Line data    Source code

       1             : //# VLAArchiveInput.cc: This class reads and reconstructs VLA archive records
       2             : //# Copyright (C) 1995,1999,2000,2001,2002
       3             : //# Associated Universities, Inc. Washington DC, USA.
       4             : //#
       5             : //# This library is free software; you can redistribute it and/or modify it
       6             : //# under the terms of the GNU Library General Public License as published by
       7             : //# the Free Software Foundation; either version 2 of the License, or (at your
       8             : //# option) any later version.
       9             : //#
      10             : //# This library is distributed in the hope that it will be useful, but WITHOUT
      11             : //# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
      12             : //# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
      13             : //# License for more details.
      14             : //#
      15             : //# You should have received a copy of the GNU Library General Public License
      16             : //# along with this library; if not, write to the Free Software Foundation,
      17             : //# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
      18             : //#
      19             : //# Correspondence concerning AIPS++ should be addressed as follows:
      20             : //#        Internet email: aips2-request@nrao.edu.
      21             : //#        Postal address: AIPS++ Project Office
      22             : //#                        National Radio Astronomy Observatory
      23             : //#                        520 Edgemont Road
      24             : //#                        Charlottesville, VA 22903-2475 USA
      25             : //#
      26             : //# $Id$
      27             : 
      28             : #include <nrao/VLA/VLATapeInput.h>
      29             : #include <casacore/casa/Utilities/Assert.h>
      30             : #include <casacore/casa/Exceptions/Error.h>
      31             : #include <casacore/casa/IO/MemoryIO.h>
      32             : 
      33             : const uInt VLATapeInput::ReadSize = VLAArchiveInput::BlockSize *
      34             :                                    VLAArchiveInput::MaxBlocksPerPhysicalRecord;
      35             : 
      36           0 : VLATapeInput::VLATapeInput(const Path& device, uInt whichFile)
      37             :   :VLAArchiveInput(),
      38             :    itsTape(device),
      39             :    itsFiles(1,whichFile),
      40             :    itsCurFile(-1),
      41           0 :    itsBuffer(VLATapeInput::ReadSize)
      42             : {
      43           0 :   itsTape.setVariableBlockSize();
      44           0 :   if (!nextFile()) {
      45           0 :     throw(AipsError("VLATapeInput:: problem positioning the tape to file " +
      46           0 :                     String::toString(whichFile)));
      47             :   }
      48           0 : }
      49             : 
      50           0 : VLATapeInput::VLATapeInput(const Path& device, const Block<uInt>& whichFiles)
      51             :   :VLAArchiveInput(),
      52             :    itsTape(device),
      53             :    itsFiles(whichFiles),
      54             :    itsCurFile(-1),
      55           0 :    itsBuffer(VLATapeInput::ReadSize)
      56             : {
      57           0 :   itsTape.setVariableBlockSize();
      58           0 :   const uInt nFiles = itsFiles.nelements();
      59           0 :   if (nFiles == 0) {
      60           0 :     throw(AipsError("VLATapeInput:: no tape file specified"));
      61             :   }
      62           0 :   uInt lastFile = 0;
      63           0 :   for (uInt i = 0; i < nFiles; i++) {
      64           0 :     uInt& thisFile = itsFiles[i];
      65           0 :     if ((thisFile == 0) && (lastFile != 0)) {
      66           0 :       thisFile = lastFile + 1;
      67             :     }
      68           0 :     if ((thisFile != 0) && (thisFile <= lastFile)) {
      69             :       throw(AipsError
      70           0 :             ("VLATapeInput:: badly ordered or incorrect file numbers"));
      71             :     }
      72           0 :     lastFile = thisFile;
      73             :   }
      74           0 :   if (!nextFile()) {
      75           0 :     throw(AipsError("VLATapeInput:: problem positioning the tape to file " +
      76           0 :                     String::toString(whichFiles[0])));
      77             :   }
      78           0 : }
      79             : 
      80           0 : VLATapeInput::~VLATapeInput() {
      81           0 : }
      82             : 
      83           0 : Bool VLATapeInput::read() {
      84           0 :   while (nextRecord() == false && nextFile() == true);
      85           0 :   return hasData();
      86             : }
      87             : 
      88             : // Find an initial record. An initial record MUST have the first 2-byte integer
      89             : // as 1 and the next 2-byte integer as a number greater than zero. If we have
      90             : // not found an initial record after searching 5MBytes worth of data then just
      91             : // give up.
