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// CPreInputStack.cpp:  Implementation of a preprocessor-specific token buffer
// that supports nesting of included files.

#include "CPreInputStack.h"
#include "tokens.h"
#include <deque>
#include <stack>
#include "CPreParser.h"
#include "ATokenStream.h"

CPreInputStack::CPreInputStack(
   ANTLRTokenStream *in
) :
   parser(0)
{
   #ifndef NDEBUG
      magic = Magic;
   #endif
   streamStack = new StreamStack;
   PushStream(in);

   // initialize LT1
   LT1 = GetToken();
}

CPreInputStack::~CPreInputStack() 
{
   delete streamStack;
}

// discard current LT1 and get another token
void
CPreInputStack::consume()
{
   LT1 = GetToken();
}

// Push a new stream on the stream input stack
// Note that this does not change the lookahead LT1.  
// It is assumed that the LT1 will be consumed after the 
// installation of the new stack (and not before!).
void 
CPreInputStack::PushStream(
   ANTLRTokenStream *in
)
{
   validate();
   // Put the stream on the stack
   streamStack->push(in);
}

// Get a token from the topmost stream.  If that stream
// returns TOK_Eof, and there is more than 
// one stream on the stack, then pop the stack and try again.
// If that fails, return TOK_Eof.
ANTLRTokenPtr
CPreInputStack::GetToken()
{
   validate();

   while (true)
   {
      // Try a token from the stream on the top of the stack
      ANTLRTokenPtr tokptr = streamStack->top()->getToken();
      if (tokptr->getType() != TOK_Eof)
      {
         // Success -- return token from input stream
         return tokptr;
      }
 
      // Failing that, see if we can pop the stack and try again
      if (streamStack->size() > 1)
      {
         PopStream();
         // ... and keep trying
      } else {
         // Return TOK_Eof.  There is no more input from any source.
         assert(tokptr->getType() == TOK_Eof);
         return tokptr;
      }
   }

   // Should not get here
   assert(false);
   return NULL;
}

// Pop an input token stream from the stack.
void
CPreInputStack::PopStream()
{
   validate();
   OnIncludeEof();      // allows for cleanup of popped input stream
   streamStack->pop();
}

void 
CPreInputStack::OnIncludeEof() 
{ 
   if (parser != 0) {
      parser->OnIncludeEof(); 
   }
}