/**
* Returns the block of size equal or greater than current size for reallocation which is marked
* as free.
*
* @param capacity
* @return null when it fails to search a valid sized block
*/
private Pointer firstMatch(int capacity) {
synchronized (pointers) {
for (Pointer ptr : pointers) {
// Find a frame with right size. Comapaction problems to be dealt.
if (ptr.isFree() && (ptr.getEnd() - ptr.getStart()) > capacity) {
return ptr;
}
}
}
return null;
}
/*
* (non-Javadoc)
*
* @see com.prashant.memory.MemoryBuffer#update(com.prashant.memory.Pointer, byte[], int)
*/
public void update(Pointer pointer, byte[] payload, int offset)
throws DMFrameLimitExcededException {
if (pointer.getStart() + offset + payload.length - 1 <= pointer.getEnd()) {
ByteBuffer buf;
synchronized (buffer) {
buf = buffer.duplicate();
}
buf.position(pointer.getStart() + offset);
buf.put(payload);
return;
}
throw new DMFrameLimitExcededException(
"Trying to write to a position out of bounds for this pointer.", null);
}
/**
* Resize an existing block to new capacity by slicing the <code>Pointer</code> pointed to by
* existing pointer. The new <code>Pointer</code> is a slice present before the existing.
*
* @param existing points to existing Pointer(referring existing block).
* @param capacity to be resized to.
* @return Pointer to resized block.
*/
private Pointer slice(Pointer existing, int capacity) {
if ((existing.getEnd() - existing.getStart()) == capacity + 1 && existing.isFree()) {
return existing;
}
Pointer fresh = new Pointer();
fresh.setBlockNumber(existing.getBlockNumber());
fresh.setStart(existing.getStart());
fresh.setEnd(fresh.getStart() + capacity);
fresh.setFree(true);
fresh.setPrev(existing.getPrev());
existing.setPrev(fresh);
fresh.setNext(existing);
existing.setStart(existing.getStart() + (capacity + 1));
return fresh;
}
/*
* (non-Javadoc)
*
* @see com.prashant.memory.MemoryBuffer#retrieve(com.prashant.memory.Pointer, int, int)
*/
public byte[] retrieve(Pointer pointer, int offset, int len) throws DMFrameLimitExcededException {
int checkLength = pointer.getStart() + offset + len;
ByteBuffer buf = null;
if (checkLength <= pointer.getEnd()) {
synchronized (buffer) {
buf = buffer.duplicate();
}
buf.position(pointer.getStart() + offset);
final byte[] swp = new byte[len];
buf.get(swp);
return swp;
}
throw new DMFrameLimitExcededException(
"Trying to read to a position out of bounds for this pointer.", null);
}
/*
* (non-Javadoc)
*
* @see com.prashant.memory.MemoryBuffer#free(com.prashant.memory.Pointer)
*/
public long free(Pointer pointer2free) {
used.addAndGet(-(pointer2free.getEnd() - pointer2free.getStart()));
freeAndMerge(pointer2free);
return pointer2free.getEnd() - pointer2free.getStart();
}
/*
* (non-Javadoc)
*
* @see com.prashant.memory.MemoryBuffer#retrieve(com.prashant.memory.Pointer)
*/
public byte[] retrieve(Pointer pointer) throws DMFrameLimitExcededException {
return retrieve(pointer, 0, pointer.getEnd() - pointer.getStart());
}