Class FileAllocator

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable, Allocator

    public class FileAllocator
    extends java.lang.Object
    implements Allocator
    The FileAllocator object is used to create buffers that can be written to the file system. This creates buffers as files if they are larger than the specified limit. This ensures that buffers of arbitrary large size can be created. All buffer sizes under the limit are created using byte arrays allocated on the executing VM heap. This ensures that optimal performance is maintained for buffers of reasonable size.
    Author:
    Niall Gallagher
    • Constructor Summary

      Constructors 
      Constructor Description
      FileAllocator()
      Constructor for the FileAllocator object.
      FileAllocator​(int limit)
      Constructor for the FileAllocator object.
      FileAllocator​(java.lang.String prefix)
      Constructor for the FileAllocator object.
      FileAllocator​(java.lang.String prefix, int limit)
      Constructor for the FileAllocator object.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      Buffer allocate()
      This will allocate a file buffer which will write data for the buffer to a file.
      Buffer allocate​(int size)
      This will allocate a file buffer which will write data for the buffer to a file.
      void close()
      This method is used to close the allocator so that resources that are occupied by the allocator can be freed.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Constructor Detail

      • FileAllocator

        public FileAllocator()
                      throws java.io.IOException
        Constructor for the FileAllocator object. This is used to create buffers in memory up to a threshold size. If a buffer is required over the threshold size then the data is written to a file, where it can be retrieved at a later point.
        Throws:
        java.io.IOException
      • FileAllocator

        public FileAllocator​(int limit)
                      throws java.io.IOException
        Constructor for the FileAllocator object. This is used to create buffers in memory up to a threshold size. If a buffer is required over the threshold size then the data is written to a file, where it can be retrieved at a later point.
        Parameters:
        limit - this is the maximum size for a heap buffer
        Throws:
        java.io.IOException
      • FileAllocator

        public FileAllocator​(java.lang.String prefix)
                      throws java.io.IOException
        Constructor for the FileAllocator object. This is used to create buffers in memory up to a threshold size. If a buffer is required over the threshold size then the data is written to a file, where it can be retrieved at a later point.
        Parameters:
        prefix - this is the file prefix for the file buffers
        Throws:
        java.io.IOException
      • FileAllocator

        public FileAllocator​(java.lang.String prefix,
                             int limit)
                      throws java.io.IOException
        Constructor for the FileAllocator object. This is used to create buffers in memory up to a threshold size. If a buffer is required over the threshold size then the data is written to a file, where it can be retrieved at a later point.
        Parameters:
        prefix - this is the file prefix for the file buffers
        limit - this is the maximum size for a heap buffer
        Throws:
        java.io.IOException
    • Method Detail

      • allocate

        public Buffer allocate()
                        throws java.io.IOException
        This will allocate a file buffer which will write data for the buffer to a file. Buffers allocated by this method can be of arbitrary size as data is appended directly to a temporary file. This ensures there is no upper limit for appended data.
        Specified by:
        allocate in interface Allocator
        Returns:
        a buffer which will write to a temporary file
        Throws:
        java.io.IOException
      • allocate

        public Buffer allocate​(int size)
                        throws java.io.IOException
        This will allocate a file buffer which will write data for the buffer to a file. Buffers allocated by this method can be of arbitrary size as data is appended directly to a temporary file. This ensures there is no upper limit for appended data. If the size required is less than the limit then the buffer is an in memory array which provides optimal performance.
        Specified by:
        allocate in interface Allocator
        Parameters:
        size - this is the size of the buffer to be created
        Returns:
        a buffer which will write to a created temporary file
        Throws:
        java.io.IOException
      • close

        public void close()
                   throws java.io.IOException
        This method is used to close the allocator so that resources that are occupied by the allocator can be freed. This will allow the allocator to be created and closed repeatedly in a single process without holding on to resources such as mapped file buffers or threads.
        Specified by:
        close in interface Allocator
        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Throws:
        java.io.IOException