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10 | '\" The definitions below are for supplemental macros used in Tcl/Tk | |
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208 | .SH "STANDARD OPTIONS" | |
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219 | See the \\fBoptions\\fR manual entry for details on the standard options. | |
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226 | Command-Line Name: \\fB\\$1\\fR | |
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244 | \\$1\l'|0\(ul'\\$2 | |
245 | .. | |
246 | .TH Tcl_SetResult 3 8.0 Tcl "Tcl Library Procedures" | |
247 | .BS | |
248 | .SH NAME | |
249 | Tcl_SetObjResult, Tcl_GetObjResult, Tcl_SetResult, Tcl_GetStringResult, Tcl_AppendResult, Tcl_AppendResultVA, Tcl_AppendElement, Tcl_ResetResult, Tcl_FreeResult \- manipulate Tcl result | |
250 | .SH SYNOPSIS | |
251 | .nf | |
252 | \fB#include <tcl.h>\fR | |
253 | .sp | |
254 | \fBTcl_SetObjResult\fR(\fIinterp, objPtr\fR) | |
255 | .sp | |
256 | Tcl_Obj * | |
257 | \fBTcl_GetObjResult\fR(\fIinterp\fR) | |
258 | .sp | |
259 | \fBTcl_SetResult\fR(\fIinterp, string, freeProc\fR) | |
260 | .sp | |
261 | CONST char * | |
262 | \fBTcl_GetStringResult\fR(\fIinterp\fR) | |
263 | .sp | |
264 | \fBTcl_AppendResult\fR(\fIinterp, string, string, ... , \fB(char *) NULL\fR) | |
265 | .sp | |
266 | \fBTcl_AppendResultVA\fR(\fIinterp, argList\fR) | |
267 | .sp | |
268 | \fBTcl_AppendElement\fR(\fIinterp, string\fR) | |
269 | .sp | |
270 | \fBTcl_ResetResult\fR(\fIinterp\fR) | |
271 | .sp | |
272 | \fBTcl_FreeResult\fR(\fIinterp\fR) | |
273 | .SH ARGUMENTS | |
274 | .AS Tcl_FreeProc freeProc | |
275 | .AP Tcl_Interp *interp out | |
276 | Interpreter whose result is to be modified or read. | |
277 | .AP Tcl_Obj *objPtr in | |
278 | Object value to become result for \fIinterp\fR. | |
279 | .AP char *string in | |
280 | String value to become result for \fIinterp\fR or to be | |
281 | appended to the existing result. | |
282 | .AP Tcl_FreeProc *freeProc in | |
283 | Address of procedure to call to release storage at | |
284 | \fIstring\fR, or \fBTCL_STATIC\fR, \fBTCL_DYNAMIC\fR, or | |
285 | \fBTCL_VOLATILE\fR. | |
286 | .AP va_list argList in | |
287 | An argument list which must have been initialised using | |
288 | \fBTCL_VARARGS_START\fR, and cleared using \fBva_end\fR. | |
289 | .BE | |
290 | ||
291 | .SH DESCRIPTION | |
292 | .PP | |
293 | The procedures described here are utilities for manipulating the | |
294 | result value in a Tcl interpreter. | |
295 | The interpreter result may be either a Tcl object or a string. | |
296 | For example, \fBTcl_SetObjResult\fR and \fBTcl_SetResult\fR | |
297 | set the interpreter result to, respectively, an object and a string. | |
298 | Similarly, \fBTcl_GetObjResult\fR and \fBTcl_GetStringResult\fR | |
299 | return the interpreter result as an object and as a string. | |
300 | The procedures always keep the string and object forms | |
301 | of the interpreter result consistent. | |
302 | For example, if \fBTcl_SetObjResult\fR is called to set | |
303 | the result to an object, | |
304 | then \fBTcl_GetStringResult\fR is called, | |
305 | it will return the object's string value. | |
306 | .PP | |
307 | \fBTcl_SetObjResult\fR | |
308 | arranges for \fIobjPtr\fR to be the result for \fIinterp\fR, | |
309 | replacing any existing result. | |
310 | The result is left pointing to the object | |
311 | referenced by \fIobjPtr\fR. | |
312 | \fIobjPtr\fR's reference count is incremented | |
313 | since there is now a new reference to it from \fIinterp\fR. | |
314 | The reference count for any old result object | |
315 | is decremented and the old result object is freed if no | |
316 | references to it remain. | |
317 | .PP | |
318 | \fBTcl_GetObjResult\fR returns the result for \fIinterp\fR as an object. | |
319 | The object's reference count is not incremented; | |
320 | if the caller needs to retain a long-term pointer to the object | |
321 | they should use \fBTcl_IncrRefCount\fR to increment its reference count | |
