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Package Samples:
• org.apache.derby.impl.services.bytecode
• org.apache.derby.impl.services.cache
• org.apache.derby.impl.services.daemon
• org.apache.derby.impl.services.jce
• org.apache.derby.impl.services.locks
• org.apache.derby.impl.services.monitor
• org.apache.derby.impl.services.reflect
• org.apache.derby.impl.services.stream
• org.apache.derby.impl.services.uuid
Classes:
• BCJava: Debugging problems with generated classes When the code has been generated incorrectly, all sorts of odd things can go wrong. This is one recommended approach to finding the problem. First, turn on ByteCodeGenInstr and DumpClassFile. Look for missing files (right now they are consecutively numbered by the activation class builder; later on they won't be, but BytCodeGenInstr dumps messages about the classes it has). Look at the log to make sure that all "GEN starting class/method" messages are paired with a "GEN ending class/method" message. If a file is missing or the pairing is missing, then something ...
• Clock: A cache manager that uses a Hashtable and a ArrayList. The ArrayList holds CachedItem objects, each with a holder object. The Hashtable is keyed by the identity of the holder object (Cacheable.getIdentity()) and the data portion is a pointer to the CachedItem. CachedItems that have holder objects with no identity do not have entries in the hashtable. CachedItems can in various state. isValid - the entry has a valid identity inCreate - the entry is being created or being faulted in from persistent store inClean - the entry is being written out to persistent store isKept - the entry is currently ...
• BasicDaemon: A BasicDaemon is a background worker thread which does asynchronous I/O and general clean up. It should not be used as a general worker thread for parallel execution. One cannot count on the order of request or count on when the daemon will wake up, even with serviceNow requests. Request are not persistent and not recoverable, they are all lost when the system crashes or is shutdown. System shutdown, even orderly ones, do not wait for daemons to finish its work or empty its queue. Furthermore, any Serviceable subscriptions, including onDemandOnly, must tolerate spurrious services. The BasicDaemon ...
• CachedItem: A generic class to represent the cache related infomation of a cached object (Cacheable). The relationship between isValid and settingIdentity can be explain by the following life cycle of a cached item. Stage 1 2 3 ---------------------- isValid F T T settingIdentity X T F In Stage 1, the CachedItem is created but it is invalid and has an entry that is just a holder object with no identity. In Stage 2, the identity has been set and the item is being created or being faulted into the cache. In Stage 3, the item found in the CachedItem entry Remove is set if this item is being removed out of existance, ...
• BasicUUIDFactory: A hack implementation of something similar to a DCE UUID generator. Generates unique 128-bit numbers based on the current machine's internet address, the current time, and a sequence number. This implementation should be made to conform to the DCE specification. ("DEC/HP, Network Computing Architecture, Remote Procedure Call Runtime Extensions Specification, version OSF TX1.0.11," Steven Miller, July 23, 1992. This is part of the OSF DCE Documentation. Chapter 10 describes the UUID generation algorithm.) Some known deficiencies: Rather than using the 48-bit hardware network address, it uses the ...
• BCMethod: MethodBuilder is used to piece together a method when building a java class definition. When a method is first created, it has: a return type modifiers a name an empty parameter list an empty throws list an empty statement block MethodBuilder implementations are required to supply a way for Statements and Expressions to give them code. Most typically, they may have a stream to which their contents writes the code that is of the type to satisfy what the contents represent. MethodBuilder implementations also have to have a way to supply ClassBuilders with their code, that satisfies the type of class ...
• LockSet: A LockSet is a complete lock table. A lock table is a hash table keyed by a Lockable and with a LockControl as the data element. A LockControl contains information about the locks held on a Lockable. MT - Mutable - Container Object : Thread Safe The Hashtable we extend is synchronized on this, all addition, searching of the hashtable is performed using java synchroization(this). The class creates ActiveLock and LockControl objects. LockControl objects are never passed out of this class, All the methods of LockControl are called while being synchronized on this, thus providing the single threading ...
