/*!
* \brief
* Change to a new input stream, remembering the old one.
*
* \param lexer
* Pointer to the lexer instance to switch input streams for.
*
* \param input
* New input stream to install as the current one.
*
* Switches the current character input stream to
* a new one, saving the old one, which we will revert to at the end of this
* new one.
*/
void Lexer::pushCharStream(CharStreamPtr input)
{
// We have a stack, so we can save the current input stream
// into it.
//
RecognizerSharedState::StreamState save = { input_->mark(), charStream() };
state_->streams.push(save);
// And now we can install this new one
//
setCharStream(input);
}
ANTLR3_API pANTLR3_LEXER
antlr3LexerNewStream(ANTLR3_UINT32 sizeHint, pANTLR3_INPUT_STREAM input, pANTLR3_RECOGNIZER_SHARED_STATE state)
{
pANTLR3_LEXER lexer;
// Create a basic lexer first
//
lexer = antlr3LexerNew(sizeHint, state);
if (lexer != NULL)
{
// Install the input stream and reset the lexer
//
setCharStream(lexer, input);
}
return lexer;
}
/*!
* \brief
* Stops using the current input stream and reverts to any prior
* input stream on the stack.
*
* \param lexer
* Description of parameter lexer.
*
* Pointer to a function that abandons the current input stream, whether it
* is empty or not and reverts to the previous stacked input stream.
*
* \remark
* The function fails silently if there are no prior input streams.
*/
void Lexer::popCharStream()
{
// If we do not have a stream stack or we are already at the
// stack bottom, then do nothing.
//
if (!state_->streams.empty())
{
// We just leave the current stream to its fate, we do not close
// it or anything as we do not know what the programmer intended
// for it. This method can always be overridden of course.
// So just find out what was currently saved on the stack and use
// that now, then pop it from the stack.
//
auto save = state_->streams.top();
state_->streams.pop();
// Now install the stream as the current one.
//
setCharStream(save.stream);
save.marker->rewind();
}
}
Lexer::Lexer(CharStreamPtr input, RecognizerSharedStatePtr state)
: Lexer(state)
{
setCharStream(std::move(input));
}
