| static private GetExpectedTag ( byte tag, ISchema schema ) : Tag | ||
| tag | byte | The input context tag |
| schema | ISchema | The schema |
| Результат | Tag | |
/// <summary>
/// Determines whether an option has a value
/// </summary>
/// <returns>True if the option has a value, false otherwise</returns>
public bool OptionHasValue()
{
_require(StreamOp.Option);
// get the expected tag for an option of this type
var option = (OptionSchema)_state.Schema;
var expected = Utils.GetExpectedTag(_state.Tag, option.ElementType);
bool hasValue = _reader.AtTag(expected.ContextTag, expected.ApplicationTag);
if (hasValue)
{
_stack.Push(_state);
_state = new SchemaState(option.ElementType, _state.Tag, -1);
}
else
{
_moveNext();
}
return(hasValue);
}
/// <summary>
/// Enters a choice value
/// </summary>
/// <returns>The index of the active choice</returns>
public byte EnterChoice()
{
_require(StreamOp.EnterChoice);
_reader.ReadOpenTag(_state.Tag);
var choice = ((ChoiceSchema)_state.Schema);
for (int i = 0; i < choice.Fields.Length; i++)
{
var field = choice.Fields[i];
var expected = Utils.GetExpectedTag(field.Tag, field.Type);
if (_reader.AtTag(expected.ContextTag, expected.ApplicationTag))
{
_stack.Push(new SchemaState(choice, _state.Tag, (byte)i));
_state = new SchemaState(field.Type, field.Tag, -1);
return((byte)i);
}
}
throw new UnexpectedTagException();
}
/// <summary>
/// Moves the current state to the next value to read
/// </summary>
private void _moveNext()
{
if (_stack.Count == 0)
{
_state = new SchemaState(PrimitiveSchema.EOF, 255, -1);
return;
}
var parent = _stack.Pop();
if (parent.Schema.Type == Types.ValueType.Option)
{
// we skip option states on the way back up
_moveNext();
}
else if (parent.Schema.Type == Types.ValueType.Sequence)
{
var sequence = (SequenceSchema)parent.Schema;
var newParent = new SchemaState(sequence, parent.Tag, parent.Index + 1);
if (newParent.Index == sequence.Fields.Length)
{
// we have read all of fields
_state = newParent;
}
else
{
// we still have at least 1 field to read
_stack.Push(newParent);
var field = sequence.Fields[newParent.Index];
_state = new SchemaState(field.Type, field.Tag, -1);
}
}
else if (parent.Schema.Type == Types.ValueType.Choice)
{
var choice = (ChoiceSchema)parent.Schema;
_state = new SchemaState(choice, parent.Tag, choice.Fields.Length);
}
else if (parent.Schema.Type == Types.ValueType.Array)
{
var array = (ArraySchema)parent.Schema;
// TODO: Might still need better logic for detecting
// whether we are at the end of the array
if (_reader.EOF())
{
_state = new SchemaState(array, parent.Tag, parent.Index + 1);
}
else if (array.ElementType == PrimitiveSchema.GenericSchema)
{
if (_reader.AtTag(parent.Tag, ApplicationTag.Null))
{
_state = new SchemaState(array, parent.Tag, parent.Index + 1);
}
else
{
var newParent = new SchemaState(array, parent.Tag, parent.Index + 1);
_stack.Push(newParent);
_state = new SchemaState(array.ElementType, 255, -1);
}
}
else
{
var elementExpected = Utils.GetExpectedTag(255, array.ElementType);
if (_reader.AtTag(elementExpected.ContextTag, elementExpected.ApplicationTag))
{
var newParent = new SchemaState(array, parent.Tag, parent.Index + 1);
_stack.Push(newParent);
_state = new SchemaState(array.ElementType, 255, -1);
}
else
{
_state = new SchemaState(array, parent.Tag, parent.Index + 1);
}
}
}
else
{
throw new Exception("unknown parent schema state, can't move next");
}
}