private bool CheckBackUpIndex()
{
var path = Path.GetDirectoryName(m_fileFullName);
var fileName = Path.Combine(path, BACK_UP).Replace("\\", "/");
if (File.Exists(fileName))
{
var fileInfo = new FileInfo(fileName);
var fileSize = fileInfo.Length;
var fileStream = File.Open(fileName, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite);
m_packageInfo = GetPackageInfo(fileStream, fileSize);
if (m_packageInfo == null || m_packageInfo.IndexOffset == 0)
return true;
var indexSize = (int)(fileSize - PackageInfo.GetPackageSize());//计算索引信息大小
var indexData = new Byte[indexSize];
fileStream.Position = 0;
fileStream.Read(indexData, 0, indexSize);//获取索引信息
LoadIndexInfo(indexData, false);
return true;
}
else
return false;
}
/// <summary>
/// 获取包信息。
/// </summary>
/// <param name="fileSize"></param>
private PackageInfo GetPackageInfo(FileStream fileStream, long fileSize)
{
var packageInfo = new PackageInfo();
if (fileSize < PackageInfo.GetPackageSize())
return new PackageInfo();
fileStream.Position = fileSize - PackageInfo.GetPackageSize();//索引信息起始位置存放在文件结尾处。
var lengthData = new Byte[PackageInfo.GetPackageSize()];
fileStream.Read(lengthData, 0, PackageInfo.GetPackageSize());
var index = 0;
packageInfo.IndexOffset = EncodeDecoder.DecodeUInt32(lengthData, ref index);//获取索引信息起始位置
return packageInfo;
}
/// <summary>
/// 获取索引信息。
/// </summary>
/// <param name="fileSize">文件包大小。</param>
/// <param name="needBackUpIndex">是否备份索引信息。</param>
private void GetIndexInfo(long fileSize, bool needBackUpIndex)
{
lock (m_locker)
{
m_packageInfo = GetPackageInfo(m_fileStream, fileSize);
if (m_packageInfo == null || m_packageInfo.IndexOffset == 0)
return;
var indexSize = (int)(fileSize - PackageInfo.GetPackageSize() - m_packageInfo.IndexOffset);//计算索引信息大小
var indexData = new Byte[indexSize];
m_fileStream.Position = m_packageInfo.IndexOffset;
m_fileStream.Read(indexData, 0, indexSize);//获取索引信息
LoadIndexInfo(indexData, needBackUpIndex);
}
}
