org.eclipse.jgit/src/org/eclipse/jgit/revwalk/MergeBaseGenerator.java - sop/jgit - Git at Google

 /*
  * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
  * and other copyright owners as documented in the project's IP log.
  *
  * This program and the accompanying materials are made available
  * under the terms of the Eclipse Distribution License v1.0 which
  * accompanies this distribution, is reproduced below, and is
  * available at http://www.eclipse.org/org/documents/edl-v10.php
  *
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or
  * without modification, are permitted provided that the following
  * conditions are met:
  *
  * - Redistributions of source code must retain the above copyright
  *   notice, this list of conditions and the following disclaimer.
  *
  * - Redistributions in binary form must reproduce the above
  *   copyright notice, this list of conditions and the following
  *   disclaimer in the documentation and/or other materials provided
  *   with the distribution.
  *
  * - Neither the name of the Eclipse Foundation, Inc. nor the
  *   names of its contributors may be used to endorse or promote
  *   products derived from this software without specific prior
  *   written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 package org.eclipse.jgit.revwalk;

 import java.io.IOException;
 import java.text.MessageFormat;
 import java.util.LinkedList;

 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.internal.JGitText;

 /**
  * Computes the merge base(s) of the starting commits.
  * <p>
  * This generator is selected if the RevFilter is only
  * {@link org.eclipse.jgit.revwalk.filter.RevFilter#MERGE_BASE}.
  * <p>
  * To compute the merge base we assign a temporary flag to each of the starting
  * commits. The maximum number of starting commits is bounded by the number of
  * free flags available in the RevWalk when the generator is initialized. These
  * flags will be automatically released on the next reset of the RevWalk, but
  * not until then, as they are assigned to commits throughout the history.
  * <p>
  * Several internal flags are reused here for a different purpose, but this
  * should not have any impact as this generator should be run alone, and without
  * any other generators wrapped around it.
  */
 class MergeBaseGenerator extends Generator {
 	private static final int PARSED = RevWalk.PARSED;
 	private static final int IN_PENDING = RevWalk.SEEN;
 	private static final int POPPED = RevWalk.TEMP_MARK;
 	private static final int MERGE_BASE = RevWalk.REWRITE;

 	private final RevWalk walker;
 	private final DateRevQueue pending;

 	private int branchMask;
 	private int recarryTest;
 	private int recarryMask;
 	private int mergeBaseAncestor = -1;
 	private LinkedList<RevCommit> ret = new LinkedList<>();

 	private CarryStack stack;

 	MergeBaseGenerator(final RevWalk w) {
 		walker = w;
 		pending = new DateRevQueue();
 	}

 	void init(final AbstractRevQueue p) throws IOException {
 		try {
 			for (;;) {
 				final RevCommit c = p.next();
 				if (c == null)
 					break;
 				add(c);
 			}
 			// Setup the condition used by carryOntoOne to detect a late
 			// merge base and produce it on the next round.
 			//
 			recarryTest = branchMask | POPPED;
 			recarryMask = branchMask | POPPED | MERGE_BASE;
 			mergeBaseAncestor = walker.allocFlag();

 			for (;;) {
 				RevCommit c = _next();
 				if (c == null) {
 					break;
 				}
 				ret.add(c);
 			}
 		} finally {
 			// Always free the flags immediately. This ensures the flags
 			// will be available for reuse when the walk resets.
 			//
 			walker.freeFlag(branchMask | mergeBaseAncestor);
 		}
 	}

 	private void add(final RevCommit c) {
 		final int flag = walker.allocFlag();
 		branchMask |= flag;
 		if ((c.flags & branchMask) != 0) {
 			// This should never happen. RevWalk ensures we get a
 			// commit admitted to the initial queue only once. If
 			// we see this marks aren't correctly erased.
 			//
 			throw new IllegalStateException(MessageFormat.format(JGitText.get().staleRevFlagsOn, c.name()));
 		}
 		c.flags |= flag;
 		pending.add(c);
 	}

