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Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3) ______________________________________________________________________________ NAME Tcl_NewStringObj, Tcl_NewUnicodeObj, Tcl_SetStringObj, Tcl_SetUni- codeObj, Tcl_GetStringFromObj, Tcl_GetString, Tcl_GetUnicodeFromObj, Tcl_GetUnicode, Tcl_GetUniChar, Tcl_GetCharLength, Tcl_GetRange, Tcl_AppendToObj, Tcl_AppendUnicodeToObj, Tcl_AppendObjToObj, Tcl_Ap- pendStringsToObj, Tcl_AppendStringsToObjVA, Tcl_AppendLimitedToObj, Tcl_Format, Tcl_AppendFormatToObj, Tcl_ObjPrintf, Tcl_AppendPrint- fToObj, Tcl_SetObjLength, Tcl_AttemptSetObjLength, Tcl_ConcatObj - ma- nipulate Tcl objects as strings SYNOPSIS #include <tcl.h> Tcl_Obj * Tcl_NewStringObj(bytes, length) Tcl_Obj * Tcl_NewUnicodeObj(unicode, numChars) void Tcl_SetStringObj(objPtr, bytes, length) void Tcl_SetUnicodeObj(objPtr, unicode, numChars) char * Tcl_GetStringFromObj(objPtr, lengthPtr) char * Tcl_GetString(objPtr) Tcl_UniChar * Tcl_GetUnicodeFromObj(objPtr, lengthPtr) Tcl_UniChar * Tcl_GetUnicode(objPtr) Tcl_UniChar Tcl_GetUniChar(objPtr, index) int Tcl_GetCharLength(objPtr) Tcl_Obj * Tcl_GetRange(objPtr, first, last) void Tcl_AppendToObj(objPtr, bytes, length) void Tcl_AppendUnicodeToObj(objPtr, unicode, numChars) void Tcl_AppendObjToObj(objPtr, appendObjPtr) void Tcl_AppendStringsToObj(objPtr, string, string, ... (char *) NULL) void Tcl_AppendStringsToObjVA(objPtr, argList) void | Tcl_AppendLimitedToObj(objPtr, bytes, length, limit, ellipsis) | Tcl_Obj * | Tcl_Format(interp, format, objc, objv) | int | Tcl_AppendFormatToObj(interp, objPtr, format, objc, objv) | Tcl_Obj * | Tcl_ObjPrintf(format, ...) | int | Tcl_AppendPrintfToObj(objPtr, format, ...) | void Tcl_SetObjLength(objPtr, newLength) int Tcl_AttemptSetObjLength(objPtr, newLength) Tcl_Obj * Tcl_ConcatObj(objc, objv) ARGUMENTS const char *bytes (in) Points to the first byte of an array of UTF-8-en- coded bytes used to set or append to a string ob- ject. This byte array may contain embedded null characters unless num- Chars is negative. (Ap- plications needing null bytes should represent them as the two-byte se- quence \700\600, use Tcl_ExternalToUtf to con- vert, or Tcl_NewByteAr- rayObj if the string is a collection of uninter- preted bytes.) int length (in) The number of bytes to copy from bytes when ini- tializing, setting, or appending to a string ob- ject. If negative, all bytes up to the first null are used. const Tcl_UniChar *unicode (in) Points to the first byte of an array of Unicode characters used to set or append to a string ob- ject. This byte array may contain embedded null characters unless num- Chars is negative. int numChars (in) The number of Unicode characters to copy from unicode when initializ- ing, setting, or append- ing to a string object. If negative, all charac- ters up to the first null character are used. int index (in) The index of the Unicode character to return. int first (in) The index of the first Unicode character in the Unicode range to be re- turned as a new object. int last (in) The index of the last Unicode character in the Unicode range to be re- turned as a new object. Tcl_Obj *objPtr (in/out) Points to an object to manipulate. Tcl_Obj *appendObjPtr (in) The object to append to objPtr in Tcl_AppendObj- ToObj. int *lengthPtr (out) If non-NULL, the location where Tcl_GetStringFro- mObj will store the length of an object's string representation. const char *string (in) Null-terminated string value to append to ob- jPtr. va_list argList (in) An argument list which must have been ini- tialised using va_start, and cleared using va_end. int limit (in) Maximum number of bytes to be appended. const char *ellipsis (in) Suffix to append when the limit leads to string truncation. If NULL is passed then the suffix "..." is used. const char *format (in) Format control string in- cluding % conversion specifiers. int objc (in) The number of elements to format or concatenate. Tcl_Obj *objv[] (in) The array of objects to format or concatenate. int newLength (in) New length for the string value of objPtr, not in- cluding the final null character. ______________________________________________________________________________ DESCRIPTION The procedures described in this manual entry allow Tcl objects to be manipulated as string values. They use the internal representation of the object to store additional information to make the string manipula- tions more efficient. In particular, they make a series of append op- erations efficient by allocating extra storage space for the string so that it does not have to be copied for each append. Also, indexing and length computations are optimized because the Unicode string represen- tation is calculated and cached as needed. When using the Tcl_Append* family of functions where the interpreter's result is the object being appended to, it is important to call Tcl_ResetResult first to ensure you are not unintentionally appending to existing data in the result object. Tcl_NewStringObj and Tcl_SetStringObj create a new object or modify an existing object to hold a copy of the string given by bytes and length. Tcl_NewUnicodeObj