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2 | '\" Copyright (c) 1996-1997 Sun Microsystems, Inc. | |
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7 | '\" RCS: @(#) $Id: ObjectType.3,v 1.7 2002/08/16 13:45:36 dkf Exp $ | |
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9 | '\" The definitions below are for supplemental macros used in Tcl/Tk | |
10 | '\" manual entries. | |
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72 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. | |
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205 | '\" # SO - start of list of standard options | |
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207 | .SH "STANDARD OPTIONS" | |
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213 | '\" # SE - end of list of standard options | |
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218 | See the \\fBoptions\\fR manual entry for details on the standard options. | |
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225 | Command-Line Name: \\fB\\$1\\fR | |
226 | Database Name: \\fB\\$2\\fR | |
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243 | \\$1\l'|0\(ul'\\$2 | |
244 | .. | |
245 | .TH Tcl_ObjType 3 8.0 Tcl "Tcl Library Procedures" | |
246 | .BS | |
247 | .SH NAME | |
248 | Tcl_RegisterObjType, Tcl_GetObjType, Tcl_AppendAllObjTypes, Tcl_ConvertToType \- manipulate Tcl object types | |
249 | .SH SYNOPSIS | |
250 | .nf | |
251 | \fB#include <tcl.h>\fR | |
252 | .sp | |
253 | \fBTcl_RegisterObjType\fR(\fItypePtr\fR) | |
254 | .sp | |
255 | Tcl_ObjType * | |
256 | \fBTcl_GetObjType\fR(\fItypeName\fR) | |
257 | .sp | |
258 | int | |
259 | \fBTcl_AppendAllObjTypes\fR(\fIinterp, objPtr\fR) | |
260 | .sp | |
261 | int | |
262 | \fBTcl_ConvertToType\fR(\fIinterp, objPtr, typePtr\fR) | |
263 | .SH ARGUMENTS | |
264 | .AS Tcl_ObjType *typeName in | |
265 | .AP Tcl_ObjType *typePtr in | |
266 | Points to the structure containing information about the Tcl object type. | |
267 | This storage must live forever, | |
268 | typically by being statically allocated. | |
269 | .AP "CONST char" *typeName in | |
270 | The name of a Tcl object type that \fBTcl_GetObjType\fR should look up. | |
271 | .AP Tcl_Interp *interp in | |
272 | Interpreter to use for error reporting. | |
273 | .AP Tcl_Obj *objPtr in | |
274 | For \fBTcl_AppendAllObjTypes\fR, this points to the object onto which | |
275 | it appends the name of each object type as a list element. | |
276 | For \fBTcl_ConvertToType\fR, this points to an object that | |
277 | must have been the result of a previous call to \fBTcl_NewObj\fR. | |
278 | .BE | |
279 | ||
280 | .SH DESCRIPTION | |
281 | .PP | |
282 | The procedures in this man page manage Tcl object types. | |
283 | The are used to register new object types, | |
284 | look up types, | |
285 | and force conversions from one type to another. | |
286 | .PP | |
287 | \fBTcl_RegisterObjType\fR registers a new Tcl object type | |
288 | in the table of all object types supported by Tcl. | |
289 | The argument \fItypePtr\fR points to a Tcl_ObjType structure that | |
290 | describes the new type by giving its name | |
291 | and by supplying pointers to four procedures | |
292 | that implement the type. | |
293 | If the type table already contains a type | |
294 | with the same name as in \fItypePtr\fR, | |
295 | it is replaced with the new type. | |
296 | The Tcl_ObjType structure is described | |
297 | in the section \fBTHE TCL_OBJTYPE STRUCTURE\fR below. | |
298 | .PP | |
299 | \fBTcl_GetObjType\fR returns a pointer to the Tcl_ObjType | |
300 | with name \fItypeName\fR. | |
301 | It returns NULL if no type with that name is registered. | |