      92           0 : Bool VLATapeInput::findFirstRecord(Short& m) {
      93           0 :   const uInt maxBytesToSearch = 5*1024*1024;
      94           0 :   Short n = 0 ;
      95           0 :   m = 0;
      96           0 :   uInt bytesSearched = 0;
      97             :   // Search for the correct sequence number or give up after a while.
      98           0 :   uInt bytesRead = 0;
      99           0 :   while (!(n == 1 && m > 0) && (bytesSearched <= maxBytesToSearch)) {
     100           0 :     bytesSearched += bytesRead;
     101           0 :     bytesRead = VLATapeInput::ReadSize;
     102           0 :     if (fillBuffer(bytesRead) == false) return false;
     103             : // copy just enough bytes into the MemoryIO object to find out what the
     104             : // sequence numbers are
     105           0 :     itsRecord.seek(0);
     106           0 :     itsRecord.write(VLAArchiveInput::HeaderSize, itsBuffer.storage());
     107           0 :     itsRecord.seek(0);
     108           0 :     itsRecord >> n;
     109           0 :     itsRecord >> m;
     110             :   }
     111           0 :   if (bytesSearched > maxBytesToSearch) {
     112           0 :     itsMemIO->clear();
     113           0 :     return false;
     114             :   }
     115             :   // OK so we have found the beginning of the first record. Copy the rest of
     116             :   // the buffer into the record.
     117             :   uInt bytesToCopy;
     118           0 :   if (m != 1) { // Need to copy VLATapeInput::ReadSize bytes
     119           0 :     bytesToCopy = VLATapeInput::ReadSize - VLAArchiveInput::HeaderSize;
     120             :   } else {// If m=1 we probably can copy less bytes than the amount of
     121             :     // data read. To work this out we need to find the logical record size.
     122           0 :     itsRecord.seek(0);
     123           0 :     itsRecord.write(4, itsBuffer.storage() + VLAArchiveInput::HeaderSize);
     124           0 :     itsRecord.seek(0);
     125             :     Int logicalRecordSize;
     126           0 :     itsRecord >> logicalRecordSize;
     127           0 :     bytesToCopy = logicalRecordSize * 2;
     128             :   }
     129           0 :   itsRecord.seek(0);
     130           0 :   itsRecord.write(bytesToCopy,
     131           0 :                   itsBuffer.storage() + VLAArchiveInput::HeaderSize);
     132           0 :   DebugAssert(n == 1, AipsError);
     133           0 :   DebugAssert(m > 0, AipsError);
     134           0 :   return true;
     135             : }
     136             : 
     137           0 : Bool VLATapeInput::fillBuffer(uInt& bytesToRead) {
     138             : //   cerr << "  Trying to read " << bytesToRead << " bytes" << endl;
     139           0 :   DebugAssert(bytesToRead <= VLATapeInput::ReadSize, AipsError);
     140           0 :   DebugAssert(bytesToRead%VLAArchiveInput::BlockSize == 0, AipsError);
     141           0 :   const Int bytesRead = itsTape.read(bytesToRead, itsBuffer.storage(), false);
     142             : //   cerr << "  Bytes read: " << bytesRead
     143             : //        << " Position: " << itsInputPtr->seek(0L, ByteIO::Current)
     144             : //        << " Length: " << itsInputPtr->length()
     145             : //        << endl;
     146           0 :   if ((bytesRead <= 0) || (bytesRead%VLAArchiveInput::BlockSize != 0)) {
     147           0 :     itsMemIO->clear();
     148           0 :     return false;
     149             :   }
     150           0 :   bytesToRead = bytesRead;
     151           0 :   return true;
     152             : }
     153             : 
     154           0 : Bool VLATapeInput::nextFile() {
     155           0 :   if (itsCurFile == static_cast<Int>(itsFiles.nelements()) - 1) return false;
     156             :   Int skip;
     157           0 :   if (itsCurFile < 0) {
     158           0 :     itsCurFile = 0;
     159           0 :     if (itsFiles[0] > 0) {
     160           0 :       itsTape.rewind();
     161           0 :       skip = itsFiles[0] - 1;
     162             :     } else {
     163           0 :       skip = 0;
     164             :     }
     165             :   } else {
     166           0 :     const Int curFile = itsFiles[itsCurFile];
     167           0 :     itsCurFile++;
     168           0 :     const Int nextFile = itsFiles[itsCurFile];
     169           0 :     if ((nextFile != 0) && (curFile == 0)) {
     170           0 :       itsTape.rewind();
     171           0 :       skip = nextFile - 1;
     172             :     } else {
     173           0 :       skip = nextFile - curFile - 1;
     174             :     }
     175             :   }
     176           0 :   DebugAssert(skip >= 0, AipsError);
     177           0 :   if (skip > 0) itsTape.skip(skip);
     178           0 :   return true;
     179             : }
     180             : 
     181           0 : Bool VLATapeInput::nextRecord() {
     182             :   // Clear the internal buffers and reset the flags as we will try to read some
     183             :   // more data.
