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RepositoryCache.cs
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RepositoryCache.cs
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/*
* Copyright (C) 2009, Google Inc.
*
* 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.
*/
using System.Collections.Generic;
using System.IO;
using GitSharp.Core.Exceptions;
using GitSharp.Core.Util;
namespace GitSharp.Core
{
public class RepositoryCache
{
private static readonly RepositoryCache Cache = new RepositoryCache();
public static RepositoryCache Instance
{
get { return Cache; }
}
public static Repository open(Key location)
{
return open(location, true);
}
public static Repository open(Key location, bool mustExist)
{
return Cache.openRepository(location, mustExist);
}
public static void register(Repository db)
{
if (db == null)
throw new System.ArgumentNullException ("db");
Cache.registerRepository(FileKey.exact(db.Directory), db);
}
public static void close(Repository db)
{
if (db == null)
throw new System.ArgumentNullException ("db");
Cache.unregisterRepository(FileKey.exact(db.Directory));
}
public static void clear()
{
Cache.clearAll();
}
private readonly Dictionary<Key, WeakReference<Repository>> cacheMap;
private readonly Lock[] openLocks;
public RepositoryCache()
{
cacheMap = new Dictionary<Key, WeakReference<Repository>>();
openLocks = new Lock[4];
for (int i = 0; i < openLocks.Length; i++)
openLocks[i] = new Lock();
}
private Repository openRepository(Key location, bool mustExist)
{
WeakReference<Repository> @ref = cacheMap.GetValue(location);
Repository db = @ref != null ? @ref.get() : null;
if (db == null)
{
lock (lockFor(location))
{
@ref = cacheMap.GetValue(location);
db = @ref != null ? @ref.get() : null;
if (db == null)
{
db = location.open(mustExist);
@ref = new WeakReference<Repository>(db);
cacheMap.AddOrReplace(location, @ref);
}
}
}
db.IncrementOpen();
return db;
}
private void registerRepository(Key location, Repository db)
{
db.IncrementOpen();
WeakReference<Repository> newRef = new WeakReference<Repository>(db);
WeakReference<Repository> oldRef = cacheMap.put(location, newRef);
Repository oldDb = oldRef != null ? oldRef.get() : null;
if (oldDb != null)
oldDb.Dispose();
}
private void unregisterRepository(Key location)
{
WeakReference<Repository> oldRef = cacheMap.GetValue(location);
cacheMap.Remove(location);
Repository oldDb = oldRef != null ? oldRef.get() : null;
if (oldDb != null)
oldDb.Dispose();
}
private void clearAll()
{
for (int stage = 0; stage < 2; stage++)
{
var keysToRemove = new List<Key>();
foreach (KeyValuePair<Key, WeakReference<Repository>> e in cacheMap)
{
Repository db = e.Value.get();
if (db != null)
db.Dispose();
keysToRemove.Add(e.Key);
}
foreach (Key key in keysToRemove)
{
cacheMap.Remove(key);
}
}
}
private Lock lockFor(Key location)
{
return openLocks[(((uint) location.GetHashCode()) >> 1)%openLocks.Length];
}
private class Lock
{
} ;
public interface Key
{
Repository open(bool mustExist);
}
public class FileKey : Key
{
public static FileKey exact(DirectoryInfo dir)
{
return new FileKey(dir);
}
public static FileKey lenient(DirectoryInfo dir)
{
DirectoryInfo gitdir = resolve(dir);
return new FileKey(gitdir ?? dir);
}
private readonly DirectoryInfo path;
public FileKey(DirectoryInfo dir)
{
path = dir;
}
public DirectoryInfo getFile()
{
return path;
}
public Repository open(bool mustExist)
{
if (mustExist && !isGitRepository(path))
throw new RepositoryNotFoundException(path);
return new Repository(path);
}
public override int GetHashCode()
{
return path.FullName.GetHashCode();
}
public override bool Equals(object obj)
{
FileKey fk = (obj as FileKey);
if ( fk != null)
{
return path.FullName.Equals(fk.path.FullName);
}
return false;
}
public override string ToString()
{
return path.FullName;
}
public static bool isGitRepository(DirectoryInfo dir)
{
return FS.resolve(dir, "objects").Exists && FS.resolve(dir, "refs").Exists &&
isValidHead(new FileInfo(Path.Combine(dir.FullName, Constants.HEAD)));
}
private static bool isValidHead(FileInfo head)
{
string r = readFirstLine(head);
return head.Exists && r != null && (r.StartsWith("ref: refs/") || ObjectId.IsId(r));
}
private static string readFirstLine(FileInfo head)
{
try
{
byte[] buf = IO.ReadFully(head, 4096);
int n = buf.Length;
if (n == 0)
return null;
if (buf[n - 1] == '\n')
n--;
return RawParseUtils.decode(buf, 0, n);
}
catch (IOException)
{
return null;
}
}
private static DirectoryInfo resolve(DirectoryInfo directory)
{
if (isGitRepository(directory))
{
return directory;
}
if (isGitRepository(PathUtil.CombineDirectoryPath(directory, Constants.DOT_GIT)))
{
return PathUtil.CombineDirectoryPath(directory, Constants.DOT_GIT);
}
string name = directory.Name;
DirectoryInfo parent = directory.Parent;
if (isGitRepository(new DirectoryInfo(Path.Combine(parent.FullName, name + Constants.DOT_GIT_EXT))))
{
return new DirectoryInfo(Path.Combine(parent.FullName, name + Constants.DOT_GIT_EXT));
}
return null;
}
}
}
}