counter and stubby lock

lib/rudis/structure.rb

@@ -55,7 +55,9 @@ def watch(tries=0)
   end
 end
 
+require_local 'structures/counter'
 require_local 'structures/list'
+require_local 'structures/lock'
 require_local 'structures/hash'
 require_local 'structures/set'
 require_local 'structures/string'

lib/rudis/structures/counter.rb

@@ -0,0 +1,27 @@
+class Rudis
+  class Counter < Structure
+    def incr
+      redis.incr(key)
+    end
+
+    def decr
+      redis.decr(key)
+    end
+
+    def incrby(i)
+      redis.incrby(key, i.to_i)
+    end
+
+    def decrby(i)
+      redis.decrby(key, i.to_i)
+    end
+
+    def to_i
+      redis.get(key).to_i
+    end
+
+    def zero?
+      to_i.zero?
+    end
+  end
+end

lib/rudis/structures/lock.rb

@@ -0,0 +1,59 @@
+class Rudis
+  class Lock < Structure
+    class LockFailed < Exception; end
+
+    def acquire(options={})
+      options.rmerge!(
+        :tries => 1,
+        :sleep => 1
+      )
+
+      return set(options) unless block_given?
+
+      1.upto options[:tries] do
+        if set(options)
+          return begin
+            yield
+          ensure
+            clear
+          end
+        end
+        sleep options[:sleep]
+      end
+
+      # oops, we couldn't get the lock
+      raise LockFailed, <<-msg.squish
+        Unable to acquire lock after #{options[:tries]} time(s)
+      msg
+      return false
+    end
+
+    def set(options={})
+      options.rmerge!(
+        :timeout => 30
+      )
+      if redis.setnx(key, timestamp(options[:timeout]))
+        return true
+      else
+        # check the timestamp
+        old = redis.getset(key, timestamp(options[:timeout]))
+        if old < timestamp
+          # expired lock, we're good
+          return true
+        else
+          # lock is not expired, put it back
+          redis.set(key, old)
+          return false
+        end
+      end
+    end
+
+    alias clear del
+
+  private
+    def timestamp(timeout=0)
+      Time.now.to_i + timeout
+    end
+
+  end
+end

spec/counter_spec.rb

@@ -0,0 +1,17 @@
+describe Rudis::Counter do
+  before :each do
+    Rudis::Counter.redis.flushdb
+    @c = Rudis::Counter.new('my_counter')
+  end
+
+  it "counts!" do
+    @c.to_i.should == 0
+    @c.should be_zero
+    @c.incr.should == 1
+    @c.incr.should == 2
+    @c.decr.should == 1
+    @c.incrby(4).should == 5
+    @c.decrby(2).should == 3
+    @c.incrby(-1).should == 2
+  end
+end