• BCClass: ClassBuilder is used to construct a java class's byte array representation. Limitations: No checking for language use violations such as invalid modifiers or duplicate field names. All classes must have a superclass; java.lang.Object must be supplied if there is no superclass. When a class is first created, it has: a superclass modifiers a name a package no superinterfaces, methods, fields, or constructors an empty static initializer an empty initializer MethodBuilder implementations are required to supply a way for Generators to give them code. Most typically, they may have a stream to which the ...
• DatabaseClasses: An abstract implementation of the ClassFactory. This package can be extended to fully implement a ClassFactory. Implementations can differ in two areas, how they load a class and how they invoke methods of the generated class. This class manages a hash table of loaded generated classes and their GeneratedClass objects. A loaded class may be referenced multiple times -- each class has a reference count associated with it. When a load request arrives, if the class has already been loaded, its ref count is incremented. For a remove request, the ref count is decremented unless it is the last reference, ...
• SingleStream: The Basic Services provide InfoStreams for reporting information. Two streams are provided: trace and error. It is configurable where these streams are directed. Errors will be printed to the error stream in addition to being sent to the client. By default both streams are sent to an error log for the system. When creating a message for a stream, you can create an initial entry with header information and then append to it as many times as desired. Note: if character encodings are needed, the use of java.io.*OutputStream's should be replaced with java.io.*Writer's (assuming the Writer interface ...
• SinglePool: An implementation of LockFactory that uses a single pool for the locks, i.e. all lock requests go through a single point of synchronisation. The default concrete class "SinglePool.java", prints nothing and thus incurs no overhead associated with the code to dump lock information. An alternate concrete class "LockDebug/TracingSinglePool.java", attempts to output only lock information that "makes sense" to a user - for instance it doesn't print latch locks. MT - Mutable - Container Object : Thread Aware
• CodeChunk: This class represents a chunk of code in a CodeAttribute. Typically, a CodeAttribute represents the code in a method. If there is a try/catch block, each catch block will get its own code chunk. This allows the catch blocks to all be put at the end of the generated code for a method, which eliminates the need to generate a jump around each catch block, which would be a forward reference.
• Conditional: A code chunk that gets pushed to handle if-else blocks. When this is created the mainChunk will already have the conditional check code. if condition then code else code what actually gets built is if !condition goto eb: then code goto end: eb: else code end:
• LockSpace: A LockSpace represents the complete set of locks held within a single compatability space, broken into groups of locks. A LockSpace is a hashtable keyed by the group reference, the data for each key is a Hashtable of Lock's.
• OpcodeDebug: This contains mnemonics for all of the opcodes of the JVM. It is a separate class so that it will not get loaded if the system does not need it (i.e. when compiled without debugging). We even leave out the initialization in that case.
• LockControl: A LockControl contains a reference to the item being locked and doubly linked lists for the granted locks and the waiting locks. MT - Mutable - Container object : single thread required
• BCMethodDescriptor: A method descriptor. Ie. something that describes the type of a method, parameter types and return types. It is not an instance of a method. This has no generated class specific state.
• BasicHeaderPrintWriter: Basic class to print lines with headers. STUB: Should include code to emit a new line before a header which is not the first thing on the line.
• BasicGetLogHeader: Get a header to prepend to a line of output. * A HeaderPrintWriter requires an object which implements this interface to construct line headers.
• LockTableVTI: This provides an Enumeration of Latch's from a clone of the lock table. A Latch is badly named, it represents lock information.
• ClockFactory: Multithreading considerations: no need to be MT-safe, caller (module control) provides synchronization. Besides, this class is stateless.
• PersistentServiceImpl: This class implements the PersistentService interface using a StorageFactory class. It handles all subSubProtocols except for cache.
• VMTypeIdCacheable: This class implements a Cacheable for a Byte code generator cache of VMTypeIds. It maps a Java class or type name to a VM type ID.
• BCExpr: To be able to identify the expressions as belonging to this implementation, and to be able to generate code off of it if so.
• ActiveLock: A Lock represents a granted or waiting lock request. MT - Mutable - Immutable identity : Thread Aware
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