public ZText(byte[] memory)
{
this.memory = memory;
this.alphabetTable = new AlphabetTable(memory);
this.version = Header.ReadVersion(memory);
this.builder = new StringBuilder();
this.abbreviationAlphabetTable = new AlphabetTable(memory);
this.abbreviationBuilder = new StringBuilder();
}
private string ZWordsAsString(ushort[] zwords, ZTextFlags flags, AlphabetTable alphabetTable, StringBuilder builder)
{
var zchars = ZWordsToZChars(zwords);
builder.Clear();
if (builder.Capacity < zchars.Length)
{
builder.Capacity = zchars.Length;
}
alphabetTable.FullReset();
var i = 0;
while (i < zchars.Length)
{
var zchar = zchars[i];
if (zchar == 0)
{
builder.Append(' ');
}
else if (zchar >= 1 && zchar <= 3)
{
if (version == 1 || (version == 2 && zchar >= 2))
{
switch (zchar)
{
case 1:
builder.Append('\n');
break;
case 2:
alphabetTable.Shift();
break;
case 3:
alphabetTable.DoubleShift();
break;
}
}
else // abbeviations
{
if ((flags & ZTextFlags.AllowAbbreviations) == 0)
{
throw new InvalidOperationException("Encountered ZSCII code for an illegal abbreviation.");
}
if (i + 1 < zchars.Length)
{
var abbreviationCode = zchars[++i];
var abbreviationIndex = (32 * (zchar - 1)) + abbreviationCode;
var abbreviationZWords = ReadAbbreviation(memory, abbreviationIndex);
var abbreviationText = ZWordsAsString(abbreviationZWords, ZTextFlags.None, abbreviationAlphabetTable, abbreviationBuilder);
builder.Append(abbreviationText);
}
}
}
else if (zchar == 4)
{
if (version <= 2)
{
alphabetTable.ShiftLock();
}
else
{
alphabetTable.Shift();
}
}
else if (zchar == 5)
{
if (version <= 2)
{
alphabetTable.DoubleShiftLock();
}
else
{
alphabetTable.DoubleShift();
}
}
else if (zchar == 6 && alphabetTable.CurrentAlphabet == 2)
{
// If this is character 6 in A2, it's a multibyte ZSCII character
// Note that it can be legal for the stream to end in the middle of a
// multi-byte ZSCII character (i.e. in the dictionary table). In that case,
// the value is discared or an exception is thrown if that behavior
// isn't allowed.
// The alphabet table must be reset to ensure that the next zcode
// after the multi-byte ZSCII character uses the correct alphabet.
alphabetTable.Reset();
if (i + 2 < zchars.Length)
{
var zscii1 = zchars[++i];
var zscii2 = zchars[++i];
var zscii = ((zscii1 & 0x1f) << 5) | zscii2;
builder.Append((char)zscii);
}
else
{
if ((flags & ZTextFlags.AllowIncompleteMultibyteChars) == 0)
{
throw new InvalidOperationException("Encountered illegal incomplete multi-byte ZSCII character.");
}
}
}
else if (zchar > 31)
{
throw new InvalidOperationException("Unexpected ZSCII character value: " + zchar + ". Legal values are from 0 to 31.");
}
else
{
builder.Append(alphabetTable.ReadChar(zchar));
}
i++;
}
return(builder.ToString());
}