Tcl_AppendStringsToObjVA(3tcl)
Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
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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_AppendObjToObj,
Tcl_AppendStringsToObj, Tcl_AppendStringsToObjVA,
Tcl_AppendLimitedToObj, Tcl_Format, Tcl_AppendFormatToObj,
Tcl_ObjPrintf, Tcl_AppendPrintfToObj, Tcl_SetObjLength,
Tcl_AttemptSetObjLength, Tcl_ConcatObj - manipulate 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)
Tcl Last change: 8.1 1
Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
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-encoded
bytes used to
set or append
to a string
object. This
byte array may
contain embed-
ded null char-
acters unless
numChars is
negative.
(Applications
Tcl Last change: 8.1 2
Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
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
bytes to copy
from bytes
when 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 of
Unicode char-
acters used to
set or append
to a string
object. This
byte array may
contain embed-
ded null char-
acters unless
numChars is
negative.
int numChars (in) The number of
Unicode char-
acters to copy
from unicode
when initial-
izing, set-
ting, or
appending to a
string object.
Tcl Last change: 8.1 3
Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
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 first
Unicode char-
acter in the
Unicode range
to be returned
as a new
object.
int last (in) The index of
the last
Unicode 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 in
Tcl_AppendObjToObj.
int *lengthPtr (out) If non-NULL,
the location
where
Tcl_GetStringFromObj
will store the
length of an
object's
string
representa-
tion.
const char *string (in) Null-
terminated
Tcl Last change: 8.1 4
Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
string value
to append to
objPtr.
va_list argList (in) An argument
list which
must have been
initialised
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 trunca-
tion. If NULL
is passed then
the suffix
"..." is used.
const char *format (in) Format control
string includ-
ing % conver-
sion specif-
iers.
int objc (in) The number of
elements to
format or con-
catenate.
Tcl_Obj *objv[] (in) The array of
objects to
format or con-
catenate.
int newLength (in) New length for
the string
value of
objPtr, not
including the
final null
character.
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Tcl Last change: 8.1 5
Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
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 does not 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 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 unicode
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 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 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 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 Last change: 8.1 6
Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
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 refer-
enced by the returned byte pointer is owned by the object
manager 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 converted
form 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
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 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 Last change: 8.1 7
Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
Tcl_AppendStringsToObjVA is the same as
Tcl_AppendStringsToObj except that instead of taking a vari-
able number of arguments it takes an argument list.
Tcl_AppendLimitedToObj is similar to Tcl_AppendToObj except |
that it imposes 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 constructed should not be |
allowed to grow without bound. A common usage is when con- |
structing 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 prevents 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 append- |
ing fewer bytes is necessary to append only whole multi-byte |
characters. |
Tcl_Format is the C-level interface to the engine of the |
format command. 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 argu- |
ment, following the documentation 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 returned, |
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 append- |
ing functionality is needed. |
Tcl_ObjPrintf serves as a replacement for the common |
sequence |
char buf[SOME_SUITABLE_LENGTH]; |
sprintf(buf, format, ...); |
Tcl_NewStringObj(buf, -1); |
Tcl Last change: 8.1 8
Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
but with greater convenience and no need to determine |
SOME_SUITABLE_LENGTH. The formatting is done with the same |
core formatting engine 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 arguments |
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 pro- |
duced by Tcl_ObjPrintf 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 append- |
ing functionality is needed.
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 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 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 the
request, Tcl_AttemptSetObjLength behaves just like
Tcl Last change: 8.1 9
Tcl_StringObj(3) Tcl Library Procedures Tcl_StringObj(3)
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 object 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, con-
catenate, unicode
Tcl Last change: 8.1 10
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