Other Alias
Tcl_RegisterObjType, Tcl_AppendAllObjTypes, Tcl_ConvertToTypeSYNOPSIS
#include <tcl.h>
Tcl_RegisterObjType(typePtr)
Tcl_ObjType *
Tcl_GetObjType(typeName)
int
Tcl_AppendAllObjTypes(interp, objPtr)
int
Tcl_ConvertToType(interp, objPtr, typePtr)
ARGUMENTS
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Tcl_ObjType *typePtr (in)
Points to the structure containing information about the Tcl object type. This storage must live forever, typically by being statically allocated. -
CONST char *typeName (in)
The name of a Tcl object type that Tcl_GetObjType should look up. -
Tcl_Interp *interp (in)
Interpreter to use for error reporting. -
Tcl_Obj *objPtr (in)
For Tcl_AppendAllObjTypes, this points to the object onto which it appends the name of each object type as a list element. For Tcl_ConvertToType, this points to an object that must have been the result of a previous call to Tcl_NewObj.
DESCRIPTION
The procedures in this man page manage Tcl object types. The are used to register new object types, look up types, and force conversions from one type to another.
Tcl_RegisterObjType registers a new Tcl object type in the table of all object types supported by Tcl. The argument typePtr points to a Tcl_ObjType structure that describes the new type by giving its name and by supplying pointers to four procedures that implement the type. If the type table already contains a type with the same name as in typePtr, it is replaced with the new type. The Tcl_ObjType structure is described in the section THE TCL_OBJTYPE STRUCTURE below.
Tcl_GetObjType returns a pointer to the Tcl_ObjType with name typeName. It returns NULL if no type with that name is registered.
Tcl_AppendAllObjTypes appends the name of each object type as a list element onto the Tcl object referenced by objPtr. The return value is TCL_OK unless there was an error converting objPtr to a list object; in that case TCL_ERROR is returned.
Tcl_ConvertToType converts an object from one type to another if possible. It creates a new internal representation for objPtr appropriate for the target type typePtr and sets its typePtr member to that type. Any internal representation for objPtr's old type is freed. If an error occurs during conversion, it returns TCL_ERROR and leaves an error message in the result object for interp unless interp is NULL. Otherwise, it returns TCL_OK. Passing a NULL interp allows this procedure to be used as a test whether the conversion can be done (and in fact was done).
THE TCL_OBJTYPE STRUCTURE
Extension writers can define new object types by defining four procedures, initializing a Tcl_ObjType structure to describe the type, and calling Tcl_RegisterObjType. The Tcl_ObjType structure is defined as follows:
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typedef struct Tcl_ObjType { char *name; Tcl_FreeInternalRepProc *freeIntRepProc; Tcl_DupInternalRepProc *dupIntRepProc; Tcl_UpdateStringProc *updateStringProc; Tcl_SetFromAnyProc *setFromAnyProc; } Tcl_ObjType;
The name member describes the name of the type, e.g. int. Extension writers can look up an object type using its name with the Tcl_GetObjType procedure. The remaining four members are pointers to procedures called by the generic Tcl object code:
The setFromAnyProc member contains the address of a function called to create a valid internal representation from an object's string representation.
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typedef int (Tcl_SetFromAnyProc) (Tcl_Interp *interp, Tcl_Obj *objPtr);
The updateStringProc member contains the address of a function called to create a valid string representation from an object's internal representation.
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typedef void (Tcl_UpdateStringProc) (Tcl_Obj *objPtr);
The dupIntRepProc member contains the address of a function called to copy an internal representation from one object to another.
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typedef void (Tcl_DupInternalRepProc) (Tcl_Obj *srcPtr, Tcl_Obj *dupPtr);
The freeIntRepProc member contains the address of a function that is called when an object is freed.
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typedef void (Tcl_FreeInternalRepProc) (Tcl_Obj *objPtr);
KEYWORDS
internal representation, object, object type, string representation, type conversion