/*
* Copyright (C) 2016, Google Inc.
* 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,
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* 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.
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package org.eclipse.jgit.internal.storage.reftree;
import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
import static org.eclipse.jgit.lib.Constants.R_REFS;
import static org.eclipse.jgit.lib.Constants.encode;
import static org.eclipse.jgit.lib.FileMode.TYPE_GITLINK;
import static org.eclipse.jgit.lib.FileMode.TYPE_SYMLINK;
import static org.eclipse.jgit.lib.FileMode.TYPE_TREE;
import static org.eclipse.jgit.lib.Ref.Storage.NEW;
import static org.eclipse.jgit.lib.Ref.Storage.PACKED;
import static org.eclipse.jgit.lib.RefDatabase.MAX_SYMBOLIC_REF_DEPTH;
import java.io.IOException;
import org.eclipse.jgit.annotations.Nullable;
import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectIdRef;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.lib.SymbolicRef;
import org.eclipse.jgit.revwalk.RevTree;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.treewalk.AbstractTreeIterator;
import org.eclipse.jgit.treewalk.CanonicalTreeParser;
import org.eclipse.jgit.treewalk.TreeWalk;
import org.eclipse.jgit.util.Paths;
import org.eclipse.jgit.util.RawParseUtils;
import org.eclipse.jgit.util.RefList;
/** A tree parser that extracts references from a {@link RefTree}. */
class Scanner {
private static final int MAX_SYMLINK_BYTES = 10 << 10;
private static final byte[] BINARY_R_REFS = encode(R_REFS);
private static final byte[] REFS_DOT_DOT = encode("refs/.."); //$NON-NLS-1$
static class Result {
final ObjectId refTreeId;
final RefList<Ref> all;
final RefList<Ref> sym;
Result(ObjectId id, RefList<Ref> all, RefList<Ref> sym) {
this.refTreeId = id;
this.all = all;
this.sym = sym;
}
}
/**
* Scan a {@link RefTree} and parse entries into {@link Ref} instances.
*
* @param repo
* source repository containing the commit and tree objects that
* make up the RefTree.
* @param src
* bootstrap reference such as {@code refs/txn/committed} to read
* the reference tree tip from. The current ObjectId will be
* included in {@link Result#refTreeId}.
* @param prefix
* if non-empty a reference prefix to scan only a subdirectory.
* For example {@code prefix = "refs/heads/"} will limit the scan
* to only the {@code "heads"} directory of the RefTree, avoiding
* other directories like {@code "tags"}. Empty string reads all
* entries in the RefTree.
* @param recursive
* if true recurse into subdirectories of the reference tree;
* false to read only one level. Callers may use false during an
* implementation of {@code exactRef(String)} where only one
* reference is needed out of a specific subtree.
* @return sorted list of references after parsing.
* @throws IOException
* tree cannot be accessed from the repository.
*/
static Result scanRefTree(Repository repo, @Nullable Ref src, String prefix,
boolean recursive) throws IOException {
RefList.Builder<Ref> all = new RefList.Builder<>();
RefList.Builder<Ref> sym = new RefList.Builder<>();
ObjectId srcId;
if (src != null && src.getObjectId() != null) {
try (ObjectReader reader = repo.newObjectReader()) {
srcId = src.getObjectId();
scan(reader, srcId, prefix, recursive, all, sym);
}
} else {
srcId = ObjectId.zeroId();
}
RefList<Ref> aList = all.toRefList();
for (int idx = 0; idx < sym.size();) {
Ref s = sym.get(idx);
Ref r = resolve(s, 0, aList);
if (r != null) {
sym.set(idx++, r);
} else {
// Remove broken symbolic reference, they don't exist.
