/// <summary>
/// Encoding length determinant procedure.
/// ITU-T X.691. 10.9. General rules for encoding a length determinant
/// </summary>
protected virtual int encodeLengthDeterminant(int length, BitArrayOutputStream stream)
{
int result = 0;
doAlign(stream);
if (length >= 0 && length < 0x80)
{
// NOTE 2. a) ("n" less than 128)
stream.WriteByte(length); // a single octet containing "n" with bit 8 set to zero;
result = 1;
}
else if (length < 0x4000)
{
// NOTE 2. b) ("n" less than 16K) two octets
// containing "n" with bit 8 of the first octet
// set to 1 and bit 7 set to zero;
stream.WriteByte((length >> 8) & 0x3f | 0x80);
stream.WriteByte(length);
result = 2;
}
else
{
// NOTE 2. b) (large "n") a single octet containing a count "m"
// with bit 8 set to 1 and bit 7 set to 1.
// The count "m" is one to four, and the length indicates that
// a fragment of the material follows (a multiple "m" of 16K items).
// For all values of "m", the fragment is then followed
// by another length encoding for the remainder of the material.
throw new ApplicationException("Not supported for this version. Length too big!");
}
return(result);
}
/// <summary>
/// Encoding of a constrained whole number
/// ITU-T X.691. 10.5.
/// NOTE – (Tutorial) This subclause is referenced by other clauses,
/// and itself references earlier clauses for the production of
/// a nonnegative-binary-integer or a 2's-complement-binary-integer encoding.
/// </summary>
protected virtual int encodeConstraintNumber(long val, long min, long max, BitArrayOutputStream stream)
{
int result = 0;
long valueRange = max - min;
long narrowedVal = val - min;
int maxBitLen = PERCoderUtils.getMaxBitLength(valueRange);
if (valueRange == 0)
{
return(result);
}
// The rest of this Note addresses the ALIGNED variant.
if (valueRange > 0 && valueRange < 256)
{
/*
* 1. Where the range is less than or equal to 255, the value encodes
* into a bit-field of the minimum size for the range.
* 2. Where the range is exactly 256, the value encodes
* into a single octet octet-aligned bit-field.
*/
doAlign(stream);
for (int i = maxBitLen - 1; i >= 0; i--)
{
int bitValue = (int)((narrowedVal >> i) & 0x1);
stream.writeBit(bitValue);
}
result = 1;
}
else if (valueRange > 0 && valueRange < 65536)
{
/*
* 3. Where the range is 257 to 64K, the value encodes into
* a two octet octet-aligned bit-field.
*/
doAlign(stream);
stream.WriteByte((byte)(narrowedVal >> 8));
stream.WriteByte((byte)(narrowedVal & 0xFF));
result = 2;
}
else
{
/*
* 4. Where the range is greater than 64K, the range is ignored
* and the value encodes into an octet-aligned bit-field
* which is the minimum number of octets for the value.
* In this latter case, later procedures (see 10.9)
* also encode a length field (usually a single octet) to indicate
* the length of the encoding. For the other cases, the length
* of the encoding is independent of the value being encoded,
* and is not explicitly encoded.
*/
result = encodeConstraintLengthDeterminant(CoderUtils.getIntegerLength(narrowedVal), 1, CoderUtils.getPositiveIntegerLength(valueRange), stream);
doAlign(stream);
result += encodeIntegerValueAsBytes(narrowedVal, stream);
}
return(result);
}
protected override int encodeConstraintNumber(long val, long min, long max, BitArrayOutputStream stream)
{
int result = 0;
long valueRange = max - min;
long narrowedVal = val - min;
int maxBitLen = PERCoderUtils.getMaxBitLength(valueRange);
if (valueRange == 0)
{
return(result);
}
//For the UNALIGNED variant the value is always encoded in the minimum
// number of bits necessary to represent the range (defined in 10.5.3).
int currentBit = maxBitLen;
while (currentBit > 8)
{
currentBit -= 8;
result++;
stream.WriteByte((byte)(narrowedVal >> currentBit));
}
if (currentBit > 0)
{
for (int i = currentBit - 1; i >= 0; i--)
{
int bitValue = (int)((narrowedVal >> i) & 0x1);
stream.writeBit(bitValue);
}
result += 1;
}
return(result);
}
/// <seealso cref="BitArrayOutputStream.write(int)">
/// </seealso>
public virtual void testWrite()
{
BitArrayOutputStream stream = new BitArrayOutputStream();
stream.WriteByte(0xFF);
stream.writeBit(true);
stream.writeBit(false);
stream.writeBit(true);
stream.writeBit(false);
stream.WriteByte(0xFF);
stream.WriteByte(0x0F);
stream.writeBit(true);
stream.writeBit(true);
stream.writeBit(true);
stream.writeBit(true);
System.Console.Out.WriteLine("Write " + ByteTools.byteArrayToHexString(stream.ToArray()));
ByteTools.checkBuffers(stream.ToArray(), new byte[] { 0xFF, 0xAF, 0xF0, 0xFF });
stream.writeBit(true);
stream.writeBit(false);
stream.writeBit(true);
stream.writeBit(false);
byte[] temp_byteArray;
temp_byteArray = new byte[] { (0xCC), (0xFF), (0xFF), (0xBB) };
stream.Write(temp_byteArray, 0, temp_byteArray.Length);
System.Console.Out.WriteLine("After buf write " + ByteTools.byteArrayToHexString(stream.ToArray()));
ByteTools.checkBuffers(stream.ToArray(), new byte[] { (0xFF), (0xAF), (0xF0), (0xFF), (0xAC), (0xCF), (0xFF), (0xFB), (0xB0) });
stream.align();
stream.writeBit(true);
stream.writeBit(true);
stream.align();
stream.WriteByte(0xFF);
System.Console.Out.WriteLine("After align " + ByteTools.byteArrayToHexString(stream.ToArray()));
ByteTools.checkBuffers(stream.ToArray(), new byte[] { (0xFF), (0xAF), (0xF0), (0xFF), (0xAC), (0xCF), (0xFF), (0xFB), (0xB0), (0xC0), (0xFF) });
}
