/// <summary>
/// Get a page from cache or from disk (get from cache or from disk)
/// </summary>
public T GetPage <T>(uint pageID)
where T : BasePage
{
lock (_disk)
{
var page = _cache.GetPage(pageID);
// is not on cache? load from disk
if (page == null)
{
var buffer = _disk.ReadPage(pageID);
// if datafile are encrypted, decrypt buffer (header are not encrypted)
if (_crypto != null && pageID > 0)
{
buffer = _crypto.Decrypt(buffer);
}
page = BasePage.ReadPage(buffer);
_cache.AddPage(page);
}
return((T)page);
}
}
/// <summary>
/// Get journal pages and override all into datafile
/// </summary>
public void Recovery()
{
_log.Write(Logger.RECOVERY, "initializing recovery mode");
using (_locker.Write())
{
// double check in header need recovery (could be already recover from another thread)
var header = BasePage.ReadPage(_disk.ReadPage(0)) as HeaderPage;
if (header.Recovery == false)
{
return;
}
// read all journal pages
foreach (var buffer in _disk.ReadJournal(header.LastPageID))
{
// read pageID (first 4 bytes)
var pageID = BitConverter.ToUInt32(buffer, 0);
_log.Write(Logger.RECOVERY, "recover page #{0:0000}", pageID);
// write in stream (encrypt if datafile is encrypted)
_disk.WritePage(pageID, _crypto == null || pageID == 0 ? buffer : _crypto.Encrypt(buffer));
}
// shrink datafile
_disk.ClearJournal(header.LastPageID);
}
}
/// <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(nameof(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>
/// Test if cache still valid (if datafile was changed by another process reset cache)
/// Returns true if file was changed
/// [Thread Safe]
/// </summary>
private bool DetectDatabaseChanges()
{
// if disk are exclusive don't need check dirty read
if (_disk.IsExclusive)
{
return(false);
}
// empty cache? just exit
if (_cache.CleanUsed == 0)
{
return(false);
}
_log.Write(Logger.CACHE, "checking disk to detect database changes from another process");
// get ChangeID from cache
var header = _cache.GetPage(0) as HeaderPage;
var changeID = header == null ? 0 : header.ChangeID;
// and get header from disk
var disk = BasePage.ReadPage(_disk.ReadPage(0)) as HeaderPage;
// if disk header are in recovery mode, throw exception to datafile re-open and recovery pages
if (disk.Recovery)
{
_log.Write(Logger.ERROR, "datafile in recovery mode, need re-open database");
throw LiteException.NeedRecover();
}
// if header change, clear cache and add new header to cache
if (disk.ChangeID != changeID)
{
_log.Write(Logger.CACHE, "file changed from another process, cleaning all cache pages");
_cache.ClearPages();
_cache.AddPage(disk);
return(true);
}
return(false);
}
/// <summary>
/// Reduce disk size re-arranging unused spaces. Can change password. If temporary disk was not provided, use MemoryStream temp disk
/// </summary>
public long Shrink(string password = null, IDiskService tempDisk = null)
{
var originalSize = _disk.FileLength;
// if temp disk are not passed, use memory stream disk
using (var temp = tempDisk ?? new StreamDiskService(new MemoryStream()))
using (_locker.Write())
using (var engine = new LiteEngine(temp, password))
{
// read all collection
foreach (var collectionName in this.GetCollectionNames())
{
// first create all user indexes (exclude _id index)
foreach (var index in this.GetIndexes(collectionName).Where(x => x.Field != "_id"))
{
engine.EnsureIndex(collectionName, index.Field, index.Unique);
}
// now copy documents
var docs = this.Find(collectionName, Query.All());
engine.InsertBulk(collectionName, docs);
// fix collection sequence number
var seq = _collections.Get(collectionName).Sequence;
engine.Transaction(collectionName, true, (col) =>
{
col.Sequence = seq;
engine._pager.SetDirty(col);
return(true);
});
}
// copy user version
engine.UserVersion = this.UserVersion;
// set current disk size to exact new disk usage
_disk.SetLength(temp.FileLength);
// read new header page to start copy
var header = BasePage.ReadPage(temp.ReadPage(0)) as HeaderPage;
// copy (as is) all pages from temp disk to original disk
for (uint i = 0; i <= header.LastPageID; i++)
{
// skip lock page
if (i == 1)
{
continue;
}
var page = temp.ReadPage(i);
_disk.WritePage(i, page);
}
// create/destroy crypto class
if (_crypto != null)
{
_crypto.Dispose();
}
_crypto = password == null ? null : new AesEncryption(password, header.Salt);
// initialize all services again (crypto can be changed)
this.InitializeServices();
// return how many bytes are reduced
return(originalSize - temp.FileLength);
}
}
