Add poll_oneoff for POSIX hosts to WASI.swift

Package.swift

@@ -13,7 +13,7 @@ let DarwinPlatforms: [Platform]
 
 let package = Package(
     name: "WasmKit",
-    platforms: [.macOS(.v10_13), .iOS(.v12)],
+    platforms: [.macOS(.v13), .iOS(.v16)],
     products: [
         .executable(name: "wasmkit-cli", targets: ["CLI"]),
         .library(name: "WasmKit", targets: ["WasmKit"]),

Sources/WASI/CMakeLists.txt

@@ -9,6 +9,7 @@ add_wasmkit_library(WASI
   FileSystem.swift
   GuestMemorySupport.swift
   Clock.swift
+  Poll.swift
   RandomBufferGenerator.swift
   WASI.swift
 )

Sources/WASI/Poll.swift

@@ -0,0 +1,83 @@
+import SystemPackage
+import WasmTypes
+
+#if canImport(Darwin)
+    import Darwin
+#elseif canImport(Glibc)
+    import Glibc
+#elseif canImport(Musl)
+    import Musl
+#elseif canImport(Android)
+    import Android
+#elseif os(Windows)
+    import ucrt
+#else
+    #error("Unsupported Platform")
+#endif
+
+extension FdTable {
+    func fileDescriptor(fd: WASIAbi.Fd) throws -> FileDescriptor {
+        guard case let .file(entry) = self[fd], let fd = (entry as? FdWASIEntry)?.fd else {
+            throw WASIAbi.Errno.EBADF
+        }
+
+        return fd
+    }
+}
+
+func poll(
+    subscriptions: some Sequence<WASIAbi.Subscription>,
+    events: UnsafeGuestBufferPointer<WASIAbi.Event>,
+    _ fdTable: FdTable
+) throws -> WASIAbi.Size {
+    #if os(Windows)
+        throw WASIAbi.Errno.ENOTSUP
+    #else
+        var pollfds = [pollfd]()
+        var fdUserData = [WASIAbi.UserData]()
+        var timeoutMilliseconds = UInt.max
+        var clockUserData: WASIAbi.UserData?
+
+        for subscription in subscriptions {
+            let union = subscription.union
+            switch union {
+            case .clock(let clock):
+                timeoutMilliseconds = min(timeoutMilliseconds, .init(clock.timeout / 1_000_000))
+                clockUserData = subscription.userData
+            case .fdRead(let fd):
+                pollfds.append(.init(fd: try fdTable.fileDescriptor(fd: fd).rawValue, events: .init(POLLIN), revents: 0))
+                fdUserData.append(subscription.userData)
+            case .fdWrite(let fd):
+                pollfds.append(.init(fd: try fdTable.fileDescriptor(fd: fd).rawValue, events: .init(POLLOUT), revents: 0))
+                fdUserData.append(subscription.userData)
+            }
+        }
+
+        let result = poll(&pollfds, .init(pollfds.count), .init(timeoutMilliseconds))
+        let err = errno  // Preserve `errno` global immediately after `poll`
+        var updatedEvents: WASIAbi.Size = 0
+        if result == 0, let clockUserData {
+            updatedEvents += 1
+            events[0] = .init(userData: clockUserData, error: .SUCCESS, eventType: .clock, fdReadWrite: .init(nBytes: 0, flags: .init(rawValue: 0)))
+        } else if result > 0 {
+            for (i, fd) in pollfds.enumerated() {
+                updatedEvents += 1
+                switch fd.revents {
+                case .init(POLLIN):
+                    events[.init(i)] = .init(userData: fdUserData[i], error: .SUCCESS, eventType: .fdRead, fdReadWrite: .init(nBytes: 0, flags: []))
+                case .init(POLLOUT):
+                    events[.init(i)] = .init(userData: fdUserData[i], error: .SUCCESS, eventType: .fdWrite, fdReadWrite: .init(nBytes: 0, flags: []))
+                default: throw WASIAbi.Errno.ENOTSUP
+                }
+            }
+        } else {
+            switch err {
+            case ENOMEM: throw WASIAbi.Errno.ENOMEM
+            case EINTR: throw WASIAbi.Errno.EINTR
+            case EINVAL: throw WASIAbi.Errno.EINVAL
+            default: throw WASIAbi.Errno.ENOTSUP
+            }
+        }
+        return updatedEvents
+    #endif
+}