IMPORTANT If you haven’t yet read Calling BSD Sockets from Swift, do that first.
Here are some straightforward wrappers for the getsockopt and setsockopt calls:
extension FileDescriptor {
/// Gets a socket option.
///
/// Equivalent to the `getsockopt` BSD Sockets call.
///
/// For simple socket options, consider using
/// ``getSocketOption(_:_:as:retryOnInterrupt:)``.
public func getSocketOption(_ level: CInt, _ name: CInt, _ optionValue: UnsafeMutableRawPointer, optionLen: inout Int, retryOnInterrupt: Bool = true) throws {
guard var optionSockLen = socklen_t(exactly: optionLen), optionLen >= 0 else { fatalError() }
try errnoQ(retryOnInterrupt: retryOnInterrupt) {
Foundation.getsockopt(self.rawValue, level, name, optionValue, &optionSockLen)
}
optionLen = Int(optionSockLen)
}
/// Sets a socket option.
///
/// Equivalent to the `setsockopt` BSD Sockets call.
///
/// For simple socket options, consider using
/// ``setSocketOption(_:_:_:retryOnInterrupt:)``.
public func setSocketOption(_ level: CInt, _ name: CInt, _ optionValue: UnsafeRawPointer, _ optionLen: Int, retryOnInterrupt: Bool = true) throws {
guard let optionSockLen = socklen_t(exactly: optionLen), optionLen >= 0 else { fatalError() }
try errnoQ(retryOnInterrupt: retryOnInterrupt) {
Foundation.setsockopt(self.rawValue, level, name, optionValue, optionSockLen)
}
}
}
These work fine but they’re a little primitive. I like adding a layer that makes it easier to work with standard types:
extension FileDescriptor {
/// Gets a simple socket option.
///
/// This allows you to get a simple socket option without messing around
/// with the unsafe pointer malarkely involved in
/// ``getSocketOption(_:_:_:optionLen:retryOnInterrupt:)``. See
/// `QSocketOptionConvertible` for more about how this works.
public func getSocketOption<T>(_ level: CInt, _ name: CInt, as: T.Type, retryOnInterrupt: Bool = true) throws -> T
where T: QSocketOptionConvertible
{
var result = T()
try withUnsafeMutableBytes(of: &result) { buf in
var bufCount = buf.count
try self.getSocketOption(level, name, buf.baseAddress!, optionLen: &bufCount, retryOnInterrupt: retryOnInterrupt)
guard bufCount == buf.count else {
throw Errno.noBufferSpace
}
}
return result
}
/// Sets a simple socket option.
///
/// This allows you to set a simple socket option without messing around
/// with the unsafe pointer malarkely involved in
/// ``setSocketOption(_:_:_:_:retryOnInterrupt:)``. See
/// ``QSocketOptionConvertible`` for more about how this works.
public func setSocketOption<T>(_ level: CInt, _ name: CInt, _ optionValue: T, retryOnInterrupt: Bool = true) throws
where T: QSocketOptionConvertible
{
// Can’t use `&value` because of a new compiler warning. We work around
// that per the [docs][ref]. One day there may be a ‘bitwise copyable’
// protocol that we can add to `QSocketOptionConvertible` to actually
// expression what’s going on here at the type layer.
//
// [ref]: <https://github.com/atrick/swift-evolution/blob/diagnose-implicit-raw-bitwise/proposals/nnnn-implicit-raw-bitwise-conversion.md#workarounds-for-common-cases>
var value = optionValue
try withUnsafeBytes(of: &value) { buf in
try self.setSocketOption(level, name, buf.baseAddress!, buf.count, retryOnInterrupt: retryOnInterrupt)
}
}
}
/// Indicates that a type can be used as a socket option.
///
/// This has one true constraint, namely that the type has a default value.
/// There are, however, two implicit constraints:
///
/// * The type must be just data. If, for example, the type contains an object
/// reference, bad things would happen.
///
/// * The type’s size is compatible with `socklen_t`.
///
/// We specifically conform various types, like `CInt` and `timeval`, to this
/// protocol but you can add to that list if necessary.
public protocol QSocketOptionConvertible {
init()
}
extension UInt8: QSocketOptionConvertible { }
extension CInt: QSocketOptionConvertible { }
extension CUnsignedInt: QSocketOptionConvertible { }
extension timeval: QSocketOptionConvertible { }
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—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"
