/**
  @file

  @ingroup cudd

  @brief Translation from %BDD to %ADD and vice versa and transfer
  between different managers.

  @author Fabio Somenzi

  @copyright@parblock
  Copyright (c) 1995-2015, Regents of the University of Colorado

  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions
  are met:

  Redistributions of source code must retain the above copyright
  notice, this list of conditions and the following disclaimer.

  Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.

  Neither the name of the University of Colorado nor the names of its
  contributors may be used to endorse or promote products derived from
  this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  POSSIBILITY OF SUCH DAMAGE.
  @endparblock

*/

#include "util.h"
#include "cuddInt.h"

/*---------------------------------------------------------------------------*/
/* Constant declarations                                                     */
/*---------------------------------------------------------------------------*/


/*---------------------------------------------------------------------------*/
/* Stucture declarations                                                     */
/*---------------------------------------------------------------------------*/


/*---------------------------------------------------------------------------*/
/* Type declarations                                                         */
/*---------------------------------------------------------------------------*/


/*---------------------------------------------------------------------------*/
/* Variable declarations                                                     */
/*---------------------------------------------------------------------------*/


/*---------------------------------------------------------------------------*/
/* Macro declarations                                                        */
/*---------------------------------------------------------------------------*/

/** \cond */

/*---------------------------------------------------------------------------*/
/* Static function prototypes                                                */
/*---------------------------------------------------------------------------*/

static DdNode * addBddDoThreshold (DdManager *dd, DdNode *f, DdNode *val);
static DdNode * addBddDoStrictThreshold (DdManager *dd, DdNode *f, DdNode *val);
static DdNode * addBddDoInterval (DdManager *dd, DdNode *f, DdNode *l, DdNode *u);
static DdNode * addBddDoIthBit (DdManager *dd, DdNode *f, DdNode *index);
static DdNode * ddBddToAddRecur (DdManager *dd, DdNode *B);
static DdNode * cuddBddTransferRecur (DdManager *ddS, DdManager *ddD, DdNode *f, st_table *table);

/** \endcond */

/*---------------------------------------------------------------------------*/
/* Definition of exported functions                                          */
/*---------------------------------------------------------------------------*/


/**
  @brief Converts an %ADD to a %BDD.

  @details Replaces all discriminants greater than or equal to value
  with 1, and all other discriminants with 0.

  @return a pointer to the resulting %BDD if successful; NULL
  otherwise.

  @sideeffect None

  @see Cudd_addBddInterval Cudd_addBddPattern Cudd_BddToAdd
  Cudd_addBddStrictThreshold

*/
DdNode *
Cudd_addBddThreshold(
  DdManager * dd,
  DdNode * f,
  CUDD_VALUE_TYPE  value)
{
    DdNode *res;
    DdNode *val;
    
    val = cuddUniqueConst(dd,value);
    if (val == NULL) return(NULL);
    cuddRef(val);

    do {
	dd->reordered = 0;
	res = addBddDoThreshold(dd, f, val);
    } while (dd->reordered == 1);

    if (res == NULL) {
	Cudd_RecursiveDeref(dd, val);
        if (dd->errorCode == CUDD_TIMEOUT_EXPIRED && dd->timeoutHandler) {
            dd->timeoutHandler(dd, dd->tohArg);
        }
	return(NULL);
    }
    cuddRef(res);
    Cudd_RecursiveDeref(dd, val);
    cuddDeref(res);
    return(res);

} /* end of Cudd_addBddThreshold */


/**
  @brief Converts an %ADD to a %BDD.

  @details Replaces all discriminants STRICTLY greater than value with
  1, and all other discriminants with 0.

  @return a pointer to the resulting %BDD if successful; NULL
  otherwise.

