OffHeapMemory (Tools based on sun.misc.Unsafe 1.4.4 API)

java.lang.Object
- com.alexkasko.unsafe.offheap.OffHeapMemory

Direct Known Subclasses:

DirectOffHeapMemory, OnHeapMemory, UnsafeOffHeapMemory
```
public abstract class OffHeapMemory
extends Object
```
Allocates an area of off-heap memory that is not a subject to GC. Default implementation uses sun.misc.Unsafe, with all operations guarded with assert boundary checks. With assert enabled in runtime (-ea java switch) AssertionError will be thrown on illegal input. Without assertions illegal input will crash JVM.
Fallback implementation uses ByteBuffer.allocateDirect(int) that may (OpenJDK) or may not (Dalvik) use sun.misc.Unsafe under the hood. Note: only unsafe implementation (allocateMemoryUnsafe(long)) may use memory areas longer than Integer.MAX_VALUE
Unsafe implementation uses native endianness (LE on most platforms). Fallback implementation uses Little Endian byte order.
Provides methods to access allocated memory. More complex data structures (off-heap quasi-objects) may be constructed wrapping this class, see OffHeapLongArray.
Memory may be freed manually calling free() (thread-safe and may be called safely more than one time), or it will be freed when OffHeapMemory instance itself will be garbage collected.

Author:

alexkasko Date: 1/14/13

Constructor Summary

Constructors
Constructor and Description

OffHeapMemory()

Constructors
Constructor and Description
`OffHeapMemory()`

Method Summary

Methods
Modifier and Type	Method and Description
`static OffHeapMemory`	`allocateMemory(long bytes)` Allocates memory using `sun.misc.Unsafe` if it's proper implementation is available.
`static OffHeapMemory`	`allocateMemoryDirect(long bytes)` Allocates memory using `ByteBuffer.allocateDirect(int)`
`static OffHeapMemory`	`allocateMemoryOnHeap(ByteArrayTool bt, long bytes)` Allocates memory using byte array
`static OffHeapMemory`	`allocateMemoryUnsafe(long bytes)` Allocates memory using `sun.misc.Unsafe`
`abstract OffHeapMemory`	`clone()` Creates new instance of `OffHeapMemory` and copies there current instance contents
`abstract void`	`copy(long offset, OffHeapMemory destination, long destOffset, long bytes)` Copies memory from this instance's area into another instance's area
`abstract void`	`free()` Frees allocated memory, may be called multiple times from any thread
`abstract void`	`get(long offset, byte[] buffer)` Copies part of memory area into byte array
`abstract void`	`get(long offset, byte[] buffer, int bufferOffset, int bytes)` Copies part of memory area into byte array
`abstract byte`	`getByte(long offset)` Gets byte from memory area
`abstract int`	`getInt(long offset)` Gets four bytes from memory area as int
`abstract long`	`getLong(long offset)` Gets eight bytes from memory area as long
`abstract short`	`getShort(long offset)` Gets two bytes from memory area as short
`abstract short`	`getUnsignedByte(long offset)` Gets one byte (stored as one signed byte), converts it to unsigned and returns it as short
`abstract long`	`getUnsignedInt(long offset)` Gets unsigned int (stored as 4 bytes) and returns it as long
`abstract int`	`getUnsignedShort(long offset)` Gets unsigned short from memory area (stored as two bytes) and returns it as int
`abstract boolean`	`isUnsafe()` Whether current implementation uses `sun.misc.Unsafe`
`abstract long`	`length()` Returns length of allocated memory area
`abstract void`	`put(long offset, byte[] buffer)` Copies byte array contents into memory area
`abstract void`	`put(long offset, byte[] buffer, int bufferOffset, int bytes)` Copies byte array contents into memory area
`abstract void`	`putByte(long offset, byte value)` Puts byte into memory area
`abstract void`	`putInt(long offset, int value)` Puts int into memory area as four bytes
`abstract void`	`putLong(long offset, long value)` Puts long into memory area as eight bytes
`abstract void`	`putShort(long offset, short value)` Puts short into memory area as two bytes
`abstract void`	`putUnsignedByte(long offset, short value)` Puts short with value from 0 to 255 inclusive into memory area as one signed byte
`abstract void`	`putUnsignedInt(long offset, long value)` Puts long value from 0 to 4294967295 inclusive into memory area as four bytes
`abstract void`	`putUnsignedShort(long offset, int value)` Puts int with value from 0 to 65535 inclusive into memory are as two bytes

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - OffHeapMemory
```
public OffHeapMemory()
```
- Method Detail
  - allocateMemory
```
public static OffHeapMemory allocateMemory(long bytes)
```
    Allocates memory using sun.misc.Unsafe if it's proper implementation is available. Allocates using ByteBuffer.allocateDirect(int) otherwise.
    
