org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/MergedReftable.java - jgit - Git at Google

 /*
  * Copyright (C) 2017, Google Inc. and others
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Distribution License v. 1.0 which is available at
  * https://www.eclipse.org/org/documents/edl-v10.php.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */

 package org.eclipse.jgit.internal.storage.reftable;

 import java.io.IOException;
 import java.util.List;
 import java.util.PriorityQueue;

 import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.ReflogEntry;

 /**
  * Merges multiple reference tables together.
  * <p>
  * A {@link org.eclipse.jgit.internal.storage.reftable.MergedReftable}
  * merge-joins multiple
  * {@link org.eclipse.jgit.internal.storage.reftable.ReftableReader} on the fly.
  * Tables higher/later in the stack shadow lower/earlier tables, hiding
  * references that been updated/replaced.
  * <p>
  * By default deleted references are skipped and not returned to the caller.
  * {@link #setIncludeDeletes(boolean)} can be used to modify this behavior if
  * the caller needs to preserve deletions during partial compaction.
  * <p>
  * A {@code MergedReftable} is not thread-safe.
  */
 public class MergedReftable extends Reftable {
 	private final ReftableReader[] tables;

 	/**
 	 * Initialize a merged table reader.
 	 * <p>
 	 *
 	 * @param tableStack
 	 *            stack of tables to read from. The base of the stack is at
 	 *            index 0, the most recent should be at the top of the stack at
 	 *            {@code tableStack.size() - 1}. The top of the stack (higher
 	 *            index) shadows the base of the stack (lower index).
 	 */
 	public MergedReftable(List<ReftableReader> tableStack) {
 		tables = tableStack.toArray(new ReftableReader[0]);

 		// Tables must expose deletes to this instance to correctly
 		// shadow references from lower tables.
 		for (ReftableReader t : tables) {
 			t.setIncludeDeletes(true);
 		}
 	}

 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public long maxUpdateIndex() throws IOException {
 		if (tables.length == 0) {
 			return 0;
 		}
 		long maxUpdateIndex = tables[tables.length - 1].maxUpdateIndex();
 		for (int i = tables.length - 2; i >= 0; i--) {
 			if (maxUpdateIndex < tables[i].maxUpdateIndex()) {
 				maxUpdateIndex = tables[i].maxUpdateIndex();
 			}
 		}
 		return maxUpdateIndex;
 	}

 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public long minUpdateIndex() throws IOException {
 		if (tables.length == 0) {
 			return 0;
 		}
 		long minUpdateIndex = tables[0].minUpdateIndex();
 		for (int i = 0; i < tables.length - 1; i++) {
 			if (tables[i].minUpdateIndex() < minUpdateIndex) {
 				minUpdateIndex = tables[i].minUpdateIndex();
 			}
 		}
 		return minUpdateIndex;
 	}

 	/** {@inheritDoc} */
 	@Override
 	public boolean hasObjectMap() throws IOException {
 		boolean has = true;
 		for (int i = 0; has && i < tables.length; i++) {
 			has = has && tables[i].hasObjectMap();
 		}
 		return has;
 	}

 	/** {@inheritDoc} */
 	@Override
 	public RefCursor allRefs() throws IOException {
 		MergedRefCursor m = new MergedRefCursor();
 		for (int i = 0; i < tables.length; i++) {
 			m.add(new RefQueueEntry(tables[i].allRefs(), i));
 		}
 		return m;
 	}

 	/** {@inheritDoc} */
 	@Override
 	public RefCursor seekRef(String name) throws IOException {
 		MergedRefCursor m = new MergedRefCursor();
 		for (int i = 0; i < tables.length; i++) {
 			m.add(new RefQueueEntry(tables[i].seekRef(name), i));
 		}
 		return m;
 	}

 	/** {@inheritDoc} */
 	@Override
 	public RefCursor seekRefsWithPrefix(String prefix) throws IOException {
 		MergedRefCursor m = new MergedRefCursor();
 		for (int i = 0; i < tables.length; i++) {
 			m.add(new RefQueueEntry(tables[i].seekRefsWithPrefix(prefix), i));
 		}
 		return m;
 	}

 	/** {@inheritDoc} */
 	@Override
 	public RefCursor byObjectId(AnyObjectId name) throws IOException {
 		MergedRefCursor m = new FilteringMergedRefCursor(name);
 		for (int i = 0; i < tables.length; i++) {
 			m.add(new RefQueueEntry(tables[i].byObjectId(name), i));
 		}
 		return m;
 	}

