Package com.google.common.jimfs

Class HeapDisk

  • final class HeapDisk
extends java.lang.Object
    A resizable pseudo-disk acting as a shared space for storing file data. A disk allocates fixed size blocks of bytes to files as needed and may cache blocks that have been freed for reuse. A memory disk has a fixed maximum number of blocks it will allocate at a time (which sets the total "size" of the disk) and a maximum number of unused blocks it will cache for reuse at a time (which sets the minimum amount of space the disk will use once

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private int allocatedBlockCount
      The current total number of blocks that are currently allocated to files.
      (package private) RegularFile blockCache
      Cache of free blocks to be allocated to files.
      private int blockSize
      Fixed size of each block for this disk.
      private int maxBlockCount
      Maximum total number of blocks that the disk may contain at any time.
      private int maxCachedBlockCount
      Maximum total number of unused blocks that may be cached for reuse at any time.

    • Constructor Summary

      Constructors 
      Constructor Description
      HeapDisk​(int blockSize, int maxBlockCount, int maxCachedBlockCount)
      Creates a new disk with the given blockSize, maxBlockCount and maxCachedBlockCount.
      HeapDisk​(Configuration config)
      Creates a new disk using settings from the given configuration.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void allocate​(RegularFile file, int count)
      Allocates the given number of blocks and adds them to the given file.
      int blockSize()
      Returns the size of blocks created by this disk.
      private RegularFile createBlockCache​(int maxCachedBlockCount)  
      void free​(RegularFile file)
      Frees all blocks in the given file.
      void free​(RegularFile file, int count)
      Frees the last count blocks from the given file.
      long getTotalSpace()
      Returns the total size of this disk.
      long getUnallocatedSpace()
      Returns the current number of unallocated bytes on this disk.
      private static int toBlockCount​(long size, int blockSize)
      Returns the nearest multiple of blockSize that is <= size.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • blockSize

        private final int blockSize
        Fixed size of each block for this disk.

      • maxBlockCount

        private final int maxBlockCount
        Maximum total number of blocks that the disk may contain at any time.

      • maxCachedBlockCount

        private final int maxCachedBlockCount
        Maximum total number of unused blocks that may be cached for reuse at any time.

      • blockCache

        final RegularFile blockCache
        Cache of free blocks to be allocated to files. While this is stored as a file, it isn't used like a normal file: only the methods for accessing its blocks are used.

      • allocatedBlockCount

        private int allocatedBlockCount
        The current total number of blocks that are currently allocated to files.

    • Constructor Detail

      • HeapDisk

        public HeapDisk​(Configuration config)
        Creates a new disk using settings from the given configuration.

      • HeapDisk

        public HeapDisk​(int blockSize,
                int maxBlockCount,
                int maxCachedBlockCount)
        Creates a new disk with the given blockSize, maxBlockCount and maxCachedBlockCount.

    • Method Detail

      • toBlockCount

        private static int toBlockCount​(long size,
                                int blockSize)
        Returns the nearest multiple of blockSize that is <= size.

      • createBlockCache

        private RegularFile createBlockCache​(int maxCachedBlockCount)

      • blockSize

        public int blockSize()
        Returns the size of blocks created by this disk.

      • getTotalSpace

        public long getTotalSpace()
        Returns the total size of this disk. This is the maximum size of the disk and does not reflect the amount of data currently allocated or cached.

      • getUnallocatedSpace

        public long getUnallocatedSpace()
        Returns the current number of unallocated bytes on this disk. This is the maximum number of additional bytes that could be allocated and does not reflect the number of bytes currently actually cached in the disk.

      • allocate

        public void allocate​(RegularFile file,
                     int count)
              throws java.io.IOException
        Allocates the given number of blocks and adds them to the given file.
        Throws:
        java.io.IOException

      • free

        public void free​(RegularFile file)
        Frees all blocks in the given file.

      • free

        public void free​(RegularFile file,
                 int count)
        Frees the last count blocks from the given file.