public int ReadRecord(out bool binary, out byte[] mrecord) /* reads a record as array of 6-bit value from tape-file, retun -1:ende of input file 0: EOF marker read, 1: record read; binary=true: binary record false: bcd record */
{
int b; /* current character */
mrecord = null;
binary = false;
if (stored) /* fist byte of record already read? */
{
b = last; /* use it */
stored = false;
}
else
{
b = f.ReadByte(); /* read byte */
}
if (b < 0) /* end of media ? */
{
return(-1); /* EOM */
}
recpos.Push(f.Position - 1); /* store startposition of record for backspace*/
if ((b & 128) == 0) /* The first byte of a records must have bit 7 set */
{
throw new InvalidDataException("TapeFile:Bit 7 not set at record start");
}
List <byte> trecord = new List <byte>()
{
(byte)(b & 127)
}; /* remove record start marker, store character */
do
{
b = f.ReadByte();
if (b < 0 || (b & 128) != 0) /* next record or EOF */
{
stored = true; /* set flag */
last = b; /* store value for next call*/
break;
}
trecord.Add((byte)b);
}while (true);
TapeConverter.FromTape(trecord.ToArray(), out binary, out mrecord);
if (!binary && mrecord.Length == 1 && mrecord[0] == 15)
{
return(0); /* EOF */
}
return(1); /* no EOF */
}
public void WriteRecord(bool binary, byte[] mrecord)
{
if (stored && last != -1)
{
f.Seek(-1, SeekOrigin.Current);
}
stored = false;
TapeConverter.ToTape(binary, mrecord, out byte[] trecord);
recpos.Push(f.Position);
trecord[0] |= 0x80; /* add record marker */
f.Write(trecord, 0, trecord.Length);
if (f.Position != f.Length) /* not at end of file? */
{
f.SetLength(f.Position); /* cut remaining parts */
}
}
public void WriteRecord(bool binary, byte[] mrecord)
{
if (stored && last != -1) /* first byte of record already read ? */
{
f.Seek(-1, SeekOrigin.Current); /* go back to start of record */
}
stored = false;
TapeConverter.ToTape(binary, mrecord, out byte[] trecord); /* convert to tape format, generate parity */
recpos.Push(f.Position); /* store startpos of record on stack */
trecord[0] |= 0x80; /* add record marker */
f.Write(trecord, 0, trecord.Length);
if (f.Position != f.Length) /* currently not at end of the tape-file? */
{
f.SetLength(f.Position); /* cut remaining parts of the file */
}
}
