import java.nio.BufferOverflowException;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.zip.CRC32;
-import java.util.zip.Checksum;
/**
* Segment writer.
*
* @author <a href="http://github.com/kuujo">Jordan Halterman</a>
*/
-class FileChannelJournalSegmentWriter<E> implements JournalWriter<E> {
+final class FileChannelJournalSegmentWriter<E> extends JournalSegmentWriter<E> {
+ private static final ByteBuffer ZERO_ENTRY_HEADER = ByteBuffer.wrap(new byte[Integer.BYTES + Integer.BYTES]);
+
private final FileChannel channel;
- private final JournalSegment<E> segment;
- private final int maxEntrySize;
- private final JournalIndex index;
- private final JournalSerdes namespace;
private final ByteBuffer memory;
- private final long firstIndex;
private Indexed<E> lastEntry;
+ private long currentPosition;
FileChannelJournalSegmentWriter(
FileChannel channel,
int maxEntrySize,
JournalIndex index,
JournalSerdes namespace) {
+ super(segment, maxEntrySize, index, namespace);
this.channel = channel;
- this.segment = segment;
- this.maxEntrySize = maxEntrySize;
- this.index = index;
this.memory = ByteBuffer.allocate((maxEntrySize + Integer.BYTES + Integer.BYTES) * 2);
memory.limit(0);
- this.namespace = namespace;
- this.firstIndex = segment.index();
reset(0);
}
+ @Override
+ MappedByteBuffer buffer() {
+ return null;
+ }
+
@Override
public void reset(long index) {
long nextIndex = firstIndex;
// Clear the buffer indexes.
+ currentPosition = JournalSegmentDescriptor.BYTES;
+
try {
- channel.position(JournalSegmentDescriptor.BYTES);
- memory.clear().flip();
-
- // Record the current buffer position.
- long position = channel.position();
-
- // Read more bytes from the segment if necessary.
- if (memory.remaining() < maxEntrySize) {
- memory.clear();
- channel.read(memory);
- channel.position(position);
- memory.flip();
- }
+ // Clear memory buffer and read fist chunk
+ memory.clear();
+ channel.read(memory, JournalSegmentDescriptor.BYTES);
+ memory.flip();
// Read the entry length.
- memory.mark();
int length = memory.getInt();
// If the length is non-zero, read the entry.
// Read the checksum of the entry.
final long checksum = memory.getInt() & 0xFFFFFFFFL;
+ // Slice off the entry's bytes
+ final ByteBuffer entryBytes = memory.slice();
+ entryBytes.limit(length);
+
// Compute the checksum for the entry bytes.
- final Checksum crc32 = new CRC32();
- crc32.update(memory.array(), memory.position(), length);
-
- // If the stored checksum equals the computed checksum, return the entry.
- if (checksum == crc32.getValue()) {
- int limit = memory.limit();
- memory.limit(memory.position() + length);
- final E entry = namespace.deserialize(memory);
- memory.limit(limit);
- lastEntry = new Indexed<>(nextIndex, entry, length);
- this.index.index(nextIndex, (int) position);
- nextIndex++;
- } else {
+ final CRC32 crc32 = new CRC32();
+ crc32.update(entryBytes);
+
+ // If the stored checksum does not equal the computed checksum, do not proceed further
+ if (checksum != crc32.getValue()) {
break;
}
+ entryBytes.rewind();
+ final E entry = namespace.deserialize(entryBytes);
+ lastEntry = new Indexed<>(nextIndex, entry, length);
+ this.index.index(nextIndex, (int) currentPosition);
+ nextIndex++;
+
// Update the current position for indexing.
- position = channel.position() + memory.position();
+ currentPosition = currentPosition + Integer.BYTES + Integer.BYTES + length;
+ memory.position(memory.position() + length);
// Read more bytes from the segment if necessary.
if (memory.remaining() < maxEntrySize) {
- channel.position(position);
memory.clear();
- channel.read(memory);
- channel.position(position);
+ channel.read(memory, currentPosition);
memory.flip();
}
- memory.mark();
length = memory.getInt();
}
-
- // Reset the buffer to the previous mark.
- channel.position(channel.position() + memory.reset().position());
} catch (BufferUnderflowException e) {
- try {
- channel.position(channel.position() + memory.reset().position());
- } catch (IOException e2) {
- throw new StorageException(e2);
- }
+ // No-op, position is only updated on success
} catch (IOException e) {
throw new StorageException(e);
}
}
}
- /**
- * Returns the size of the underlying buffer.
- *
- * @return The size of the underlying buffer.
- */
- public long size() {
- try {
- return channel.position();
- } catch (IOException e) {
- throw new StorageException(e);
- }
- }
-
- /**
- * Returns a boolean indicating whether the segment is empty.
- *
- * @return Indicates whether the segment is empty.
- */
- public boolean isEmpty() {
- return lastEntry == null;
- }
-
- /**
- * Returns a boolean indicating whether the segment is full.
- *
- * @return Indicates whether the segment is full.
- */
- public boolean isFull() {
- return size() >= segment.descriptor().maxSegmentSize()
- || getNextIndex() - firstIndex >= segment.descriptor().maxEntries();
- }
-
- /**
- * Returns the first index written to the segment.
