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Task/Queue-Definition/CoffeeScript/queue-definition.coffee

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+# Implement a fifo as an array of arrays, to
+# greatly amortize dequeue costs, at some expense of
+# memory overhead and insertion time.  The speedup
+# depends on the underlying JS implementation, but
+# it's significant on node.js.
+Fifo = ->
+  max_chunk = 512
+  arr = [] # array of arrays
+  count = 0
+
+  self =
+    enqueue: (elem) ->
+      if count == 0 or arr[arr.length-1].length >= max_chunk
+        arr.push []
+      count += 1
+      arr[arr.length-1].push elem
+    dequeue: (elem) ->
+      throw Error("queue is empty") if count == 0
+      val = arr[0].shift()
+      count -= 1
+      if arr[0].length == 0
+        arr.shift()
+      val
+    is_empty: (elem) ->
+      count == 0
+
+# test
+do ->
+  max = 5000000
+  q = Fifo()
+  for i in [1..max]
+    q.enqueue
+      number: i
+
+  console.log q.dequeue()
+  while !q.is_empty()
+    v = q.dequeue()
+  console.log v