and Tcl_SetUnicodeObj create a new object or modify an existing object to hold a copy of the Unicode string given by uni- code and numChars. Tcl_NewStringObj and Tcl_NewUnicodeObj return a pointer to a newly created object with reference count zero. All four procedures set the object to hold a copy of the specified string. Tcl_SetStringObj and Tcl_SetUnicodeObj free any old string representa- tion as well as any old internal representation of the object. Tcl_GetStringFromObj and Tcl_GetString return an object's string repre- sentation. This is given by the returned byte pointer and (for Tcl_GetStringFromObj) length, which is stored in lengthPtr if it is non-NULL. If the object's UTF string representation is invalid (its byte pointer is NULL), the string representation is regenerated from the object's internal representation. The storage referenced by the returned byte pointer is owned by the object manager. It is passed back as a writable pointer so that extension author creating their own Tcl_ObjType will be able to modify the string representation within the Tcl_UpdateStringProc of their Tcl_ObjType. Except for that limited purpose, the pointer returned by Tcl_GetStringFromObj or Tcl_GetString should be treated as read-only. It is recommended that this pointer be assigned to a (const char *) variable. Even in the limited situations where writing to this pointer is acceptable, one should take care to respect the copy-on-write semantics required by Tcl_Obj's, with appro- priate calls to Tcl_IsShared and Tcl_DuplicateObj prior to any in-place modification of the string representation. The procedure Tcl_GetString is used in the common case where the caller does not need the length of the string representation. Tcl_GetUnicodeFromObj and Tcl_GetUnicode return an object's value as a Unicode string. This is given by the returned pointer and (for Tcl_GetUnicodeFromObj) length, which is stored in lengthPtr if it is non-NULL. The storage referenced by the returned byte pointer is owned by the object manager and should not be modified by the caller. The procedure Tcl_GetUnicode is used in the common case where the caller does not need the length of the unicode string representation. Tcl_GetUniChar returns the index'th character in the object's Unicode representation. Tcl_GetRange returns a newly created object comprised of the characters between first and last (inclusive) in the object's Unicode representa- tion. If the object's Unicode representation is invalid, the Unicode representation is regenerated from the object's string representation. Tcl_GetCharLength returns the number of characters (as opposed to bytes) in the string object. Tcl_AppendToObj appends the data given by bytes and length to the string representation of the object specified by objPtr. If the object has an invalid string representation, then an attempt is made to con- vert bytes is to the Unicode format. If the conversion is successful, then the converted form of bytes is appended to the object's Unicode representation. Otherwise, the object's Unicode representation is in- validated and converted to the UTF format, and bytes is appended to the object's new string representation. Tcl_AppendUnicodeToObj appends the Unicode string given by unicode and numChars to the object specified by objPtr. If the object has an in- valid Unicode representation, then unicode is converted to the UTF for- mat and appended to the object's string representation. Appends are optimized to handle repeated appends relatively efficiently (it overal- locates the string or Unicode space to avoid repeated reallocations and copies of object's string value). Tcl_AppendObjToObj is similar to Tcl_AppendToObj, but it appends the string or Unicode value (whichever exists and is best suited to be ap- pended to objPtr) of appendObjPtr to objPtr. Tcl_AppendStringsToObj is similar to Tcl_AppendToObj except that it can be passed more than one value to append and each value must be a null- terminated string (i.e. none of the values may contain internal null characters). Any number of string arguments may be provided, but the last argument must be a NULL pointer to indicate the end of the list. Tcl_AppendStringsToObjVA is the same as Tcl_AppendStringsToObj except that instead of taking a variable number of arguments it takes an argu- ment list. Tcl_AppendLimitedToObj is similar to Tcl_AppendToObj except that it im- | poses a limit on how many bytes are appended. This can be handy when | the string to be appended might be very large, but the value being con- | structed should not be allowed to grow without bound. A common usage is | when constructing an error message, where the end result should be kept | short enough to be read. Bytes from bytes are appended to objPtr, but | no more than limit bytes total are to be appended. If the limit pre- | vents all length bytes that are available from being appended, then the | appending is done so that the last bytes appended are from the string | ellipsis. This allows for an indication of the truncation to be left in | the string. When length is -1, all bytes up to the first zero byte are | appended, subject to