AsnValueReader.cs

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namespace System.Formats.Asn1;
 
internal ref struct AsnValueReader
{
    private static readonly byte[] s_singleByte = new byte[1];
 
    private ReadOnlySpan<byte> _span;
 
    private readonly AsnEncodingRules _ruleSet;
 
    internal bool HasData => !_span.IsEmpty;
 
    internal AsnValueReader(ReadOnlySpan<byte> span, AsnEncodingRules ruleSet)
    {
        _span = span;
        _ruleSet = ruleSet;
    }
 
    internal void ThrowIfNotEmpty()
    {
        if (!_span.IsEmpty)
        {
            new AsnReader(s_singleByte, _ruleSet).ThrowIfNotEmpty();
        }
    }
 
    internal Asn1Tag PeekTag()
    {
        int bytesConsumed;
        return Asn1Tag.Decode(_span, out bytesConsumed);
    }
 
    internal ReadOnlySpan<byte> PeekEncodedValue()
    {
        AsnDecoder.ReadEncodedValue(_span, _ruleSet, out var _, out var _, out var bytesConsumed);
        return _span.Slice(0, bytesConsumed);
    }
 
    internal ReadOnlySpan<byte> ReadEncodedValue()
    {
        ReadOnlySpan<byte> result = PeekEncodedValue();
        _span = _span.Slice(result.Length);
        return result;
    }
 
    internal bool TryReadInt32(out int value, Asn1Tag? expectedTag = null)
    {
        int bytesConsumed;
        bool result = AsnDecoder.TryReadInt32(_span, _ruleSet, out value, out bytesConsumed, expectedTag);
        _span = _span.Slice(bytesConsumed);
        return result;
    }
 
    internal ReadOnlySpan<byte> ReadIntegerBytes(Asn1Tag? expectedTag = null)
    {
        int bytesConsumed;
        ReadOnlySpan<byte> result = AsnDecoder.ReadIntegerBytes(_span, _ruleSet, out bytesConsumed, expectedTag);
        _span = _span.Slice(bytesConsumed);
        return result;
    }
 
    internal bool TryReadPrimitiveBitString(out int unusedBitCount, out ReadOnlySpan<byte> value, Asn1Tag? expectedTag = null)
    {
        int bytesConsumed;
        bool result = AsnDecoder.TryReadPrimitiveBitString(_span, _ruleSet, out unusedBitCount, out value, out bytesConsumed, expectedTag);
        _span = _span.Slice(bytesConsumed);
        return result;
    }
 
    internal byte[] ReadBitString(out int unusedBitCount, Asn1Tag? expectedTag = null)
    {
        int bytesConsumed;
        byte[] result = AsnDecoder.ReadBitString(_span, _ruleSet, out unusedBitCount, out bytesConsumed, expectedTag);
        _span = _span.Slice(bytesConsumed);
        return result;
    }
 
    internal bool TryReadPrimitiveOctetString(out ReadOnlySpan<byte> value, Asn1Tag? expectedTag = null)
    {
        int bytesConsumed;
        bool result = AsnDecoder.TryReadPrimitiveOctetString(_span, _ruleSet, out value, out bytesConsumed, expectedTag);
        _span = _span.Slice(bytesConsumed);
        return result;
    }
 
    internal byte[] ReadOctetString(Asn1Tag? expectedTag = null)
    {
        int bytesConsumed;
        byte[] result = AsnDecoder.ReadOctetString(_span, _ruleSet, out bytesConsumed, expectedTag);
        _span = _span.Slice(bytesConsumed);
        return result;
    }
 
    internal string ReadObjectIdentifier(Asn1Tag? expectedTag = null)
    {
        int bytesConsumed;
        string result = AsnDecoder.ReadObjectIdentifier(_span, _ruleSet, out bytesConsumed, expectedTag);
        _span = _span.Slice(bytesConsumed);
        return result;
    }
 
    internal System.Formats.Asn1.AsnValueReader ReadSequence(Asn1Tag? expectedTag = null)
    {
        AsnDecoder.ReadSequence(_span, _ruleSet, out var contentOffset, out var contentLength, out var bytesConsumed, expectedTag);
        ReadOnlySpan<byte> span = _span.Slice(contentOffset, contentLength);
        _span = _span.Slice(bytesConsumed);
        return new System.Formats.Asn1.AsnValueReader(span, _ruleSet);
    }
 
    internal System.Formats.Asn1.AsnValueReader ReadSetOf(Asn1Tag? expectedTag = null)
    {
        AsnDecoder.ReadSetOf(_span, _ruleSet, out var contentOffset, out var contentLength, out var bytesConsumed, skipSortOrderValidation: false, expectedTag);
        ReadOnlySpan<byte> span = _span.Slice(contentOffset, contentLength);
        _span = _span.Slice(bytesConsumed);
        return new System.Formats.Asn1.AsnValueReader(span, _ruleSet);
    }
}