Module com.aoapps.lang
Package com.aoapps.lang.util

Class BufferManager

java.lang.Object
com.aoapps.lang.util.BufferManager
public final class BufferManager extends Object

BufferManager manages a reusable pool of byte[] and char[] buffers. This avoids the repetitive allocation of memory for an operation that only needs a temporary buffer. The buffers are stored as ThreadLocal to maximize cache locality.

Do not use if intra-thread security is more important than performance.

The buffers are not necessarily cleared between invocations so the results of previous operations may be available to additional callers. On the scale of security versus performance, this is biased toward performance. However, being thread local there remains some control over the visibility of the data.

Buffers should not be passed between threads. Giving a thread a buffer you didn't get from it could result in a memory or information leak. Soft references are used to avoid full-on memory leaks, but keeping buffers to a single thread is optimal.

Under no circumstances should a buffer be released more than once. This may result in the buffer being allocated twice at the same time, with resulting data corruption.

The Java virtual machine has improved greatly over the years. However, we still believe this buffer management to be valuable to reduce garbage collection pressure. If this ever proves to not be the case, the implementation here can be simply changed to create new arrays on each use.

Author:
AO Industries, Inc.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    BUFFER_SIZE
    The size of buffers that are returned.

  • Method Summary

    Modifier and Type
    Method
    Description
    static long
    getByteBufferCreates()
    Gets the number of byte[] buffers instantiated.
    static long
    getByteBuffersCollected()
    Gets the number of byte[] buffers detected to have been garbage collected.
    static long
    getByteBufferUses()
    Gets the number of time byte[] buffers have been used.
    static long
    getByteBufferZeroFills()
    Gets the number of time byte[] buffers have been zero-filled on release.
    static byte[]
    getBytes()
    Gets a byte[] of length BUFFER_SIZE that may be temporarily used for any purpose.
    static long
    getCharBufferCreates()
    Gets the number of char[] buffers instantiated.
    static long
    getCharBuffersCollected()
    Gets the number of char[] buffers detected to have been garbage collected.
    static long
    getCharBufferUses()
    Gets the number of time char[] buffers have been used.
    static long
    getCharBufferZeroFills()
    Gets the number of time char[] buffers have been zero-filled on release.
    static char[]
    getChars()
    Gets a char[] of length BUFFER_SIZE that may be temporarily used for any purpose.
    static void
    release(byte[] buffer)
    Deprecated.
    May obtain greater performance by avoiding zero fill on non-sensitive data.
    static void
    release(byte[] buffer, boolean zeroFill)
    Releases a byte[] that was obtained by a call to getBytes.
    static void
    release(char[] buffer)
    Deprecated.
    May obtain greater performance by avoiding zero fill on non-sensitive data.
    static void
    release(char[] buffer, boolean zeroFill)
    Releases a char[] that was obtained by a call to getChars.

    Methods inherited from class java.lang.Object

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

  • Field Details

    • BUFFER_SIZE

      public static final int BUFFER_SIZE
      The size of buffers that are returned.
      See Also:

  • Method Details

    • getBytes

      public static byte[] getBytes()
      Gets a byte[] of length BUFFER_SIZE that may be temporarily used for any purpose. Once done with the buffer, release should be called, this is best accomplished in a finally block. The buffer is not necessarily zero-filled and may contain data from a previous use.

    • getChars

      public static char[] getChars()
      Gets a char[] of length BUFFER_SIZE that may be temporarily used for any purpose. Once done with the buffer, release should be called, this is best accomplished in a finally block. The buffer is not necessarily zero-filled and may contain data from a previous use.

    • release

      @Deprecated public static void release(byte[] buffer)
      Deprecated.
      May obtain greater performance by avoiding zero fill on non-sensitive data.

    • release

      public static void release(byte[] buffer, boolean zeroFill)
      Releases a byte[] that was obtained by a call to getBytes. A buffer must not be released more than once.
      Parameters:
      buffer - the byte[] to release
      zeroFill - if the data in the buffer may be sensitive, it is best to zero-fill the buffer on release.

    • release

      @Deprecated public static void release(char[] buffer)
      Deprecated.
      May obtain greater performance by avoiding zero fill on non-sensitive data.

    • release

      public static void release(char[] buffer, boolean zeroFill)
      Releases a char[] that was obtained by a call to getChars. A buffer must not be released more than once.
      Parameters:
      buffer - the char[] to release
      zeroFill - if the data in the buffer may be sensitive, it is best to zero-fill the buffer on release.

    • getByteBufferCreates

      public static long getByteBufferCreates()
      Gets the number of byte[] buffers instantiated.

    • getByteBufferUses

      public static long getByteBufferUses()
      Gets the number of time byte[] buffers have been used.

    • getByteBufferZeroFills

      public static long getByteBufferZeroFills()
      Gets the number of time byte[] buffers have been zero-filled on release.

    • getByteBuffersCollected

      public static long getByteBuffersCollected()
      Gets the number of byte[] buffers detected to have been garbage collected.

    • getCharBufferCreates

      public static long getCharBufferCreates()
      Gets the number of char[] buffers instantiated.

    • getCharBufferUses

      public static long getCharBufferUses()
      Gets the number of time char[] buffers have been used.

    • getCharBufferZeroFills

      public static long getCharBufferZeroFills()
      Gets the number of time char[] buffers have been zero-filled on release.

    • getCharBuffersCollected

      public static long getCharBuffersCollected()
      Gets the number of char[] buffers detected to have been garbage collected.