Adjusted the naming of the library in the Package file.

Sources/PlaydateKit/Lua.swift

@@ -0,0 +1,296 @@
+//
+//  Lua.swift
+//  Wraps `playdate->lua` (pd_api_lua.h).
+//
+//  Lua callbacks are C function pointers without userdata, so functions
+//  registered here must be `@convention(c)` (the `CFunction` typealias), not
+//  capturing closures.
+//
+
+public import CPlaydate
+
+private var luaAPI: UnsafePointer<playdate_lua> { Playdate.luaAPI.unsafelyUnwrapped }
+
+/// The Lua bridge: registering C functions and classes, and exchanging
+/// values with Lua code.
+public enum Lua {}
+
+extension Lua {
+    /// A function callable from Lua. Returns the number of values it pushed
+    /// onto the stack.
+    public typealias CFunction = lua_CFunction
+
+    /// The type of a value on the Lua stack.
+    public enum Kind: UInt32, Sendable {
+        case `nil` = 0
+        case bool = 1
+        case int = 2
+        case float = 3
+        case string = 4
+        case table = 5
+        case function = 6
+        case thread = 7
+        case object = 8
+
+        init(_ type: LuaType) { self = Kind(rawValue: UInt32(type.rawValue)) ?? .nil }
+    }
+
+    /// A constant published on a registered class.
+    public enum ClassValue {
+        case int(name: String, value: UInt32)
+        case float(name: String, value: Float)
+        case string(name: String, value: String)
+    }
+
+    /// Buffers passed to `registerClass`/`addFunction`; the OS may keep
+    /// referencing them, so they are retained for the life of the game.
+    nonisolated(unsafe) private static var retainedBuffers: [UnsafeMutableRawPointer] = []
+
+    private static func retainedCString(_ string: String) -> UnsafePointer<CChar> {
+        let copy = string.copiedPlaydateCString()
+        retainedBuffers.append(UnsafeMutableRawPointer(copy))
+        return UnsafePointer(copy)
+    }
+
+    // MARK: - Registration
+
+    /// Makes `function` callable from Lua as `name` (which may contain dots
+    /// for namespacing, e.g. "mylib.myfunc").
+    public static func addFunction(_ function: CFunction, name: String) throws(PlaydateError) {
+        var error: UnsafePointer<CChar>?
+        let ok = name.withPlaydateCString {
+            luaAPI.pointee.addFunction.unsafelyUnwrapped(function, $0, &error) != 0
+        }
+        if !ok { throw PlaydateError(cString: error) }
+    }
+
+    /// Registers a Lua class named `name` with the given methods and
+    /// constants. When `isStatic` is `true` a plain table of functions is
+    /// created instead of a class.
+    public static func registerClass(name: String,
+                                     functions: [(name: String, function: CFunction)],
+                                     values: [ClassValue] = [],
+                                     isStatic: Bool = false) throws(PlaydateError) {
+        // The registration tables are kept alive permanently: the OS
+        // documents no copying guarantees for them.
+        var registrations: [lua_reg] = functions.map { entry in
+            lua_reg(name: retainedCString(entry.name), func: entry.function)
+        }
+        registrations.append(lua_reg(name: nil, func: nil))
+
+        var constants: [lua_val] = values.map { value in
+            switch value {
+            case .int(let name, let intValue):
+                return lua_val(name: retainedCString(name), type: kInt, v: .init(intval: intValue))
+            case .float(let name, let floatValue):
+                return lua_val(name: retainedCString(name), type: kFloat, v: .init(floatval: floatValue))
+            case .string(let name, let stringValue):
+                return lua_val(name: retainedCString(name), type: kStr,
+                               v: .init(strval: retainedCString(stringValue)))
+            }
+        }
+        constants.append(lua_val(name: nil, type: kInt, v: .init(intval: 0)))
+
+        let registrationsBuffer = UnsafeMutablePointer<lua_reg>.allocate(capacity: registrations.count)
+        registrationsBuffer.initialize(from: registrations, count: registrations.count)
+        retainedBuffers.append(UnsafeMutableRawPointer(registrationsBuffer))
+
+        let constantsBuffer = UnsafeMutablePointer<lua_val>.allocate(capacity: constants.count)
+        constantsBuffer.initialize(from: constants, count: constants.count)
+        retainedBuffers.append(UnsafeMutableRawPointer(constantsBuffer))
+
+        var error: UnsafePointer<CChar>?
