/// <summary>
/// 单文件数据库上下文，代表一个单文件数据库。SharpFileDB的核心类型。
/// </summary>
/// <param name="fullname">数据库文件据对路径。</param>
/// <param name="config">数据库配置信息。只有在新建数据库时此参数才会发挥作用。</param>
/// <param name="onlyRead">只读方式打开。</param>
public FileDBContext(string fullname, DBConfig config = null, bool onlyRead = false)
{
this.transaction = new Transaction(this);
this.Fullname = fullname;
if (!onlyRead)
{
if (!File.Exists(fullname))
{
if (config == null)
{
config = new DBConfig();
}
CreateDB(fullname, config);
}
InitializeDB(fullname, onlyRead);
}
else
{
InitializeDB(fullname, onlyRead);
}
}
/// <summary>
/// 创建初始状态的数据库文件。
/// </summary>
/// <param name="fullname">数据库文件据对路径。</param>
/// <param name="config">数据库配置信息。</param>
private void CreateDB(string fullname, DBConfig config)
{
FileInfo fileInfo = new FileInfo(fullname);
Directory.CreateDirectory(fileInfo.DirectoryName);
using (FileStream fs = new FileStream(fullname, FileMode.CreateNew, FileAccess.Write, FileShare.None, Consts.pageSize))
{
PageHeaderBlock page = new PageHeaderBlock()
{
OccupiedBytes = Consts.pageSize, AvailableBytes = 0,
};
fs.WriteBlock(page);
DBHeaderBlock dbHeader = new DBHeaderBlock()
{
MaxLevelOfSkipList = config.MaxLevelOfSkipList, ProbabilityOfSkipList = config.ProbabilityOfSkipList, MaxSunkCountInMemory = config.MaxSunkCountInMemory, LockTimeout = config.LockTimeout, ThisPos = fs.Position
};
fs.WriteBlock(dbHeader);
TableBlock tableHead = new TableBlock()
{
ThisPos = fs.Position,
};
fs.WriteBlock(tableHead);
byte[] leftSpace = new byte[Consts.pageSize - fs.Length];
fs.Write(leftSpace, 0, leftSpace.Length);
BlockCache.TryRemoveFloatingBlock(page);
BlockCache.TryRemoveFloatingBlock(dbHeader);
BlockCache.TryRemoveFloatingBlock(tableHead);
BlockCache.TryRemoveSunkBlock(page);
BlockCache.TryRemoveSunkBlock(dbHeader);
BlockCache.TryRemoveSunkBlock(tableHead);
}
}
