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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 values 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)

       int
       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, ...)

       void
       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
						     value.  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    \300\200,   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
						     value.  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	value.
						     This byte array may  con-
						     tain  embedded null char-
						     acters unless numChars is
						     negative.

       int numChars (in)			     The   number  of  Unicode
						     characters	to  copy  from
						     unicode  when  initializ-
						     ing, setting, or  append-
						     ing  to  a	 string	value.
						     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 value.

       int last	(in)				     The  index	 of  the  last
						     Unicode  character	in the
						     Unicode range to  be  re-
						     turned as a new value.

       Tcl_Obj *objPtr (in/out)			     Points  to	a value	to ma-
						     nipulate.

       Tcl_Obj *appendObjPtr (in)		     The value	to  append  to
						     objPtr  in	Tcl_AppendObj-
						     ToObj.

       size_t |	(int)				     The    location	 where
						     Tcl_GetStringFromObj will
						     store  the	 length	 of  a
						     value's  string represen-
						     tation.   May   be	  (int
						     *)NULL when not used.

       const char *string (in)			     Null-terminated	string
						     value to  append  to  ob-
						     jPtr.

       va_list argList (in)			     An	 argument  list	 which
						     must have	been  initial-
						     ized  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  values  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	values	to  be
       manipulated  as string values.  They use	the internal representation of
       the value 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  value	 being
       appended	 to,  it  is important to call Tcl_ResetResult first to	ensure
       you are not unintentionally appending to	existing data  in  the	result
       value.

       Tcl_NewStringObj	 and  Tcl_SetStringObj create a	new value or modify an
       existing	value to hold a	copy of	the string given by bytes and  length.
       Tcl_NewUnicodeObj and Tcl_SetUnicodeObj create a	new value or modify an
       existing	value to hold a	copy of	the Unicode string  given  by  unicode
       and  numChars.  Tcl_NewStringObj	and Tcl_NewUnicodeObj return a pointer
       to a newly created value	with reference count zero.   All  four	proce-
       dures  set  the value to	hold a copy of the specified string.  Tcl_Set-
       StringObj and Tcl_SetUnicodeObj free any	old string  representation  as
       well as any old internal	representation of the value.

       Tcl_GetStringFromObj  and  Tcl_GetString	return a value'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 value's UTF string  representation  is	 invalid  (its
       byte  pointer  is  NULL), the string representation is regenerated from
       the value's internal representation.  The storage referenced by the re-
       turned  byte  pointer is	owned by the value 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 a value'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	value  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 value's Unicode
       representation. If the index is out of range or	it  references	a  low
       surrogate preceded by a high surrogate, it returns -1;

       Tcl_GetRange  returns a newly created value comprised of	the characters
       between first and last (inclusive) in the value's  Unicode  representa-
       tion.   If  the	value's	Unicode	representation is invalid, the Unicode
       representation is regenerated from the value's string representation.

       Tcl_GetCharLength returns the  number  of  characters  (as  opposed  to
       bytes) in the string value.

       Tcl_AppendToObj	appends	 the  data  given  by  bytes and length	to the
       string representation of	the value specified by objPtr.	If  the	 value
       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 value's Unicode
       representation.	Otherwise, the value's Unicode representation  is  in-
       validated and converted to the UTF format, and bytes is appended	to the
       value's new string representation.

       Tcl_AppendUnicodeToObj appends the Unicode string given by unicode  and
       numChars	to the value specified by objPtr.  If the value	has an invalid
       Unicode representation, then unicode is converted to the	UTF format and
       appended	 to  the value's string	representation.	 Appends are optimized
       to handle repeated appends relatively  efficiently  (it	over-allocates
       the  string or Unicode space to avoid repeated reallocations and	copies
       of value'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.  Interfaces using argument lists have	been found to be  non-
       portable	 in  practice. This function is	deprecated and will be removed
       in Tcl 9.0.

       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);
	      Tcl_DecrRefCount(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 int.

	      int 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.  It is  impossi-
       ble  however  to	 provide runtime protection against mismatches between
       the format and any subsequent arguments.	 Compile-time  protection  may
       be provided by some compilers.

       Tcl_AppendPrintfToObj is	an appending alternative form of Tcl_ObjPrintf
       with functionality equivalent to

	      Tcl_Obj *newPtr =	Tcl_ObjPrintf(format, ...);
	      Tcl_AppendObjToObj(objPtr, newPtr);
	      Tcl_DecrRefCount(newPtr);

       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 value'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	value's	string,	with objPtr-_length is reduced without
       reallocating the	string space; the  original  allocated	size  for  the
       string  is  recorded in the value, 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 value'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 value  whose  value  is
       the  space-separated concatenation of the string	representations	of all
       of the values 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 value 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
       value whose ref count is	zero.

REFERENCE COUNT	MANAGEMENT
       Tcl_NewStringObj,  Tcl_NewUnicodeObj,  Tcl_Format,  Tcl_ObjPrintf,  and
       Tcl_ConcatObj   always	return	a  zero-reference  object,  much  like
       Tcl_NewObj.

       Tcl_GetStringFromObj, Tcl_GetString, Tcl_GetUnicodeFromObj, Tcl_GetUni-
       code, Tcl_GetUniChar, Tcl_GetCharLength,	and Tcl_GetRange all only work
       with an existing	value; they do not manipulate its reference  count  in
       any way.

       Tcl_SetStringObj,  Tcl_SetUnicodeObj,  Tcl_AppendToObj,	Tcl_AppendUni-
       codeToObj,  Tcl_AppendObjToObj,	 Tcl_AppendStringsToObj,   Tcl_Append-
       StringsToObjVA,	Tcl_AppendLimitedToObj,	Tcl_AppendFormatToObj, Tcl_Ap-
       pendPrintfToObj,	Tcl_SetObjLength, and Tcl_AttemptSetObjLength and  re-
       quire  their  objPtr to be an unshared value (i.e, a reference count no
       more than 1) as they will modify	it.

       Additional arguments to the above functions (the	appendObjPtr  argument
       to  Tcl_AppendObjToObj,	values	in  the	 objv  argument	to Tcl_Format,
       Tcl_AppendFormatToObj, and Tcl_ConcatObj) can have any reference	count,
       but reference counts of zero are	not recommended.

       Tcl_Format and Tcl_AppendFormatToObj may	modify the interpreter result,
       which involves changing the reference count of a	value.

SEE ALSO
       Tcl_NewObj(3),  Tcl_IncrRefCount(3),  Tcl_DecrRefCount(3),   format(n),
       sprintf(3)

KEYWORDS
       append,	internal  representation,  value,  value  type,	 string	value,
       string type, string representation, concat, concatenate,	unicode

Tcl				      8.1		      Tcl_StringObj(3)

NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | REFERENCE COUNT MANAGEMENT | SEE ALSO | KEYWORDS

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