  @sideeffect None

  @see Cudd_addBddInterval Cudd_addBddPattern Cudd_BddToAdd 
  Cudd_addBddThreshold

*/
DdNode *
Cudd_addBddStrictThreshold(
  DdManager * dd,
  DdNode * f,
  CUDD_VALUE_TYPE  value)
{
    DdNode *res;
    DdNode *val;
    
    val = cuddUniqueConst(dd,value);
    if (val == NULL) return(NULL);
    cuddRef(val);

    do {
	dd->reordered = 0;
	res = addBddDoStrictThreshold(dd, f, val);
    } while (dd->reordered == 1);

    if (res == NULL) {
	Cudd_RecursiveDeref(dd, val);
        if (dd->errorCode == CUDD_TIMEOUT_EXPIRED && dd->timeoutHandler) {
            dd->timeoutHandler(dd, dd->tohArg);
        }
	return(NULL);
    }
    cuddRef(res);
    Cudd_RecursiveDeref(dd, val);
    cuddDeref(res);
    return(res);

} /* end of Cudd_addBddStrictThreshold */


/**
  @brief Converts an %ADD to a %BDD.

  @details Replaces all discriminants greater than or equal to lower
  and less than or equal to upper with 1, and all other discriminants
  with 0.

  @return a pointer to the resulting %BDD if successful; NULL
  otherwise.

  @sideeffect None

  @see Cudd_addBddThreshold Cudd_addBddStrictThreshold 
  Cudd_addBddPattern Cudd_BddToAdd

*/
DdNode *
Cudd_addBddInterval(
  DdManager * dd,
  DdNode * f,
  CUDD_VALUE_TYPE  lower,
  CUDD_VALUE_TYPE  upper)
{
    DdNode *res;
    DdNode *l;
    DdNode *u;
    
    /* Create constant nodes for the interval bounds, so that we can use
    ** the global cache.
    */
    l = cuddUniqueConst(dd,lower);
    if (l == NULL) return(NULL);
    cuddRef(l);
    u = cuddUniqueConst(dd,upper);
    if (u == NULL) {
	Cudd_RecursiveDeref(dd,l);
	return(NULL);
    }
    cuddRef(u);

    do {
	dd->reordered = 0;
	res = addBddDoInterval(dd, f, l, u);
    } while (dd->reordered == 1);

    if (res == NULL) {
	Cudd_RecursiveDeref(dd, l);
	Cudd_RecursiveDeref(dd, u);
        if (dd->errorCode == CUDD_TIMEOUT_EXPIRED && dd->timeoutHandler) {
            dd->timeoutHandler(dd, dd->tohArg);
        }
	return(NULL);
    }
    cuddRef(res);
    Cudd_RecursiveDeref(dd, l);
    Cudd_RecursiveDeref(dd, u);
    cuddDeref(res);
    return(res);

} /* end of Cudd_addBddInterval */


/**
  @brief Converts an %ADD to a %BDD by extracting the i-th bit from
  the leaves.

  @details Converts an %ADD to a %BDD by replacing all
  discriminants whose i-th bit is equal to 1 with 1, and all other
  discriminants with 0.  The i-th bit refers to the integer
  representation of the leaf value.  If the value has a fractional
  part, it is ignored.  Repeated calls to this procedure allow one to
  transform an integer-valued %ADD into an array of BDDs, one for each
  bit of the leaf values.

  @return a pointer to the resulting %BDD if successful; NULL
  otherwise.

  @sideeffect None

  @see Cudd_addBddInterval Cudd_addBddPattern Cudd_BddToAdd

*/
DdNode *
Cudd_addBddIthBit(
  DdManager * dd,
  DdNode * f,
  int  bit)
{
    DdNode *res;
    DdNode *index;
    
    index = cuddUniqueConst(dd,(CUDD_VALUE_TYPE) bit);
    if (index == NULL) return(NULL);
    cuddRef(index);

    do {
	dd->reordered = 0;
	res = addBddDoIthBit(dd, f, index);
    } while (dd->reordered == 1);

    if (res == NULL) {
	Cudd_RecursiveDeref(dd, index);
        if (dd->errorCode == CUDD_TIMEOUT_EXPIRED && dd->timeoutHandler) {
            dd->timeoutHandler(dd, dd->tohArg);
        }
	return(NULL);
    }
    cuddRef(res);
    Cudd_RecursiveDeref(dd, index);
    cuddDeref(res);
    return(res);

} /* end of Cudd_addBddIthBit */


/**
  @brief Converts a %BDD to a 0-1 %ADD.

