/// <summary>
/// Read page into buffer: n - page number; nbuf - buffer number
/// !!! NOT APPLICABLE TO IMO
/// </summary>
/// <param name="n"></param>
/// <param name="nbuf"></param>
private void page_read(long n, int sg, int pg, int nbuf)
{
for (int i = 0; i < pd.Length; i++)
{
if ((n >= pd[i].start_page) & (n <= pd[i].end_page))
{
// Absolute address (beginning of system area
long addr = (long)((n - pd[i].start_page) * (DESCRIPTOR.PageSize + DEFS.SYSTEM_USED_PAGE_SPACE));
uint encr = pd[i].fs.ReadUInt(addr); // Encryption
uint old_crc = pd[i].fs.ReadUInt(addr + 4); // Crc32
if (encr == DEFS.DATA_ENCRYPTED)
{
e_buf = pd[i].fs.ReadBytes(addr + DEFS.SYSTEM_USED_PAGE_SPACE, (int)page_size);
VSCrypto.Decrypt(ref e_buf, ref segment_table[0].cache[nbuf].buf, e_key, 0);
}
else
{
segment_table[0].cache[nbuf].buf = pd[i].fs.ReadBytes(addr + DEFS.SYSTEM_USED_PAGE_SPACE, (int)page_size);
}
if (old_crc != 0)
{
uint new_crc = VSCRC32.CountCrc(segment_table[0].cache[nbuf].buf);
if (old_crc != new_crc)
{
throw new VSException(DEFS.E0033_INVALID_CRC_CODE, "Space: " + DESCRIPTOR.name + ", Page#: " + n.ToString());
}
}
PGRead++;
// Update page table entry by but# ans sett 'read' state
segment_table[sg].page_table[pg].page_state = DEFS.PAGE_READ;
segment_table[sg].page_table[pg].bufno = nbuf;
// Update cache entry by page#
segment_table[0].cache[nbuf].page_no = n;
}
}
}
////////////////////////////////////////////////////////////////////
//////////////// READ METHODS //////////////////////////////////////
////////////////////////////////////////////////////////////////////
/// <summary>
/// Read bytes
/// </summary>
/// <returns></returns>
public byte[] ReadBytes(long offset, int len)
{
if (offset >= 0)
{
fs.Seek(offset, SeekOrigin.Begin);
}
byte[] b = new byte[len];
long pos = fs.Position;
fs.Read(b, 0, len);
if (!_encrypt)
{
return(b);
}
byte[] b_ret = new byte[len];
VSCrypto.Decrypt(ref b, ref b_ret, xkey_b, pos);
return(b_ret);
}