/*!
* \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.
*/
static void
popCharStream (pANTLR3_LEXER lexer)
{
pANTLR3_INPUT_STREAM input;
// If we do not have a stream stack or we are already at the
// stack bottom, then do nothing.
//
if (lexer->rec->state->streams != NULL && lexer->rec->state->streams->size(lexer->rec->state->streams) > 0)
{
// 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.
//
input = (pANTLR3_INPUT_STREAM)(lexer->rec->state->streams->top);
lexer->rec->state->streams->pop(lexer->rec->state->streams);
// Now install the stream as the current one.
//
lexer->setCharStream(lexer, input);
lexer->input->istream->rewindLast(lexer->input->istream);
}
return;
}
/*!
* \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.
*/
static void
pushCharStream (pANTLR3_LEXER lexer, pANTLR3_INPUT_STREAM input)
{
// Do we need a new input stream stack?
//
if (lexer->rec->state->streams == NULL)
{
// This is the first call to stack a new
// stream and so we must create the stack first.
//
lexer->rec->state->streams = antlr3StackNew(0);
if (lexer->rec->state->streams == NULL)
{
// Could not do this, we just fail to push it.
// TODO: Consider if this is what we want to do, but then
// any programmer can override this method to do something else.
return;
}
}
// We have a stack, so we can save the current input stream
// into it.
//
lexer->input->istream->mark(lexer->input->istream);
lexer->rec->state->streams->push(lexer->rec->state->streams, lexer->input, NULL);
// And now we can install this new one
//
lexer->setCharStream(lexer, input);
}
