org.lmdbjava

Class BufferProxy<T>

java.lang.Object

org.lmdbjava.BufferProxy<T>

Type Parameters:

T - buffer type

Direct Known Subclasses:

ByteArrayProxy, DirectBufferProxy

public abstract class BufferProxy<T>
extends java.lang.Object

The strategy for mapping memory address to a given buffer type.

The proxy is passed to the Env.create(org.lmdbjava.BufferProxy) method and is subsequently used by every Txn, Dbi and Cursor associated with the Env.

Field Summary

Fields

Modifier and Type	Field and Description
protected static int	MDB_VAL_STRUCT_SIZE Size of a MDB_val pointer in bytes.
protected static int	STRUCT_FIELD_OFFSET_DATA Offset from a pointer of the MDB_val.mv_data field.
protected static int	STRUCT_FIELD_OFFSET_SIZE Offset from a pointer of the MDB_val.mv_size field.

Constructor Summary

Constructors

Constructor and Description
BufferProxy()

Method Summary

Modifier and Type	Method and Description
protected abstract T	allocate() Allocate a new buffer suitable for passing to out(java.lang.Object, jnr.ffi.Pointer, long).
protected abstract int	compare(T o1, T o2) Compare the two buffers.
protected abstract void	deallocate(T buff) Deallocate a buffer that was previously provided by allocate().
protected abstract byte[]	getBytes(T buffer) Obtain a copy of the bytes contained within the passed buffer.
protected abstract void	in(T buffer, int size, jnr.ffi.Pointer ptr, long ptrAddr) Called when the MDB_val should be set to reflect the passed buffer.
protected abstract void	in(T buffer, jnr.ffi.Pointer ptr, long ptrAddr) Called when the MDB_val should be set to reflect the passed buffer.
protected abstract T	out(T buffer, jnr.ffi.Pointer ptr, long ptrAddr) Called when the MDB_val may have changed and the passed buffer should be modified to reflect the new MDB_val.

Methods inherited from class java.lang.Object

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

Field Detail

MDB_VAL_STRUCT_SIZE

protected static final int MDB_VAL_STRUCT_SIZE

Size of a MDB_val pointer in bytes.

See Also:

Constant Field Values

STRUCT_FIELD_OFFSET_DATA

protected static final int STRUCT_FIELD_OFFSET_DATA

Offset from a pointer of the MDB_val.mv_data field.

See Also:

Constant Field Values

STRUCT_FIELD_OFFSET_SIZE

protected static final int STRUCT_FIELD_OFFSET_SIZE

Offset from a pointer of the MDB_val.mv_size field.

See Also:

Constant Field Values

Constructor Detail

BufferProxy

public BufferProxy()

Method Detail

allocate

protected abstract T allocate()

Allocate a new buffer suitable for passing to out(java.lang.Object, jnr.ffi.Pointer, long).

Returns:

a buffer for passing to the out method

compare

protected abstract int compare(T o1,
                               T o2)

Compare the two buffers.

Implemented as a protected method to discourage use of the buffer proxy in collections etc (given by design it wraps a temporary value only).

Parameters:

o1 - left operand

o2 - right operand

Returns:

as per Comparable

deallocate

protected abstract void deallocate(T buff)

Deallocate a buffer that was previously provided by allocate().

Parameters:

buff - the buffer to deallocate (required)

getBytes

protected abstract byte[] getBytes(T buffer)

Obtain a copy of the bytes contained within the passed buffer.

Parameters:

buffer - a non-null buffer created by this proxy instance

Returns:

a copy of the bytes this buffer is currently representing

in

protected abstract void in(T buffer,
                           jnr.ffi.Pointer ptr,
                           long ptrAddr)

Called when the MDB_val should be set to reflect the passed buffer. This buffer will have been created by end users, not allocate().

Parameters:

buffer - the buffer to write to MDB_val

ptr - the pointer to the MDB_val

ptrAddr - the address of the MDB_val pointer

in

protected abstract void in(T buffer,
                           int size,
                           jnr.ffi.Pointer ptr,
                           long ptrAddr)

Called when the MDB_val should be set to reflect the passed buffer.

Parameters:

buffer - the buffer to write to MDB_val

size - the buffer size to write to MDB_val

ptr - the pointer to the MDB_val

ptrAddr - the address of the MDB_val pointer

out

protected abstract T out(T buffer,
                         jnr.ffi.Pointer ptr,
                         long ptrAddr)

Called when the MDB_val may have changed and the passed buffer should be modified to reflect the new MDB_val.

Parameters:

buffer - the buffer to write to MDB_val

ptr - the pointer to the MDB_val

ptrAddr - the address of the MDB_val pointer

Returns:

the buffer for MDB_val