/** Parse the command from the byte buffer. */
private boolean unroll(ByteBuffer b, Map<String, Integer> manifest) throws KevaDBException {
long time = b.getLong();
// Check if there are any sstables that are older than
// this WAL entry. If so, we can safely skip this entry since
// we know the results have already been persisted.
if (manifest != null) {
for (String uuid : manifest.keySet()) {
SSTable table = db.getDiskService().getSSTable(db, uuid, manifest.get(uuid));
if (table.getModificationTime() <= time) {
return true;
}
}
}
// Check if this is a valid entry.
short magic = b.getShort();
if (magic != MAGIC_NUMBER) {
return false;
}
// Read in the various lengths.
int keyLength = b.getInt();
int valueLength = b.getInt();
int compressedLength = b.getInt();
int optionLength = b.getInt();
// Instantiate the various buffers.
byte[] keyBuffer = new byte[keyLength];
byte[] valueBuffer = new byte[valueLength];
byte[] compressedBuffer = new byte[compressedLength];
b.get(keyBuffer);
b.get(compressedBuffer);
// Now we need to decompress the value buffer.
decompressor.decompress(compressedBuffer, 0, valueBuffer, 0, valueLength);
// Now get the write options.
WriteOptions options = null;
if (optionLength > 0) {
byte[] optionBuffer = new byte[optionLength];
b.get(optionBuffer);
options = OptionsSerializer.writeOptionsFromBytes(optionBuffer);
}
TableKey key = TableKey.fromBytes(ByteBuffer.wrap(keyBuffer));
TableValue value = TableValueFactory.fromBytes(valueBuffer, valueLength);
// Now put the value into the DB.
db.put(key, value, options);
return true;
}
/** Serialize the write. */
private ByteBuffer serialize(
final TableKey key, final TableValue value, final WriteOptions options) {
int size;
int optionSize = 0;
byte[] optionBuf = null;
byte[] keyData = key.serialize();
byte[] valueData = value.getBytes();
int maxCompressed = compressor.maxCompressedLength(valueData.length);
byte[] compressed = new byte[maxCompressed];
int actualCompressed =
compressor.compress(valueData, 0, valueData.length, compressed, 0, maxCompressed);
size =
(Short.SIZE / 8)
+ 4 * (Integer.SIZE / 8)
+ (Long.SIZE / 8)
+ keyData.length
+ actualCompressed;
if (options != null) {
optionBuf = OptionsSerializer.getBytes(options);
if (optionBuf != null) {
optionSize = optionBuf.length;
} else {
optionSize = 0;
}
size += optionSize;
}
ByteBuffer buf = ByteBuffer.allocateDirect(size);
buf.putLong(System.currentTimeMillis());
buf.putShort(MAGIC_NUMBER); // Magic number.
buf.putInt(keyData.length);
buf.putInt(valueData.length);
buf.putInt(actualCompressed);
buf.putInt(optionSize);
buf.put(keyData);
buf.put(compressed, 0, actualCompressed);
if (optionBuf != null) {
buf.put(optionBuf);
}
return buf;
}