  @return a pointer to the resulting %ADD if successful; NULL
  otherwise.

  @sideeffect None

  @see Cudd_addBddPattern Cudd_addBddThreshold Cudd_addBddInterval
  Cudd_addBddStrictThreshold

*/
DdNode *
Cudd_BddToAdd(
  DdManager * dd,
  DdNode * B)
{
    DdNode *res;

    do {
	dd->reordered = 0;
	res = ddBddToAddRecur(dd, B);
    } while (dd->reordered ==1);
    return(res);

} /* end of Cudd_BddToAdd */


/**
  @brief Converts an %ADD to a %BDD.

  @details Replaces all discriminants different from 0 with 1.

  @return a pointer to the resulting %BDD if successful; NULL
  otherwise.

  @sideeffect None

  @see Cudd_BddToAdd Cudd_addBddThreshold Cudd_addBddInterval
  Cudd_addBddStrictThreshold

*/
DdNode *
Cudd_addBddPattern(
  DdManager * dd,
  DdNode * f)
{
    DdNode *res;
    
    do {
	dd->reordered = 0;
	res = cuddAddBddDoPattern(dd, f);
    } while (dd->reordered == 1);
    if (dd->errorCode == CUDD_TIMEOUT_EXPIRED && dd->timeoutHandler) {
        dd->timeoutHandler(dd, dd->tohArg);
    }
    return(res);

} /* end of Cudd_addBddPattern */


/**
  @brief Convert a %BDD from a manager to another one.

  @details The orders of the variables in the two managers may be
  different.

  @return a pointer to the %BDD in the destination manager if
  successful; NULL otherwise.

  @sideeffect None

*/
DdNode *
Cudd_bddTransfer(
  DdManager * ddSource,
  DdManager * ddDestination,
  DdNode * f)
{
    DdNode *res;
    do {
	ddDestination->reordered = 0;
	res = cuddBddTransfer(ddSource, ddDestination, f);
    } while (ddDestination->reordered == 1);
    if (ddDestination->errorCode == CUDD_TIMEOUT_EXPIRED &&
        ddDestination->timeoutHandler) {
        ddDestination->timeoutHandler(ddDestination, ddDestination->tohArg);
    }
    return(res);

} /* end of Cudd_bddTransfer */


/*---------------------------------------------------------------------------*/
/* Definition of internal functions                                          */
/*---------------------------------------------------------------------------*/


/**
  @brief Convert a %BDD from a manager to another one.

  @return a pointer to the %BDD in the destination manager if
  successful; NULL otherwise.

  @sideeffect None

  @see Cudd_bddTransfer

*/
DdNode *
cuddBddTransfer(
  DdManager * ddS,
  DdManager * ddD,
  DdNode * f)
{
    DdNode *res;
    st_table *table = NULL;
    st_generator *gen = NULL;
    DdNode *key, *value;

    table = st_init_table(st_ptrcmp,st_ptrhash);
    if (table == NULL) goto failure;
    res = cuddBddTransferRecur(ddS, ddD, f, table);
    if (res != NULL) cuddRef(res);

    /* Dereference all elements in the table and dispose of the table.
    ** This must be done also if res is NULL to avoid leaks in case of
    ** reordering. */
    gen = st_init_gen(table);
    if (gen == NULL) goto failure;
    while (st_gen(gen, (void **) &key, (void **) &value)) {
	Cudd_RecursiveDeref(ddD, value);
    }
    st_free_gen(gen); gen = NULL;
    st_free_table(table); table = NULL;

    if (res != NULL) cuddDeref(res);
    return(res);

failure:
    /* No need to free gen because it is always NULL here. */
    if (table != NULL) st_free_table(table);
    return(NULL);

} /* end of cuddBddTransfer */


/**
  @brief Performs the recursive step for Cudd_addBddPattern.

