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// Copyright 2025 Shota FUJI
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0

//! Atomic Reference Counting based on example code on `std.atomic.Value`.
//! https://ziglang.org/documentation/0.14.0/std/#std.atomic.Value

const std = @import("std");

count: std.atomic.Value(usize) = std.atomic.Value(usize).init(0),

const Arc = @This();

/// Increment reference count by one.
pub fn ref(arc: *Arc) void {
    _ = arc.count.fetchAdd(1, .monotonic);
}

/// Decrement reference count by one, returns `true` if no reference is alive.
pub fn unref(arc: *Arc) bool {
    if (arc.count.fetchSub(1, .release) == 1) {
        _ = arc.count.load(.acquire);
        return true;
    } else {
        return false;
    }
}