public _frinfo2(_frinfo info)
{
_blockStart = info._blockStart;
if (_blockStart == -1)
{
throw new InvalidOperationException(IOResources.ERR_FRecordStream_Empty);
}
_currPosition = info._currPosition;
_blockLen = info._blockLen;
}
/// <summary>
/// Loads necessary information before further operations.
/// <para>!!! Note that <see cref="FRecordStream"/> remembers its previous position when the last time <c>UnloadInfo</c> is called.
/// Always call <c>Reset</c> before reading from the beginning. </para>
/// </summary>
public void LoadInfo()
{
if (_info == null)
{
lock (_base)
{
_base.SeekTo(_startPosition);
_info = new _frinfo(_base);
}
}
}
/// <summary>
/// Initializes a new instance of <see cref="FRecordStream"/> that represents either a new record (when <paramref name="startPosition"/> is assigned -1) or an existing record.
/// <para>!!! If this instance represents an existing record (<paramref name="startPosition"/> not set -1), invoking <c>LoadInfo</c> method is necessary before many operations. </para>
/// <para>!!! Also note its initial position is the previously saved position rather than 0, and call <c>Reset</c> method if reading from the beginning is intended.</para>
/// </summary>
/// <param name="baseStream">A <see cref="System.IO.Stream"/> where data are actually stored.</param>
/// <param name="startPosition">Specifies a non-negative integer to indicate the location of an existing record in <paramref name="baseStream"/>, or -1 to create a new record.</param>
/// <param name="minimumBlockSize">Specifies the minimum size in bytes of a data block.</param>
/// <param name="bytesForLength">Specifies how many bytes are enough to describe the size of a data block. For example, if the maximum size of a data block is 64KB, then 2 bytes are sufficient.</param>
/// <param name="bytesForPosition">Specifies how many bytes are enough to describe the total size of data. For example, if the maximum size of all data is 4GB, then 4 bytes are sufficient.</param>
/// <exception cref="System.ArgumentNullException"><paramref name="baseStream"/> is <c>null</c>.</exception>
/// <exception cref="System.ArgumentException"><paramref name="baseStream"/> must be seekable, readable and writable.</exception>
public FRecordStream(Stream baseStream, Int64 startPosition, ushort minimumBlockSize, byte bytesForLength, byte bytesForPosition)
{
if (baseStream == null)
{
throw new ArgumentNullException("baseStream");
}
if (!baseStream.CanSeek && !baseStream.CanRead && !baseStream.CanWrite)
{
throw new ArgumentException(IOResources.ERR_FRecordStream_InvalidBaseStream);
}
_base = baseStream;
_startPosition = startPosition;
if (_startPosition == -1)
{
_info = new _frinfo()
{
_bytesFor = (byte)((byte)bytesForLength | (byte)(bytesForPosition << 4)),
_blockStart = -1,
_autoalloc = minimumBlockSize
};
}
}
public _frinfo21(_frinfo info) : base(info)
{
_prevStatus = info._prevStatus;
}
/// <summary>
/// Clears all data stored in this <see cref="FRecordStream"/>.
/// </summary>
public void Clear()
{
_info = null;
_startPosition = -1;
}
/// <summary>
/// Permanently preserves the current status of this <see cref="FRecordStream"/> and unloads some information to save memory.
/// This method put this <see cref="FRecordStream"/> into a status where most operations are invalid. You need to call <c>LoadInfo</c> again.
/// <para>!!! All temporary status stored by <c>SaveStatus</c> method will be discarded.</para>
/// </summary>
public void UnloadInfo()
{
SaveInfo();
_info = null;
}
