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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_SetObjLength, TclConcatObj \- manipulate Tcl objects as strings

.SH SYNOPSIS

.nf

\fB#include \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_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 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

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