+        let ok = name.withPlaydateCString {
+            luaAPI.pointee.registerClass.unsafelyUnwrapped($0, registrationsBuffer,
+                                                   values.isEmpty ? nil : constantsBuffer,
+                                                   isStatic ? 1 : 0, &error) != 0
+        }
+        if !ok { throw PlaydateError(cString: error) }
+    }
+
+    /// Pushes a function onto the stack, e.g. for `setUserValue`.
+    public static func pushFunction(_ function: CFunction) {
+        luaAPI.pointee.pushFunction.unsafelyUnwrapped(function)
+    }
+
+    /// From a class's `__index` callback: looks up the key in the instance
+    /// metatable first. Returns 1 if a value was found.
+    public static func indexMetatable() -> Bool {
+        luaAPI.pointee.indexMetatable.unsafelyUnwrapped() != 0
+    }
+
+    /// Pauses the Lua runtime.
+    public static func stop() {
+        luaAPI.pointee.stop.unsafelyUnwrapped()
+    }
+
+    /// Resumes the Lua runtime.
+    public static func start() {
+        luaAPI.pointee.start.unsafelyUnwrapped()
+    }
+
+    // MARK: - Arguments
+
+    /// The number of arguments the Lua caller passed. Positions are 1-based.
+    public static var argumentCount: Int {
+        Int(luaAPI.pointee.getArgCount.unsafelyUnwrapped())
+    }
+
+    /// The type of the argument at 1-based `position`; for objects, also the
+    /// class name.
+    public static func argumentType(at position: Int) -> (kind: Kind, className: String?) {
+        var className: UnsafePointer<CChar>?
+        let type = luaAPI.pointee.getArgType.unsafelyUnwrapped(Int32(position), &className)
+        return (Kind(type), String(playdateCString: className))
+    }
+
+    public static func argumentIsNil(at position: Int) -> Bool {
+        luaAPI.pointee.argIsNil.unsafelyUnwrapped(Int32(position)) != 0
+    }
+
+    public static func boolArgument(at position: Int) -> Bool {
+        luaAPI.pointee.getArgBool.unsafelyUnwrapped(Int32(position)) != 0
+    }
+
+    public static func intArgument(at position: Int) -> Int {
+        Int(luaAPI.pointee.getArgInt.unsafelyUnwrapped(Int32(position)))
+    }
+
+    public static func floatArgument(at position: Int) -> Float {
+        luaAPI.pointee.getArgFloat.unsafelyUnwrapped(Int32(position))
+    }
+
+    public static func stringArgument(at position: Int) -> String? {
+        String(playdateCString: luaAPI.pointee.getArgString.unsafelyUnwrapped(Int32(position)))
+    }
+
+    /// The argument as raw bytes (which may contain embedded zeros).
+    public static func bytesArgument(at position: Int) -> [UInt8]? {
+        var length = 0
+        guard let bytes = luaAPI.pointee.getArgBytes.unsafelyUnwrapped(Int32(position), &length) else {
+            return nil
+        }
+        let buffer = UnsafeRawBufferPointer(start: bytes, count: length)
+        return [UInt8](buffer)
+    }
+
+    /// The argument as an object instance of class `type`, with the
+    /// `UDObject` handle for retaining it.
+    public static func objectArgument(at position: Int, type: String)
+        -> (object: UnsafeMutableRawPointer?, userdataObject: UDObject?) {
+        var userdataObject: OpaquePointer?
+        // The C API takes a non-const class name but only reads it, so the
+        // stack copy can be passed with a mutating cast.
+        let object = type.withPlaydateCString { cType in
+            luaAPI.pointee.getArgObject.unsafelyUnwrapped(
+                Int32(position), UnsafeMutablePointer(mutating: cType), &userdataObject)
+        }
+        return (object, userdataObject.map { UDObject(pointer: $0) })
+    }
+
+    /// The argument as a bitmap. References an object owned by Lua; retain
+    /// the Lua value while using it.
+    public static func bitmapArgument(at position: Int) -> Graphics.Bitmap? {
+        guard let bitmap = luaAPI.pointee.getBitmap.unsafelyUnwrapped(Int32(position)) else { return nil }
+        return Graphics.Bitmap(pointer: bitmap, isOwned: false)
+    }
+
+    /// The argument as a sprite.