the limit. When ellipsis is NULL, the default | string ... is used. When ellipsis is non-NULL, it must point to a zero- | byte-terminated string in Tcl's internal UTF encoding. The number of | bytes appended can be less than the lesser of length and limit when ap- | pending fewer bytes is necessary to append only whole multi-byte char- | acters. | Tcl_Format is the C-level interface to the engine of the format com- | mand. The actual command procedure for format is little more than | Tcl_Format(interp, Tcl_GetString(objv[1]), objc-2, objv+2); | The objc Tcl_Obj values in objv are formatted into a string according | to the conversion specification in format argument, following the docu- | mentation for the format command. The resulting formatted string is | converted to a new Tcl_Obj with refcount of zero and returned. If some | error happens during production of the formatted string, NULL is re- | turned, and an error message is recorded in interp, if interp is non- | NULL. | Tcl_AppendFormatToObj is an appending alternative form of Tcl_Format | with functionality equivalent to | Tcl_Obj *newPtr = Tcl_Format(interp, format, objc, objv); | if (newPtr == NULL) return TCL_ERROR; | Tcl_AppendObjToObj(objPtr, newPtr); | return TCL_OK; | but with greater convenience and efficiency when the appending func- | tionality is needed. | Tcl_ObjPrintf serves as a replacement for the common sequence | char buf[SOME_SUITABLE_LENGTH]; | sprintf(buf, format, ...); | Tcl_NewStringObj(buf, -1); | but with greater convenience and no need to determine SOME_SUIT- | ABLE_LENGTH. The formatting is done with the same core formatting en- | gine used by Tcl_Format. This means the set of supported conversion | specifiers is that of the format command and not that of the sprintf | routine where the two sets differ. When a conversion specifier passed | to Tcl_ObjPrintf includes a precision, the value is taken as a number | of bytes, as sprintf does, and not as a number of characters, as format | does. This is done on the assumption that C code is more likely to | know how many bytes it is passing around than the number of encoded | characters those bytes happen to represent. The variable number of ar- | guments passed in should be of the types that would be suitable for | passing to sprintf. Note in this example usage, x is of type long. | long x = 5; | Tcl_Obj *objPtr = Tcl_ObjPrintf("Value is %d", x); | If the value of format contains internal inconsistencies or invalid | specifier formats, the formatted string result produced by Tcl_Ob- | jPrintf will be an error message describing the error. | Tcl_AppendPrintfToObj is an appending alternative form of Tcl_ObjPrintf | with functionality equivalent to | Tcl_AppendObjToObj(objPtr, Tcl_ObjPrintf(format, ...)); | but with greater convenience and efficiency when the appending func- | tionality is needed. The Tcl_SetObjLength procedure changes the length of the string value of its objPtr argument. If the newLength argument is greater than the space allocated for the object's string, then the string space is re- allocated and the old value is copied to the new space; the bytes be- tween the old length of the string and the new length may have arbi- trary values. If the newLength argument is less than the current length of the object's string, with objPtr-_length is reduced without reallocating the string space; the original allocated size for the string is recorded in the object, so that the string length can be en- larged in a subsequent call to Tcl_SetObjLength without reallocating storage. In all cases Tcl_SetObjLength leaves a null character at ob- jPtr-_bytes[newLength]. Tcl_AttemptSetObjLength is identical in function to Tcl_SetObjLength except that if sufficient memory to satisfy the request cannot be allo- cated, it does not cause the Tcl interpreter to panic. Thus, if newLength is greater than the space allocated for the object's string, and there is not enough memory available to satisfy the request, Tcl_AttemptSetObjLength will take no action and return 0 to indicate failure. If there is enough memory to satisfy the request, Tcl_At- temptSetObjLength behaves just like Tcl_SetObjLength and returns 1 to indicate success. The Tcl_ConcatObj function returns a new string object whose value is the space-separated concatenation of the string representations of all of the objects in the objv array. Tcl_ConcatObj eliminates leading and trailing white space as it copies the string representations of the objv array to the result. If an element of the objv array consists of nothing but white space, then that object is ignored entirely. This white-space removal was added to make the output of the concat command cleaner-looking. Tcl_ConcatObj returns a pointer to a newly-created ob- ject whose ref count is zero. SEE ALSO Tcl_NewObj, Tcl_IncrRefCount, Tcl_DecrRefCount, format, sprintf KEYWORDS append, internal representation, object, object type, string object, string type, string representation, concat, concatenate, unicode Tcl 8.1 Tcl_StringObj(3)
NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | SEE ALSO | KEYWORDS
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