/*
* Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
*
* 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 Git Development Community 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.spearce.jgit.revwalk;
import java.io.IOException;
import org.spearce.jgit.errors.IncorrectObjectTypeException;
import org.spearce.jgit.errors.MissingObjectException;
/**
* Computes the merge base(s) of the starting commits.
* <p>
* This generator is selected if the RevFilter is only
* {@link org.spearce.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;
MergeBaseGenerator(final RevWalk w) {
walker = w;
pending = new DateRevQueue();
}
void init(final AbstractRevQueue p) {
try {
for (;;) {
final RevCommit c = p.next();
if (c == null)
break;
add(c);
}
} finally {
// Always free the flags immediately. This ensures the flags
// will be available for reuse when the walk resets.
//
walker.freeFlag(branchMask);
// 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;
}
}
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("Stale RevFlags on " + c.name());
}
c.flags |= flag;
pending.add(c);
}
@Override
int outputType() {
return 0;
}
@Override
RevCommit next() throws MissingObjectException,
IncorrectObjectTypeException, IOException {
for (;;) {
final RevCommit c = pending.next();
if (c == null) {
walker.curs.release();
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;
}
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;
}
}
}
private void carryOntoHistory(RevCommit c, final int carry) {
for (;;) {
final RevCommit[] pList = c.parents;
if (pList == null)
return;
final int n = pList.length;
if (n == 0)
return;
for (int i = 1; i < n; i++) {
final RevCommit p = pList[i];
if (!carryOntoOne(p, carry))
carryOntoHistory(p, carry);
}
c = pList[0];
if (carryOntoOne(c, carry))
break;
}
}
private boolean carryOntoOne(final RevCommit p, final int carry) {
final boolean haveAll = (p.flags & carry) == carry;
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);
carryOntoHistory(p, branchMask | MERGE_BASE);
return true;
}
// If we already had all carried flags, our parents do too.
// Return true to stop the caller from running down this leg
// of the revision graph any further.
//
return haveAll;
}
}