Package com.mckoi.store

Class LoggingBufferManager.BMPage

  • Enclosing class:
    LoggingBufferManager
    private static final class LoggingBufferManager.BMPage
extends java.lang.Object
    A page from a store that is currently being cached in memory. This is also an element in the cache.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      (package private) int access_count
      The number of times this page has been accessed since it was created.
      private byte[] buffer
      The buffer that contains the data for this page.
      private JournalledResource data
      The StoreDataAccessor that the page content is part of.
      private int first_write_position
      The first position in the buffer that was last written.
      (package private) LoggingBufferManager.BMPage hash_next
      A reference to the next page with this hash key.
      private boolean initialized
      True if this page is initialized.
      private int last_write_position
      The last position in the buffer that was last written.
      private long page
      The page number.
      private int page_size
      The size of the page.
      private int reference_count
      The number of references on this page.
      (package private) long t
      The time this page was last accessed.

    • Constructor Summary

      Constructors 
      Constructor Description
      BMPage​(JournalledResource data, long page, int page_size)
      Constructs the page.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      (package private) void dispose()
      Disposes of the page buffer if it can be disposed (there are no references to the page and the page is initialized).
      boolean equals​(java.lang.Object ob)  
      (package private) void flush()
      Flushes this page out to disk, but does not remove from memory.
      (package private) long getID()
      Returns the id of the JournalledResource that is being buffered.
      (package private) void initialize()
      Initializes the page buffer.
      (package private) boolean isPage​(long in_id, long in_page)
      Returns true if this page matches the given id/page_number.
      (package private) boolean notInUse()
      Returns true if this PageBuffer is not in use (has 0 reference count and is not inialized.
      (package private) byte read​(int pos)
      Reads a single byte from the cached page from memory.
      (package private) void read​(int pos, byte[] buf, int off, int len)
      Reads a part of this page into the cached page from memory.
      private void readPageContent​(long page_number, byte[] buf, int pos)
      Reads the current page content into memory.
      (package private) void referenceAdd()
      Adds 1 to the reference counter on this page.
      private void referenceRemove()
      Removes 1 from the reference counter on this page.
      (package private) void reset()
      Resets this object.
      (package private) void write​(int pos, byte v)
      Writes a single byte to the page in memory.
      (package private) void write​(int pos, byte[] buf, int off, int len)
      Writes to the given part of the page in memory.

      • Methods inherited from class java.lang.Object

        clone, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • data

        private final JournalledResource data
        The StoreDataAccessor that the page content is part of.

      • page

        private final long page
        The page number.

      • page_size

        private final int page_size
        The size of the page.

      • buffer

        private byte[] buffer
        The buffer that contains the data for this page.

      • initialized

        private boolean initialized
        True if this page is initialized.

      • t

        long t
        The time this page was last accessed. This value is reset each time the page is requested.

      • access_count

        int access_count
        The number of times this page has been accessed since it was created.

      • first_write_position

        private int first_write_position
        The first position in the buffer that was last written.

      • last_write_position

        private int last_write_position
        The last position in the buffer that was last written.

      • reference_count

        private int reference_count
        The number of references on this page.

    • Constructor Detail

      • BMPage

        BMPage​(JournalledResource data,
       long page,
       int page_size)
        Constructs the page.

    • Method Detail

      • reset

        void reset()
        Resets this object.

      • getID

        long getID()
        Returns the id of the JournalledResource that is being buffered.

      • referenceAdd

        void referenceAdd()
        Adds 1 to the reference counter on this page.

      • referenceRemove

        private void referenceRemove()
        Removes 1 from the reference counter on this page.

      • notInUse

        boolean notInUse()
        Returns true if this PageBuffer is not in use (has 0 reference count and is not inialized.

      • isPage

        boolean isPage​(long in_id,
               long in_page)
        Returns true if this page matches the given id/page_number.

      • readPageContent

        private void readPageContent​(long page_number,
                             byte[] buf,
                             int pos)
                      throws java.io.IOException
        Reads the current page content into memory. This may read from the data files or from a log.
        Throws:
        java.io.IOException

      • flush

        void flush()
    throws java.io.IOException
        Flushes this page out to disk, but does not remove from memory. In a logging system this will flush the changes out to a log.
        Throws:
        java.io.IOException

      • initialize

        void initialize()
         throws java.io.IOException
        Initializes the page buffer. If the buffer is already initialized then we just return. If it's not initialized we set up any internal structures that are required to be set up for access to this page.
        Throws:
        java.io.IOException

      • dispose

        void dispose()
      throws java.io.IOException
        Disposes of the page buffer if it can be disposed (there are no references to the page and the page is initialized). When disposed the memory used by the page is reclaimed and the content is written out to disk.
        Throws:
        java.io.IOException

      • read

        byte read​(int pos)
        Reads a single byte from the cached page from memory.

      • read

        void read​(int pos,
          byte[] buf,
          int off,
          int len)
        Reads a part of this page into the cached page from memory.

      • write

        void write​(int pos,
           byte v)
        Writes a single byte to the page in memory.

      • write

        void write​(int pos,
           byte[] buf,
           int off,
           int len)
        Writes to the given part of the page in memory.

      • equals

        public boolean equals​(java.lang.Object ob)
        Overrides:
        equals in class java.lang.Object