322 | in order to keep it from being freed too early or accidently changed. | |
323 | .PP | |
324 | \fBTcl_SetResult\fR | |
325 | arranges for \fIstring\fR to be the result for the current Tcl | |
326 | command in \fIinterp\fR, replacing any existing result. | |
327 | The \fIfreeProc\fR argument specifies how to manage the storage | |
328 | for the \fIstring\fR argument; | |
329 | it is discussed in the section | |
330 | \fBTHE TCL_FREEPROC ARGUMENT TO TCL_SETRESULT\fR below. | |
331 | If \fIstring\fR is \fBNULL\fR, then \fIfreeProc\fR is ignored | |
332 | and \fBTcl_SetResult\fR | |
333 | re-initializes \fIinterp\fR's result to point to an empty string. | |
334 | .PP | |
335 | \fBTcl_GetStringResult\fR returns the result for \fIinterp\fR as an string. | |
336 | If the result was set to an object by a \fBTcl_SetObjResult\fR call, | |
337 | the object form will be converted to a string and returned. | |
338 | If the object's string representation contains null bytes, | |
339 | this conversion will lose information. | |
340 | For this reason, programmers are encouraged to | |
341 | write their code to use the new object API procedures | |
342 | and to call \fBTcl_GetObjResult\fR instead. | |
343 | .PP | |
344 | \fBTcl_ResetResult\fR clears the result for \fIinterp\fR | |
345 | and leaves the result in its normal empty initialized state. | |
346 | If the result is an object, | |
347 | its reference count is decremented and the result is left | |
348 | pointing to an unshared object representing an empty string. | |
349 | If the result is a dynamically allocated string, its memory is free*d | |
350 | and the result is left as a empty string. | |
351 | \fBTcl_ResetResult\fR also clears the error state managed by | |
352 | \fBTcl_AddErrorInfo\fR, \fBTcl_AddObjErrorInfo\fR, | |
353 | and \fBTcl_SetErrorCode\fR. | |
354 | ||
355 | .SH "OLD STRING PROCEDURES" | |
356 | .PP | |
357 | Use of the following procedures is deprecated | |
358 | since they manipulate the Tcl result as a string. | |
359 | Procedures such as \fBTcl_SetObjResult\fR | |
360 | that manipulate the result as an object | |
361 | can be significantly more efficient. | |
362 | .PP | |
363 | \fBTcl_AppendResult\fR makes it easy to build up Tcl results in pieces. | |
364 | It takes each of its \fIstring\fR arguments and appends them in order | |
365 | to the current result associated with \fIinterp\fR. | |
366 | If the result is in its initialized empty state (e.g. a command procedure | |
367 | was just invoked or \fBTcl_ResetResult\fR was just called), | |
368 | then \fBTcl_AppendResult\fR sets the result to the concatenation of | |
369 | its \fIstring\fR arguments. | |
370 | \fBTcl_AppendResult\fR may be called repeatedly as additional pieces | |
371 | of the result are produced. | |
372 | \fBTcl_AppendResult\fR takes care of all the | |
373 | storage management issues associated with managing \fIinterp\fR's | |
374 | result, such as allocating a larger result area if necessary. | |
375 | It also converts the current interpreter result from an object | |
376 | to a string, if necessary, before appending the argument strings. | |
377 | Any number of \fIstring\fR arguments may be passed in a single | |
378 | call; the last argument in the list must be a NULL pointer. | |
379 | .PP | |
380 | \fBTcl_AppendResultVA\fR is the same as \fBTcl_AppendResult\fR except that | |
381 | instead of taking a variable number of arguments it takes an argument list. | |
382 | .PP | |
383 | \fBTcl_AppendElement\fR is similar to \fBTcl_AppendResult\fR in | |
384 | that it allows results to be built up in pieces. | |
385 | However, \fBTcl_AppendElement\fR takes only a single \fIstring\fR | |
386 | argument and it appends that argument to the current result | |
387 | as a proper Tcl list element. | |
388 | \fBTcl_AppendElement\fR adds backslashes or braces if necessary | |
389 | to ensure that \fIinterp\fR's result can be parsed as a list and that | |
390 | \fIstring\fR will be extracted as a single element. | |