 	@Override
 	int outputType() {
 		return 0;
 	}

 	private RevCommit _next() throws MissingObjectException,
 			IncorrectObjectTypeException, IOException {
 		for (;;) {
 			final RevCommit c = pending.next();
 			if (c == null) {
 				return null;
 			}

 			for (final RevCommit p : c.parents) {
 				if ((p.flags & IN_PENDING) != 0)
 					continue;
 				if ((p.flags & PARSED) == 0)
 					p.parseHeaders(walker);
 				p.flags |= IN_PENDING;
 				pending.add(p);
 			}

 			int carry = c.flags & branchMask;
 			boolean mb = carry == branchMask;
 			if (mb) {
 				// If we are a merge base make sure our ancestors are
 				// also flagged as being popped, so that they do not
 				// generate to the caller.
 				//
 				carry |= MERGE_BASE | mergeBaseAncestor;
 			}
 			carryOntoHistory(c, carry);

 			if ((c.flags & MERGE_BASE) != 0) {
 				// This commit is an ancestor of a merge base we already
 				// popped back to the caller. If everyone in pending is
 				// that way we are done traversing; if not we just need
 				// to move to the next available commit and try again.
 				//
 				if (pending.everbodyHasFlag(MERGE_BASE))
 					return null;
 				continue;
 			}
 			c.flags |= POPPED;

 			if (mb) {
 				c.flags |= MERGE_BASE;
 				return c;
 			}
 		}
 	}

 	@Override
 	RevCommit next() throws MissingObjectException,
 			IncorrectObjectTypeException, IOException {
 		while (!ret.isEmpty()) {
 			RevCommit commit = ret.remove();
 			if ((commit.flags & mergeBaseAncestor) == 0) {
 				return commit;
 			}
 		}
 		return null;
 	}

 	private void carryOntoHistory(RevCommit c, int carry) {
 		stack = null;
 		for (;;) {
 			carryOntoHistoryInnerLoop(c, carry);
 			if (stack == null) {
 				break;
 			}
 			c = stack.c;
 			carry = stack.carry;
 			stack = stack.prev;
 		}
 	}

 	private void carryOntoHistoryInnerLoop(RevCommit c, int carry) {
 		for (;;) {
 			RevCommit[] parents = c.parents;
 			if (parents == null || parents.length == 0) {
 				break;
 			}

 			int e = parents.length - 1;
 			for (int i = 0; i < e; i++) {
 				RevCommit p = parents[i];
 				if (carryOntoOne(p, carry) == CONTINUE) {
 					// Walking p will be required, buffer p on stack.
 					stack = new CarryStack(stack, p, carry);
 				}
 				// For other results from carryOntoOne:
 				// HAVE_ALL: p has all bits, do nothing to skip that path.
 				// CONTINUE_ON_STACK: callee pushed StackElement for p.
 			}

 			c = parents[e];
 			if (carryOntoOne(c, carry) != CONTINUE) {
 				break;
 			}
 		}
 	}

 	private static final int CONTINUE = 0;
 	private static final int HAVE_ALL = 1;
 	private static final int CONTINUE_ON_STACK = 2;

 	private int carryOntoOne(RevCommit p, int carry) {
 		// If we already had all carried flags, our parents do too.
 		// Return HAVE_ALL to stop caller from running down this leg
 		// of the revision graph any further.
 		//
 		// Otherwise return CONTINUE to ask the caller to walk history.
 		int rc = (p.flags & carry) == carry ? HAVE_ALL : CONTINUE;
 		p.flags |= carry;

 		if ((p.flags & recarryMask) == recarryTest) {
 			// We were popped without being a merge base, but we just got
 			// voted to be one. Inject ourselves back at the front of the
 			// pending queue and tell all of our ancestors they are within
 			// the merge base now.
 			p.flags &= ~POPPED;
 			pending.add(p);
 			stack = new CarryStack(stack, p, branchMask | MERGE_BASE);
 			return CONTINUE_ON_STACK;
 		}
 		return rc;
 	}

 	private static class CarryStack {
 		final CarryStack prev;
 		final RevCommit c;
 		final int carry;

