1Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
2______________________________________________________________________________
6
8 Tcl_NewStringObj, Tcl_NewUnicodeObj, Tcl_SetStringObj, Tcl_SetUni‐
9 codeObj, Tcl_GetStringFromObj, Tcl_GetString, Tcl_GetUnicodeFromObj,
10 Tcl_GetUnicode, Tcl_GetUniChar, Tcl_GetCharLength, Tcl_GetRange,
11 Tcl_AppendToObj, Tcl_AppendUnicodeToObj, Tcl_AppendObjToObj, Tcl_Ap‐
12 pendStringsToObj, Tcl_AppendStringsToObjVA, Tcl_AppendLimitedToObj,
13 Tcl_Format, Tcl_AppendFormatToObj, Tcl_ObjPrintf, Tcl_AppendPrint‐
14 fToObj, Tcl_SetObjLength, Tcl_AttemptSetObjLength, Tcl_ConcatObj - ma‐
15 nipulate Tcl values as strings
16
18 #include <tcl.h>
19 Tcl_Obj *
21 Tcl_NewStringObj(bytes, length)
22 Tcl_Obj *
24 Tcl_NewUnicodeObj(unicode, numChars)
25 void
27 Tcl_SetStringObj(objPtr, bytes, length)
28 void
30 Tcl_SetUnicodeObj(objPtr, unicode, numChars)
31 char *
33 Tcl_GetStringFromObj(objPtr, lengthPtr)
34 char *
36 Tcl_GetString(objPtr)
37 Tcl_UniChar *
39 Tcl_GetUnicodeFromObj(objPtr, lengthPtr)
40 Tcl_UniChar *
42 Tcl_GetUnicode(objPtr)
43 Tcl_UniChar
45 Tcl_GetUniChar(objPtr, index)
46 int
48 Tcl_GetCharLength(objPtr)
49 Tcl_Obj *
51 Tcl_GetRange(objPtr, first, last)
52 void
54 Tcl_AppendToObj(objPtr, bytes, length)
55 void
57 Tcl_AppendUnicodeToObj(objPtr, unicode, numChars)
58 void
60 Tcl_AppendObjToObj(objPtr, appendObjPtr)
61 void
63 Tcl_AppendStringsToObj(objPtr, string, string, ... (char *) NULL)
64 void
66 Tcl_AppendStringsToObjVA(objPtr, argList)
67 void
69 Tcl_AppendLimitedToObj(objPtr, bytes, length, limit, ellipsis)
70 Tcl_Obj *
72 Tcl_Format(interp, format, objc, objv)
73 int
75 Tcl_AppendFormatToObj(interp, objPtr, format, objc, objv)
76 Tcl_Obj *
78 Tcl_ObjPrintf(format, ...)
79 void
81 Tcl_AppendPrintfToObj(objPtr, format, ...)
82 void
84 Tcl_SetObjLength(objPtr, newLength)
85 int
87 Tcl_AttemptSetObjLength(objPtr, newLength)
88 Tcl_Obj *
90 Tcl_ConcatObj(objc, objv)
91
93 const char *bytes (in) Points to the first byte
94 of an array of UTF-8-en‐
95 coded bytes used to set
96 or append to a string
97 value. This byte array
98 may contain embedded null
99 characters unless num‐
100 Chars is negative. (Ap‐
101 plications needing null
102 bytes should represent
103 them as the two-byte se‐
104 quence \300\200, use
105 Tcl_ExternalToUtf to con‐
106 vert, or Tcl_NewByteAr‐
107 rayObj if the string is a
108 collection of uninter‐
109 preted bytes.)
110 int length (in) The number of bytes to
112 copy from bytes when ini‐
113 tializing, setting, or
114 appending to a string
115 value. If negative, all
116 bytes up to the first
117 null are used.
118 const Tcl_UniChar *unicode (in) Points to the first byte
120 of an array of Unicode
121 characters used to set or
122 append to a string value.
123 This byte array may con‐
124 tain embedded null char‐
125 acters unless numChars is
126 negative.
127 int numChars (in) The number of Unicode
129 characters to copy from
130 unicode when initializ‐
131 ing, setting, or append‐
132 ing to a string value.
