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src/common.c  view on Meta::CPAN

int32_t
skip_id3v2(PerlIO* infile) {
  unsigned char buf[10];
  uint32_t has_footer;
  int32_t  size;

  // seek to first byte of mpc data
  if (PerlIO_seek(infile, 0, SEEK_SET) < 0)
    return 0;

  PerlIO_read(infile, &buf, sizeof(buf));

  // check id3-tag
  if (memcmp(buf, "ID3", 3) != 0)
    return 0;

  // read flags
  has_footer = buf[5] & 0x10;

  if (buf[5] & 0x0F)
    return -1;

  if ((buf[6] | buf[7] | buf[8] | buf[9]) & 0x80)
    return -1;

  // read header size (syncsave: 4 * $0xxxxxxx = 28 significant bits)
  size  = buf[6] << 21;
  size += buf[7] << 14;
  size += buf[8] <<  7;
  size += buf[9]      ;
  size += 10;

  if (has_footer)
    size += 10;

  return size;
}

uint32_t
_bitrate(uint32_t audio_size, uint32_t song_length_ms)
{
  return ( (audio_size * 1.0) / song_length_ms ) * 8000;
}

off_t
_file_size(PerlIO *infile)
{
#ifdef _MSC_VER
  // Win32 doesn't work right with fstat
  off_t file_size;

  PerlIO_seek(infile, 0, SEEK_END);
  file_size = PerlIO_tell(infile);
  PerlIO_seek(infile, 0, SEEK_SET);

  return file_size;
#else
  struct stat buf;

  if ( !fstat( PerlIO_fileno(infile), &buf ) ) {
    return buf.st_size;
  }

  warn("Unable to stat: %s\n", strerror(errno));

  return 0;
#endif
}

int
_env_true(const char *name)
{
  char *value;

  value = getenv(name);

  if ( value == NULL || value[0] == '0' ) {
    return 0;
  }

  return 1;
}

// from http://jeremie.com/frolic/base64/
int
_decode_base64(char *s)
{
  char *b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  int bit_offset, byte_offset, idx, i, n;
  unsigned char *d = (unsigned char *)s;
  char *p;

  n = i = 0;

  while (*s && (p=strchr(b64,*s))) {
    idx = (int)(p - b64);
    byte_offset = (i*6)/8;
    bit_offset = (i*6)%8;
    d[byte_offset] &= ~((1<<(8-bit_offset))-1);

    if (bit_offset < 3) {
      d[byte_offset] |= (idx << (2-bit_offset));
      n = byte_offset+1;
    }
    else {
      d[byte_offset] |= (idx >> (bit_offset-2));
      d[byte_offset+1] = 0;
      d[byte_offset+1] |= (idx << (8-(bit_offset-2))) & 0xFF;
      n = byte_offset+2;
    }
    s++;
    i++;
  }

  /* null terminate */
  d[n] = 0;

  return n;
}