frame_render.cpp

FreeAMP(MP3播放)程序源代码-用来研究MP3解码

// $Id: frame_render.cpp,v 1.2 2001/01/16 21:08:01 robert Exp $

// id3lib: a C++ library for creating and manipulating id3v1/v2 tags
// Copyright 1999, 2000  Scott Thomas Haug

// 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 "id3config.h"
#include <string.h>
#include <memory.h>
#ifdef HAVE_ZLIB
#include <zlib.h>
#endif

#include "tag.h"
#include "utils.h"
#include "frame_impl.h"
#include "io_decorators.h"
#include "io_strings.h"
#include "io_helpers.h"

using namespace dami;

namespace 
{
  void renderFields(ID3_Writer& writer, const ID3_FrameImpl& frame)
  {
    ID3_TextEnc enc = ID3TE_ASCII;
    for (ID3_FrameImpl::const_iterator fi = frame.begin(); fi != frame.end(); ++fi)
    {
      ID3_Field* fld = *fi;
      if (fld != NULL && fld->InScope(frame.GetSpec()))
      {
        if (fld->GetID() == ID3FN_TEXTENC)  
        {
          enc = static_cast<ID3_TextEnc>(fld->Get());  
          ID3D_NOTICE( "id3::v2::renderFields(): found encoding = " << enc );
        }
        else
        {
          fld->SetEncoding(enc);
        }
        fld->Render(writer);
      }
    }
  }
}
  
void ID3_FrameImpl::Render(ID3_Writer& writer) const
{
  // Return immediately if we have no fields, which (usually) means we're
  // trying to render a frame which has been Cleared or hasn't been initialized
  if (!this->NumFields())
  {
    return;
  }

  ID3_FrameHeader hdr;
  
  const size_t hdr_size = hdr.Size();

  // 1.  Write out the field data to the buffer, with the assumption that
  //     we won't be decompressing, since this is the usual behavior
  String flds;
  io::StringWriter fldWriter(flds);
  size_t origSize = 0;
  if (!this->GetCompression())
  {
    renderFields(fldWriter, *this);
    origSize = flds.size();
    ID3D_NOTICE ( "ID3_FrameImpl::Render(): uncompressed fields" );
  }
#ifdef HAVE_ZLIB
  else
  {
    io::CompressedWriter cr(fldWriter);
    renderFields(cr, *this);
    cr.flush();
    origSize = cr.getOrigSize();
    ID3D_NOTICE ( "ID3_FrameImpl::Render(): compressed fields, orig size = " <<
                  origSize );
  }
#endif
  size_t fldSize = flds.size();
  ID3D_NOTICE ( "ID3_FrameImpl::Render(): field size = " << fldSize );
  if (fldSize == 0)
  {
    ID3D_WARNING ( "ID3_FrameImpl::Render(): no field data" );
    return;
  }
  
  // determine which flags need to be set
  uchar eID = this->GetEncryptionID(), gID = this->GetGroupingID();
  hdr.SetFrameID(this->GetID());
  hdr.SetEncryption(eID > 0);
  hdr.SetGrouping(gID > 0);
  hdr.SetCompression(origSize > fldSize);
  hdr.SetDataSize(fldSize + ((hdr.GetCompression() ? 4 : 0) + 
                             (hdr.GetEncryption()  ? 1 : 0) + 
                             (hdr.GetGrouping()    ? 1 : 0)));

  // write out the header
  hdr.Render(writer);

  // No-man's land!  Not part of the header, not part of the data
  if (hdr.GetCompression())
  {
    io::writeBENumber(writer, origSize, sizeof(uint32));
    ID3D_NOTICE( "ID3_FrameImpl::Render(): frame is compressed, wrote origSize = " << origSize );
  }
  if (hdr.GetEncryption())
  {
    writer.writeChar(eID);
    ID3D_NOTICE( "ID3_FrameImpl::Render(): frame is compressed, encryption id = " << eID );
  }
  if (hdr.GetGrouping())
  {
    writer.writeChar(gID);
    ID3D_NOTICE( "ID3_FrameImpl::Render(): frame is compressed, grouping id = " << gID );
  }

  // Write the field data
  writer.writeChars(flds.data(), fldSize);
  _changed = false;
}