 	/** {@inheritDoc} */
 	@Override
 	public LogCursor allLogs() throws IOException {
 		MergedLogCursor m = new MergedLogCursor();
 		for (int i = 0; i < tables.length; i++) {
 			m.add(new LogQueueEntry(tables[i].allLogs(), i));
 		}
 		return m;
 	}

 	/** {@inheritDoc} */
 	@Override
 	public LogCursor seekLog(String refName, long updateIdx)
 			throws IOException {
 		MergedLogCursor m = new MergedLogCursor();
 		for (int i = 0; i < tables.length; i++) {
 			m.add(new LogQueueEntry(tables[i].seekLog(refName, updateIdx), i));
 		}
 		return m;
 	}

 	int queueSize() {
 		return Math.max(1, tables.length);
 	}

 	private class MergedRefCursor extends RefCursor {
 		private final PriorityQueue<RefQueueEntry> queue;
 		private RefQueueEntry head;
 		private Ref ref;

 		MergedRefCursor() {
 			queue = new PriorityQueue<>(queueSize(), RefQueueEntry::compare);
 		}

 		void add(RefQueueEntry t) throws IOException {
 			// Common case is many iterations over the same RefQueueEntry
 			// for the bottom of the stack (scanning all refs). Its almost
 			// always less than the top of the queue. Avoid the queue's
 			// O(log N) insertion and removal costs for this common case.
 			if (!t.rc.next()) {
 				t.rc.close();
 			} else if (head == null) {
 				RefQueueEntry p = queue.peek();
 				if (p == null || RefQueueEntry.compare(t, p) < 0) {
 					head = t;
 				} else {
 					head = queue.poll();
 					queue.add(t);
 				}
 			} else if (RefQueueEntry.compare(t, head) > 0) {
 				queue.add(t);
 			} else {
 				queue.add(head);
 				head = t;
 			}
 		}

 		@Override
 		public boolean next() throws IOException {
 			for (;;) {
 				RefQueueEntry t = poll();
 				if (t == null) {
 					return false;
 				}

 				ref = t.rc.getRef();
 				boolean include = includeDeletes || !t.rc.wasDeleted();
 				add(t);
 				skipShadowedRefs(ref.getName());
 				if (include) {
 					return true;
 				}
 			}
 		}

 		private RefQueueEntry poll() {
 			RefQueueEntry e = head;
 			if (e != null) {
 				head = null;
 				return e;
 			}
 			return queue.poll();
 		}

 		private void skipShadowedRefs(String name) throws IOException {
 			for (;;) {
 				RefQueueEntry t = head != null ? head : queue.peek();
 				if (t != null && name.equals(t.name())) {
 					add(poll());
 				} else {
 					break;
 				}
 			}
 		}

 		@Override
 		public Ref getRef() {
 			return ref;
 		}

 		@Override
 		public void close() {
 			if (head != null) {
 				head.rc.close();
 				head = null;
 			}
 			while (!queue.isEmpty()) {
 				queue.remove().rc.close();
 			}
 		}
 	}

 	private class FilteringMergedRefCursor extends MergedRefCursor {
 		final AnyObjectId filterId;
 		Ref filteredRef;

 		FilteringMergedRefCursor(AnyObjectId id) {
 			filterId = id;
 			filteredRef = null;
 		}

 		@Override
 		public Ref getRef() {
 			return filteredRef;
 		}

 		@Override
 		public boolean next() throws IOException {
 			for (;;) {
 				boolean ok = super.next();
 				if (!ok) {
 					return false;
 				}

 				String name = super.getRef().getName();

 				try (RefCursor c = seekRef(name)) {
 					if (c.next()) {
 						if (filterId.equals(c.getRef().getObjectId())) {
 							filteredRef = c.getRef();
 							return true;
 						}
 					}
 				}
 			}
 		}
 	}

 	private static class RefQueueEntry {
 		static int compare(RefQueueEntry a, RefQueueEntry b) {
 			int cmp = a.name().compareTo(b.name());
 			if (cmp == 0) {
 				// higher updateIndex shadows lower updateIndex.
 				cmp = Long.signum(b.updateIndex() - a.updateIndex());
 			}
 			if (cmp == 0) {
 				// higher index shadows lower index, so higher index first.
 				cmp = b.stackIdx - a.stackIdx;
 			}
 			return cmp;
 		}

 		final RefCursor rc;
 		final int stackIdx;

 		RefQueueEntry(RefCursor rc, int stackIdx) {
 			this.rc = rc;
 			this.stackIdx = stackIdx;
 		}

