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SirixDB is a hybrid on-disk and in-memory document oriented, versioned database system. It has a lightweight buffer manager, stores everything in a huge persistent and durable tree and allows efficient reconstruction of every revision. Furthermore, SirixDB implements change tracking, diffing and supports time travel queries.
package io.sirix.index.art;
import java.util.Arrays;
class Node48 extends InnerNode {
/*
48 * 8 (child pointers) + 256 = 640 bytes
*/
static final int NODE_SIZE = 48;
static final int KEY_INDEX_SIZE = 256;
// for partial keys of one byte size, you index directly into this array to find the
// array index of the child pointer array
// the index value can only be between 0 and 47 (to index into the child pointer array)
private final byte[] keyIndex = new byte[KEY_INDEX_SIZE];
// so that when you use the partial key to index into keyIndex,
// and you see a -1, you know there's no mapping for this key
static final byte ABSENT = -1;
Node48(Node16 node) {
super(node, NODE_SIZE);
assert node.isFull();
Arrays.fill(keyIndex, ABSENT);
byte[] keys = node.getKeys();
Node[] children = node.getChildren();
for (int i = 0; i < Node16.NODE_SIZE; i++) {
byte key = BinaryComparableUtils.signed(keys[i]);
int index = Byte.toUnsignedInt(key);
keyIndex[index] = (byte) i;
this.children[i] = children[i];
// update up link
replaceUplink(this, this.children[i]);
}
}
Node48(Node256 node256) {
super(node256, NODE_SIZE);
assert node256.shouldShrink();
Arrays.fill(keyIndex, ABSENT);
Node[] children = node256.getChildren();
byte j = 0;
for (int i = 0; i < Node256.NODE_SIZE; i++) {
if (children[i] != null) {
keyIndex[i] = j;
this.children[j] = children[i];
replaceUplink(this, this.children[j]);
j++;
}
}
assert j == NODE_SIZE;
}
@Override
public Node findChild(byte partialKey) {
byte index = keyIndex[Byte.toUnsignedInt(partialKey)];
if (index == ABSENT) {
return null;
}
assert index >= 0 && index <= 47;
return children[index];
}
@Override
public void addChild(byte partialKey, Node child) {
assert !isFull();
int index = Byte.toUnsignedInt(partialKey);
assert keyIndex[index] == ABSENT;
// find a null place, left fragmented by a removeChild or has always been null
byte insertPosition = 0;
for (; this.children[insertPosition] != null && insertPosition < NODE_SIZE; insertPosition++) ;
this.children[insertPosition] = child;
keyIndex[index] = insertPosition;
noOfChildren++;
createUplink(this, child, partialKey);
}
@Override
public void replace(byte partialKey, Node newChild) {
byte index = keyIndex[Byte.toUnsignedInt(partialKey)];
assert index >= 0 && index <= 47;
children[index] = newChild;
createUplink(this, newChild, partialKey);
}
@Override
public void removeChild(byte partialKey) {
assert !shouldShrink();
int index = Byte.toUnsignedInt(partialKey);
int pos = keyIndex[index];
assert pos != ABSENT;
removeUplink(children[pos]);
children[pos] = null; // fragment
keyIndex[index] = ABSENT;
noOfChildren--;
}
@Override
public InnerNode grow() {
assert isFull();
return new Node256(this);
}
@Override
public boolean shouldShrink() {
return noOfChildren == Node16.NODE_SIZE;
}
@Override
public InnerNode shrink() {
assert shouldShrink();
return new Node16(this);
}
@Override
public Node first() {
assert noOfChildren > Node16.NODE_SIZE;
int i = 0;
while(keyIndex[i] == ABSENT)i++;
return children[keyIndex[i]];
}
@Override
public Node last() {
assert noOfChildren > Node16.NODE_SIZE;
int i = KEY_INDEX_SIZE - 1;
while(keyIndex[i] == ABSENT)i--;
return children[keyIndex[i]];
}
@Override
public boolean isFull() {
return noOfChildren == NODE_SIZE;
}
@Override
public Node ceil(byte partialKey) {
for (int i = Byte.toUnsignedInt(partialKey); i < KEY_INDEX_SIZE; i++) {
if (keyIndex[i] != ABSENT) {
return children[keyIndex[i]];
}
}
return null;
}
@Override
public Node greater(byte partialKey) {
for (int i = Byte.toUnsignedInt(partialKey) + 1; i < KEY_INDEX_SIZE; i++) {
if (keyIndex[i] != ABSENT) {
return children[keyIndex[i]];
}
}
return null;
}
@Override
public Node lesser(byte partialKey) {
for (int i = Byte.toUnsignedInt(partialKey) - 1; i >= 0; i--) {
if (keyIndex[i] != ABSENT) {
return children[keyIndex[i]];
}
}
return null;
}
@Override
public Node floor(byte partialKey) {
for (int i = Byte.toUnsignedInt(partialKey); i >= 0; i--) {
if (keyIndex[i] != ABSENT) {
return children[keyIndex[i]];
}
}
return null;
}
byte[] getKeyIndex() {
return keyIndex;
}
}
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