System.Xml.XmlUTF8TextReader.ReadDeclaration C# (CSharp) Méthode

        private void ReadDeclaration()
        {
            if (!_buffered)
                BufferElement();
            int offset;
            byte[] buffer = BufferReader.GetBuffer(5, out offset);
            if (buffer[offset + 0] != (byte)'?' ||
                buffer[offset + 1] != (byte)'x' ||
                buffer[offset + 2] != (byte)'m' ||
                buffer[offset + 3] != (byte)'l' ||
                (s_charType[buffer[offset + 4]] & CharType.Whitespace) == 0)
            {
                XmlExceptionHelper.ThrowProcessingInstructionNotSupported(this);
            }
            // If anything came before the "<?xml ?>" it's an error.
            if (this.Node.ReadState != ReadState.Initial)
            {
                XmlExceptionHelper.ThrowDeclarationNotFirst(this);
            }
            BufferReader.Advance(5);

            int localNameOffset = offset + 1;
            int localNameLength = 3;

            int valueOffset = BufferReader.Offset;
            SkipWhitespace();
            ReadAttributes();
            int valueLength = BufferReader.Offset - valueOffset;

            // Backoff the spaces
            while (valueLength > 0)
            {
                byte ch = BufferReader.GetByte(valueOffset + valueLength - 1);
                if ((s_charType[ch] & CharType.Whitespace) == 0)
                    break;
                valueLength--;
            }

            buffer = BufferReader.GetBuffer(2, out offset);
            if (buffer[offset + 0] != (byte)'?' ||
                buffer[offset + 1] != (byte)'>')
            {
                XmlExceptionHelper.ThrowTokenExpected(this, "?>", Encoding.UTF8.GetString(buffer, offset, 2));
            }
            BufferReader.Advance(2);
            XmlDeclarationNode declarationNode = MoveToDeclaration();
            declarationNode.LocalName.SetValue(localNameOffset, localNameLength);
            declarationNode.Value.SetValue(ValueHandleType.UTF8, valueOffset, valueLength);
        }