 		CarryStack(CarryStack prev, RevCommit c, int carry) {
 			this.prev = prev;
 			this.c = c;
 			this.carry = carry;
 		}
 	}
 }
	/*
	* Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
	* and other copyright owners as documented in the project's IP log.
	*
	* This program and the accompanying materials are made available
	* under the terms of the Eclipse Distribution License v1.0 which
	* accompanies this distribution, is reproduced below, and is
	* available at http://www.eclipse.org/org/documents/edl-v10.php
	*
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or
	* without modification, are permitted provided that the following
	* conditions are met:
	*
	* - Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	*
	* - Redistributions in binary form must reproduce the above
	* copyright notice, this list of conditions and the following
	* disclaimer in the documentation and/or other materials provided
	* with the distribution.
	*
	* - Neither the name of the Eclipse Foundation, Inc. nor the
	* names of its contributors may be used to endorse or promote
	* products derived from this software without specific prior
	* written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
	* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
	* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
	* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
	* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
	* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	package org.eclipse.jgit.revwalk;

	import java.io.IOException;
	import java.text.MessageFormat;
	import java.util.LinkedList;

	import org.eclipse.jgit.errors.IncorrectObjectTypeException;
	import org.eclipse.jgit.errors.MissingObjectException;
	import org.eclipse.jgit.internal.JGitText;

	/**
	* Computes the merge base(s) of the starting commits.
	* <p>
	* This generator is selected if the RevFilter is only
	* {@link org.eclipse.jgit.revwalk.filter.RevFilter#MERGE_BASE}.
	* <p>
	* To compute the merge base we assign a temporary flag to each of the starting
	* commits. The maximum number of starting commits is bounded by the number of
	* free flags available in the RevWalk when the generator is initialized. These
	* flags will be automatically released on the next reset of the RevWalk, but
	* not until then, as they are assigned to commits throughout the history.
	* <p>
	* Several internal flags are reused here for a different purpose, but this
	* should not have any impact as this generator should be run alone, and without
	* any other generators wrapped around it.
	*/
	class MergeBaseGenerator extends Generator {
	private static final int PARSED = RevWalk.PARSED;
	private static final int IN_PENDING = RevWalk.SEEN;
	private static final int POPPED = RevWalk.TEMP_MARK;
	private static final int MERGE_BASE = RevWalk.REWRITE;

	private final RevWalk walker;
	private final DateRevQueue pending;

	private int branchMask;
	private int recarryTest;
	private int recarryMask;
	private int mergeBaseAncestor = -1;
	private LinkedList<RevCommit> ret = new LinkedList<>();

	private CarryStack stack;

	MergeBaseGenerator(final RevWalk w) {
	walker = w;
	pending = new DateRevQueue();
	}

	void init(final AbstractRevQueue p) throws IOException {
	try {
	for (;;) {
	final RevCommit c = p.next();
	if (c == null)
	break;
	add(c);
	}
	// Setup the condition used by carryOntoOne to detect a late
	// merge base and produce it on the next round.
	//
	recarryTest = branchMask \| POPPED;
	recarryMask = branchMask \| POPPED \| MERGE_BASE;
	mergeBaseAncestor = walker.allocFlag();

	for (;;) {
	RevCommit c = _next();
	if (c == null) {
	break;
	}
	ret.add(c);
	}
	} finally {
	// Always free the flags immediately. This ensures the flags
	// will be available for reuse when the walk resets.
	//
	walker.freeFlag(branchMask \| mergeBaseAncestor);
	}
	}

	private void add(final RevCommit c) {
	final int flag = walker.allocFlag();
	branchMask \|= flag;
	if ((c.flags & branchMask) != 0) {
	// This should never happen. RevWalk ensures we get a
	// commit admitted to the initial queue only once. If
	// we see this marks aren't correctly erased.
	//
	throw new IllegalStateException(MessageFormat.format(JGitText.get().staleRevFlagsOn, c.name()));
	}
	c.flags \|= flag;
	pending.add(c);
	}

