Index of Section 3 Manual Pages
| Interix / SUA | Tcl_GetUnicode.3 | Interix / SUA |
Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
_________________________________________________________________
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_SetOb-
jLength, Tcl_ConcatObj, Tcl_AttemptSetObjLength - manipu-
late Tcl objects as strings
SYNOPSIS
#include
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_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-encoded|
bytes used |
to set or |
append to a |
string |
object. |
This byte |
array should |
not contain |
embedded |
null bytes |
unless |
length is |
negative. |
(Applica- |
tions need- |
ing null |
bytes should |
represent |
them as the |
two-byte |
sequence |
\700\600, |
use |
Tcl_ExternalToUtf|
to convert, |
or Tcl_New- |
ByteArrayObj |
if the |
string is a |
collection |
of uninter- |
preted |
bytes.)
int length (in) The number
of bytes to
copy from
bytes when
initializ-
ing, 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 of
Unicode
characters
used to set
or append to
a string
object.
This byte
array may
contain
embedded
null charac-
ters unless
numChars is
negative.
int numChars (in) The number
of Unicode
characters
to copy from
unicode when
initializ-
ing, set-
ting, or
appending to
a string
object. If
negative,
all charac-
ters up to
the first
null charac-
ter 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
returned as
a new
object.
int last (in) The index of
the last
Unicode
character 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 in
Tcl_Appen-
dObjToObj.
int *lengthPtr (out) If non-NULL,
the location
where
Tcl_Get-
StringFro-
mObj will
store the
the length
of an
object's
string rep-
resentation.
CONST char *string (in) Null-termi-
nated string
value to
append to
objPtr.
va_list argList (in) An argument
list which
must have
been ini-
tialised
using
TCL_VARARGS_START,
and cleared
using
va_end.
int newLength (in) New length
for the
string value
of objPtr,
not includ-
ing the
final null
character.
int objc (in) The number
of elements
to concate-
nate.
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 effi-
cient. In particular, they make a series of append opera-
tions efficient 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 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 uninten-
tionally 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 exist-
ing object to hold a copy of the Unicode string given by
unicode and numChars. Tcl_NewStringObj and Tcl_NewUni-
codeObj 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 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 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 man-
ager. 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_Get-
StringFromObj 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 appropriate 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 stor-
age 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 com-
mon 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 representa-
tion, then an attempt is made to convert bytes is to the
Unicode format. If the conversion is successful, then the
converted form of bytes is appended to the object's Uni-
code representation. Otherwise, the object's Unicode rep-
resentation is invalidated and converted to the UTF for-
mat, and bytes is appended to the object's new string rep-
resentation.
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
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 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 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_Append-
StringsToObj except that instead of taking a variable num-
ber 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
argument 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 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
enlarged in a subsequent call to 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 sat-
isfy 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 the request, Tcl_AttemptSetObjLength behaves
just like Tcl_SetObjLength and returns 1 to indicate suc-
cess.
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 con-
sists 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 object
whose ref count is zero.
SEE ALSO
Tcl_NewObj, Tcl_IncrRefCount, Tcl_DecrRefCount
KEYWORDS
append, internal representation, object, object type,
string object, string type, string representation, concat,
concatenate, unicode
Tcl 8.1 Tcl_StringObj(3)