Tcl_StringObj(3) Tcl (8.0) 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
negative.
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
location where
Tcl_GetStringFromObj
will store the the
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Tcl_StringObj(3) Tcl (8.0) Tcl_StringObj(3)
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 character.
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 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.
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 representation of
the object.
Tcl_GetStringFromObj returns an object's string
representation. 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
reallocations and copies of object's string value).
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Tcl_StringObj(3) Tcl (8.0) Tcl_StringObj(3)
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 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
KEYWORDS
append, internal representation, object, object type, string
object, string type, string representation, concat,
concatenate
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