	@Override
	int outputType() {
	return 0;
	}

	private RevCommit _next() throws MissingObjectException,
	IncorrectObjectTypeException, IOException {
	for (;;) {
	final RevCommit c = pending.next();
	if (c == null) {
	return null;
	}

	for (final RevCommit p : c.parents) {
	if ((p.flags & IN_PENDING) != 0)
	continue;
	if ((p.flags & PARSED) == 0)
	p.parseHeaders(walker);
	p.flags \|= IN_PENDING;
	pending.add(p);
	}

	int carry = c.flags & branchMask;
	boolean mb = carry == branchMask;
	if (mb) {
	// If we are a merge base make sure our ancestors are
	// also flagged as being popped, so that they do not
	// generate to the caller.
	//
	carry \|= MERGE_BASE \| mergeBaseAncestor;
	}
	carryOntoHistory(c, carry);

	if ((c.flags & MERGE_BASE) != 0) {
	// This commit is an ancestor of a merge base we already
	// popped back to the caller. If everyone in pending is
	// that way we are done traversing; if not we just need
	// to move to the next available commit and try again.
	//
	if (pending.everbodyHasFlag(MERGE_BASE))
	return null;
	continue;
	}
	c.flags \|= POPPED;

	if (mb) {
	c.flags \|= MERGE_BASE;
	return c;
	}
	}
	}

	@Override
	RevCommit next() throws MissingObjectException,
	IncorrectObjectTypeException, IOException {
	while (!ret.isEmpty()) {
	RevCommit commit = ret.remove();
	if ((commit.flags & mergeBaseAncestor) == 0) {
	return commit;
	}
	}
	return null;
	}

	private void carryOntoHistory(RevCommit c, int carry) {
	stack = null;
	for (;;) {
	carryOntoHistoryInnerLoop(c, carry);
	if (stack == null) {
	break;
	}
	c = stack.c;
	carry = stack.carry;
	stack = stack.prev;
	}
	}

	private void carryOntoHistoryInnerLoop(RevCommit c, int carry) {
	for (;;) {
	RevCommit[] parents = c.parents;
	if (parents == null \|\| parents.length == 0) {
	break;
	}

	int e = parents.length - 1;
	for (int i = 0; i < e; i++) {
	RevCommit p = parents[i];
	if (carryOntoOne(p, carry) == CONTINUE) {
	// Walking p will be required, buffer p on stack.
	stack = new CarryStack(stack, p, carry);
	}
	// For other results from carryOntoOne:
	// HAVE_ALL: p has all bits, do nothing to skip that path.
	// CONTINUE_ON_STACK: callee pushed StackElement for p.
	}

	c = parents[e];
	if (carryOntoOne(c, carry) != CONTINUE) {
	break;
	}
	}
	}

	private static final int CONTINUE = 0;
	private static final int HAVE_ALL = 1;
	private static final int CONTINUE_ON_STACK = 2;

	private int carryOntoOne(RevCommit p, int carry) {
	// If we already had all carried flags, our parents do too.
	// Return HAVE_ALL to stop caller from running down this leg
	// of the revision graph any further.
	//
	// Otherwise return CONTINUE to ask the caller to walk history.
	int rc = (p.flags & carry) == carry ? HAVE_ALL : CONTINUE;
	p.flags \|= carry;

	if ((p.flags & recarryMask) == recarryTest) {
	// We were popped without being a merge base, but we just got
	// voted to be one. Inject ourselves back at the front of the
	// pending queue and tell all of our ancestors they are within
	// the merge base now.
	p.flags &= ~POPPED;
	pending.add(p);
	stack = new CarryStack(stack, p, branchMask \| MERGE_BASE);
	return CONTINUE_ON_STACK;
	}
	return rc;
	}

	private static class CarryStack {
	final CarryStack prev;
	final RevCommit c;
	final int carry;

	CarryStack(CarryStack prev, RevCommit c, int carry) {
	this.prev = prev;
	this.c = c;
	this.carry = carry;
	}
	}
	}