  @return a pointer to the resulting %BDD if successful; NULL
  otherwise.

  @sideeffect None

*/
DdNode *
cuddAddBddDoPattern(
  DdManager * dd,
  DdNode * f)
{
    DdNode *res, *T, *E;
    DdNode *fv, *fvn;
    unsigned int v;

    statLine(dd);
    /* Check terminal case. */
    if (cuddIsConstant(f)) {
	return(Cudd_NotCond(DD_ONE(dd),f == DD_ZERO(dd)));
    }

    /* Check cache. */
    res = cuddCacheLookup1(dd,Cudd_addBddPattern,f);
    if (res != NULL) return(res);

    checkWhetherToGiveUp(dd);

    /* Recursive step. */
    v = f->index;
    fv = cuddT(f); fvn = cuddE(f);

    T = cuddAddBddDoPattern(dd,fv);
    if (T == NULL) return(NULL);
    cuddRef(T);

    E = cuddAddBddDoPattern(dd,fvn);
    if (E == NULL) {
	Cudd_RecursiveDeref(dd, T);
	return(NULL);
    }
    cuddRef(E);
    if (Cudd_IsComplement(T)) {
	res = (T == E) ? Cudd_Not(T) : cuddUniqueInter(dd,v,Cudd_Not(T),Cudd_Not(E));
	if (res == NULL) {
	    Cudd_RecursiveDeref(dd, T);
	    Cudd_RecursiveDeref(dd, E);
	    return(NULL);
	}
	res = Cudd_Not(res);
    } else {
	res = (T == E) ? T : cuddUniqueInter(dd,v,T,E);
	if (res == NULL) {
	    Cudd_RecursiveDeref(dd, T);
	    Cudd_RecursiveDeref(dd, E);
	    return(NULL);
	}
    }
    cuddDeref(T);
    cuddDeref(E);

    /* Store result. */
    cuddCacheInsert1(dd,Cudd_addBddPattern,f,res);

    return(res);

} /* end of cuddAddBddDoPattern */


/*---------------------------------------------------------------------------*/
/* Definition of static functions                                            */
/*---------------------------------------------------------------------------*/


/**
  @brief Performs the recursive step for Cudd_addBddThreshold.

  @return a pointer to the %BDD if successful; NULL otherwise.

  @sideeffect None

  @see addBddDoStrictThreshold

*/
static DdNode *
addBddDoThreshold(
  DdManager * dd,
  DdNode * f,
  DdNode * val)
{
    DdNode *res, *T, *E;
    DdNode *fv, *fvn;
    unsigned int v;

    statLine(dd);
    /* Check terminal case. */
    if (cuddIsConstant(f)) {
	return(Cudd_NotCond(DD_ONE(dd),cuddV(f) < cuddV(val)));
    }

    /* Check cache. */
    res = cuddCacheLookup2(dd,addBddDoThreshold,f,val);
    if (res != NULL) return(res);

    checkWhetherToGiveUp(dd);

    /* Recursive step. */
    v = f->index;
    fv = cuddT(f); fvn = cuddE(f);

    T = addBddDoThreshold(dd,fv,val);
    if (T == NULL) return(NULL);
    cuddRef(T);

    E = addBddDoThreshold(dd,fvn,val);
    if (E == NULL) {
	Cudd_RecursiveDeref(dd, T);
	return(NULL);
    }
    cuddRef(E);
    if (Cudd_IsComplement(T)) {
	res = (T == E) ? Cudd_Not(T) : cuddUniqueInter(dd,v,Cudd_Not(T),Cudd_Not(E));
	if (res == NULL) {
	    Cudd_RecursiveDeref(dd, T);
	    Cudd_RecursiveDeref(dd, E);
	    return(NULL);
	}
	res = Cudd_Not(res);
    } else {
	res = (T == E) ? T : cuddUniqueInter(dd,v,T,E);
	if (res == NULL) {
	    Cudd_RecursiveDeref(dd, T);
	    Cudd_RecursiveDeref(dd, E);
	    return(NULL);
	}
    }
    cuddDeref(T);
    cuddDeref(E);

    /* Store result. */
    cuddCacheInsert2(dd,addBddDoThreshold,f,val,res);

    return(res);

} /* end of addBddDoThreshold */


/**
  @brief Performs the recursive step for Cudd_addBddStrictThreshold.

