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author | Christopher Vogt <oss.nsp@cvogt.org> | 2016-03-14 23:00:55 -0400 |
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committer | Christopher Vogt <oss.nsp@cvogt.org> | 2016-03-19 21:13:49 -0400 |
commit | 957ac4a3080383135738a9ce90790ef7692bb3c0 (patch) | |
tree | 4215e3b959df3c2b292aec6bd9d75ddf246eb1f1 /stage1/KeyLockedLazyCache.scala | |
parent | 48780e341b8c094548641ba986f8a2b77f10d1da (diff) | |
download | cbt-957ac4a3080383135738a9ce90790ef7692bb3c0.tar.gz cbt-957ac4a3080383135738a9ce90790ef7692bb3c0.tar.bz2 cbt-957ac4a3080383135738a9ce90790ef7692bb3c0.zip |
move KeyLockedLazyCache to its own file
Diffstat (limited to 'stage1/KeyLockedLazyCache.scala')
-rw-r--r-- | stage1/KeyLockedLazyCache.scala | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/stage1/KeyLockedLazyCache.scala b/stage1/KeyLockedLazyCache.scala new file mode 100644 index 0000000..50c6f9e --- /dev/null +++ b/stage1/KeyLockedLazyCache.scala @@ -0,0 +1,47 @@ +package cbt + +import java.util.concurrent.ConcurrentHashMap + +private[cbt] class LockableKey +/** +A cache that lazily computes values if needed during lookup. +Locking occurs on the key, so separate keys can be looked up +simultaneously without a deadlock. +*/ +final private[cbt] class KeyLockedLazyCache[Key <: AnyRef,Value <: AnyRef]( + val keys: ConcurrentHashMap[Key,AnyRef], + val values: ConcurrentHashMap[AnyRef,Value], + logger: Option[Logger] +){ + def get( key: Key, value: => Value ): Value = { + val lockableKey = keys.synchronized{ + if( ! (keys containsKey key) ){ + val lockableKey = new LockableKey + //logger.foreach(_.resolver("CACHE MISS: " ++ key.toString)) + keys.put( key, lockableKey ) + lockableKey + } else { + val lockableKey = keys get key + //logger.foreach(_.resolver("CACHE HIT: " ++ lockableKey.toString ++ " -> " ++ key.toString)) + lockableKey + } + } + import collection.JavaConversions._ + //logger.resolver("CACHE: \n" ++ keys.mkString("\n")) + // synchronizing on key only, so asking for a particular key does + // not block the whole cache, but just that cache entry + key.synchronized{ + if( ! (values containsKey lockableKey) ){ + values.put( lockableKey, value ) + } + values get lockableKey + } + } + def remove( key: Key ) = keys.synchronized{ + assert(keys containsKey key) + val lockableKey = keys get key + keys.remove( key ) + assert(values containsKey lockableKey) + values.remove( lockableKey ) + } +} |