An atomic reference implementation for JRuby, Rubinius, and MRI.

Changes since 1.1.0

58d3e34 Convert README to rdoc and try again. f519385 Attempting to get description to look nice on rubygems.org. 2c5ab6c Include README and oneline logs in gem description. 6aeb053 Add @funny-falcon to authors. aa24d4d Bump version to 1.1.1. dc327eb Merge pull request #16 from funny-falcon/patch-1 1b68767 Fix JRUBYREFERENCE8_ALLOCATOR

An atomic reference implementation for JRuby, Rubinius, and MRI.

Summary

This library provides:

• an Atomic class that guarantees atomic updates to its contained value

The Atomic class provides accessors for the contained “value” plus two update

methods:

• update will run the provided block, passing the current value and replacing

  it with the block result iff the value has not been changed in the mean time.

  It may run the block repeatedly if there are other concurrent updates in

  progress.

• try_update will run the provided block, passing the current value and

  replacing it with the block result. If the value changes before the update

  can happen, it will throw Atomic::ConcurrentUpdateError.

The atomic repository is at github.com/headius/ruby-atomic.

Usage

The simplest way to use “atomic” is to call the “update” or “try_update”

methods.

“try_update” and “update” both call the given block, passing the current

value and using the block’s result as the new value. If the value is updated

by another thread before the block completes, “try update” raises a

ConcurrentUpdateError and “update” retries the block. Because “update” may call

the block several times when multiple threads are all updating the same value,

the block’s logic should be kept as simple as possible.

““ruby

require ‘atomic’

my_atomic = Atomic.new(0)

my_atomic.update {|v| v + 1}

begin

my_atomic.try_update {|v| v + 1}

rescue Atomic::ConcurrentUpdateError => cue

# deal with it (retry, propagate, etc)

end

““

It’s also possible to use the regular get/set operations on the Atomic, if you

want to avoid the exception and respond to contended changes in some other way.

““ruby

my_atomic = Atomic.new(0)

my_atomic.value # => 0

my_atomic.value = 1

my_atomic.swap(2) # => 1

my_atomic.compare_and_swap(2, 3) # => true, updated to 3

my_atomic.compare_and_swap(2, 3) # => false, current is not 2

““

Building

As of 1.1.0, JDK8 is required to build the atomic gem, since it attempts to use

the new atomic Unsafe.getAndSetObject method only in JDK8. The resulting code

should still work fine as far back as Java 5.