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Manual Pages for UNIX Operating System command usage for man Tcl_GetObjType

Tcl Library Procedures Tcl_ObjType(3TCL)

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NAME

Tcl_RegisterObjType, Tcl_GetObjType, Tcl_AppendAllObjTypes,

Tcl_ConvertToType - manipulate Tcl object types

SYNOPSIS

#include

Tcl_RegisterObjType(typePtr)

Tcl_ObjType *

Tcl_GetObjType(typeName)

int

Tcl_AppendAllObjTypes(interp, objPtr)

int

Tcl_ConvertToType(interp, objPtr, typePtr)

ARGUMENTS

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.

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Tcl Last change: 8.0 1

Tcl Library Procedures Tcl_ObjType(3TCL)

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 con-

verting 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 representa-

tion 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:

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

Tcl Last change: 8.0 2

Tcl Library Procedures Tcl_ObjType(3TCL)

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.

typedef int (Tcl_SetFromAnyProc) (Tcl_Interp *interp, Tcl_Obj *objPtr);

If an internal representation can't be created from the

string, it returns TCL_ERROR and puts a message describing

the error in the result object for interp unless interp is NULL. If setFromAnyProc is successful, it stores the new internal representation, sets objPtr's typePtr member to

point to setFromAnyProc's Tcl_ObjType, and returns TCL_OK.

Before setting the new internal representation, the set-

FromAnyProc must free any internal representation of objPtr's old type; it does this by calling the old type's

freeIntRepProc if it is not NULL. As an example, the set-

FromAnyProc for the builtin Tcl integer type gets an up-to-

date string representation for objPtr by calling

Tcl_GetStringFromObj. It parses the string to obtain an

integer and, if this succeeds, stores the integer in objPtr's internal representation and sets objPtr's typePtr

member to point to the integer type's Tcl_ObjType structure.

Do not release objPtr's old internal representation unless you replace it with a new one or reset the typePtr member to NULL.

The updateStringProc member contains the address of a func-

tion called to create a valid string representation from an object's internal representation.

typedef void (Tcl_UpdateStringProc) (Tcl_Obj *objPtr);

objPtr's bytes member is always NULL when it is called. It

must always set bytes non-NULL before returning. We require

the string representation's byte array to have a null after the last byte, at offset length; this allows string representations that do not contain null bytes to be treated

as conventional null character-terminated C strings.

Storage for the byte array must be allocated in the heap by

Tcl_Alloc or ckalloc. Note that updateStringProcs must

allocate enough storage for the string's bytes and the ter-

minating null byte. The updateStringProc for Tcl's builtin list type, for example, builds an array of strings for each

element object and then calls Tcl_Merge to construct a

string with proper Tcl list structure. It stores this string as the list object's string representation. The dupIntRepProc member contains the address of a function called to copy an internal representation from one object to another.

typedef void (Tcl_DupInternalRepProc) (Tcl_Obj *srcPtr, Tcl_Obj *dupPtr);

dupPtr's internal representation is made a copy of srcPtr's internal representation. Before the call, srcPtr's internal Tcl Last change: 8.0 3

Tcl Library Procedures Tcl_ObjType(3TCL)

representation is valid and dupPtr's is not. srcPtr's

object type determines what copying its internal representa-

tion means. For example, the dupIntRepProc for the Tcl integer type simply copies an integer. The builtin list type's dupIntRepProc allocates a new array that points at the original element objects; the elements are shared

between the two lists (and their reference counts are incre-

mented to reflect the new references). The freeIntRepProc member contains the address of a function that is called when an object is freed.

typedef void (Tcl_FreeInternalRepProc) (Tcl_Obj *objPtr);

The freeIntRepProc function can deallocate the storage for

the object's internal representation and do other type-

specific processing necessary when an object is freed. For example, Tcl list objects have an internalRep.otherValuePtr that points to an array of pointers to each element in the

list. The list type's freeIntRepProc decrements the refer-

ence count for each element object (since the list will no longer refer to those objects), then deallocates the storage for the array of pointers. The freeIntRepProc member can be set to NULL to indicate that the internal representation does not require freeing.

ATTRIBUTES

See attributes(5) for descriptions of the following attri-

butes:

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| ATTRIBUTE TYPE | ATTRIBUTE VALUE|

|____________________|__________________|_

| Availability | runtime/tcl-8 |

|____________________|__________________|_

| Interface Stability| Uncommitted |

|____________________|_________________|

NOTES Source for Tcl is available on http://opensolaris.org. Tcl Last change: 8.0 4

Manual Pages for UNIX Operating System command usage for man Tcl_GetObjType

NAME

Tcl_RegisterObjType, Tcl_GetObjType, Tcl_AppendAllObjTypes,

SYNOPSIS

Tcl_GetObjType(typeName)

type that Tcl_GetObjType

DESCRIPTION

Tcl_GetObjType returns a pointer to the Tcl_ObjType with

verting objPtr to a list object; in that case TCL_ERROR is

occurs during conversion, it returns TCL_ERROR and leaves an

with the Tcl_GetObjType procedure. The remaining four

string, it returns TCL_ERROR and puts a message describing

SEE ALSO

ATTRIBUTES

| ATTRIBUTE TYPE | ATTRIBUTE VALUE|