    Parameters:
    bytes - amount of memory to allocate
    
    Returns:
    OffHeapMemory instance
  - allocateMemoryUnsafe
```
public static OffHeapMemory allocateMemoryUnsafe(long bytes)
                                          throws Exception
```
    Allocates memory using sun.misc.Unsafe
    
    Parameters:
    bytes - amount of memory to allocate
    
    Returns:
    OffHeapMemory instance
    
    Throws:
    
    Exception - if proper sun.misc.Unsafe not available
  - allocateMemoryDirect
```
public static OffHeapMemory allocateMemoryDirect(long bytes)
```
    Allocates memory using ByteBuffer.allocateDirect(int)
    
    Parameters:
    bytes - amount of memory to allocate
    
    Returns:
    OffHeapMemory instance
  - allocateMemoryOnHeap
```
public static OffHeapMemory allocateMemoryOnHeap(ByteArrayTool bt,
                                 long bytes)
```
    Allocates memory using byte array
    
    Parameters:
    bytes - amount of memory to allocate
    bt - byte array tool to use for on-heap memory management
    
    Returns:
    OffHeapMemory instance
  - isUnsafe
```
public abstract boolean isUnsafe()
```
    Whether current implementation uses sun.misc.Unsafe
    
    Returns:
    whether unsafe
  - length
```
public abstract long length()
```
    Returns length of allocated memory area
    
    Returns:
    length of allocated memory area
  - free
```
public abstract void free()
```
    Frees allocated memory, may be called multiple times from any thread
  - put
```
public abstract void put(long offset,
       byte[] buffer,
       int bufferOffset,
       int bytes)
```
    Copies byte array contents into memory area
    
    Parameters:
    offset - memory area offset
    buffer - source byte array
    bufferOffset - position in byte array
    bytes - bytes length to copy
  - put
```
public abstract void put(long offset,
       byte[] buffer)
```
    Copies byte array contents into memory area
    
    Parameters:
    offset - memory area offset
    buffer - source byte array
  - get
```
public abstract void get(long offset,
       byte[] buffer,
       int bufferOffset,
       int bytes)
```
    Copies part of memory area into byte array
    
    Parameters:
    offset - memory area offset
    buffer - destination byte array
    bufferOffset - position in byte array
    bytes - bytes length to copy
  - get
```
public abstract void get(long offset,
       byte[] buffer)
```
    Copies part of memory area into byte array
    
    Parameters:
    offset - memory area offset
    buffer - destination byte array
  - getByte
```
public abstract byte getByte(long offset)
```
    Gets byte from memory area
    
    Parameters:
    offset - memory area offset
    
    Returns:
    byte value
  - putByte
```
public abstract void putByte(long offset,
           byte value)
```
    Puts byte into memory area
    
    Parameters:
    offset - memory area offset
    value - byte value
  - getUnsignedByte
```
public abstract short getUnsignedByte(long offset)
```
    Gets one byte (stored as one signed byte), converts it to unsigned and returns it as short
    
    Parameters:
    offset - memory area offset
    
    Returns:
    unsigned byte as short
  - putUnsignedByte
```
public abstract void putUnsignedByte(long offset,
                   short value)
```
    Puts short with value from 0 to 255 inclusive into memory area as one signed byte
    
    Parameters:
    offset - memory area offset
    value - unsigned byte as short
  - getShort
```
public abstract short getShort(long offset)
```
    Gets two bytes from memory area as short
    
    Parameters:
    offset - memory area offset
    
    Returns:
    short value
  - putShort
```
public abstract void putShort(long offset,
            short value)
```
    Puts short into memory area as two bytes
    
    Parameters:
    offset - memory area offset
    value - short value
  - getUnsignedShort
```
public abstract int getUnsignedShort(long offset)
```
    Gets unsigned short from memory area (stored as two bytes) and returns it as int
    
    Parameters:
    offset - memory area offset
    
    Returns:
    unsigned short as int
  - putUnsignedShort
```
public abstract void putUnsignedShort(long offset,
                    int value)
```
    Puts int with value from 0 to 65535 inclusive into memory are as two bytes
    
    Parameters:
    offset - memory area offset
    value - unsigned short as int
  - getInt
```
public abstract int getInt(long offset)
```
    Gets four bytes from memory area as int
    
    Parameters:
    offset - memory area offset
    
    Returns:
    int value
  - putInt
```
public abstract void putInt(long offset,
          int value)
```
    Puts int into memory area as four bytes
    
    Parameters:
    offset - memory area offset
    value - int value
  - getUnsignedInt
```
public abstract long getUnsignedInt(long offset)
```
    Gets unsigned int (stored as 4 bytes) and returns it as long
    
    Parameters:
    offset - memory area offset
    
    Returns:
    unsigned int as long
  - putUnsignedInt
```
public abstract void putUnsignedInt(long offset,
                  long value)
```
    Puts long value from 0 to 4294967295 inclusive into memory area as four bytes
    
    Parameters:
    offset - memory area offset
    value - unsigned int as long
  - getLong
```
public abstract long getLong(long offset)
```
    Gets eight bytes from memory area as long
    
    Parameters:
    offset - memory area offset
    
    Returns:
    long value
  - putLong
```
public abstract void putLong(long offset,
           long value)
```
    Puts long into memory area as eight bytes
    
    Parameters:
    offset - memory area offset
    value - long value
  - copy
```
public abstract void copy(long offset,
        OffHeapMemory destination,
        long destOffset,
        long bytes)
```
    Copies memory from this instance's area into another instance's area
    
    Parameters:
    offset - this memory area offset
    destination - destination memory area
    destOffset - destination memory area offset
    bytes - memory length in bytes to copy
  - clone
```
public abstract OffHeapMemory clone()
```
    Creates new instance of OffHeapMemory and copies there current instance contents
    
    Overrides:
    
    clone in class Object
    
    Returns:
    new instance of OffHeapMemory

Class OffHeapMemory

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

OffHeapMemory

Method Detail

allocateMemory

allocateMemoryUnsafe

allocateMemoryDirect

allocateMemoryOnHeap

isUnsafe

length

free

put

put

get

get

getByte

putByte

getUnsignedByte

putUnsignedByte

getShort

putShort

getUnsignedShort

putUnsignedShort

getInt

putInt

getUnsignedInt

putUnsignedInt

getLong

putLong

copy

clone