302 | .PP | |
303 | \fBTcl_AppendAllObjTypes\fR appends the name of each object type | |
304 | as a list element onto the Tcl object referenced by \fIobjPtr\fR. | |
305 | The return value is \fBTCL_OK\fR unless there was an error | |
306 | converting \fIobjPtr\fR to a list object; | |
307 | in that case \fBTCL_ERROR\fR is returned. | |
308 | .PP | |
309 | \fBTcl_ConvertToType\fR converts an object from one type to another | |
310 | if possible. | |
311 | It creates a new internal representation for \fIobjPtr\fR | |
312 | appropriate for the target type \fItypePtr\fR | |
313 | and sets its \fItypePtr\fR member to that type. | |
314 | Any internal representation for \fIobjPtr\fR's old type is freed. | |
315 | If an error occurs during conversion, it returns \fBTCL_ERROR\fR | |
316 | and leaves an error message in the result object for \fIinterp\fR | |
317 | unless \fIinterp\fR is NULL. | |
318 | Otherwise, it returns \fBTCL_OK\fR. | |
319 | Passing a NULL \fIinterp\fR allows this procedure to be used | |
320 | as a test whether the conversion can be done (and in fact was done). | |
321 | ||
322 | .SH "THE TCL_OBJTYPE STRUCTURE" | |
323 | .PP | |
324 | Extension writers can define new object types by defining four | |
325 | procedures, | |
326 | initializing a Tcl_ObjType structure to describe the type, | |
327 | and calling \fBTcl_RegisterObjType\fR. | |
328 | The \fBTcl_ObjType\fR structure is defined as follows: | |
329 | .CS | |
330 | typedef struct Tcl_ObjType { | |
331 | char *\fIname\fR; | |
332 | Tcl_FreeInternalRepProc *\fIfreeIntRepProc\fR; | |
333 | Tcl_DupInternalRepProc *\fIdupIntRepProc\fR; | |
334 | Tcl_UpdateStringProc *\fIupdateStringProc\fR; | |
335 | Tcl_SetFromAnyProc *\fIsetFromAnyProc\fR; | |
336 | } Tcl_ObjType; | |
337 | .CE | |
338 | .PP | |
339 | The \fIname\fR member describes the name of the type, e.g. \fBint\fR. | |
340 | Extension writers can look up an object type using its name | |
341 | with the \fBTcl_GetObjType\fR procedure. | |
342 | The remaining four members are pointers to procedures | |
343 | called by the generic Tcl object code: | |
344 | .PP | |
345 | The \fIsetFromAnyProc\fR member contains the address of a function | |
346 | called to create a valid internal representation | |
347 | from an object's string representation. | |
348 | .CS | |
349 | typedef int (Tcl_SetFromAnyProc) (Tcl_Interp *\fIinterp\fR, Tcl_Obj *\fIobjPtr\fR); | |
350 | .CE | |
351 | If an internal representation can't be created from the string, | |
352 | it returns \fBTCL_ERROR\fR and puts a message | |
353 | describing the error in the result object for \fIinterp\fR | |
354 | unless \fIinterp\fR is NULL. | |
355 | If \fIsetFromAnyProc\fR is successful, | |
356 | it stores the new internal representation, | |
357 | sets \fIobjPtr\fR's \fItypePtr\fR member to point to | |
358 | \fIsetFromAnyProc\fR's \fBTcl_ObjType\fR, and returns \fBTCL_OK\fR. | |
359 | Before setting the new internal representation, | |
360 | the \fIsetFromAnyProc\fR must free any internal representation | |
361 | of \fIobjPtr\fR's old type; | |
362 | it does this by calling the old type's \fIfreeIntRepProc\fR | |
363 | if it is not NULL. | |
364 | As an example, the \fIsetFromAnyProc\fR for the builtin Tcl integer type | |
365 | gets an up-to-date string representation for \fIobjPtr\fR | |
366 | by calling \fBTcl_GetStringFromObj\fR. | |
367 | It parses the string to obtain an integer and, | |
368 | if this succeeds, | |
369 | stores the integer in \fIobjPtr\fR's internal representation | |
370 | and sets \fIobjPtr\fR's \fItypePtr\fR member to point to the integer type's | |
371 | Tcl_ObjType structure. | |
