Safe 1.2.0

Maintained by Josh Baker.

You want to add pod 'Safe', '~> 1.2' similar to the following to your Podfile:

target 'MyApp' do
  pod 'Safe', '~> 1.2'
end

Then run a pod install inside your terminal, or from CocoaPods.app.

Alternatively to give it a test run, run the command:

pod try Safe

Safe 1.2.0

By
Josh Baker
tidwall

Features

Simple Atomic<T> class for numbers and strings.
Uncomplicated dispatch keyword for firing off background routines.
Awesome Chan<T> for conncurent communication.
Useful sync APIs. Mutex, Cond, Once, WaitGroup

Atomic

Types

Int, Int8, Int16, Int32, Int64, UInt, UInt8, UInt16, UInt32, UInt64, Float, Double, Bool, String

Operators

==, !=, &&, ||, <=, >=, >, <, !
+, -, *, /, %, <<, >>, ^, &, &+, &-, &*, ++, --, +=, -=, *=, /=, %=, +=, <<=, >>=, ^=, &=

var anum = IntA(100)      // IntA is an alias for Atomic<Int>.
anum += 15                // Adds a value atomically.
let res = anum % 4        // Modulo operation atomically.
print("\(anum) \(res)")   // prints '115 3'.

Dispatch

Safe adds an uncomplicated method for dispatching routines.

dispatch {
    print("Background")
}
print("Foreground")

Channels

A new Chan<T> class provides a clean and simple model for concurrently sharing objects. Chan<T> is modeled after Go channels.

Sharing Memory by Communicating

Example

let jobs = Chan<Int>(5)  // buffered channel
let done = Chan<Bool>()  // unbuffered channel

dispatch {
    for ;; {
        if let j = <-jobs {
            print("received job \(j)")
        } else {
            print("received all jobs")
            done <- true
            return
        }
    }
}

for var j = 1; j <= 3; j++ {
    jobs <- j
    print("sent job \(j)")
}
jobs.close()
print("sent all jobs")

<-done

Iterate

A channel can also be iterated through.

while let j = <-jobs {
    print("received job \(j)")
}
print("received all jobs")

Select

The _select keyword is a multiway communications multiplexer that works on multiple channels. _select, _case, and _default start with underscores so that they do not conflict with the select, case, and default syscall and keywords. When a _select encounters multiple channels with data, the chosen _case is selected at random

let jobs1 = Chan<Int>()
let jobs2 = Chan<Int>()

dispatch {
    for ;; {
        _select {
            _case(jobs1){ j in
                print("received 1: \(j)")
            }
            _case(jobs2){ j in
                print("received 2: \(j)")
            }
        }
    }
}

for var j = 1; ; j++ {
    jobs1 <- (j * 1000)
    jobs2 <- (j * 2000)
    NSThread.sleepForTimeInterval(1)
}

Select with Default

A _select can contain a single _default for non-blocking operations.

_select {
    _case(jobs1){ j in
        print("received 1: \(j)")
    }
    _case(jobs2){ j in
        print("received 2: \(j)")
    }
    _default {
        print("channels not ready")
    }
}

Mutex, Cond, Once, WaitGroup

Incredibly useful sync APIs.

Mutex

let m = Mutex()
m.lock()           
m.unlock()         
m.lock {
    // this block is locked
}

Cond

let c = Cond(Mutex())
c.wait()                // wait for signal.
c.wait(0.25)            // wait for signal or 250ms to pass.
c.signal()              // signal to one wait.
c.broadcast()           // signal to all waits.

Once

func f(){
    print("hey there")
}

let o = Once()
o.doit(f)               // runs once
o.doit(f)               // noop: cannot run twice

WaitGroup

let dosomething : (NSTimeInterval, WaitGroup)->() = { (delay, wg) in
    NSThread.sleepForTimeInterval(delay)
    print("Function in background, duration: \(delay)")
    wg.done()
}
let wg = WaitGroup()
wg.add(1)
dispatch { dosomething(0.40, wg) }
wg.add(1)
dispatch { dosomething(0.30, wg) }
wg.add(1)
dispatch { dosomething(0.15, wg) }
wg.add(1)
dispatch { dosomething(0.60, wg) }
wg.wait()
print("done")

Installation (iOS and OS X)

Manually

Copy the Source/*.swift file into your project.

There is no need for import Safe when manually installing.

Contact

Josh Baker @tidwall

License

The Safe source code is available under the MIT License.