/// <summary>
/// Default constructor.
/// </summary>
/// <param name="dataPageDataAreaSize">Specifies how much data data page can store.</param>
/// <param name="ownerDB">Owner DB file..</param>
/// <param name="startOffset">Data page start offset pointer.</param>
public DataPage(int dataPageDataAreaSize,DbFile ownerDB,long startOffset)
{
/* DataPage structure
2 bytes - CRLF
1 byte - used (f - unused,u - used)
8 byte - owner object id
8 bytes - owner data page pointer
8 bytes - continuing data page pointer
4 bytes - stored data length in data area
2 bytes - CRLF
1000 bytes - data area
*/
m_DataAreaSize = dataPageDataAreaSize;
m_pOwnerDB = ownerDB;
m_StartPointer = startOffset;
byte[] dataPageInfo = new byte[33];
ownerDB.SetFilePosition(startOffset);
ownerDB.ReadFromFile(dataPageInfo,0,dataPageInfo.Length);
m_Data = new byte[dataPageDataAreaSize];
ownerDB.ReadFromFile(m_Data,0,dataPageDataAreaSize);
// CRLF
if(dataPageInfo[0] != (byte)'\r'){
throw new Exception("Not right data page startOffset, or invalid data page <CR> is expected but is '" + (int)dataPageInfo[0] + "' !");
}
if(dataPageInfo[1] != (byte)'\n'){
throw new Exception("Not right data page startOffset, or invalid data page <LF> is expected but is '" + (int)dataPageInfo[1] + "' !");
}
// used
if(dataPageInfo[2] == (byte)'u'){
m_Used = true;
}
else{
m_Used = false;
}
// owner object id
m_OwnerID = ldb_Utils.ByteToLong(dataPageInfo,3);
// owner data page pointer
m_OwnerDataPagePointer = ldb_Utils.ByteToLong(dataPageInfo,11);
// continuing data page pointer
m_NextDataPagePointer = ldb_Utils.ByteToLong(dataPageInfo,19);
// stored data length in data area
m_StoredDataLength = ldb_Utils.ByteToInt(dataPageInfo,27);
// CRLF
if(dataPageInfo[31] != (byte)'\r'){
throw new Exception("Not right data page startOffset, or invalid data page <CR> is expected but is '" + (int)dataPageInfo[31] + "' !");
}
if(dataPageInfo[32] != (byte)'\n'){
throw new Exception("Not right data page startOffset, or invalid data page <LF> is expected but is '" + (int)dataPageInfo[32] + "' !");
}
}
/// <summary>
/// Writed data to data page.
/// </summary>
/// <param name="data">Data to write.</param>
public void WriteData(byte[] data)
{
if (data.Length > this.DataAreaSize)
{
throw new Exception("Data page can't store more than " + this.DataAreaSize + " bytes, use mutliple data pages !");
}
// Set stored data length
m_pOwnerDB.SetFilePosition(m_StartPointer + 27);
m_pOwnerDB.WriteToFile(ldb_Utils.IntToByte(data.Length), 0, 4);
// Store data
m_pOwnerDB.SetFilePosition(m_StartPointer + 33);
m_pOwnerDB.WriteToFile(data, 0, data.Length);
m_StoredDataLength = data.Length;
}
/// <summary>
/// Default constructor.
/// </summary>
/// <param name="dataPageDataAreaSize">Specifies how much data data page can store.</param>
/// <param name="ownerDB">Owner DB file..</param>
/// <param name="startOffset">Data page start offset pointer.</param>
public DataPage(int dataPageDataAreaSize, DbFile ownerDB, long startOffset)
{
/* DataPage structure
* 2 bytes - CRLF
* 1 byte - used (f - unused,u - used)
* 8 byte - owner object id
* 8 bytes - owner data page pointer
* 8 bytes - continuing data page pointer
* 4 bytes - stored data length in data area
* 2 bytes - CRLF
* 1000 bytes - data area
*/
m_DataAreaSize = dataPageDataAreaSize;
m_pOwnerDB = ownerDB;
m_StartPointer = startOffset;
byte[] dataPageInfo = new byte[33];
ownerDB.SetFilePosition(startOffset);
ownerDB.ReadFromFile(dataPageInfo, 0, dataPageInfo.Length);
m_Data = new byte[dataPageDataAreaSize];
ownerDB.ReadFromFile(m_Data, 0, dataPageDataAreaSize);
// CRLF
if (dataPageInfo[0] != (byte)'\r')
{
throw new Exception("Not right data page startOffset, or invalid data page <CR> is expected but is '" + (int)dataPageInfo[0] + "' !");
}
if (dataPageInfo[1] != (byte)'\n')
{
throw new Exception("Not right data page startOffset, or invalid data page <LF> is expected but is '" + (int)dataPageInfo[1] + "' !");
}
// used
if (dataPageInfo[2] == (byte)'u')
{
m_Used = true;
}
else
{
m_Used = false;
}
// owner object id
m_OwnerID = ldb_Utils.ByteToLong(dataPageInfo, 3);
// owner data page pointer
m_OwnerDataPagePointer = ldb_Utils.ByteToLong(dataPageInfo, 11);
// continuing data page pointer
m_NextDataPagePointer = ldb_Utils.ByteToLong(dataPageInfo, 19);
// stored data length in data area
m_StoredDataLength = ldb_Utils.ByteToInt(dataPageInfo, 27);
// CRLF
if (dataPageInfo[31] != (byte)'\r')
{
throw new Exception("Not right data page startOffset, or invalid data page <CR> is expected but is '" + (int)dataPageInfo[31] + "' !");
}
if (dataPageInfo[32] != (byte)'\n')
{
throw new Exception("Not right data page startOffset, or invalid data page <LF> is expected but is '" + (int)dataPageInfo[32] + "' !");
}
}