- */
- public long firstIndex() {
- return firstIndex;
- }
-
@Override
public void append(Indexed<E> entry) {
final long nextIndex = getNextIndex();
// Store the entry index.
final long index = getNextIndex();
+ // Serialize the entry.
+ memory.clear();
+ memory.position(Integer.BYTES + Integer.BYTES);
try {
- // Serialize the entry.
- memory.clear();
- memory.position(Integer.BYTES + Integer.BYTES);
- try {
- namespace.serialize(entry, memory);
- } catch (KryoException e) {
- throw new StorageException.TooLarge("Entry size exceeds maximum allowed bytes (" + maxEntrySize + ")");
- }
- memory.flip();
+ namespace.serialize(entry, memory);
+ } catch (KryoException e) {
+ throw new StorageException.TooLarge("Entry size exceeds maximum allowed bytes (" + maxEntrySize + ")");
+ }
+ memory.flip();
- final int length = memory.limit() - (Integer.BYTES + Integer.BYTES);
+ final int length = memory.limit() - (Integer.BYTES + Integer.BYTES);
- // Ensure there's enough space left in the buffer to store the entry.
- long position = channel.position();
- if (segment.descriptor().maxSegmentSize() - position < length + Integer.BYTES + Integer.BYTES) {
- throw new BufferOverflowException();
- }
+ // Ensure there's enough space left in the buffer to store the entry.
+ if (segment.descriptor().maxSegmentSize() - currentPosition < length + Integer.BYTES + Integer.BYTES) {
+ throw new BufferOverflowException();
+ }
- // If the entry length exceeds the maximum entry size then throw an exception.
- if (length > maxEntrySize) {
- throw new StorageException.TooLarge("Entry size " + length + " exceeds maximum allowed bytes (" + maxEntrySize + ")");
- }
+ // If the entry length exceeds the maximum entry size then throw an exception.
+ if (length > maxEntrySize) {
+ throw new StorageException.TooLarge("Entry size " + length + " exceeds maximum allowed bytes (" + maxEntrySize + ")");
+ }
+
+ // Compute the checksum for the entry.
+ final CRC32 crc32 = new CRC32();
+ crc32.update(memory.array(), Integer.BYTES + Integer.BYTES, memory.limit() - (Integer.BYTES + Integer.BYTES));
+ final long checksum = crc32.getValue();
- // Compute the checksum for the entry.
- final Checksum crc32 = new CRC32();
- crc32.update(memory.array(), Integer.BYTES + Integer.BYTES, memory.limit() - (Integer.BYTES + Integer.BYTES));
- final long checksum = crc32.getValue();
-
- // Create a single byte[] in memory for the entire entry and write it as a batch to the underlying buffer.
- memory.putInt(0, length);
- memory.putInt(Integer.BYTES, (int) checksum);
- channel.write(memory);
-
- // Update the last entry with the correct index/term/length.
- Indexed<E> indexedEntry = new Indexed<>(index, entry, length);
- this.lastEntry = indexedEntry;
- this.index.index(index, (int) position);
- return (Indexed<T>) indexedEntry;
+ // Create a single byte[] in memory for the entire entry and write it as a batch to the underlying buffer.
+ memory.putInt(0, length);
+ memory.putInt(Integer.BYTES, (int) checksum);
+ try {
+ channel.write(memory, currentPosition);
} catch (IOException e) {
throw new StorageException(e);
}
- }
- @Override
- public void commit(long index) {
+ // Update the last entry with the correct index/term/length.
+ Indexed<E> indexedEntry = new Indexed<>(index, entry, length);
+ this.lastEntry = indexedEntry;
+ this.index.index(index, (int) currentPosition);
+ currentPosition = currentPosition + Integer.BYTES + Integer.BYTES + length;
+ return (Indexed<T>) indexedEntry;
}
@Override
// Reset the last entry.
lastEntry = null;
- try {
- // Truncate the index.
- this.index.truncate(index);
+ // Truncate the index.
+ this.index.truncate(index);
+ try {
if (index < segment.index()) {
- channel.position(JournalSegmentDescriptor.BYTES);
- channel.write(zero());
- channel.position(JournalSegmentDescriptor.BYTES);
+ // Reset the writer to the first entry.
+ currentPosition = JournalSegmentDescriptor.BYTES;
} else {
// Reset the writer to the given index.
reset(index);
-
- // Zero entries after the given index.
- long position = channel.position();
- channel.write(zero());
- channel.position(position);
}
+
+ // Zero the entry header at current channel position.
+ channel.write(ZERO_ENTRY_HEADER.asReadOnlyBuffer(), currentPosition);
} catch (IOException e) {
throw new StorageException(e);
}
}
- /**
- * Returns a zeroed out byte buffer.
- */
- private ByteBuffer zero() {
- memory.clear();
- for (int i = 0; i < memory.limit(); i++) {
- memory.put(i, (byte) 0);
- }
- return memory;
- }
-
@Override
public void flush() {
try {
Code Review / controller.git / blobdiff