391 | Under normal conditions, \fBTcl_AppendElement\fR will add a space | |
392 | character to \fIinterp\fR's result just before adding the new | |
393 | list element, so that the list elements in the result are properly | |
394 | separated. | |
395 | However if the new list element is the first in a list or sub-list | |
396 | (i.e. \fIinterp\fR's current result is empty, or consists of the | |
397 | single character ``{'', or ends in the characters `` {'') then no | |
398 | space is added. | |
399 | .PP | |
400 | \fBTcl_FreeResult\fR performs part of the work | |
401 | of \fBTcl_ResetResult\fR. | |
402 | It frees up the memory associated with \fIinterp\fR's result. | |
403 | It also sets \fIinterp->freeProc\fR to zero, but doesn't | |
404 | change \fIinterp->result\fR or clear error state. | |
405 | \fBTcl_FreeResult\fR is most commonly used when a procedure | |
406 | is about to replace one result value with another. | |
407 | ||
408 | .SH "DIRECT ACCESS TO INTERP->RESULT IS DEPRECATED" | |
409 | .PP | |
410 | It used to be legal for programs to | |
411 | directly read and write \fIinterp->result\fR | |
412 | to manipulate the interpreter result. | |
413 | Direct access to \fIinterp->result\fR is now strongly deprecated | |
414 | because it can make the result's string and object forms inconsistent. | |
415 | Programs should always read the result | |
416 | using the procedures \fBTcl_GetObjResult\fR or \fBTcl_GetStringResult\fR, | |
417 | and write the result using \fBTcl_SetObjResult\fR or \fBTcl_SetResult\fR. | |
418 | ||
419 | .SH "THE TCL_FREEPROC ARGUMENT TO TCL_SETRESULT" | |
420 | .PP | |
421 | \fBTcl_SetResult\fR's \fIfreeProc\fR argument specifies how | |
422 | the Tcl system is to manage the storage for the \fIstring\fR argument. | |
423 | If \fBTcl_SetResult\fR or \fBTcl_SetObjResult\fR are called | |
424 | at a time when \fIinterp\fR holds a string result, | |
425 | they do whatever is necessary to dispose of the old string result | |
426 | (see the \fBTcl_Interp\fR manual entry for details on this). | |
427 | .PP | |
428 | If \fIfreeProc\fR is \fBTCL_STATIC\fR it means that \fIstring\fR | |
429 | refers to an area of static storage that is guaranteed not to be | |
430 | modified until at least the next call to \fBTcl_Eval\fR. | |
431 | If \fIfreeProc\fR | |
432 | is \fBTCL_DYNAMIC\fR it means that \fIstring\fR was allocated with a call | |
433 | to \fBTcl_Alloc\fR and is now the property of the Tcl system. | |
434 | \fBTcl_SetResult\fR will arrange for the string's storage to be | |
435 | released by calling \fBTcl_Free\fR when it is no longer needed. | |
436 | If \fIfreeProc\fR is \fBTCL_VOLATILE\fR it means that \fIstring\fR | |
437 | points to an area of memory that is likely to be overwritten when | |
438 | \fBTcl_SetResult\fR returns (e.g. it points to something in a stack frame). | |
439 | In this case \fBTcl_SetResult\fR will make a copy of the string in | |
440 | dynamically allocated storage and arrange for the copy to be the | |
441 | result for the current Tcl command. | |
442 | .PP | |
443 | If \fIfreeProc\fR isn't one of the values \fBTCL_STATIC\fR, | |
444 | \fBTCL_DYNAMIC\fR, and \fBTCL_VOLATILE\fR, then it is the address | |
445 | of a procedure that Tcl should call to free the string. | |
446 | This allows applications to use non-standard storage allocators. | |
447 | When Tcl no longer needs the storage for the string, it will | |
448 | call \fIfreeProc\fR. \fIFreeProc\fR should have arguments and | |
449 | result that match the type \fBTcl_FreeProc\fR: | |
450 | .CS | |
451 | typedef void Tcl_FreeProc(char *\fIblockPtr\fR); | |
452 | .CE | |
453 | When \fIfreeProc\fR is called, its \fIblockPtr\fR will be set to | |
454 | the value of \fIstring\fR passed to \fBTcl_SetResult\fR. | |
455 | ||
456 | .SH "SEE ALSO" | |
457 | Tcl_AddErrorInfo, Tcl_CreateObjCommand, Tcl_SetErrorCode, Tcl_Interp | |
458 | ||
459 | .SH KEYWORDS | |
460 | append, command, element, list, object, result, return value, interpreter |