/// <remarks>
/// This method essentially just loops through characters skipping whitespace, validating and
/// changing state (e.g. from ObjectBeforeColon to ObjectAfterColon)
/// until it reaches something which will be a genuine token (e.g. a start object, or a value) at which point
/// it returns the token. Although the method is large, it would be relatively hard to break down further... most
/// of it is the large switch statement, which sometimes returns and sometimes doesn't.
/// </remarks>
protected override JsonToken NextImpl()
{
if (state == State.ReaderExhausted)
{
throw new InvalidOperationException("Next() called after end of document");
}
while (true)
{
var next = reader.Read();
if (next == null)
{
ValidateState(State.ExpectedEndOfDocument, "Unexpected end of document in state: ");
state = State.ReaderExhausted;
return(JsonToken.EndDocument);
}
switch (next.Value)
{
// Skip whitespace between tokens
case ' ':
case '\t':
case '\r':
case '\n':
break;
case ':':
ValidateState(State.ObjectBeforeColon, "Invalid state to read a colon: ");
state = State.ObjectAfterColon;
break;
case ',':
ValidateState(State.ObjectAfterProperty | State.ArrayAfterValue, "Invalid state to read a colon: ");
state = state == State.ObjectAfterProperty ? State.ObjectAfterComma : State.ArrayAfterComma;
break;
case '"':
string stringValue = ReadString();
if ((state & (State.ObjectStart | State.ObjectAfterComma)) != 0)
{
state = State.ObjectBeforeColon;
return(JsonToken.Name(stringValue));
}
else
{
ValidateAndModifyStateForValue("Invalid state to read a double quote: ");
return(JsonToken.Value(stringValue));
}
case '{':
ValidateState(ValueStates, "Invalid state to read an open brace: ");
state = State.ObjectStart;
containerStack.Push(ContainerType.Object);
return(JsonToken.StartObject);
case '}':
ValidateState(State.ObjectAfterProperty | State.ObjectStart, "Invalid state to read a close brace: ");
PopContainer();
return(JsonToken.EndObject);
case '[':
ValidateState(ValueStates, "Invalid state to read an open square bracket: ");
state = State.ArrayStart;
containerStack.Push(ContainerType.Array);
return(JsonToken.StartArray);
case ']':
ValidateState(State.ArrayAfterValue | State.ArrayStart, "Invalid state to read a close square bracket: ");
PopContainer();
return(JsonToken.EndArray);
case 'n': // Start of null
ConsumeLiteral("null");
ValidateAndModifyStateForValue("Invalid state to read a null literal: ");
return(JsonToken.Null);
case 't': // Start of true
ConsumeLiteral("true");
ValidateAndModifyStateForValue("Invalid state to read a true literal: ");
return(JsonToken.True);
case 'f': // Start of false
ConsumeLiteral("false");
ValidateAndModifyStateForValue("Invalid state to read a false literal: ");
return(JsonToken.False);
case '-': // Start of a number
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
double number = ReadNumber(next.Value);
ValidateAndModifyStateForValue("Invalid state to read a number token: ");
return(JsonToken.Value(number));
default:
throw new InvalidJsonException("Invalid first character of token: " + next.Value);
}
}
}