// T-REC-X.690-201508 sec 9.2, 8.6
private void WriteConstructedCerBitString(Asn1Tag tag, ReadOnlySpan <byte> payload, int unusedBitCount)
{
const int MaxCERSegmentSize = AsnReader.MaxCERSegmentSize;
// Every segment has an "unused bit count" byte.
const int MaxCERContentSize = MaxCERSegmentSize - 1;
Debug.Assert(payload.Length > MaxCERContentSize);
int expectedSize = DetermineCerBitStringTotalLength(tag, payload.Length);
this.EnsureWriteCapacity(expectedSize);
int savedOffset = this._offset;
this.WriteTag(tag.AsConstructed());
// T-REC-X.690-201508 sec 9.1
// Constructed CER uses the indefinite form.
this.WriteLength(-1);
byte[] ensureNoExtraCopy = this._buffer;
ReadOnlySpan <byte> remainingData = payload;
Span <byte> dest;
Asn1Tag primitiveBitString = Asn1Tag.PrimitiveBitString;
while (remainingData.Length > MaxCERContentSize)
{
// T-REC-X.690-201508 sec 8.6.4.1
this.WriteTag(primitiveBitString);
this.WriteLength(MaxCERSegmentSize);
// 0 unused bits in this segment.
this._buffer[this._offset] = 0;
this._offset++;
dest = this._buffer.AsSpan(this._offset);
remainingData.Slice(0, MaxCERContentSize).CopyTo(dest);
remainingData = remainingData.Slice(MaxCERContentSize);
this._offset += MaxCERContentSize;
}
this.WriteTag(primitiveBitString);
this.WriteLength(remainingData.Length + 1);
this._buffer[this._offset] = (byte)unusedBitCount;
this._offset++;
dest = this._buffer.AsSpan(this._offset);
remainingData.CopyTo(dest);
this._offset += remainingData.Length;
this.WriteEndOfContents();
Debug.Assert(this._offset - savedOffset == expectedSize, $"expected size was {expectedSize}, actual was {this._offset - savedOffset}");
Debug.Assert(this._buffer == ensureNoExtraCopy, $"_buffer was replaced during {nameof(this.WriteConstructedCerBitString)}");
}
// T-REC-X.690-201508 sec 9.2, 8.6
private void WriteConstructedCerBitString(Asn1Tag tag, ReadOnlySpan <byte> payload, int unusedBitCount)
{
const int MaxCERSegmentSize = AsnReader.MaxCERSegmentSize;
// Every segment has an "unused bit count" byte.
const int MaxCERContentSize = MaxCERSegmentSize - 1;
Debug.Assert(payload.Length > MaxCERContentSize);
WriteTag(tag.AsConstructed());
// T-REC-X.690-201508 sec 9.1
// Constructed CER uses the indefinite form.
WriteLength(-1);
int fullSegments = Math.DivRem(payload.Length, MaxCERContentSize, out int lastContentSize);
// The tag size is 1 byte.
// The length will always be encoded as 82 03 E8 (3 bytes)
// And 1000 content octets (by T-REC-X.690-201508 sec 9.2)
const int FullSegmentEncodedSize = 1004;
Debug.Assert(
FullSegmentEncodedSize == 1 + 1 + MaxCERSegmentSize + GetEncodedLengthSubsequentByteCount(MaxCERSegmentSize));
int remainingEncodedSize;
if (lastContentSize == 0)
{
remainingEncodedSize = 0;
}
else
{
// One byte of tag, minimum one byte of length, and one byte of unused bit count.
remainingEncodedSize = 3 + lastContentSize + GetEncodedLengthSubsequentByteCount(lastContentSize);
}
// Reduce the number of copies by pre-calculating the size.