  @return a pointer to the %BDD if successful; NULL otherwise.

  @sideeffect None

  @see addBddDoThreshold

*/
static DdNode *
addBddDoStrictThreshold(
  DdManager * dd,
  DdNode * f,
  DdNode * val)
{
    DdNode *res, *T, *E;
    DdNode *fv, *fvn;
    unsigned int v;

    statLine(dd);
    /* Check terminal case. */
    if (cuddIsConstant(f)) {
	return(Cudd_NotCond(DD_ONE(dd),cuddV(f) <= cuddV(val)));
    }

    /* Check cache. */
    res = cuddCacheLookup2(dd,addBddDoStrictThreshold,f,val);
    if (res != NULL) return(res);

    checkWhetherToGiveUp(dd);

    /* Recursive step. */
    v = f->index;
    fv = cuddT(f); fvn = cuddE(f);

    T = addBddDoStrictThreshold(dd,fv,val);
    if (T == NULL) return(NULL);
    cuddRef(T);

    E = addBddDoStrictThreshold(dd,fvn,val);
    if (E == NULL) {
	Cudd_RecursiveDeref(dd, T);
	return(NULL);
    }
    cuddRef(E);
    if (Cudd_IsComplement(T)) {
	res = (T == E) ? Cudd_Not(T) : cuddUniqueInter(dd,v,Cudd_Not(T),Cudd_Not(E));
	if (res == NULL) {
	    Cudd_RecursiveDeref(dd, T);
	    Cudd_RecursiveDeref(dd, E);
	    return(NULL);
	}
	res = Cudd_Not(res);
    } else {
	res = (T == E) ? T : cuddUniqueInter(dd,v,T,E);
	if (res == NULL) {
	    Cudd_RecursiveDeref(dd, T);
	    Cudd_RecursiveDeref(dd, E);
	    return(NULL);
	}
    }
    cuddDeref(T);
    cuddDeref(E);

    /* Store result. */
    cuddCacheInsert2(dd,addBddDoStrictThreshold,f,val,res);

    return(res);

} /* end of addBddDoStrictThreshold */


/**
  @brief Performs the recursive step for Cudd_addBddInterval.

  @return a pointer to the %BDD if successful; NULL otherwise.

  @sideeffect None

  @see addBddDoThreshold addBddDoStrictThreshold

*/
static DdNode *
addBddDoInterval(
  DdManager * dd,
  DdNode * f,
  DdNode * l,
  DdNode * u)
{
    DdNode *res, *T, *E;
    DdNode *fv, *fvn;
    unsigned int v;

    statLine(dd);
    /* Check terminal case. */
    if (cuddIsConstant(f)) {
	return(Cudd_NotCond(DD_ONE(dd),cuddV(f) < cuddV(l) || cuddV(f) > cuddV(u)));
    }

    /* Check cache. */
    res = cuddCacheLookup(dd,DD_ADD_BDD_DO_INTERVAL_TAG,f,l,u);
    if (res != NULL) return(res);

    checkWhetherToGiveUp(dd);

    /* Recursive step. */
    v = f->index;
    fv = cuddT(f); fvn = cuddE(f);

    T = addBddDoInterval(dd,fv,l,u);
    if (T == NULL) return(NULL);
    cuddRef(T);

    E = addBddDoInterval(dd,fvn,l,u);
    if (E == NULL) {
	Cudd_RecursiveDeref(dd, T);
	return(NULL);
    }
    cuddRef(E);
    if (Cudd_IsComplement(T)) {
	res = (T == E) ? Cudd_Not(T) : cuddUniqueInter(dd,v,Cudd_Not(T),Cudd_Not(E));
	if (res == NULL) {
	    Cudd_RecursiveDeref(dd, T);
	    Cudd_RecursiveDeref(dd, E);
	    return(NULL);
	}
	res = Cudd_Not(res);
    } else {
	res = (T == E) ? T : cuddUniqueInter(dd,v,T,E);
	if (res == NULL) {
	    Cudd_RecursiveDeref(dd, T);
	    Cudd_RecursiveDeref(dd, E);
	    return(NULL);
	}
    }
    cuddDeref(T);
    cuddDeref(E);

