initial commit

Sources/PFFFT/SetupCache.swift

@@ -0,0 +1,46 @@
+import Foundation
+
+public class SetupCache: @unchecked Sendable {
+    struct CacheKey: Hashable {
+        let n: Int
+        let type: ObjectIdentifier
+
+        init(n: Int, type: any FFTElement.Type) {
+            self.n = n
+            self.type = ObjectIdentifier(type)
+        }
+    }
+
+    var cache: [CacheKey: Setup?] = [:]
+    let queue = DispatchQueue(label: String(describing: SetupCache.self), attributes: .concurrent)
+
+    public init() {}
+
+    public func get<T: FFTElement>(n: Int, type: T.Type) throws -> Setup {
+        var setup: Setup??
+        queue.sync {
+            setup = cache[CacheKey(n: n, type: type)]
+        }
+        if setup == nil {
+            queue.sync(flags: .barrier) {
+                let key = CacheKey(n: n, type: type)
+                setup = cache[key]
+                if setup == nil {
+                    let entry = try? Setup(n: n, type: type)
+                    cache[key] = entry
+                    setup = entry
+                }
+            }
+        }
+        guard let s = setup! else { throw FFTError.invalidSize }
+        return s
+    }
+
+    public func clear() {
+        queue.sync(flags: .barrier) {
+            cache.removeAll()
+        }
+    }
+
+    public static let shared = SetupCache()
+}