// +2 for End-Of-Contents
int expectedSize = fullSegments * FullSegmentEncodedSize + remainingEncodedSize + 2;
EnsureWriteCapacity(expectedSize);
byte[] ensureNoExtraCopy = _buffer;
int savedOffset = _offset;
ReadOnlySpan <byte> remainingData = payload;
Span <byte> dest;
Asn1Tag primitiveBitString = Asn1Tag.PrimitiveBitString;
while (remainingData.Length > MaxCERContentSize)
{
// T-REC-X.690-201508 sec 8.6.4.1
WriteTag(primitiveBitString);
WriteLength(MaxCERSegmentSize);
// 0 unused bits in this segment.
_buffer[_offset] = 0;
_offset++;
dest = _buffer.AsSpan(_offset);
remainingData.Slice(0, MaxCERContentSize).CopyTo(dest);
remainingData = remainingData.Slice(MaxCERContentSize);
_offset += MaxCERContentSize;
}
WriteTag(primitiveBitString);
WriteLength(remainingData.Length + 1);
_buffer[_offset] = (byte)unusedBitCount;
_offset++;
dest = _buffer.AsSpan(_offset);
remainingData.CopyTo(dest);
_offset += remainingData.Length;
WriteEndOfContents();
Debug.Assert(_offset - savedOffset == expectedSize, $"expected size was {expectedSize}, actual was {_offset - savedOffset}");
Debug.Assert(_buffer == ensureNoExtraCopy, $"_buffer was replaced during {nameof(WriteConstructedCerBitString)}");
}
// T-REC-X.690-201508 sec 9.2, 8.7
private void WriteConstructedCerOctetString(Asn1Tag tag, ReadOnlySpan <byte> payload)
{
const int MaxCERSegmentSize = AsnReader.MaxCERSegmentSize;
Debug.Assert(payload.Length > MaxCERSegmentSize);
this.WriteTag(tag.AsConstructed());
this.WriteLength(-1);
int fullSegments = Math.DivRem(payload.Length, MaxCERSegmentSize, out int lastSegmentSize);
// The tag size is 1 byte.
// The length will always be encoded as 82 03 E8 (3 bytes)
// And 1000 content octets (by T-REC-X.690-201508 sec 9.2)
const int FullSegmentEncodedSize = 1004;
Debug.Assert(
1 + 1 + MaxCERSegmentSize + GetEncodedLengthSubsequentByteCount(MaxCERSegmentSize) == FullSegmentEncodedSize);
int remainingEncodedSize;
if (lastSegmentSize == 0)
{
remainingEncodedSize = 0;
}
else
{
// One byte of tag, and minimum one byte of length.
remainingEncodedSize = 2 + lastSegmentSize + GetEncodedLengthSubsequentByteCount(lastSegmentSize);
}
// Reduce the number of copies by pre-calculating the size.
// +2 for End-Of-Contents
int expectedSize = (fullSegments * FullSegmentEncodedSize) + remainingEncodedSize + 2;
this.EnsureWriteCapacity(expectedSize);
byte[] ensureNoExtraCopy = this._buffer;
int savedOffset = this._offset;
ReadOnlySpan <byte> remainingData = payload;
Span <byte> dest;
Asn1Tag primitiveOctetString = Asn1Tag.PrimitiveOctetString;
while (remainingData.Length > MaxCERSegmentSize)
{
// T-REC-X.690-201508 sec 8.7.3.2-note2
this.WriteTag(primitiveOctetString);
this.WriteLength(MaxCERSegmentSize);
dest = this._buffer.AsSpan(this._offset);
remainingData.Slice(0, MaxCERSegmentSize).CopyTo(dest);
this._offset += MaxCERSegmentSize;
remainingData = remainingData.Slice(MaxCERSegmentSize);
}
this.WriteTag(primitiveOctetString);
this.WriteLength(remainingData.Length);
dest = this._buffer.AsSpan(this._offset);
remainingData.CopyTo(dest);
this._offset += remainingData.Length;
this.WriteEndOfContents();
Debug.Assert(this._offset - savedOffset == expectedSize, $"expected size was {expectedSize}, actual was {this._offset - savedOffset}");
Debug.Assert(this._buffer == ensureNoExtraCopy, $"_buffer was replaced during {nameof(this.WriteConstructedCerOctetString)}");
}