private static ReadOnlySpan <byte> GetPrimitiveContentSpan(
ReadOnlySpan <byte> source,
AsnEncodingRules ruleSet,
Asn1Tag expectedTag,
UniversalTagNumber tagNumber,
out int bytesConsumed)
{
CheckEncodingRules(ruleSet);
Asn1Tag localTag = Asn1Tag.Decode(source, out int tagLength);
int? encodedLength = ReadLength(source.Slice(tagLength), ruleSet, out int lengthLength);
int headerLength = tagLength + lengthLength;
// Get caller(-of-my-caller) errors out of the way, first.
CheckExpectedTag(localTag, expectedTag, tagNumber);
// T-REC-X.690-201508 sec 8.1.3.2 says primitive encodings must use a definite form,
// and the caller says they only want primitive values.
if (localTag.IsConstructed)
{
throw new AsnContentException(
SR.Format(SR.ContentException_PrimitiveEncodingRequired, tagNumber));
}
if (encodedLength == null)
{
throw new AsnContentException();
}
ReadOnlySpan <byte> ret = Slice(source, headerLength, encodedLength.Value);
bytesConsumed = headerLength + ret.Length;
return(ret);
}
private static Asn1Tag ReadTagAndLength(
ReadOnlySpan <byte> source,
AsnEncodingRules ruleSet,
out int?contentsLength,
out int bytesRead)
{
Asn1Tag tag = Asn1Tag.Decode(source, out int tagBytesRead);
int? length = ReadLength(source.Slice(tagBytesRead), ruleSet, out int lengthBytesRead);
int allBytesRead = tagBytesRead + lengthBytesRead;
if (tag.IsConstructed)
{
// T-REC-X.690-201508 sec 9.1 (CER: Length forms) says constructed is always indefinite.
if (ruleSet == AsnEncodingRules.CER && length != null)
{
throw GetValidityException(LengthValidity.CerRequiresIndefinite);
}
}
else if (length == null)
{
// T-REC-X.690-201508 sec 8.1.3.2 says primitive encodings must use a definite form.
throw GetValidityException(LengthValidity.PrimitiveEncodingRequiresDefinite);
}
bytesRead = allBytesRead;
contentsLength = length;
return(tag);
}
/// <summary>
/// Locates the contents range for the encoded value at the beginning of the
/// <paramref name="source"/> buffer using the specified encoding rules.
/// </summary>
/// <param name="source">The buffer containing encoded data.</param>
/// <param name="ruleSet">The encoding constraints to use when interpreting the data.</param>
/// <param name="contentOffset">
/// When this method returns, the offset of the content payload relative to the start of
/// <paramref name="source"/>.
/// This parameter is treated as uninitialized.
/// </param>
/// <param name="contentLength">
/// When this method returns, the number of bytes in the content payload (which may be 0).
/// This parameter is treated as uninitialized.
/// </param>
/// <param name="bytesConsumed">
/// When this method returns, the total number of bytes for the encoded value.
/// This parameter is treated as uninitialized.
/// </param>
/// <returns>
/// The tag identifying the content.
/// </returns>
/// <remarks>
/// <para>
/// This method performs very little validation on the contents.
/// If the encoded value uses a definite length, the contents are not inspected at all.
/// If the encoded value uses an indefinite length, the contents are only inspected
/// as necessary to determine the location of the relevant end-of-contents marker.
/// </para>
/// <para>
/// When the encoded value uses an indefinite length, the <paramref name="bytesConsumed"/>
/// value will be larger than the sum of <paramref name="contentOffset"/> and
/// <paramref name="contentLength"/> to account for the end-of-contents marker.
/// </para>
/// </remarks>
/// <exception cref="ArgumentOutOfRangeException">
/// <paramref name="ruleSet"/> is not defined.
/// </exception>
/// <exception cref="AsnContentException">
/// <paramref name="source"/> does not represent a value encoded under the specified
/// encoding rules.
/// </exception>
public static Asn1Tag ReadEncodedValue(
ReadOnlySpan <byte> source,
AsnEncodingRules ruleSet,
out int contentOffset,
out int contentLength,
out int bytesConsumed)
{
CheckEncodingRules(ruleSet);
Asn1Tag tag = Asn1Tag.Decode(source, out int tagLength);
int? encodedLength = ReadLength(source.Slice(tagLength), ruleSet, out int lengthLength);
int headerLength = tagLength + lengthLength;
LengthValidity validity = ValidateLength(
source.Slice(headerLength),
ruleSet,
tag,
encodedLength,
out int len,
out int consumed);
if (validity == LengthValidity.Valid)
{
contentOffset = headerLength;
contentLength = len;
bytesConsumed = headerLength + consumed;
return(tag);
}
throw GetValidityException(validity);
}
internal Asn1Tag PeekTag()
{
return(Asn1Tag.Decode(_span, out _));
}