133 If negative, all charac‐
134 ters up to the first null
135 character are used.
136 int index (in) The index of the Unicode
138 character to return.
139 int first (in) The index of the first
141 Unicode character in the
142 Unicode range to be re‐
143 turned as a new value.
144 int last (in) The index of the last
146 Unicode character in the
147 Unicode range to be re‐
148 turned as a new value.
149 Tcl_Obj *objPtr (in/out) Points to a value to ma‐
151 nipulate.
152 Tcl_Obj *appendObjPtr (in) The value to append to
154 objPtr in Tcl_AppendObj‐
155 ToObj.
156 int *lengthPtr (out) If non-NULL, the location
158 where Tcl_GetStringFro‐
159 mObj will store the
160 length of a value's
161 string representation.
162 const char *string (in) Null-terminated string
164 value to append to ob‐
165 jPtr.
166 va_list argList (in) An argument list which
168 must have been initial‐
169 ized using va_start, and
170 cleared using va_end.
171 int limit (in) Maximum number of bytes
173 to be appended.
174 const char *ellipsis (in) Suffix to append when the
176 limit leads to string
177 truncation. If NULL is
178 passed then the suffix
179 “...” is used.
180 const char *format (in) Format control string in‐
182 cluding % conversion
183 specifiers.
184 int objc (in) The number of elements to
186 format or concatenate.
187 Tcl_Obj *objv[] (in) The array of values to
189 format or concatenate.
190 int newLength (in) New length for the string
192 value of objPtr, not in‐
193 cluding the final null
194 character.
195______________________________________________________________________________
196
198 The procedures described in this manual entry allow Tcl values to be
199 manipulated as string values. They use the internal representation of
200 the value to store additional information to make the string manipula‐
201 tions more efficient. In particular, they make a series of append op‐
202 erations efficient by allocating extra storage space for the string so
203 that it does not have to be copied for each append. Also, indexing and
204 length computations are optimized because the Unicode string represen‐
205 tation is calculated and cached as needed. When using the Tcl_Append*
206 family of functions where the interpreter's result is the value being
207 appended to, it is important to call Tcl_ResetResult first to ensure
208 you are not unintentionally appending to existing data in the result
209 value.
210 Tcl_NewStringObj and Tcl_SetStringObj create a new value or modify an
212 existing value to hold a copy of the string given by bytes and length.
213 Tcl_NewUnicodeObj and Tcl_SetUnicodeObj create a new value or modify an
214 existing value to hold a copy of the Unicode string given by unicode
215 and numChars. Tcl_NewStringObj and Tcl_NewUnicodeObj return a pointer
216 to a newly created value with reference count zero. All four proce‐
217 dures set the value to hold a copy of the specified string. Tcl_Set‐
218 StringObj and Tcl_SetUnicodeObj free any old string representation as
219 well as any old internal representation of the value.
220 Tcl_GetStringFromObj and Tcl_GetString return a value's string repre‐
222 sentation. This is given by the returned byte pointer and (for
223 Tcl_GetStringFromObj) length, which is stored in lengthPtr if it is
224 non-NULL. If the value's UTF string representation is invalid (its
225 byte pointer is NULL), the string representation is regenerated from
226 the value's internal representation. The storage referenced by the re‐
227 turned byte pointer is owned by the value manager. It is passed back
228 as a writable pointer so that extension author creating their own
229 Tcl_ObjType will be able to modify the string representation within the
230 Tcl_UpdateStringProc of their Tcl_ObjType. Except for that limited
231 purpose, the pointer returned by Tcl_GetStringFromObj or Tcl_GetString
232 should be treated as read-only. It is recommended that this pointer be
233 assigned to a (const char *) variable. Even in the limited situations
234 where writing to this pointer is acceptable, one should take care to
235 respect the copy-on-write semantics required by Tcl_Obj's, with appro‐
236 priate calls to Tcl_IsShared and Tcl_DuplicateObj prior to any in-place
237 modification of the string representation. The procedure Tcl_GetString
238 is used in the common case where the caller does not need the length of
239 the string representation.