 		String name() {
 			return rc.getRef().getName();
 		}

 		long updateIndex() {
 			return rc.getRef().getUpdateIndex();
 		}
 	}

 	private class MergedLogCursor extends LogCursor {
 		private final PriorityQueue<LogQueueEntry> queue;
 		private String refName;
 		private long updateIndex;
 		private ReflogEntry entry;

 		MergedLogCursor() {
 			queue = new PriorityQueue<>(queueSize(), LogQueueEntry::compare);
 		}

 		void add(LogQueueEntry t) throws IOException {
 			if (t.lc.next()) {
 				queue.add(t);
 			} else {
 				t.lc.close();
 			}
 		}

 		@Override
 		public boolean next() throws IOException {
 			for (;;) {
 				LogQueueEntry t = queue.poll();
 				if (t == null) {
 					return false;
 				}

 				refName = t.lc.getRefName();
 				updateIndex = t.lc.getUpdateIndex();
 				entry = t.lc.getReflogEntry();
 				boolean include = includeDeletes || entry != null;
 				skipShadowed(refName, updateIndex);
 				add(t);
 				if (include) {
 					return true;
 				}
 			}
 		}

 		private void skipShadowed(String name, long index) throws IOException {
 			for (;;) {
 				LogQueueEntry t = queue.peek();
 				if (t != null && name.equals(t.name()) && index == t.index()) {
 					add(queue.remove());
 				} else {
 					break;
 				}
 			}
 		}

 		@Override
 		public String getRefName() {
 			return refName;
 		}

 		@Override
 		public long getUpdateIndex() {
 			return updateIndex;
 		}

 		@Override
 		public ReflogEntry getReflogEntry() {
 			return entry;
 		}

 		@Override
 		public void close() {
 			while (!queue.isEmpty()) {
 				queue.remove().lc.close();
 			}
 		}
 	}

 	private static class LogQueueEntry {
 		static int compare(LogQueueEntry a, LogQueueEntry b) {
 			int cmp = a.name().compareTo(b.name());
 			if (cmp == 0) {
 				// higher update index sorts first.
 				cmp = Long.signum(b.index() - a.index());
 			}
 			if (cmp == 0) {
 				// higher index comes first.
 				cmp = b.stackIdx - a.stackIdx;
 			}
 			return cmp;
 		}

 		final LogCursor lc;
 		final int stackIdx;

 		LogQueueEntry(LogCursor lc, int stackIdx) {
 			this.lc = lc;
 			this.stackIdx = stackIdx;
 		}

 		String name() {
 			return lc.getRefName();
 		}

 		long index() {
 			return lc.getUpdateIndex();
 		}
 	}
 }
	/*
	* Copyright (C) 2017, Google Inc. and others
	*
	* This program and the accompanying materials are made available under the
	* terms of the Eclipse Distribution License v. 1.0 which is available at
	* https://www.eclipse.org/org/documents/edl-v10.php.
	*
	* SPDX-License-Identifier: BSD-3-Clause
	*/

	package org.eclipse.jgit.internal.storage.reftable;

	import java.io.IOException;
	import java.util.List;
	import java.util.PriorityQueue;

	import org.eclipse.jgit.lib.AnyObjectId;
	import org.eclipse.jgit.lib.Ref;
	import org.eclipse.jgit.lib.ReflogEntry;

	/**
	* Merges multiple reference tables together.
	* <p>
	* A {@link org.eclipse.jgit.internal.storage.reftable.MergedReftable}
	* merge-joins multiple
	* {@link org.eclipse.jgit.internal.storage.reftable.ReftableReader} on the fly.
	* Tables higher/later in the stack shadow lower/earlier tables, hiding
	* references that been updated/replaced.
	* <p>
	* By default deleted references are skipped and not returned to the caller.
	* {@link #setIncludeDeletes(boolean)} can be used to modify this behavior if
	* the caller needs to preserve deletions during partial compaction.
	* <p>
	* A {@code MergedReftable} is not thread-safe.
	*/
	public class MergedReftable extends Reftable {
	private final ReftableReader[] tables;

	/**
	* Initialize a merged table reader.
	* <p>
	*
	* @param tableStack
	* stack of tables to read from. The base of the stack is at
	* index 0, the most recent should be at the top of the stack at
	* {@code tableStack.size() - 1}. The top of the stack (higher
	* index) shadows the base of the stack (lower index).
	*/
	public MergedReftable(List<ReftableReader> tableStack) {
	tables = tableStack.toArray(new ReftableReader[0]);

