Discard changes to Sources/JavaKitVM/LockedState.swift

Author: ktoso

Sources/JavaKitVM/LockedState.swift

@@ -0,0 +1,160 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+#if canImport(os)
+internal import os
+#if FOUNDATION_FRAMEWORK && canImport(C.os.lock)
+internal import C.os.lock
+#endif
+#elseif canImport(Bionic)
+import Bionic
+#elseif canImport(Glibc)
+import Glibc
+#elseif canImport(Musl)
+import Musl
+#elseif canImport(WinSDK)
+import WinSDK
+#endif
+
+package struct LockedState<State> {
+
+    // Internal implementation for a cheap lock to aid sharing code across platforms
+    private struct _Lock {
+#if canImport(os)
+        typealias Primitive = os_unfair_lock
+#elseif canImport(Bionic) || canImport(Glibc) || canImport(Musl)
+        typealias Primitive = pthread_mutex_t
+#elseif canImport(WinSDK)
+        typealias Primitive = SRWLOCK
+#elseif os(WASI)
+        // WASI is single-threaded, so we don't need a lock.
+        typealias Primitive = Void
+#endif
+
+        typealias PlatformLock = UnsafeMutablePointer<Primitive>
+        var _platformLock: PlatformLock
+
+        fileprivate static func initialize(_ platformLock: PlatformLock) {
+#if canImport(os)
+            platformLock.initialize(to: os_unfair_lock())
+#elseif canImport(Bionic) || canImport(Glibc)
+            pthread_mutex_init(platformLock, nil)
+#elseif canImport(WinSDK)
+            InitializeSRWLock(platformLock)
+#elseif os(WASI)
+            // no-op
+#endif
+        }
+
+        fileprivate static func deinitialize(_ platformLock: PlatformLock) {
+#if canImport(Bionic) || canImport(Glibc)
+            pthread_mutex_destroy(platformLock)
+#endif
+            platformLock.deinitialize(count: 1)
+        }
+
+        static fileprivate func lock(_ platformLock: PlatformLock) {
+#if canImport(os)
+            os_unfair_lock_lock(platformLock)
+#elseif canImport(Bionic) || canImport(Glibc)
+            pthread_mutex_lock(platformLock)
+#elseif canImport(WinSDK)
+            AcquireSRWLockExclusive(platformLock)
+#elseif os(WASI)
+            // no-op
+#endif
+        }
+
+        static fileprivate func unlock(_ platformLock: PlatformLock) {
+#if canImport(os)
+            os_unfair_lock_unlock(platformLock)
+#elseif canImport(Bionic) || canImport(Glibc)
+            pthread_mutex_unlock(platformLock)
+#elseif canImport(WinSDK)
+            ReleaseSRWLockExclusive(platformLock)
+#elseif os(WASI)
+            // no-op
+#endif
+        }
+    }
+
+    private class _Buffer: ManagedBuffer<State, _Lock.Primitive> {
+        deinit {
+            withUnsafeMutablePointerToElements {
+                _Lock.deinitialize($0)
+            }
+        }
+    }
+
+    private let _buffer: ManagedBuffer<State, _Lock.Primitive>
+
+    package init(initialState: State) {
+        _buffer = _Buffer.create(minimumCapacity: 1, makingHeaderWith: { buf in
+            buf.withUnsafeMutablePointerToElements {
+                _Lock.initialize($0)
+            }
+            return initialState
+        })
+    }
+
+    package func withLock<T>(_ body: @Sendable (inout State) throws -> T) rethrows -> T {
+        try withLockUnchecked(body)
+    }
+
+    package func withLockUnchecked<T>(_ body: (inout State) throws -> T) rethrows -> T {
+        try _buffer.withUnsafeMutablePointers { state, lock in
+            _Lock.lock(lock)
+            defer { _Lock.unlock(lock) }
+            return try body(&state.pointee)
+        }
+    }
+
+    // Ensures the managed state outlives the locked scope.
+    package func withLockExtendingLifetimeOfState<T>(_ body: @Sendable (inout State) throws -> T) rethrows -> T {
+        try _buffer.withUnsafeMutablePointers { state, lock in
+            _Lock.lock(lock)
+            return try withExtendedLifetime(state.pointee) {
+                defer { _Lock.unlock(lock) }
+                return try body(&state.pointee)
+            }
+        }
+    }
+}
+
+extension LockedState where State == Void {
+    package init() {
+        self.init(initialState: ())
+    }
+
+    package func withLock<R: Sendable>(_ body: @Sendable () throws -> R) rethrows -> R {
+        return try withLock { _ in
+            try body()
+        }
+    }
+
+    package func lock() {
+        _buffer.withUnsafeMutablePointerToElements { lock in
+            _Lock.lock(lock)
+        }
+    }
+
+    package func unlock() {
+        _buffer.withUnsafeMutablePointerToElements { lock in
+            _Lock.unlock(lock)
+        }
+    }
+}
+
+extension LockedState: @unchecked Sendable where State: Sendable {}
+