| 1 | '\" |
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| 8 | '\" |
| 9 | '\" The definitions below are for supplemental macros used in Tcl/Tk |
| 10 | '\" manual entries. |
| 11 | '\" |
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| 59 | '\" End of list of standard options for a Tk widget. |
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| 61 | '\" .OP cmdName dbName dbClass |
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| 70 | '\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $ |
| 71 | '\" |
| 72 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. |
| 73 | .if t .wh -1.3i ^B |
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| 107 | .AS Tcl_Interp Tcl_CreateInterp in/out |
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| 205 | '\" # SO - start of list of standard options |
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| 207 | .SH "STANDARD OPTIONS" |
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| 212 | .. |
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| 218 | See the \\fBoptions\\fR manual entry for details on the standard options. |
| 219 | .. |
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| 225 | Command-Line Name: \\fB\\$1\\fR |
| 226 | Database Name: \\fB\\$2\\fR |
| 227 | Database Class: \\fB\\$3\\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 |