240 Tcl_GetUnicodeFromObj and Tcl_GetUnicode return a value's value as a
242 Unicode string. This is given by the returned pointer and (for
243 Tcl_GetUnicodeFromObj) length, which is stored in lengthPtr if it is
244 non-NULL. The storage referenced by the returned byte pointer is owned
245 by the value manager and should not be modified by the caller. The
246 procedure Tcl_GetUnicode is used in the common case where the caller
247 does not need the length of the unicode string representation.
248 Tcl_GetUniChar returns the index'th character in the value's Unicode
250 representation. The index is assumed to be in the appropriate range.
251 Tcl_GetRange returns a newly created value comprised of the characters
253 between first and last (inclusive) in the value's Unicode representa‐
254 tion. If the value's Unicode representation is invalid, the Unicode
255 representation is regenerated from the value's string representation.
256 Tcl_GetCharLength returns the number of characters (as opposed to
258 bytes) in the string value.
259 Tcl_AppendToObj appends the data given by bytes and length to the
261 string representation of the value specified by objPtr. If the value
262 has an invalid string representation, then an attempt is made to con‐
263 vert bytes is to the Unicode format. If the conversion is successful,
264 then the converted form of bytes is appended to the value's Unicode
265 representation. Otherwise, the value's Unicode representation is in‐
266 validated and converted to the UTF format, and bytes is appended to the
267 value's new string representation.
268 Tcl_AppendUnicodeToObj appends the Unicode string given by unicode and
270 numChars to the value specified by objPtr. If the value has an invalid
271 Unicode representation, then unicode is converted to the UTF format and
272 appended to the value's string representation. Appends are optimized
273 to handle repeated appends relatively efficiently (it over-allocates
274 the string or Unicode space to avoid repeated reallocations and copies
275 of value's string value).
276 Tcl_AppendObjToObj is similar to Tcl_AppendToObj, but it appends the
278 string or Unicode value (whichever exists and is best suited to be ap‐
279 pended to objPtr) of appendObjPtr to objPtr.
280 Tcl_AppendStringsToObj is similar to Tcl_AppendToObj except that it can
282 be passed more than one value to append and each value must be a null-
283 terminated string (i.e. none of the values may contain internal null
284 characters). Any number of string arguments may be provided, but the
285 last argument must be a NULL pointer to indicate the end of the list.
286 Tcl_AppendStringsToObjVA is the same as Tcl_AppendStringsToObj except
288 that instead of taking a variable number of arguments it takes an argu‐
289 ment list.
290 Tcl_AppendLimitedToObj is similar to Tcl_AppendToObj except that it im‐
292 poses a limit on how many bytes are appended. This can be handy when
293 the string to be appended might be very large, but the value being con‐
294 structed should not be allowed to grow without bound. A common usage is
295 when constructing an error message, where the end result should be kept
296 short enough to be read. Bytes from bytes are appended to objPtr, but
297 no more than limit bytes total are to be appended. If the limit pre‐
298 vents all length bytes that are available from being appended, then the
299 appending is done so that the last bytes appended are from the string
300 ellipsis. This allows for an indication of the truncation to be left in
301 the string. When length is -1, all bytes up to the first zero byte are
302 appended, subject to the limit. When ellipsis is NULL, the default
303 string ... is used. When ellipsis is non-NULL, it must point to a zero-
304 byte-terminated string in Tcl's internal UTF encoding. The number of
305 bytes appended can be less than the lesser of length and limit when ap‐
306 pending fewer bytes is necessary to append only whole multi-byte char‐
307 acters.
308 Tcl_Format is the C-level interface to the engine of the format com‐
310 mand. The actual command procedure for format is little more than
311 Tcl_Format(interp, Tcl_GetString(objv[1]), objc-2, objv+2);
313 The objc Tcl_Obj values in objv are formatted into a string according
315 to the conversion specification in format argument, following the docu‐
316 mentation for the format command. The resulting formatted string is
317 converted to a new Tcl_Obj with refcount of zero and returned. If some
318 error happens during production of the formatted string, NULL is re‐
319 turned, and an error message is recorded in interp, if interp is non-
320 NULL.
321 Tcl_AppendFormatToObj is an appending alternative form of Tcl_Format
323 with functionality equivalent to:
324 Tcl_Obj *newPtr = Tcl_Format(interp, format, objc, objv);
326 if (newPtr == NULL) return TCL_ERROR;
327 Tcl_AppendObjToObj(objPtr, newPtr);
328 Tcl_DecrRefCount(newPtr);
329 return TCL_OK;
330 but with greater convenience and efficiency when the appending func‐
332 tionality is needed.
