SQLite

/********************** New code to implement the "acttab" module ***********/
/*
** This module implements routines use to construct the yy_action[] table.
*/

/*
** The state of the yy_action table under construction is an instance of
** the following structure.
**
** The yy_action table maps the pair (state_number, lookahead) into an
** action_number.  The table is an array of integers pairs.  The state_number
** determines an initial offset into the yy_action array.  The lookahead
** value is then added to this initial offset to get an index X into the
** yy_action array. If the aAction[X].lookahead equals the value of the
** of the lookahead input, then the value of the action_number output is
** aAction[X].action.  If the lookaheads do not match then the
** default action for the state_number is returned.
**
** All actions associated with a single state_number are first entered
** into aLookahead[] using multiple calls to acttab_action().  Then the 
** actions for that single state_number are placed into the aAction[] 
** array with a single call to acttab_insert().  The acttab_insert() call
** also resets the aLookahead[] array in preparation for the next
** state number.
*/
typedef struct acttab acttab;
struct acttab {
  int nAction;                 /* Number of used slots in aAction[] */
  int nActionAlloc;            /* Slots allocated for aAction[] */
  struct {
    int lookahead;             /* Value of the lookahead token */

    fprintf(stderr,"Unable to allocate memory for a new acttab.");
    exit(1);
  }
  memset(p, 0, sizeof(*p));
  return p;
}

/* Add a new action to the current transaction set.  
**
** This routine is called once for each lookahead for a particular
** state.
*/
void acttab_action(acttab *p, int lookahead, int action){
  if( p->nLookahead>=p->nLookaheadAlloc ){
    p->nLookaheadAlloc += 25;
    p->aLookahead = realloc( p->aLookahead,
                             sizeof(p->aLookahead[0])*p->nLookaheadAlloc );
    if( p->aLookahead==0 ){

** into the current action table.  Then reset the transaction set back
** to an empty set in preparation for a new round of acttab_action() calls.
**
** Return the offset into the action table of the new transaction.
*/
int acttab_insert(acttab *p){
  int i, j, k, n;

  assert( p->nLookahead>0 );

  /* Make sure we have enough space to hold the expanded action table
  ** in the worst case.  The worst case occurs if the transaction set
  ** must be appended to the current action table
  */
  n = p->mxLookahead + 1;

  if( p->nAction + n >= p->nActionAlloc ){
    int oldAlloc = p->nActionAlloc;
    p->nActionAlloc = p->nAction + n + p->nActionAlloc + 20;
    p->aAction = realloc( p->aAction,
                          sizeof(p->aAction[0])*p->nActionAlloc);
    if( p->aAction==0 ){
      fprintf(stderr,"malloc failed\n");
      exit(1);
    }
    for(i=oldAlloc; i<p->nActionAlloc; i++){
      p->aAction[i].lookahead = -1;
      p->aAction[i].action = -1;
    }
  }

  /* Scan the existing action table looking for an offset that is a 
  ** duplicate of the current transaction set.  Fall out of the loop
  ** if and when the duplicate is found.

  **
  ** i is the index in p->aAction[] where p->mnLookahead is inserted.
  */
  for(i=p->nAction-1; i>=0; i--){

    if( p->aAction[i].lookahead==p->mnLookahead ){
      /* All lookaheads and actions in the aLookahead[] transaction
      ** must match against the candidate aAction[i] entry. */
      if( p->aAction[i].action!=p->mnAction ) continue;
      for(j=0; j<p->nLookahead; j++){
        k = p->aLookahead[j].lookahead - p->mnLookahead + i;
        if( k<0 || k>=p->nAction ) break;
        if( p->aLookahead[j].lookahead!=p->aAction[k].lookahead ) break;
        if( p->aLookahead[j].action!=p->aAction[k].action ) break;
      }
      if( j<p->nLookahead ) continue;

      /* No possible lookahead value that is not in the aLookahead[]
      ** transaction is allowed to match aAction[i] */
      n = 0;
      for(j=0; j<p->nAction; j++){
        if( p->aAction[j].lookahead<0 ) continue;
        if( p->aAction[j].lookahead==j+p->mnLookahead-i ) n++;
      }
      if( n==p->nLookahead ){
        break;  /* An exact match is found at offset i */
      }
    }
  }

  /* If no existing offsets exactly match the current transaction, find an
  ** an empty offset in the aAction[] table in which we can add the
  ** aLookahead[] transaction.
  */
  if( i<0 ){
    /* Look for holes in the aAction[] table that fit the current
    ** aLookahead[] transaction.  Leave i set to the offset of the hole.
    ** If no holes are found, i is left at p->nAction, which means the
    ** transaction will be appended. */
    for(i=0; i<p->nActionAlloc - p->mxLookahead; i++){
      if( p->aAction[i].lookahead<0 ){
        for(j=0; j<p->nLookahead; j++){
          k = p->aLookahead[j].lookahead - p->mnLookahead + i;
          if( k<0 ) break;
          if( p->aAction[k].lookahead>=0 ) break;
        }
        if( j<p->nLookahead ) continue;