dynamicscanner.cpp

用于词法分析的词法分析器

/* $Id: DynamicScanner.cpp,v 1.5 1997/02/02 01:31:03 matt Exp $

   Elex dynamic scanner class.

   (c) Matt Phillips 1996. */

#include "DynamicScanner.h"

// the production number for the dynamic scanner's error production.
enum {ErrorProduction = -100};

DynamicScanner::DynamicScanner (const FooObject &scandef,
				XInputStream &i) :
  ElexScanner (scannerData, i)
{
  generate (scandef);
  state = scannerData.start;
}

DynamicScanner::~DynamicScanner ()
{
  delete [] prodNames;
  for (int c = 0; c < nStates; c++)
  {
    ElexState *state = states + c;
    if (state->edges)
    {
      delete state->edges->edges;
      delete state->edges;
    }
  }
}

// Generates the corresponding ElexEdge structure for fooedges.
ElexEdge *DynamicScanner::generateEdges (const FooObject::Objects &fooedges, 
					 ElexState *states) const
{
  ElexEdge *edges = new ElexEdge [fooedges.nItems ()];

  ElexEdge *edge = edges;
  for (FooObject::Objects::Iterator e (fooedges); e; e++, edge++)
  {
    const string &range = e.ref ().getAttrString ("range");
    edge->target = states + e.ref ().getAttrInt ("target");
    edge->lower = range [0];
    if (range.length () == 3)
      edge->upper = range [2];
    else
      edge->upper = range [0];
  }

  return edges;
}

// Generates the states and edges structures that correspond to the
// scanner FSM defined in scandef.  Fills in the scannerData.start and
// nStates variables.

// NOTE: the while loop below used to be a for loop, but for some
// reason this caused an internal compiler error under g++ 2.7.2.  In
// fact, putting _anything_ after the loop seems to hose the compiler.
// Modify this function carefully!
void DynamicScanner::generate (const FooObject &scandef)
{
   const FooObject::Objects &foostates = scandef.getAttrs ("states");
   nStates = foostates.nItems ();

   // allocate storage for states and state ID -> production name
   // mapping.
   states = new ElexState [nStates];
   prodNames = new string [nStates];

   scannerData.start = states;
   scannerData.errorProd = ErrorProduction;

   // for each state...
   FooObject::Objects::Iterator s (foostates);
   while (s)
   {
     int stateNo = s.ref ().getAttrInt ("state");
     ElexState *state = states + stateNo;
     const FooObject::Objects &fooedges = s.ref ().getAttrs ("edges");

     if (fooedges.nItems () > 0)
     {
       // allocate and generate edges for state.
       state->edges = new ElexEdges;
       state->edges->nEdges = fooedges.nItems ();
       state->edges->edges = generateEdges (fooedges, states);
     } else
       state->edges = 0;

     // fill in the production name for state.
     const string &prodName = s.ref ().getAttrString ("production");
     prodNames [stateNo] = prodName;

     state->prod =
       prodName.length () > 0 ? stateNo : ElexState::NoProduction;

     s++;
   }
}

int DynamicScanner::invokeProduction (int i)
{
  if (i == ErrorProduction)
    production = "<Error>";
  else
    production = prodNames [i];

  return i;
}