Merge pull request #7154 from daurnimator/std.atomic

std.atomic.{Int,Bool}

CMakeLists.txt

@@ -318,6 +318,7 @@ set(ZIG_STAGE2_SOURCES
     "${CMAKE_SOURCE_DIR}/lib/std/array_list.zig"
     "${CMAKE_SOURCE_DIR}/lib/std/ascii.zig"
     "${CMAKE_SOURCE_DIR}/lib/std/atomic.zig"
+    "${CMAKE_SOURCE_DIR}/lib/std/atomic/bool.zig"
     "${CMAKE_SOURCE_DIR}/lib/std/atomic/int.zig"
     "${CMAKE_SOURCE_DIR}/lib/std/atomic/queue.zig"
     "${CMAKE_SOURCE_DIR}/lib/std/atomic/stack.zig"

lib/std/atomic.zig

@@ -5,10 +5,12 @@
 // and substantial portions of the software.
 pub const Stack = @import("atomic/stack.zig").Stack;
 pub const Queue = @import("atomic/queue.zig").Queue;
+pub const Bool = @import("atomic/bool.zig").Bool;
 pub const Int = @import("atomic/int.zig").Int;
 
 test "std.atomic" {
     _ = @import("atomic/stack.zig");
     _ = @import("atomic/queue.zig");
+    _ = @import("atomic/bool.zig");
     _ = @import("atomic/int.zig");
 }

lib/std/atomic/bool.zig

@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+
+const std = @import("std");
+const builtin = std.builtin;
+const testing = std.testing;
+
+/// Thread-safe, lock-free boolean
+pub const Bool = extern struct {
+    unprotected_value: bool,
+
+    pub const Self = @This();
+
+    pub fn init(init_val: bool) Self {
+        return Self{ .unprotected_value = init_val };
+    }
+
+    // xchg is only valid rmw operation for a bool
+    /// Atomically modifies memory and then returns the previous value.
+    pub fn xchg(self: *Self, operand: bool, comptime ordering: std.builtin.AtomicOrder) bool {
+        return @atomicRmw(bool, &self.unprotected_value, .Xchg, operand, ordering);
+    }
+
+    pub fn load(self: *Self, comptime ordering: std.builtin.AtomicOrder) bool {
+        return @atomicLoad(bool, &self.unprotected_value, ordering);
+    }
+
+    pub fn store(self: *Self, value: bool, comptime ordering: std.builtin.AtomicOrder) void {
+        @atomicStore(bool, &self.unprotected_value, value, ordering);
+    }
+};
+
+test "std.atomic.Bool" {
+    var a = Bool.init(false);
+    testing.expectEqual(false, a.xchg(false, .SeqCst));
+    testing.expectEqual(false, a.load(.SeqCst));
+    a.store(true, .SeqCst);
+    testing.expectEqual(true, a.xchg(false, .SeqCst));
+    testing.expectEqual(false, a.load(.SeqCst));
+}

lib/std/atomic/int.zig

@@ -4,11 +4,13 @@
 // The MIT license requires this copyright notice to be included in all copies
 // and substantial portions of the software.
 
-const builtin = @import("std").builtin;
+const std = @import("std");
+const builtin = std.builtin;
+const testing = std.testing;
 
 /// Thread-safe, lock-free integer
 pub fn Int(comptime T: type) type {
-    return struct {
+    return extern struct {
         unprotected_value: T,
 
         pub const Self = @This();
@@ -19,7 +21,7 @@ pub fn Int(comptime T: type) type {
 
         /// Read, Modify, Write
         pub fn rmw(self: *Self, comptime op: builtin.AtomicRmwOp, operand: T, comptime ordering: builtin.AtomicOrder) T {
-            return @atomicRmw(T, &self.unprotected_value, operand, ordering);
+            return @atomicRmw(T, &self.unprotected_value, op, operand, ordering);
         }
 
         pub fn load(self: *Self, comptime ordering: builtin.AtomicOrder) T {
@@ -30,11 +32,13 @@ pub fn Int(comptime T: type) type {
             @atomicStore(T, &self.unprotected_value, value, ordering);
         }
 
+        /// Twos complement wraparound increment
         /// Returns previous value
         pub fn incr(self: *Self) T {
             return self.rmw(.Add, 1, .SeqCst);
         }
 
+        /// Twos complement wraparound decrement
         /// Returns previous value
         pub fn decr(self: *Self) T {
             return self.rmw(.Sub, 1, .SeqCst);
@@ -52,8 +56,22 @@ pub fn Int(comptime T: type) type {
             return self.rmw(.Xchg, new_value, .SeqCst);
         }
 
+        /// Twos complement wraparound add
+        /// Returns previous value
         pub fn fetchAdd(self: *Self, op: T) T {
             return self.rmw(.Add, op, .SeqCst);
         }
     };
 }
+
+test "std.atomic.Int" {
+    var a = Int(u8).init(0);
+    testing.expectEqual(@as(u8, 0), a.incr());
+    testing.expectEqual(@as(u8, 1), a.load(.SeqCst));
+    a.store(42, .SeqCst);
+    testing.expectEqual(@as(u8, 42), a.decr());
+    testing.expectEqual(@as(u8, 41), a.xchg(100));
+    testing.expectEqual(@as(u8, 100), a.fetchAdd(5));
+    testing.expectEqual(@as(u8, 105), a.get());
+    a.set(200);
+}