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// RUN: %target-run-simple-swift(-Xfrontend -sil-verify-all)
// RUN: %target-run-simple-swift(-O -Xfrontend -sil-verify-all)
// REQUIRES: executable_test
enum FixedSizeQueueError : Error {
case outOfSpace
}
struct FixedSizeQueue<T> : ~Copyable {
private var readOffset: Int
private var writeOffset: Int
private var ptr: UnsafeMutableBufferPointer<T>
init(capacity: Int) {
readOffset = 0
writeOffset = 0
ptr = UnsafeMutableBufferPointer.allocate(capacity: capacity)
}
deinit {
ptr.deinitialize().deallocate()
}
mutating func read() -> T? {
if readOffset == writeOffset {
return nil
}
let x = ptr[readOffset]
readOffset = (readOffset + 1) % ptr.count
return x
}
mutating func write(_ element: T) throws {
if ((writeOffset + 1) % ptr.count) == readOffset {
throw FixedSizeQueueError.outOfSpace
}
ptr[writeOffset] = element
writeOffset = (writeOffset + 1) % ptr.count
}
private consuming func cleanupQueue() -> UnsafeMutableBufferPointer<T> {
let buffer = self.ptr
discard self
return buffer
}
// Drain the queue... returning the value.
mutating func drain() -> UnsafeMutableBufferPointer<T> {
let count = ptr.count
let buffer = cleanupQueue()
self = .init(capacity: count)
return buffer
}
}
func main() throws {
var x = FixedSizeQueue<Int>(capacity: 10)
precondition(x.read() == nil)
try x.write(0)
try x.write(9)
try x.write(1)
try x.write(3)
precondition(x.read() == 0)
precondition(x.read() == 9)
precondition(x.read() == 1)
precondition(x.read() == 3)
let d = x.drain()
precondition(d[0] == 0)
precondition(d[1] == 9)
precondition(d[2] == 1)
precondition(d[3] == 3)
precondition(x.read() == nil)
try x.write(3)
try x.write(1)
try x.write(9)
try x.write(0)
precondition(x.read() == 3)
precondition(x.read() == 1)
precondition(x.read() == 9)
precondition(x.read() == 0)
}
try main()
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