EnigmA Amiga Run 1995 October/EnigmA AMIGA RUN 01 (1995)(G.R. Edizioni)(IT)[!][issue 1995-10][Aminet 7].iso/Aminet/mus/misc/maplay1_2.lha/maplay/ibitstream.cc

C/C++ Source or Header | 1994-06-23 | 5KB | 218 lines

/*
 *  @(#) ibitstream.cc 1.8, last edit: 6/15/94 16:51:45
 *  @(#) Copyright (C) 1993, 1994 Tobias Bading ([e-mail])
 *  @(#) Berlin University of Technology
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 *  Changes from version 1.1 to 1.2:
 *    - third argument in open syscall added
 *    - minor bug in get_header() fixed
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <iostream.h>
#include "all.h"
#include "ibitstream.h"


#define swap_int32(int_32) (((int_32) << 24) | (((int_32) << 8) & 0x00ff0000) | \
               (((int_32) >> 8) & 0x0000ff00) | ((int_32) >> 24))


Ibitstream::Ibitstream (int filedescriptor)        // constructor
{
  fd = filedescriptor;
  wordpointer = buffer;
  bitindex = 0;
}


Ibitstream::Ibitstream (const char *filename)        // constructor
{
  if ((fd = open (filename, O_RDONLY, 0)) < 0)
  {
    cerr << "can't open file \"" << filename << "\" for reading!\n";
    exit (1);
  }
  wordpointer = buffer;
  bitindex = 0;
}


Ibitstream::~Ibitstream (void)                // destructor
{
  close (fd);
}


bool Ibitstream::get_header (uint32 *headerstring)
{
  int readvalue;

  if ((readvalue = read (fd, (char *)headerstring, 4)) != 4)
  {
    if (readvalue < 0)
    {
      perror ("read");
      exit (1);
    }
    else if (!readvalue)
      return False;        // EOF
    // header has not been read completely (this may happen while using a pipe)
    int length = 4 - readvalue;
    char *buffer_pos = (char *)headerstring;
    do
    {
      buffer_pos += readvalue;
      readvalue = read (fd, buffer_pos, length);
      if (readvalue < 0)
      {
    perror ("read");
    exit (1);
      }
      else if (!readvalue)
    return False;
    }
    while (length -= readvalue);
  }
#ifdef DAMN_INTEL_BYTE_ORDER
  register uint32 header = *headerstring;
  *headerstring = swap_int32 (header);
#endif
  return True;
}


bool Ibitstream::read_frame (uint32 bytesize)
{
  int readvalue;

  if (bytesize > (bufferintsize << 2))
  {
    cerr << "Internal error: framelength > bufferlength?!\n";
    exit (1);
  }

  if ((readvalue = read (fd, (char *)buffer, bytesize)) != bytesize)
  {
    if (readvalue < 0)
    {
      perror ("read");
      exit (1);
    }
    else if (!readvalue)
      return False;        // EOF
    // frame has not been read completely (this may happen while using a pipe)
    int length = bytesize - readvalue;
    char *buffer_pos = (char *)buffer;
    do
    {
      buffer_pos += readvalue;
      readvalue = read (fd, buffer_pos, length);
      if (readvalue < 0)
      {
    perror ("read");
    exit (1);
      }
      else if (!readvalue)
    return False;
    }
    while (length -= readvalue);
  }

  wordpointer = buffer;
  bitindex = 0;
  framesize = bytesize;
#ifdef DAMN_INTEL_BYTE_ORDER
  register uint32 *wordp, word;
  for (wordp = buffer + ((bytesize - 1) >> 2); wordp >= buffer; --wordp)
  {
    word = *wordp;
    *wordp = swap_int32 (word);
  }
#endif
  return True;
}


uint32 Ibitstream::get_bits (uint32 number_of_bits)
{
  static uint32 bitmask[17] =
  {
    0,    // dummy
    0x00000001, 0x00000003, 0x00000007, 0x0000000F,
    0x0000001F, 0x0000003F, 0x0000007F, 0x000000FF,
    0x000001FF, 0x000003FF, 0x000007FF, 0x00000FFF,
    0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF
  };
  uint32 returnvalue;
  uint32 sum = bitindex + number_of_bits;

#ifdef DEBUG
  if (number_of_bits < 1 || number_of_bits > 16)
  {
    cerr << "illegal parameter in Ibitstream::get_bits() !\n";
    exit (1);
  }
#endif

  if (sum <= 32)
  {
    // all bits contained in *wordpointer
    returnvalue = (*wordpointer >> (32 - sum)) & bitmask[number_of_bits];
    if ((bitindex += number_of_bits) == 32)
    {
      bitindex = 0;
      if ((char *)++wordpointer > (char *)buffer + framesize)
      {
    cerr << "Ibitstream::get_bits(): no more bits in buffer!\n";
    exit (1);
      }
    }
    return returnvalue;
  }

  // bits are in *wordpointer and *(wordpointer + 1)
  // bitindex has to be > 16
#ifndef DAMN_INTEL_BYTE_ORDER
  *(int16 *)&returnvalue = *((int16 *)wordpointer + 1);
  if ((char *)++wordpointer > (char *)buffer + framesize)
  {
    cerr << "Ibitstream::get_bits(): no more bits in buffer!\n";
    exit (1);
  }
  *((int16 *)&returnvalue + 1) = *(int16 *)wordpointer;
#else
  *((int16 *)&returnvalue + 1) = *(int16 *)wordpointer;
  if ((char *)++wordpointer > (char *)buffer + framesize)
  {
    cerr << "Ibitstream::get_bits(): no more bits in buffer!\n";
    exit (1);
  }
  *(int16 *)&returnvalue = *((int16 *)wordpointer + 1);
#endif
  returnvalue >>= 48 - sum;    // returnvalue >>= 16 - (number_of_bits - (32 - bitindex))
  returnvalue &= bitmask[number_of_bits];
  bitindex = sum - 32;
  return returnvalue;
}