     184           0 :   const Bool gotDataPrev = itsMemIO->length() > 0 ? true : false;
     185           0 :   itsMemIO->clear();
     186             :   // Find an initial record.
     187           0 :   Short n = 1, m;
     188           0 :   if (findFirstRecord(m) == false) {
     189           0 :     if (gotDataPrev) return false; // End of file
     190             :     throw(AipsError("VLATapeInput::nextRecord - Cannot find the start of the "
     191             :                     "record.\nPossible reasons are:\n"
     192             :                     "* your tape is not in VLA archive format\n"
     193             :                     "* you are trying to read the tape label\n"
     194             :                     "* you are trying to read beyond the end of the tape\n"
     195           0 :                     "* you have a corrupted tape."));
     196             : 
     197             :   }
     198           0 :   uInt thisReadSize = itsMemIO->length();
     199           0 :   DebugAssert(thisReadSize >= VLAArchiveInput::HeaderSize, AipsError);
     200             :   // We have the first physical record in Memory. Now decode how long this
     201             :   // logical record is.
     202           0 :   itsRecord.seek(0);
     203             :   Int logicalRecordSize;
     204           0 :   itsRecord >> logicalRecordSize;
     205           0 :   logicalRecordSize *= 2;
     206           0 :   itsRecord.seek(0, ByteIO::End);
     207           0 :   Int bytesToRead = logicalRecordSize - thisReadSize;
     208             : //   cerr << "Still have " << bytesToRead << " bytes to read out of "
     209             : //        << logicalRecordSize << " bytes in this record."
     210             : //        << " The buffer contains " << itsMemIO->length() << " bytes"
     211             : //        << endl;
     212           0 :   while (bytesToRead > 0) {
     213           0 :     if (bytesToRead < static_cast<Int>(VLATapeInput::ReadSize)) {
     214           0 :       thisReadSize = (bytesToRead-1)/VLAArchiveInput::BlockSize + 1;
     215           0 :       thisReadSize *= VLAArchiveInput::BlockSize;
     216             :     } else {
     217           0 :       thisReadSize = VLATapeInput::ReadSize;
     218             :     }
     219             : 
     220           0 :     if (fillBuffer(thisReadSize) == false) return false;
     221             :     // Check the sequence numbers
     222             :     {
     223           0 :       itsRecord.write(VLAArchiveInput::HeaderSize, itsBuffer.storage());
     224           0 :       itsRecord.seek(-static_cast<Int64>(VLAArchiveInput::HeaderSize),
     225             :                      ByteIO::End);
     226             :       Short newn, newm;
     227           0 :       itsRecord >> newn;
     228           0 :       itsRecord >> newm;
     229             : //       cerr << "Sequence numbers: Found m = " << newm << " n = " << newn;
     230             : //       cerr << "   Expected m = " << m << " n = " << n+1 << endl;
     231           0 :       if (newm != m || ++n != newn) {
     232           0 :         itsMemIO->clear();
     233           0 :         return false;
     234             :       }
     235           0 :       itsRecord.seek(-static_cast<Int64>(VLAArchiveInput::HeaderSize),
     236             :                      ByteIO::End);
     237             :     }
     238             :     // The sequence numbers are OK so write the rest of the data
     239           0 :     const uInt bytesToWrite = thisReadSize -4u;
     240             :     //const uInt bytesToWrite = thisReadSize < static_cast<uInt>(bytesToRead) ?
     241             :                               //(thisReadSize - 4u): thisReadSize;
     242             : 
     243           0 :     itsRecord.write(bytesToWrite,
     244           0 :                     itsBuffer.storage() + VLAArchiveInput::HeaderSize);
     245           0 :     bytesToRead -= thisReadSize;
     246             : //     cerr << "Read a logical block. Still have "
     247             : //       << bytesToRead << " bytes to read. The buffer contains "
     248             : //       << itsMemIO->length() << " bytes" << endl;
     249             :   }
     250           0 :   itsRecord.seek(0);
     251           0 :   return true;
     252             : }
     253             : // Local Variables:
     254             : // compile-command: "gmake VLATapeInput; cd test; gmake OPTLIB=1 tVLATapeInput"
     255             : // End: