Tcl Library Procedures Tcl_StringObj(3TCL)
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NAME
Tcl_NewStringObj, Tcl_NewUnicodeObj, Tcl_SetStringObj,
Tcl_SetUnicodeObj, Tcl_GetStringFromObj, Tcl_GetString,
Tcl_GetUnicodeFromObj, Tcl_GetUnicode, Tcl_GetUniChar,
Tcl_GetCharLength, Tcl_GetRange, Tcl_AppendToObj,
Tcl_AppendUnicodeToObj, Tcl_AppendStringsToObj,
Tcl_AppendStringsToObjVA, Tcl_AppendObjToObj,
Tcl_SetObjLength, Tcl_ConcatObj, Tcl_AttemptSetObjLength -
manipulate Tcl objects as stringsSYNOPSIS
#include
Tcl_Obj *
Tcl_NewStringObj(bytes, length)
Tcl_Obj *
Tcl_NewUnicodeObj(unicode, numChars)
voidTcl_SetStringObj(objPtr, bytes, length)
voidTcl_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)
intTcl_GetCharLength(objPtr)
Tcl_Obj *
Tcl_GetRange(objPtr, first, last)
voidTcl_AppendToObj(objPtr, bytes, length)
void Tcl Last change: 8.1 1Tcl Library Procedures Tcl_StringObj(3TCL)
Tcl_AppendUnicodeToObj(objPtr, unicode, numChars)
voidTcl_AppendObjToObj(objPtr, appendObjPtr)
voidTcl_AppendStringsToObj(objPtr, string, string, ... (char *) NULL)
voidTcl_AppendStringsToObjVA(objPtr, argList)
voidTcl_SetObjLength(objPtr, newLength)
intTcl_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-encoded |
bytes used to | set or append | to a string | object. This | byte array | should not |contain embed- |
ded null bytes | unless length | is negative. | (Applications | needing null | bytes should | represent them |as the two- |
byte sequence | \700\600, use |Tcl_ExternalToUtf|
to convert, or |Tcl_NewByteArrayObj|
if the string |is a collec- |
tion of unin- |
terpreted | bytes.) int length (in) The number of Tcl Last change: 8.1 2Tcl Library Procedures Tcl_StringObj(3TCL)
bytes to copy from byteswhen initial-
izing, set-
ting, or appending to a string object. If negative, all bytes up to the first null are used.CONST Tcl_UniChar *unicode (in) Points to the
first byte of an array ofUnicode char-
acters used to set or append to a string object. This byte array maycontain embed-
ded null char-
acters unless numChars is negative. int numChars (in) The number ofUnicode char-
acters to copy from unicodewhen initial-
izing, set-
ting, or appending to a string object. If negative, all characters 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 firstUnicode char-
acter in the Tcl Last change: 8.1 3Tcl Library Procedures Tcl_StringObj(3TCL)
Unicode range to be returned as a new object. int last (in) The index of the lastUnicode char-
acter in the Unicode range to be returned 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 inTcl_AppendObjToObj.
int *lengthPtr (out) If non-NULL,
the location whereTcl_GetStringFromObj
will store the the length of an object's stringrepresenta-
tion.CONST char *string (in) Null-
terminated string value to append to objPtr.va_list argList (in) An argument
list which must have been initialised usingTCL_VARARGS_START,
and clearedusing va_end.
int newLength (in) New length for the string value of Tcl Last change: 8.1 4Tcl Library Procedures Tcl_StringObj(3TCL)
objPtr, not including the final null character. int objc (in) The number of elements to concatenate.Tcl_Obj *objv[] (in) The array of
objects to concatenate._________________________________________________________________
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 manipulations more efficient.In particular, they make a series of append operations effi-
cient by allocating extra storage space for the string so that it doesn't have to be copied for each append. Also, indexing and length computations are optimized because the Unicode string representation is calculated and cached asneeded. When using the Tcl_Append* family of functions
where the interpreter's result is the object being appendedto, 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 givenby 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 unicodeand 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 ofthe specified string. Tcl_SetStringObj and
Tcl_SetUnicodeObj free any old string representation as well
as any old internal representation of the object.Tcl_GetStringFromObj and Tcl_GetString return an object's
string representation. This is given by the returned bytepointer 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 Tcl Last change: 8.1 5Tcl Library Procedures Tcl_StringObj(3TCL)
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 isacceptable, one should take care to respect the copy-on-
write semantics required by Tcl_Obj's, with appropriate
calls to Tcl_IsShared and Tcl_DuplicateObj prior to any in-
place modification of the string representation. The pro-
cedure Tcl_GetString is used in the common case where the
caller does not need the length of the string representa-
tion.Tcl_GetUnicodeFromObj and Tcl_GetUnicode return an object's
value as a Unicode string. This is given by the returnedpointer and (for Tcl_GetUnicodeFromObj) length, which is
stored in lengthPtr if it is non-NULL. The storage refer-
enced by the returned byte pointer is owned by the objectmanager and should not be modified by the caller. The pro-
cedure 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 representation. 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 convert bytes is to the Unicode format. If the conversion is successful, then the convertedform of bytes is appended to the object's Unicode represen-
tation. Otherwise, the object's Unicode representation is invalidated 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 invalid Unicode representation, then unicode is converted to the UTF format and appended to the object's string representation. Appends are optimized to Tcl Last change: 8.1 6Tcl Library Procedures Tcl_StringObj(3TCL)
handle repeated appends relatively efficiently (it overallo-
cates the string or Unicode space to avoid repeated reallo-
cations 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 appended 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 eachvalue 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 vari-
able number of arguments it takes an argument list.The Tcl_SetObjLength procedure changes the length of the
string value of its objPtr argument. If the newLength argu-
ment is greater than the space allocated for the object's string, then the string space is reallocated and the old value is copied to the new space; the bytes between the old length of the string and the new length may have arbitrary values. If the newLength argument is less than the currentlength 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 enlarged in a subsequent callto Tcl_SetObjLength without reallocating storage. In all
cases Tcl_SetObjLength leaves a null character at objPtr-
>bytes[newLength].Tcl_AttemptSetObjLength is identical in function to
Tcl_SetObjLength except that if sufficient memory to satisfy
the request cannot be allocated, 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 therequest, Tcl_AttemptSetObjLength 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 Tcl Last change: 8.1 7Tcl Library Procedures Tcl_StringObj(3TCL)
nothing but white space, then that object is ignoredentirely. 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 object whose ref count
is zero.SEE ALSO
Tcl_NewObj, Tcl_IncrRefCount, Tcl_DecrRefCount
KEYWORDS append, internal representation, object, object type, stringobject, string type, string representation, concat, con-
catenate, unicodeATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:_______________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE|
|____________________|__________________|_
| Availability | runtime/tcl-8 |
|____________________|__________________|_
| Interface Stability| Uncommitted ||____________________|_________________|
NOTES Source for Tcl is available on http://opensolaris.org. Tcl Last change: 8.1 8