header_tag.cpp

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// $Id: header_tag.cpp,v 1.25 2003/03/02 14:30:46 t1mpy Exp $
 
// id3lib: a C++ library for creating and manipulating id3v1/v2 tags
// Copyright 1999, 2000  Scott Thomas Haug
// Copyright 2002  Thijmen Klok (thijmen@id3lib.org)
 
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Library General Public License as published by
// the Free Software Foundation; either version 2 of the License, or (at your
// option) any later version.
//
// This library is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
// License for more details.
//
// You should have received a copy of the GNU Library General Public License
// along with this library; if not, write to the Free Software Foundation,
// Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 
// The id3lib authors encourage improvements and optimisations to be sent to
// the id3lib coordinator.  Please see the README file for details on where to
// send such submissions.  See the AUTHORS file for a list of people who have
// contributed to id3lib.  See the ChangeLog file for a list of changes to
// id3lib.  These files are distributed with id3lib at
// http://download.sourceforge.net/id3lib/
 
 
#include "header_tag.h"
#include "id3/utils.h" // has <config.h> "id3/id3lib_streams.h" "id3/globals.h" "id3/id3lib_strings.h"
#include "tag.h"
#include "io_helpers.h"
#include "spec.h"
#include <cstdlib> // for std::getenv (opt-in diagnostic below)
 
using namespace dami;
 
const char* const ID3_TagHeader::ID = "ID3";
 
bool ID3_TagHeader::SetSpec(ID3_V2Spec spec)
{
  bool changed = this->ID3_Header::SetSpec(spec);
  if (changed)
  {
    if (_info)
    {
      _flags.set(HEADER_FLAG_EXPERIMENTAL, _info->is_experimental);
      _flags.set(HEADER_FLAG_EXTENDED,     _info->is_extended);
    }
  }
  return changed;
}
 
size_t ID3_TagHeader::Size() const
{
  size_t bytesUsed = ID3_TagHeader::SIZE;
 
  if (_info && _info->is_extended)
  {
    bytesUsed += _info->extended_bytes;
  }
 
  return bytesUsed;
}
 
 
void ID3_TagHeader::Render(ID3_Writer& writer) const
{
  writer.writeChars((uchar *) ID, strlen(ID));
 
  writer.writeChar(ID3_V2SpecToVer(ID3V2_LATEST));
  writer.writeChar(ID3_V2SpecToRev(ID3V2_LATEST));
 
  // set the flags byte in the header
  writer.writeChar(static_cast<uchar>(_flags.get() & MASK8));
  io::writeUInt28(writer, this->GetDataSize()); //now includes the extended header
 
  // now we render the extended header
  if (_flags.test(HEADER_FLAG_EXTENDED))
  {
    if (this->GetSpec() == ID3V2_4_0)
    {
      io::writeUInt28(writer, 6); //write 4 bytes of v2.4.0 ext header containing size '6'
      io::writeBENumber(writer, 1, 1); //write that it has only one flag byte (value '1')
      io::writeBENumber(writer, 0, 1); //write flag byte with value '0'
    }
    else if (this->GetSpec() == ID3V2_3_0)
    {
      io::writeBENumber(writer, 6, sizeof(uint32));
      for (size_t i = 0; i < 6; ++i)
      {
        if (writer.writeChar('\0') == ID3_Writer::END_OF_WRITER)
        {
          break;
        }
      }
    }
  //  else //not implemented
  }
}
 
bool ID3_TagHeader::Parse(ID3_Reader& reader)
{
  io::ExitTrigger et(reader);
  if (!ID3_Tag::IsV2Tag(reader))
  {
    ID3D_NOTICE( "ID3_TagHeader::Parse(): not an id3v2 header" );
    return false;
  }
 
  uchar id[3];
  reader.readChars(id, 3);
  // The spec version is determined with the MAJOR and MINOR OFFSETs
  uchar major = reader.readChar();
  uchar minor = reader.readChar();
  this->SetSpec(ID3_VerRevToV2Spec(major, minor));
 
  // id3lib only fully supports up to ID3v2.3.0 (ID3V2_LATEST).  A higher or
  // unrecognised v2 version (e.g. ID3v2.4) cannot be parsed correctly and is
  // dropped without any indication (Debian bug #449186).  When the
  // ID3LIB_WARN_UNSUPPORTED environment variable is set, emit a single notice
  // so this case can be made observable.  The library stays silent by default
  // (a shared library must not write to stderr unsolicited, and ID3v2.4 tags
  // are common).  Parsing behaviour is unchanged either way.
  if ((this->GetSpec() == ID3V2_UNKNOWN || this->GetSpec() > ID3V2_LATEST) &&
      std::getenv("ID3LIB_WARN_UNSUPPORTED") != NULL)
  {
    std::clog << "id3lib: ID3v2." << static_cast<int>(major) << "."
              << static_cast<int>(minor)
              << " tag found, but only ID3v2.3.0 and earlier are supported; "
              << "this tag may not be read correctly" << std::endl;
  }
 