	// Tables must expose deletes to this instance to correctly
	// shadow references from lower tables.
	for (ReftableReader t : tables) {
	t.setIncludeDeletes(true);
	}
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public long maxUpdateIndex() throws IOException {
	if (tables.length == 0) {
	return 0;
	}
	long maxUpdateIndex = tables[tables.length - 1].maxUpdateIndex();
	for (int i = tables.length - 2; i >= 0; i--) {
	if (maxUpdateIndex < tables[i].maxUpdateIndex()) {
	maxUpdateIndex = tables[i].maxUpdateIndex();
	}
	}
	return maxUpdateIndex;
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public long minUpdateIndex() throws IOException {
	if (tables.length == 0) {
	return 0;
	}
	long minUpdateIndex = tables[0].minUpdateIndex();
	for (int i = 0; i < tables.length - 1; i++) {
	if (tables[i].minUpdateIndex() < minUpdateIndex) {
	minUpdateIndex = tables[i].minUpdateIndex();
	}
	}
	return minUpdateIndex;
	}

	/** {@inheritDoc} */
	@Override
	public boolean hasObjectMap() throws IOException {
	boolean has = true;
	for (int i = 0; has && i < tables.length; i++) {
	has = has && tables[i].hasObjectMap();
	}
	return has;
	}

	/** {@inheritDoc} */
	@Override
	public RefCursor allRefs() throws IOException {
	MergedRefCursor m = new MergedRefCursor();
	for (int i = 0; i < tables.length; i++) {
	m.add(new RefQueueEntry(tables[i].allRefs(), i));
	}
	return m;
	}

	/** {@inheritDoc} */
	@Override
	public RefCursor seekRef(String name) throws IOException {
	MergedRefCursor m = new MergedRefCursor();
	for (int i = 0; i < tables.length; i++) {
	m.add(new RefQueueEntry(tables[i].seekRef(name), i));
	}
	return m;
	}

	/** {@inheritDoc} */
	@Override
	public RefCursor seekRefsWithPrefix(String prefix) throws IOException {
	MergedRefCursor m = new MergedRefCursor();
	for (int i = 0; i < tables.length; i++) {
	m.add(new RefQueueEntry(tables[i].seekRefsWithPrefix(prefix), i));
	}
	return m;
	}

	/** {@inheritDoc} */
	@Override
	public RefCursor byObjectId(AnyObjectId name) throws IOException {
	MergedRefCursor m = new FilteringMergedRefCursor(name);
	for (int i = 0; i < tables.length; i++) {
	m.add(new RefQueueEntry(tables[i].byObjectId(name), i));
	}
	return m;
	}

	/** {@inheritDoc} */
	@Override
	public LogCursor allLogs() throws IOException {
	MergedLogCursor m = new MergedLogCursor();
	for (int i = 0; i < tables.length; i++) {
	m.add(new LogQueueEntry(tables[i].allLogs(), i));
	}
	return m;
	}

	/** {@inheritDoc} */
	@Override
	public LogCursor seekLog(String refName, long updateIdx)
	throws IOException {
	MergedLogCursor m = new MergedLogCursor();
	for (int i = 0; i < tables.length; i++) {
	m.add(new LogQueueEntry(tables[i].seekLog(refName, updateIdx), i));
	}
	return m;
	}

	int queueSize() {
	return Math.max(1, tables.length);
	}

	private class MergedRefCursor extends RefCursor {
	private final PriorityQueue<RefQueueEntry> queue;
	private RefQueueEntry head;
	private Ref ref;

	MergedRefCursor() {
	queue = new PriorityQueue<>(queueSize(), RefQueueEntry::compare);
	}

	void add(RefQueueEntry t) throws IOException {
	// Common case is many iterations over the same RefQueueEntry
	// for the bottom of the stack (scanning all refs). Its almost
	// always less than the top of the queue. Avoid the queue's
	// O(log N) insertion and removal costs for this common case.
	if (!t.rc.next()) {
	t.rc.close();
	} else if (head == null) {
	RefQueueEntry p = queue.peek();
	if (p == null \|\| RefQueueEntry.compare(t, p) < 0) {
	head = t;
	} else {
	head = queue.poll();
	queue.add(t);
	}
	} else if (RefQueueEntry.compare(t, head) > 0) {
	queue.add(t);
	} else {
	queue.add(head);
	head = t;
	}
	}

	@Override
	public boolean next() throws IOException {
	for (;;) {
	RefQueueEntry t = poll();
	if (t == null) {
	return false;
	}

	ref = t.rc.getRef();
	boolean include = includeDeletes \|\| !t.rc.wasDeleted();
	add(t);
	skipShadowedRefs(ref.getName());
	if (include) {
	return true;
	}
	}
	}

	private RefQueueEntry poll() {
	RefQueueEntry e = head;
	if (e != null) {
	head = null;
	return e;
	}
	return queue.poll();
	}

	private void skipShadowedRefs(String name) throws IOException {
	for (;;) {
	RefQueueEntry t = head != null ? head : queue.peek();
	if (t != null && name.equals(t.name())) {
	add(poll());
	} else {
	break;
	}
	}
	}

	@Override
	public Ref getRef() {
	return ref;
	}

	@Override
	public void close() {
	if (head != null) {
	head.rc.close();
	head = null;
	}
	while (!queue.isEmpty()) {
	queue.remove().rc.close();
	}
	}
	}

	private class FilteringMergedRefCursor extends MergedRefCursor {
	final AnyObjectId filterId;
	Ref filteredRef;

	FilteringMergedRefCursor(AnyObjectId id) {
	filterId = id;
	filteredRef = null;
	}

	@Override
	public Ref getRef() {
	return filteredRef;
	}

	@Override
	public boolean next() throws IOException {
	for (;;) {
	boolean ok = super.next();
	if (!ok) {
	return false;
	}

	String name = super.getRef().getName();

	try (RefCursor c = seekRef(name)) {
	if (c.next()) {
	if (filterId.equals(c.getRef().getObjectId())) {
	filteredRef = c.getRef();
	return true;
	}
	}
	}
	}
	}
	}

	private static class RefQueueEntry {
	static int compare(RefQueueEntry a, RefQueueEntry b) {
	int cmp = a.name().compareTo(b.name());
	if (cmp == 0) {
	// higher updateIndex shadows lower updateIndex.
	cmp = Long.signum(b.updateIndex() - a.updateIndex());
	}
	if (cmp == 0) {
	// higher index shadows lower index, so higher index first.
	cmp = b.stackIdx - a.stackIdx;
	}
	return cmp;
	}

	final RefCursor rc;
	final int stackIdx;

	RefQueueEntry(RefCursor rc, int stackIdx) {
	this.rc = rc;
	this.stackIdx = stackIdx;
	}

	String name() {
	return rc.getRef().getName();
	}

	long updateIndex() {
	return rc.getRef().getUpdateIndex();
	}
	}

	private class MergedLogCursor extends LogCursor {
	private final PriorityQueue<LogQueueEntry> queue;
	private String refName;
	private long updateIndex;
	private ReflogEntry entry;

	MergedLogCursor() {
	queue = new PriorityQueue<>(queueSize(), LogQueueEntry::compare);
	}

	void add(LogQueueEntry t) throws IOException {
	if (t.lc.next()) {
	queue.add(t);
	} else {
	t.lc.close();
	}
	}

	@Override
	public boolean next() throws IOException {
	for (;;) {
	LogQueueEntry t = queue.poll();
	if (t == null) {
	return false;
	}

	refName = t.lc.getRefName();
	updateIndex = t.lc.getUpdateIndex();
	entry = t.lc.getReflogEntry();
	boolean include = includeDeletes \|\| entry != null;
	skipShadowed(refName, updateIndex);
	add(t);
	if (include) {
	return true;
	}
	}
	}

	private void skipShadowed(String name, long index) throws IOException {
	for (;;) {
	LogQueueEntry t = queue.peek();
	if (t != null && name.equals(t.name()) && index == t.index()) {
	add(queue.remove());
	} else {
	break;
	}
	}
	}

	@Override
	public String getRefName() {
	return refName;
	}

	@Override
	public long getUpdateIndex() {
	return updateIndex;
	}

	@Override
	public ReflogEntry getReflogEntry() {
	return entry;
	}

	@Override
	public void close() {
	while (!queue.isEmpty()) {
	queue.remove().lc.close();
	}
	}
	}

	private static class LogQueueEntry {
	static int compare(LogQueueEntry a, LogQueueEntry b) {
	int cmp = a.name().compareTo(b.name());
	if (cmp == 0) {
	// higher update index sorts first.
	cmp = Long.signum(b.index() - a.index());
	}
	if (cmp == 0) {
	// higher index comes first.
	cmp = b.stackIdx - a.stackIdx;
	}
	return cmp;
	}

	final LogCursor lc;
	final int stackIdx;

	LogQueueEntry(LogCursor lc, int stackIdx) {
	this.lc = lc;
	this.stackIdx = stackIdx;
	}

	String name() {
	return lc.getRefName();
	}

	long index() {
	return lc.getUpdateIndex();
	}
	}
	}