trusty (3) Tcl_ListObjGetElements.3tcl.gz
NAME
Tcl_ListObjAppendList, Tcl_ListObjAppendElement, Tcl_NewListObj, Tcl_SetListObj, Tcl_ListObjGetElements,
Tcl_ListObjLength, Tcl_ListObjIndex, Tcl_ListObjReplace - manipulate Tcl objects as lists
SYNOPSIS
#include <tcl.h>
int
Tcl_ListObjAppendList(interp, listPtr, elemListPtr)
int
Tcl_ListObjAppendElement(interp, listPtr, objPtr)
Tcl_Obj *
Tcl_NewListObj(objc, objv)
Tcl_SetListObj(objPtr, objc, objv)
int
Tcl_ListObjGetElements(interp, listPtr, objcPtr, objvPtr)
int
Tcl_ListObjLength(interp, listPtr, intPtr)
int
Tcl_ListObjIndex(interp, listPtr, index, objPtrPtr)
int
Tcl_ListObjReplace(interp, listPtr, first, count, objc, objv)
ARGUMENTS
Tcl_Interp *interp (in) If an error occurs while converting an object to be a list object,
an error message is left in the interpreter's result object unless
interp is NULL.
Tcl_Obj *listPtr (in/out) Points to the list object to be manipulated. If listPtr does not
already point to a list object, an attempt will be made to convert
it to one.
Tcl_Obj *elemListPtr (in/out) For Tcl_ListObjAppendList, this points to a list object containing
elements to be appended onto listPtr. Each element of
*elemListPtr will become a new element of listPtr. If
*elemListPtr is not NULL and does not already point to a list
object, an attempt will be made to convert it to one.
Tcl_Obj *objPtr (in) For Tcl_ListObjAppendElement, points to the Tcl object that will
be appended to listPtr. For Tcl_SetListObj, this points to the
Tcl object that will be converted to a list object containing the
objc elements of the array referenced by objv.
int *objcPtr (in) Points to location where Tcl_ListObjGetElements stores the number
of element objects in listPtr.
Tcl_Obj ***objvPtr (out) A location where Tcl_ListObjGetElements stores a pointer to an
array of pointers to the element objects of listPtr.
int objc (in) The number of Tcl objects that Tcl_NewListObj will insert into a
new list object, and Tcl_ListObjReplace will insert into listPtr.
For Tcl_SetListObj, the number of Tcl objects to insert into
objPtr. │
Tcl_Obj "*CONST objv[]" in │
An array of pointers to objects. Tcl_NewListObj will insert these │
objects into a new list object and Tcl_ListObjReplace will insert │
them into an existing listPtr. Each object will become a separate │
list element.
int *intPtr (out) Points to location where Tcl_ListObjLength stores the length of
the list.
int index (in) Index of the list element that Tcl_ListObjIndex is to return. The
first element has index 0.
Tcl_Obj **objPtrPtr (out) Points to place where Tcl_ListObjIndex is to store a pointer to
the resulting list element object.
int first (in) Index of the starting list element that Tcl_ListObjReplace is to
replace. The list's first element has index 0.
int count (in) The number of elements that Tcl_ListObjReplace is to replace.
_________________________________________________________________
DESCRIPTION
Tcl list objects have an internal representation that supports the efficient indexing and appending. The
procedures described in this man page are used to create, modify, index, and append to Tcl list objects
from C code.
Tcl_ListObjAppendList and Tcl_ListObjAppendElement both add one or more objects to the end of the list
object referenced by listPtr. Tcl_ListObjAppendList appends each element of the list object referenced
by elemListPtr while Tcl_ListObjAppendElement appends the single object referenced by objPtr. Both
procedures will convert the object referenced by listPtr to a list object if necessary. If an error
occurs during conversion, both procedures return TCL_ERROR and leave an error message in the
interpreter's result object if interp is not NULL. Similarly, if elemListPtr does not already refer to a
list object, Tcl_ListObjAppendList will attempt to convert it to one and if an error occurs during
conversion, will return TCL_ERROR and leave an error message in the interpreter's result object if interp
is not NULL. Both procedures invalidate any old string representation of listPtr and, if it was
converted to a list object, free any old internal representation. Similarly, Tcl_ListObjAppendList frees
any old internal representation of elemListPtr if it converts it to a list object. After appending each
element in elemListPtr, Tcl_ListObjAppendList increments the element's reference count since listPtr now
also refers to it. For the same reason, Tcl_ListObjAppendElement increments objPtr's reference count.