  // Get the flags at the appropriate offset
  _flags.set(static_cast<ID3_Flags::TYPE>(reader.readChar()));
 
  // set the data size
  this->SetDataSize(io::readUInt28(reader));
 
  if (_flags.test(HEADER_FLAG_EXTENDED) && this->GetSpec() == ID3V2_2_1)
  {
    //couldn't find anything about this in the draft specifying 2.2.1 -> http://www.id3.org/pipermail/id3v2/2000-April/000126.html
    _flags.set(HEADER_FLAG_EXTENDED, false);
    _info->extended_bytes = 0;
    // rest is checked at ParseExtended()
  }
  et.setExitPos(reader.getCur());
  return true;
}
 
void ID3_TagHeader::ParseExtended(ID3_Reader& reader)
{
  if (this->GetSpec() == ID3V2_3_0)
  {
/*
    Extended header size   $xx xx xx xx
    Extended Flags         $xx xx
    Size of padding        $xx xx xx xx
*/
    // skip over header size, we are not using it anyway, we calculate it
    reader.setCur(reader.getCur()+4); //Extended header size
    //io::readBENumber(reader, 4); //Extended header size
    uint16 tmpval = io::readBENumber(reader, 2); //Extended Flags
    // skip over padding size, we are not using it anyway
    reader.setCur(reader.getCur()+4); //Size of padding
    // io::readBENumber(reader, 4); //Size of padding
    if (tmpval != 0) //there is only one flag defined in ID3V2_3_0: crc
    {
      //skip over crc data, we are not using it anyway
      reader.setCur(reader.getCur()+4); //Crc
      //io::readBENumber(reader, 4); //Crc
      _info->extended_bytes = 14;
    }
    else
      _info->extended_bytes = 10;
  }
  if (this->GetSpec() == ID3V2_4_0)
  {
/*
    Extended header size   4 * %0xxxxxxx
    Number of flag bytes       $01
    Extended Flags             $xx
*/
    uint16 i;
    uint16 extrabytes;
 
    io::readUInt28(reader);
    const int extflagbytes = reader.readChar(); //Number of flag bytes
    ID3_Flags* extflags[1]; // ID3V2_4_0 has 1 flag byte, extflagbytes should be equal to 1
    for (i = 0; i < extflagbytes; ++i)
    {
      extflags[i] = new ID3_Flags;
      extflags[i]->set(reader.readChar()); //flags
    }
    extrabytes = 0;
    //extflags[0]->test(EXT_HEADER_FLAG_BIT1); // ID3V2_4_0 ext header flag bit 1 *should* be 0
    if (extflags[0]->test(EXT_HEADER_FLAG_BIT2))
    {
      // ID3V2_4_0 ext header flag bit 2 = Tag is an update
      // read size
      extrabytes += 1; // add a byte for the char containing the extflagdatasize
      const int extheaderflagdatasize = reader.readChar();
      extrabytes += extheaderflagdatasize;
      // Set the cursor right; we are not parsing the data, no-one is using extended flags anyway
      reader.setCur(reader.getCur() + extheaderflagdatasize);
      //reader.readChars(buf, extheaderflagdatasize); //buf should be at least 127 bytes = max extended header flagdata size
    }
   if (extflags[0]->test(EXT_HEADER_FLAG_BIT3))
   {
      // ID3V2_4_0 ext header flag bit 3 = CRC data present
      // read size
      extrabytes += 1; // add a byte for the char containing the extflagdatasize
      const int extheaderflagdatasize = reader.readChar();
      extrabytes += extheaderflagdatasize;
      // Set the cursor right; we are not parsing the data, no-one is using extended flags anyway
      reader.setCur(reader.getCur() + extheaderflagdatasize);
      //reader.readChars(buf, extheaderflagdatasize); //buf should be at least 127 bytes = max extended header flagdata size
    }
    if (extflags[0]->test(EXT_HEADER_FLAG_BIT4))
    {
      // ID3V2_4_0 ext header flag bit 4 = Tag restrictions
      // read size
      extrabytes += 1; // add a byte for the char containing the extflagdatasize
      const int extheaderflagdatasize = reader.readChar();
      extrabytes += extheaderflagdatasize;
      // Set the cursor right; we are not parsing the data, no-one is using extended flags anyway
      reader.setCur(reader.getCur() + extheaderflagdatasize);
      //reader.readChars(buf, extheaderflagdatasize); //buf should be at least 127 bytes = max extended header flagdata size
    }
    _info->extended_bytes = 5 + extflagbytes + extrabytes;
  }
  // a bit unorthodox, but since we are not using any of the extended header, but were merely
  // parsing it to get the cursor right, we delete it. Be Gone !
  _flags.set(HEADER_FLAG_EXTENDED, false);
  if (_info)
  {
    _data_size -= _info->extended_bytes;
    _info->extended_bytes = 0;
  }//else there is a tag with a higher or lower version than supported
}