The usage of BitCaskKeyDir in java

This article mainly introduces "the usage of BitCaskKeyDir in java". In daily operation, I believe many people have doubts about the usage of BitCaskKeyDir in java. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts about the usage of BitCaskKeyDir in java! Next, please follow the editor to study!

Order

This paper mainly studies BitCaskKeyDir.

BitCaskKeyDir

Bitcask-java/src/main/java/com/trifork/bitcask/BitCaskKeyDir.java

Public class BitCaskKeyDir {Map map = new HashMap (); ReadWriteLock rwl = new ReentrantReadWriteLock (); private boolean is_ready; public boolean put (ByteString key, BitCaskEntry ent) {Lock writeLock = rwl.writeLock (); writeLock.lock (); try {BitCaskEntry old = map.get (key) If (old = = null) {map.put (key, ent); return true;} else if (ent.is_newer_than (old)) {map.put (key, ent) Return true;} else {return false;}} finally {writeLock.unlock () }} public BitCaskEntry get (ByteString key) {Lock readLock = rwl.readLock (); readLock.lock (); try {return map.get (key) } finally {readLock.unlock ();}} /.}

BitCaskKeyDir provides map to store BitCaskEntry; and its put method uses writeLock.lock (). If the null value is null or the new value is greater than the Old value, the put goes in, otherwise it returns false, and finally writeLock.unlock (); its get method uses readLock.lock () to read the value of the specified key from map, and finally readLock.unlock ()

Key_dirs

Bitcask-java/src/main/java/com/trifork/bitcask/BitCaskKeyDir.java

Public class BitCaskKeyDir {public static Map key_dirs = new HashMap (); public static Lock keydir_lock = new ReentrantLock (); public static BitCaskKeyDir keydir_new (File dirname, int openTimeoutSecs) throws IOException {File abs_name = dirname.getAbsoluteFile (); BitCaskKeyDir dir; keydir_lock.lock () Try {dir = key_dirs.get (abs_name); if (dir = = null) {dir = new BitCaskKeyDir (); key_dirs.put (abs_name, dir) Return dir;}} finally {keydir_lock.unlock () } if (dir.wait_for_ready (openTimeoutSecs)) {return dir;} else {throw new IOException ("timeout while waiting for keydir");}} public synchronized boolean is_ready () {return is_ready } public synchronized void mark_ready () {is_ready = true; this.notifyAll ();} public synchronized boolean wait_for_ready (int timeout_secs) {long now = System.currentTimeMillis (); long abs_timeout = now + (timeout_secs * 1000) While (! is_ready & & now < abs_timeout) {try {wait () } catch (InterruptedException e) {/ / ignore} now = System.currentTimeMillis ();} return is_ready;}}

BitCaskKeyDir defines the key_dirs of the static, which is used to store the BitCaskKeyDir; of the specified File. The keydir_new is created for the BitCaskKeyDir that does not exist, and finally waits for the ready via dir.wait_for_ready (openTimeoutSecs).

Summary

BitCaskKeyDir provides map to store BitCaskEntry; and its put method uses writeLock.lock (). If the null value is null or the new value is greater than the Old value, the put goes in, otherwise it returns false, and finally writeLock.unlock (); its get method uses readLock.lock () to read the value of the specified key from map, and finally readLock.unlock ()

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