Tcl_StringObj(3)
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NAME
Tcl_NewStringObj, Tcl_SetStringObj, Tcl_GetStringFromObj,
Tcl_AppendToObj, Tcl_AppendStringsToObj, Tcl_SetObjLength,
TclConcatObj - manipulate Tcl objects as strings
SYNOPSIS
#include <<tcl.h>>
Tcl_Obj *
Tcl_NewStringObj(bytes, length)
Tcl_SetStringObj(objPtr, bytes, length)
char *
Tcl_GetStringFromObj(objPtr, lengthPtr)
Tcl_AppendToObj(objPtr, bytes, length)
Tcl_AppendStringsToObj(objPtr, string, string, ... (char *) NULL)
Tcl_SetObjLength(objPtr, newLength)
Tcl_Obj *
Tcl_ConcatObj(objc, objv)
ARGUMENTS
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 length is nega-
tive.
int length (in) The number of bytes to
copy from bytes when
initializing, setting,
or appending to a
string object. If
negative, all bytes up
to the first null are
used.
Tcl_Obj *objPtr (in/out) Points to an object to
manipulate.
int *lengthPtr (out) If non-NULL, the loca-
tion where Tcl_Get-
StringFromObj will
store the the length
of an object's string
representation.
char *string (in) Null-terminated string
value to append to
objPtr.
int newLength (in) New length for the
string value of
objPtr, not including
the final NULL charac-
ter.
int objc (in) The number of elements
to concatenate.
Tcl_Obj *objv[] (in) The array of objects
to concatenate.
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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.
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_NewStringObj 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. Tcl_SetStringObj frees any old
string representation as well as any old internal repre-
sentation of the object.
Tcl_GetStringFromObj returns an object's string represen-
tation. This is given by the returned byte pointer and
length, which is stored in lengthPtr 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.
Tcl_AppendToObj appends the data given by bytes and length
to the object specified by objPtr. It does this in a way
that handles repeated calls relatively efficiently (it
overallocates the string space to avoid repeated realloca-
tions and copies of object's string value).
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.
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].
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