_E_COMMENT		0		/* #		*/
#define MG_E_COLOR		1		/* c		*/
#define MG_E_CCT		2		/* cct		*/
#define MG_E_CONE		3		/* cone		*/
#define MG_E_CMIX		4		/* cmix		*/
#define MG_E_CSPEC		5		/* cspec	*/
#define MG_E_CXY		6		/* cxy		*/
#define MG_E_CYL		7		/* cyl		*/
#define MG_E_ED			8		/* ed		*/
#define MG_E_FACE		9		/* f		*/
#define MG_E_INCLUDE		10		/* i		*/
#define MG_E_IES		11		/* ies		*/
#define MG_E_IR			12		/* ir		*/
#define MG_E_MATERIAL		13		/* m		*/
#define MG_E_NORMAL		14		/* n		*/
#define MG_E_OBJECT		15		/* o		*/
#define MG_E_POINT		16		/* p		*/
#define MG_E_PRISM		17		/* prism	*/
#define MG_E_RD			18		/* rd		*/
#define MG_E_RING		19		/* ring		*/
#define MG_E_RS			20		/* rs		*/
#define MG_E_SIDES		21		/* sides	*/
#define MG_E_SPH		22		/* sph		*/
#define MG_E_TD			23		/* td		*/
#define MG_E_TORUS		24		/* torus	*/
#define MG_E_TS			25		/* ts		*/
#define MG_E_VERTEX		26		/* v		*/
#define MG_E_XF			27		/* xf		*/

#define MG_NENTITIES	28		/* total # entities */

Once the mg_ehand array has been set by the program, the mg_init routine must be called to complete the initialization process. This should be done once and only once per invocation, before any other parser routines are called.

The mg_uhand variable points to the current handler for unknown entities encountered on the input. Its default value points to the mg_defuhand function, which simply increments the global variable mg_nunknown, printing a warning message on the standard error on the first offense. (This message may be avoided by incrementing mg_nunknown before processing begins.) If mg_uhand is assigned a value of NULL, then an unknown entity will return an MG_EUNK error, which will cause the parser to abort. (See the mg_load page for a list of errors.) If the mg_uhand pointer is assigned to another function, that function will receive any unknown entities and their arguments, and the parsing will abort if the new function returns a non-zero error value. This offers a convenient way to customize the language by adding non-standard entities.

DIAGNOSTICS

If an inconsistent set of entities has been set for support, the mg_init routine will print an informative message to standard error and abort the calling program with a call to exit. This is normally unacceptable behavior for a library routine, but since such an error indicates a fault with the calling program itself, recovery is impossible.

SEE ALSO

mg_load, mg_handle