If no error occurs, the two procedures return TCL_OK after appending the objects.
Tcl_NewListObj and Tcl_SetListObj create a new object or modify an existing object to hold the objc
elements of the array referenced by objv where each element is a pointer to a Tcl object. If objc is
less than or equal to zero, they return an empty object. The new object's string representation is left
invalid. The two procedures increment the reference counts of the elements in objc since the list object
now refers to them. The new list object returned by Tcl_NewListObj has reference count zero.
Tcl_ListObjGetElements returns a count and a pointer to an array of the elements in a list object. It
returns the count by storing it in the address objcPtr. Similarly, it returns the array pointer by
storing it in the address objvPtr. The memory pointed to is managed by Tcl and should not be freed by
the caller. If listPtr is not already a list object, Tcl_ListObjGetElements will attempt to convert it
to one; if the conversion fails, it returns TCL_ERROR and leaves an error message in the interpreter's
result object if interp is not NULL. Otherwise it returns TCL_OK after storing the count and array
pointer.
Tcl_ListObjLength returns the number of elements in the list object referenced by listPtr. It returns
this count by storing an integer in the address intPtr. If the object is not already a list object,
Tcl_ListObjLength will attempt to convert it to one; if the conversion fails, it returns TCL_ERROR and
leaves an error message in the interpreter's result object if interp is not NULL. Otherwise it returns
TCL_OK after storing the list's length.
The procedure Tcl_ListObjIndex returns a pointer to the object at element index in the list referenced by
listPtr. It returns this object by storing a pointer to it in the address objPtrPtr. If listPtr does
not already refer to a list object, Tcl_ListObjIndex will attempt to convert it to one; if the conversion
fails, it returns TCL_ERROR and leaves an error message in the interpreter's result object if interp is
not NULL. If the index is out of range, that is, index is negative or greater than or equal to the
number of elements in the list, Tcl_ListObjIndex stores a NULL in objPtrPtr and returns TCL_OK.
Otherwise it returns TCL_OK after storing the element's object pointer. The reference count for the list
element is not incremented; the caller must do that if it needs to retain a pointer to the element.
Tcl_ListObjReplace replaces zero or more elements of the list referenced by listPtr with the objc objects
in the array referenced by objv. If listPtr does not point to a list object, Tcl_ListObjReplace will
attempt to convert it to one; if the conversion fails, it returns TCL_ERROR and leaves an error message
in the interpreter's result object if interp is not NULL. Otherwise, it returns TCL_OK after replacing
the objects. If objv is NULL, no new elements are added. If the argument first is zero or negative, it
refers to the first element. If first is greater than or equal to the number of elements in the list,
then no elements are deleted; the new elements are appended to the list. count gives the number of
elements to replace. If count is zero or negative then no elements are deleted; the new elements are
simply inserted before the one designated by first. Tcl_ListObjReplace invalidates listPtr's old string
representation. The reference counts of any elements inserted from objv are incremented since the
resulting list now refers to them. Similarly, the reference counts for any replaced objects are
decremented.
Because Tcl_ListObjReplace combines both element insertion and deletion, it can be used to implement a
number of list operations. For example, the following code inserts the objc objects referenced by the
array of object pointers objv just before the element index of the list referenced by listPtr:
result = Tcl_ListObjReplace(interp, listPtr, index, 0, objc, objv);
Similarly, the following code appends the objc objects referenced by the array objv to the end of the
list listPtr:
result = Tcl_ListObjLength(interp, listPtr, &length);
if (result == TCL_OK) {
result = Tcl_ListObjReplace(interp, listPtr, length, 0, objc, objv);
}
The count list elements starting at first can be deleted by simply calling Tcl_ListObjReplace with a NULL
objvPtr:
result = Tcl_ListObjReplace(interp, listPtr, first, count, 0, NULL);
SEE ALSO
Tcl_NewObj, Tcl_DecrRefCount, Tcl_IncrRefCount, Tcl_GetObjResult
KEYWORDS
append, index, insert, internal representation, length, list, list object, list type, object, object
type, replace, string representation