372 | Do not release \fIobjPtr\fR's old internal representation unless you | |
373 | replace it with a new one or reset the \fItypePtr\fR member to NULL. | |
374 | .PP | |
375 | The \fIupdateStringProc\fR member contains the address of a function | |
376 | called to create a valid string representation | |
377 | from an object's internal representation. | |
378 | .CS | |
379 | typedef void (Tcl_UpdateStringProc) (Tcl_Obj *\fIobjPtr\fR); | |
380 | .CE | |
381 | \fIobjPtr\fR's \fIbytes\fR member is always NULL when it is called. | |
382 | It must always set \fIbytes\fR non-NULL before returning. | |
383 | We require the string representation's byte array | |
384 | to have a null after the last byte, at offset \fIlength\fR; | |
385 | this allows string representations that do not contain null bytes | |
386 | to be treated as conventional null character-terminated C strings. | |
387 | Storage for the byte array must be allocated in the heap by \fBTcl_Alloc\fR | |
388 | or \fBckalloc\fR. Note that \fIupdateStringProc\fRs must allocate | |
389 | enough storage for the string's bytes and the terminating null byte. | |
390 | The \fIupdateStringProc\fR for Tcl's builtin list type, for example, | |
391 | builds an array of strings for each element object | |
392 | and then calls \fBTcl_Merge\fR | |
393 | to construct a string with proper Tcl list structure. | |
394 | It stores this string as the list object's string representation. | |
395 | .PP | |
396 | The \fIdupIntRepProc\fR member contains the address of a function | |
397 | called to copy an internal representation from one object to another. | |
398 | .CS | |
399 | typedef void (Tcl_DupInternalRepProc) (Tcl_Obj *\fIsrcPtr\fR, Tcl_Obj *\fIdupPtr\fR); | |
400 | .CE | |
401 | \fIdupPtr\fR's internal representation is made a copy of \fIsrcPtr\fR's | |
402 | internal representation. | |
403 | Before the call, | |
404 | \fIsrcPtr\fR's internal representation is valid and \fIdupPtr\fR's is not. | |
405 | \fIsrcPtr\fR's object type determines what | |
406 | copying its internal representation means. | |
407 | For example, the \fIdupIntRepProc\fR for the Tcl integer type | |
408 | simply copies an integer. | |
409 | The builtin list type's \fIdupIntRepProc\fR | |
410 | allocates a new array that points at the original element objects; | |
411 | the elements are shared between the two lists | |
412 | (and their reference counts are incremented to reflect the new references). | |
413 | .PP | |
414 | The \fIfreeIntRepProc\fR member contains the address of a function | |
415 | that is called when an object is freed. | |
416 | .CS | |
417 | typedef void (Tcl_FreeInternalRepProc) (Tcl_Obj *\fIobjPtr\fR); | |
418 | .CE | |
419 | The \fIfreeIntRepProc\fR function can deallocate the storage | |
420 | for the object's internal representation | |
421 | and do other type-specific processing necessary when an object is freed. | |
422 | For example, Tcl list objects have an \fIinternalRep.otherValuePtr\fR | |
423 | that points to an array of pointers to each element in the list. | |
424 | The list type's \fIfreeIntRepProc\fR decrements | |
425 | the reference count for each element object | |
426 | (since the list will no longer refer to those objects), | |
427 | then deallocates the storage for the array of pointers. | |
428 | The \fIfreeIntRepProc\fR member can be set to NULL | |
429 | to indicate that the internal representation does not require freeing. | |
430 | ||
431 | .SH "SEE ALSO" | |
432 | Tcl_NewObj, Tcl_DecrRefCount, Tcl_IncrRefCount | |
433 | ||
434 | .SH KEYWORDS | |
435 | internal representation, object, object type, string representation, type conversion |