path: root/doc/StringObj.3

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.so man.macros
.TH Tcl_StringObj 3 8.0 Tcl "Tcl Library Procedures"
.BS
.SH NAME
Tcl_NewStringObj, Tcl_SetStringObj, Tcl_GetStringFromObj, Tcl_AppendToObj, Tcl_AppendStringsToObj, Tcl_AppendStringsToObjVA, Tcl_SetObjLength, TclConcatObj \- manipulate Tcl objects as strings
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
Tcl_Obj *
\fBTcl_NewStringObj\fR(\fIbytes, length\fR)
.sp
\fBTcl_SetStringObj\fR(\fIobjPtr, bytes, length\fR)
.sp
char *
\fBTcl_GetStringFromObj\fR(\fIobjPtr, lengthPtr\fR)
.sp
\fBTcl_AppendToObj\fR(\fIobjPtr, bytes, length\fR)
.sp
\fBTcl_AppendStringsToObj\fR(\fIobjPtr, string, string, ... \fB(char *) NULL\fR)
.sp
\fBTcl_AppendStringsToObjVA\fR(\fIobjPtr, argList\fR)
.sp
\fBTcl_SetObjLength\fR(\fIobjPtr, newLength\fR)
.sp
Tcl_Obj *
\fBTcl_ConcatObj\fR(\fIobjc, objv\fR)
.SH ARGUMENTS
.AS Tcl_Interp *lengthPtr out
.AP char *bytes in
Points to the first byte of an array of bytes
used to set or append to a string object.
This byte array may contain embedded null bytes
unless \fIlength\fR is negative.
.AP int length in
The number of bytes to copy from \fIbytes\fR when
initializing, setting, or appending to a string object.
If negative, all bytes up to the first null are used.
.AP Tcl_Obj *objPtr in/out
Points to an object to manipulate.
.AP int *lengthPtr out
If non-NULL, the location where \fBTcl_GetStringFromObj\fR will store
the the length of an object's string representation.
.AP char *string in
Null-terminated string value to append to \fIobjPtr\fR.
.AP va_list argList in
An argument list which must have been initialised using
\fBTCL_VARARGS_START\fR, and cleared using \fBva_end\fR.
.AP int newLength in
New length for the string value of \fIobjPtr\fR, not including the
final NULL character.
.AP int objc in
The number of elements to concatenate.
.AP Tcl_Obj *objv[] in
The array of objects to concatenate.
.BE

.SH DESCRIPTION
.PP
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 efficient by allocating extra storage space for the
string so that it doesn't have to be copied for each append.
.PP
\fBTcl_NewStringObj\fR and \fBTcl_SetStringObj\fR create a new object
or modify an existing object to hold a copy of
the string given by \fIbytes\fR and \fIlength\fR.
\fBTcl_NewStringObj\fR returns a pointer to a newly created object
with reference count zero.
Both procedures set the object to hold a copy of the specified string.
\fBTcl_SetStringObj\fR frees any old string representation
as well as any old internal representation of the object.
.PP
\fBTcl_GetStringFromObj\fR returns an object's string representation.
This is given by the returned byte pointer
and length, which is stored in \fIlengthPtr\fR if it is non-NULL.
If the object's 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 and should not be modified by the caller.
.PP
\fBTcl_AppendToObj\fR appends the data given by \fIbytes\fR and
\fIlength\fR to the object specified by \fIobjPtr\fR.  It does this
in a way that handles repeated calls relatively efficiently (it
overallocates the string space to avoid repeated reallocations
and copies of object's string value).
.PP
\fBTcl_AppendStringsToObj\fR is similar to \fBTcl_AppendToObj\fR
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
\fIstring\fR arguments may be provided, but the last argument
must be a NULL pointer to indicate the end of the list.
.PP
\fBTcl_AppendStringsToObjVA\fR is the same as \fBTcl_AppendStringsToObj\fR
except that instead of taking a variable number of arguments it takes an
argument list.
.PP
The \fBTcl_SetObjLength\fR procedure changes the length of the
string value of its \fIobjPtr\fR argument.  If the \fInewLength\fR
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 \fInewLength\fR argument is less than the current length
of the object's string, with \fIobjPtr->length\fR 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 \fBTcl_SetObjLength\fR without
reallocating storage.  In all cases \fBTcl_SetObjLength\fR leaves
a null character at \fIobjPtr->bytes[newLength]\fR.
.PP
The \fBTcl_ConcatObj\fR function returns a new string object whose
value is the space-separated concatenation of the string
representations of all of the objects in the \fIobjv\fR
array. \fBTcl_ConcatObj\fR eliminates leading and trailing white space
as it copies the string representations of the \fIobjv\fR array to the
result. If an element of the \fIobjv\fR 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 \fBconcat\fR command
cleaner-looking. \fBTcl_ConcatObj\fR returns a pointer to a
newly-created object whose ref count is zero.

.SH "SEE ALSO"
Tcl_NewObj, Tcl_IncrRefCount, Tcl_DecrRefCount

.SH KEYWORDS
append, internal representation, object, object type, string object,
string type, string representation, concat, concatenate