/// <summary>
/// Try enter in shared lock (read) - Call action if request a new lock
/// [Non ThreadSafe]
/// </summary>
private Action LockShared()
{
lock (_disk)
{
if (_state != LockState.Unlocked)
{
return () => { }
}
;
_disk.Lock(LockState.Shared, _timeout);
_state = LockState.Shared;
_shared = true;
_log.Write(Logger.LOCK, "entered in shared lock mode");
this.AvoidDirtyRead();
return(() =>
{
_shared = false;
_disk.Unlock(LockState.Shared);
_state = LockState.Unlocked;
_log.Write(Logger.LOCK, "exited shared lock mode");
});
}
}
/// <summary>
/// Enter in Shared lock mode.
/// </summary>
public LockControl Read()
{
// if read or write
if (_thread.IsReadLockHeld || _thread.IsWriteLockHeld)
{
return(new LockControl(false, () => { }));
}
// try enter in read mode
if (!_thread.TryEnterReadLock(_timeout))
{
throw LiteException.LockTimeout(_timeout);
}
_log.Write(Logger.LOCK, "entered in read lock mode in thread #{0}", this.ThreadId);
// lock disk in shared mode
var position = _disk.Lock(LockState.Read, _timeout);
var changed = this.DetectDatabaseChanges();
return(new LockControl(changed, () =>
{
// exit disk lock mode
_disk.Unlock(LockState.Read, position);
// exit thread lock mode
_thread.ExitReadLock();
_log.Write(Logger.LOCK, "exited read lock mode in thread #{0}", this.ThreadId);
}));
}
/// <summary>
/// Try enter in shared lock (read) - Call action if request a new lock
/// </summary>
public LockControl Shared(Action actionIfNewLock)
{
lock (_disk)
{
if (_state != LockState.Unlocked)
{
return(new LockControl(null));
}
_log.Write(Logger.DISK, "enter in shared lock mode");
_disk.Lock(LockState.Shared);
_state = LockState.Shared;
_shared = true;
actionIfNewLock();
return(new LockControl(() =>
{
_log.Write(Logger.DISK, "exit shared lock mode");
_shared = false;
_state = LockState.Unlocked;
_disk.Unlock(LockState.Shared);
}));
}
}
/// <summary>
/// Initialize LiteEngine using custom disk service implementation and full engine options
/// </summary>
public LiteEngine(IDiskService disk, string password = null, TimeSpan?timeout = null, int cacheSize = 5000, Logger log = null, bool utcDate = false)
{
if (disk == null)
{
throw new ArgumentNullException("disk");
}
_timeout = timeout ?? TimeSpan.FromMinutes(1);
_cacheSize = cacheSize;
_disk = disk;
_log = log ?? new Logger();
_bsonReader = new BsonReader(utcDate);
try
{
// initialize datafile (create) and set log instance
_disk.Initialize(_log, password);
// lock disk (read mode) before read header
var position = _disk.Lock(LockState.Read, _timeout);
var buffer = _disk.ReadPage(0);
_disk.Unlock(LockState.Read, position);
// create header instance from array bytes
var header = BasePage.ReadPage(buffer) as HeaderPage;
// hash password with sha1 or keep as empty byte[20]
var sha1 = password == null ? new byte[20] : AesEncryption.HashSHA1(password);
// compare header password with user password even if not passed password (datafile can have password)
if (sha1.BinaryCompareTo(header.Password) != 0)
{
throw LiteException.DatabaseWrongPassword();
}
// initialize AES encryptor
if (password != null)
{
_crypto = new AesEncryption(password, header.Salt);
}
// initialize all services
this.InitializeServices();
// if header are marked with recovery, do it now
if (header.Recovery)
{
_trans.Recovery();
}
}
catch (Exception)
{
// explicit dispose
this.Dispose();
throw;
}
}
/// <summary>
/// Starts a new transaction - lock database to garantee that only one processes is in a transaction
/// </summary>
public void Begin()
{
if (_trans)
{
throw new Exception("Begin transaction already exists");
}
// lock (or try to) datafile
_disk.Lock();
_trans = true;
}