# This file is part of the Fuzion language implementation.
#
# The Fuzion language implementation is free software: you can redistribute it
# and/or modify it under the terms of the GNU General Public License as published
# by the Free Software Foundation, version 3 of the License.
#
# The Fuzion language implementation is distributed in the hope that it will be
# useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
# License for more details.
#
# You should have received a copy of the GNU General Public License along with The
# Fuzion language implementation. If not, see <https://www.gnu.org/licenses/>.
# -----------------------------------------------------------------------
#
# Tokiwa Software GmbH, Germany
#
# Source code of Fuzion feature stack
#
# -----------------------------------------------------------------------
# lock-free stack using compare_and_set
# invented by R. Kent Treiber
#
public stack(T type) : container.Stack T is
Node(data T, next option Node) ref is
top := concur.atomic (option Node) nil
# push an element to the stack
#
public redef push (e T) unit =>
_ :=
for o := top.read
n := Node e o
while !top.compare_and_set o n
# pop an element from the stack
#
public redef pop option T =>
next (x option Node) =>
x.bind Node n->n.next
for o := top.read
n := next o
while !o.is_nil && !top.compare_and_set o n
else
o.bind T node->node.data
# peek at the top element from the stack
#
public redef peek option T =>
top.read.bind T node->node.data