333 Tcl_ObjPrintf serves as a replacement for the common sequence
335 char buf[SOME_SUITABLE_LENGTH];
337 sprintf(buf, format, ...);
338 Tcl_NewStringObj(buf, -1);
339 but with greater convenience and no need to determine SOME_SUIT‐
341 ABLE_LENGTH. The formatting is done with the same core formatting en‐
342 gine used by Tcl_Format. This means the set of supported conversion
343 specifiers is that of the format command and not that of the sprintf
344 routine where the two sets differ. When a conversion specifier passed
345 to Tcl_ObjPrintf includes a precision, the value is taken as a number
346 of bytes, as sprintf does, and not as a number of characters, as format
347 does. This is done on the assumption that C code is more likely to
348 know how many bytes it is passing around than the number of encoded
349 characters those bytes happen to represent. The variable number of ar‐
350 guments passed in should be of the types that would be suitable for
351 passing to sprintf. Note in this example usage, x is of type int.
352 int x = 5;
354 Tcl_Obj *objPtr = Tcl_ObjPrintf("Value is %d", x);
355 If the value of format contains internal inconsistencies or invalid
357 specifier formats, the formatted string result produced by Tcl_Ob‐
358 jPrintf will be an error message describing the error. It is impossi‐
359 ble however to provide runtime protection against mismatches between
360 the format and any subsequent arguments. Compile-time protection may
361 be provided by some compilers.
362 Tcl_AppendPrintfToObj is an appending alternative form of Tcl_ObjPrintf
364 with functionality equivalent to
365 Tcl_Obj *newPtr = Tcl_ObjPrintf(format, ...);
367 Tcl_AppendObjToObj(objPtr, newPtr);
368 Tcl_DecrRefCount(newPtr);
369 but with greater convenience and efficiency when the appending func‐
371 tionality is needed.
372 The Tcl_SetObjLength procedure changes the length of the string value
374 of its objPtr argument. If the newLength argument is greater than the
375 space allocated for the value's string, then the string space is re‐
376 allocated and the old value is copied to the new space; the bytes be‐
377 tween the old length of the string and the new length may have arbi‐
378 trary values. If the newLength argument is less than the current
379 length of the value's string, with objPtr->length is reduced without
380 reallocating the string space; the original allocated size for the
381 string is recorded in the value, so that the string length can be en‐
382 larged in a subsequent call to Tcl_SetObjLength without reallocating
383 storage. In all cases Tcl_SetObjLength leaves a null character at ob‐
384 jPtr->bytes[newLength].
385 Tcl_AttemptSetObjLength is identical in function to Tcl_SetObjLength
387 except that if sufficient memory to satisfy the request cannot be allo‐
388 cated, it does not cause the Tcl interpreter to panic. Thus, if
389 newLength is greater than the space allocated for the value's string,
390 and there is not enough memory available to satisfy the request,
391 Tcl_AttemptSetObjLength will take no action and return 0 to indicate
392 failure. If there is enough memory to satisfy the request, Tcl_At‐
393 temptSetObjLength behaves just like Tcl_SetObjLength and returns 1 to
394 indicate success.
395 The Tcl_ConcatObj function returns a new string value whose value is
397 the space-separated concatenation of the string representations of all
398 of the values in the objv array. Tcl_ConcatObj eliminates leading and
399 trailing white space as it copies the string representations of the
400 objv array to the result. If an element of the objv array consists of
401 nothing but white space, then that value is ignored entirely. This
402 white-space removal was added to make the output of the concat command
403 cleaner-looking. Tcl_ConcatObj returns a pointer to a newly-created
404 value whose ref count is zero.
405
407 Tcl_NewObj(3), Tcl_IncrRefCount(3), Tcl_DecrRefCount(3), format(n),
408 sprintf(3)
409
411 append, internal representation, value, value type, string value,
412 string type, string representation, concat, concatenate, unicode
413Tcl 8.1 Tcl_StringObj(3)