+    public static func spriteArgument(at position: Int) -> Sprite? {
+        guard let sprite = luaAPI.pointee.getSprite.unsafelyUnwrapped(Int32(position)) else { return nil }
+        return Sprite.wrapper(for: sprite)
+    }
+
+    // MARK: - Return values
+
+    public static func pushNil() {
+        luaAPI.pointee.pushNil.unsafelyUnwrapped()
+    }
+
+    public static func push(_ value: Bool) {
+        luaAPI.pointee.pushBool.unsafelyUnwrapped(value ? 1 : 0)
+    }
+
+    public static func push(_ value: Int) {
+        luaAPI.pointee.pushInt.unsafelyUnwrapped(Int32(value))
+    }
+
+    public static func push(_ value: Float) {
+        luaAPI.pointee.pushFloat.unsafelyUnwrapped(value)
+    }
+
+    public static func push(_ value: String) {
+        value.withPlaydateCString { luaAPI.pointee.pushString.unsafelyUnwrapped($0) }
+    }
+
+    public static func push(bytes: [UInt8]) {
+        bytes.withUnsafeBytes { buffer in
+            luaAPI.pointee.pushBytes.unsafelyUnwrapped(
+                buffer.baseAddress?.assumingMemoryBound(to: CChar.self), buffer.count)
+        }
+    }
+
+    public static func push(_ bitmap: Graphics.Bitmap) {
+        luaAPI.pointee.pushBitmap.unsafelyUnwrapped(bitmap.pointer)
+    }
+
+    public static func push(_ sprite: Sprite) {
+        luaAPI.pointee.pushSprite.unsafelyUnwrapped(sprite.pointer)
+    }
+
+    /// Wraps `object` in a Lua instance of class `type` and pushes it, with
+    /// `valueCount` extra user-value slots.
+    @discardableResult
+    public static func pushObject(_ object: UnsafeMutableRawPointer, type: String,
+                                  valueCount: Int = 0) -> UDObject? {
+        // The C API takes a non-const class name but only reads it, so the
+        // stack copy can be passed with a mutating cast.
+        let pointer = type.withPlaydateCString { cType in
+            luaAPI.pointee.pushObject.unsafelyUnwrapped(
+                object, UnsafeMutablePointer(mutating: cType), Int32(valueCount))
+        }
+        guard let pointer else { return nil }
+        return UDObject(pointer: pointer)
+    }
+
+    /// A handle to a Lua-owned object. Wraps `LuaUDObject`.
+    public struct UDObject {
+        let pointer: OpaquePointer
+
+        /// Prevents the object from being garbage-collected until `release()`.
+        @discardableResult
+        public func retain() -> UDObject {
+            UDObject(pointer: luaAPI.pointee.retainObject.unsafelyUnwrapped(pointer).unsafelyUnwrapped)
+        }
+
+        public func release() {
+            luaAPI.pointee.releaseObject.unsafelyUnwrapped(pointer)
+        }
+
+        /// Pops the value on top of the stack and stores it in the object's
+        /// user-value `slot` (1-based).
+        public func setUserValue(slot: UInt32) {
+            luaAPI.pointee.setUserValue.unsafelyUnwrapped(pointer, slot)
+        }
+
+        /// Pushes the value in user-value `slot` onto the stack and returns
+        /// its stack position, or `nil` if there is none.
+        @discardableResult
+        public func getUserValue(slot: UInt32) -> Int? {
+            let position = luaAPI.pointee.getUserValue.unsafelyUnwrapped(pointer, slot)
+            return position == 0 ? nil : Int(position)
+        }
+    }
+
+    // MARK: - Calling Lua
+
+    /// Calls the Lua function `name`. Push the arguments onto the stack
+    /// first. Calling Lua from Swift has overhead; use sparingly.
+    public static func callFunction(_ name: String, argumentCount: Int = 0) throws(PlaydateError) {
+        var error: UnsafePointer<CChar>?
+        let ok = name.withPlaydateCString {
+            luaAPI.pointee.callFunction.unsafelyUnwrapped($0, Int32(argumentCount), &error) != 0
+        }
+        if !ok { throw PlaydateError(cString: error) }
+    }
+}