sym.remove(idx);
int rm = aList.find(s.getName());
if (0 <= rm) {
aList = aList.remove(rm);
}
}
}
return new Result(srcId, aList, sym.toRefList());
}
private static void scan(ObjectReader reader, AnyObjectId srcId,
String prefix, boolean recursive,
RefList.Builder<Ref> all, RefList.Builder<Ref> sym)
throws IncorrectObjectTypeException, IOException {
CanonicalTreeParser p = createParserAtPath(reader, srcId, prefix);
if (p == null) {
return;
}
while (!p.eof()) {
int mode = p.getEntryRawMode();
if (mode == TYPE_TREE) {
if (recursive) {
p = p.createSubtreeIterator(reader);
} else {
p = p.next();
}
continue;
}
if (!curElementHasPeelSuffix(p)) {
Ref r = toRef(reader, mode, p);
if (r != null) {
all.add(r);
if (r.isSymbolic()) {
sym.add(r);
}
}
} else if (mode == TYPE_GITLINK) {
peel(all, p);
}
p = p.next();
}
}
private static CanonicalTreeParser createParserAtPath(ObjectReader reader,
AnyObjectId srcId, String prefix) throws IOException {
ObjectId root = toTree(reader, srcId);
if (prefix.isEmpty()) {
return new CanonicalTreeParser(BINARY_R_REFS, reader, root);
}
String dir = RefTree.refPath(Paths.stripTrailingSeparator(prefix));
TreeWalk tw = TreeWalk.forPath(reader, dir, root);
if (tw == null || !tw.isSubtree()) {
return null;
}
ObjectId id = tw.getObjectId(0);
return new CanonicalTreeParser(encode(prefix), reader, id);
}
private static Ref resolve(Ref ref, int depth, RefList<Ref> refs)
throws IOException {
if (!ref.isSymbolic()) {
return ref;
} else if (MAX_SYMBOLIC_REF_DEPTH <= depth) {
return null;
}
Ref r = refs.get(ref.getTarget().getName());
if (r == null) {
return ref;
}
Ref dst = resolve(r, depth + 1, refs);
if (dst == null) {
return null;
}
return new SymbolicRef(ref.getName(), dst);
}
@SuppressWarnings("resource")
private static RevTree toTree(ObjectReader reader, AnyObjectId id)
throws IOException {
return new RevWalk(reader).parseTree(id);
}
private static boolean curElementHasPeelSuffix(AbstractTreeIterator itr) {
int n = itr.getEntryPathLength();
byte[] c = itr.getEntryPathBuffer();
return n > 2 && c[n - 2] == ' ' && c[n - 1] == '^';
}
private static void peel(RefList.Builder<Ref> all, CanonicalTreeParser p) {
String name = refName(p, true);
for (int idx = all.size() - 1; 0 <= idx; idx--) {
Ref r = all.get(idx);
int cmp = r.getName().compareTo(name);
if (cmp == 0) {
all.set(idx, new ObjectIdRef.PeeledTag(PACKED, r.getName(),
r.getObjectId(), p.getEntryObjectId()));
break;
} else if (cmp < 0) {
// Stray peeled name without matching base name; skip entry.
break;
}
}
}
private static Ref toRef(ObjectReader reader, int mode,
CanonicalTreeParser p) throws IOException {
if (mode == TYPE_GITLINK) {
String name = refName(p, false);
ObjectId id = p.getEntryObjectId();
return new ObjectIdRef.PeeledNonTag(PACKED, name, id);
} else if (mode == TYPE_SYMLINK) {
ObjectId id = p.getEntryObjectId();
byte[] bin = reader.open(id, OBJ_BLOB)
.getCachedBytes(MAX_SYMLINK_BYTES);
String dst = RawParseUtils.decode(bin);
Ref trg = new ObjectIdRef.Unpeeled(NEW, dst, null);
String name = refName(p, false);
return new SymbolicRef(name, trg);
}
return null;
}
private static String refName(CanonicalTreeParser p, boolean peel) {
byte[] buf = p.getEntryPathBuffer();
int len = p.getEntryPathLength();
if (peel) {
len -= 2;
}
int ptr = 0;
if (RawParseUtils.match(buf, ptr, REFS_DOT_DOT) > 0) {
ptr = 7;
}
return RawParseUtils.decode(buf, ptr, len);
}
private Scanner() {
}
}