    /* Store result. */
    cuddCacheInsert(dd,DD_ADD_BDD_DO_INTERVAL_TAG,f,l,u,res);

    return(res);

} /* end of addBddDoInterval */


/**
  @brief Performs the recursive step for Cudd_addBddIthBit.

  @return a pointer to the %BDD if successful; NULL otherwise.

  @sideeffect None

*/
static DdNode *
addBddDoIthBit(
  DdManager * dd,
  DdNode * f,
  DdNode * index)
{
    DdNode *res, *T, *E;
    DdNode *fv, *fvn;
    int mask, value;
    unsigned int v;

    statLine(dd);
    /* Check terminal case. */
    if (cuddIsConstant(f)) {
	mask = 1 << ((int) cuddV(index));
	value = (int) cuddV(f);
	return(Cudd_NotCond(DD_ONE(dd),(value & mask) == 0));
    }

    /* Check cache. */
    res = cuddCacheLookup2(dd,addBddDoIthBit,f,index);
    if (res != NULL) return(res);

    checkWhetherToGiveUp(dd);

    /* Recursive step. */
    v = f->index;
    fv = cuddT(f); fvn = cuddE(f);

    T = addBddDoIthBit(dd,fv,index);
    if (T == NULL) return(NULL);
    cuddRef(T);

    E = addBddDoIthBit(dd,fvn,index);
    if (E == NULL) {
	Cudd_RecursiveDeref(dd, T);
	return(NULL);
    }
    cuddRef(E);
    if (Cudd_IsComplement(T)) {
	res = (T == E) ? Cudd_Not(T) : cuddUniqueInter(dd,v,Cudd_Not(T),Cudd_Not(E));
	if (res == NULL) {
	    Cudd_RecursiveDeref(dd, T);
	    Cudd_RecursiveDeref(dd, E);
	    return(NULL);
	}
	res = Cudd_Not(res);
    } else {
	res = (T == E) ? T : cuddUniqueInter(dd,v,T,E);
	if (res == NULL) {
	    Cudd_RecursiveDeref(dd, T);
	    Cudd_RecursiveDeref(dd, E);
	    return(NULL);
	}
    }
    cuddDeref(T);
    cuddDeref(E);

    /* Store result. */
    cuddCacheInsert2(dd,addBddDoIthBit,f,index,res);

    return(res);

} /* end of addBddDoIthBit */


/**
  @brief Performs the recursive step for Cudd_BddToAdd.

  @return a pointer to the resulting %ADD if successful; NULL
  otherwise.

  @sideeffect None

*/
static DdNode *
ddBddToAddRecur(
  DdManager * dd,
  DdNode * B)
{
    DdNode *one;
    DdNode *res, *res1, *T, *E, *Bt, *Be;
    int complement = 0;

    statLine(dd);
    one = DD_ONE(dd);

    if (Cudd_IsConstantInt(B)) {
	if (B == one) {
	    res = one;
	} else {
	    res = DD_ZERO(dd);
	}
	return(res);
    }
    /* Check visited table */
    res = cuddCacheLookup1(dd,ddBddToAddRecur,B);
    if (res != NULL) return(res);

    checkWhetherToGiveUp(dd);

    if (Cudd_IsComplement(B)) {
	complement = 1;
	Bt = cuddT(Cudd_Regular(B));
	Be = cuddE(Cudd_Regular(B));
    } else {
	Bt = cuddT(B);
	Be = cuddE(B);
    }

    T = ddBddToAddRecur(dd, Bt);
    if (T == NULL) return(NULL);
    cuddRef(T);

    E = ddBddToAddRecur(dd, Be);
    if (E == NULL) {
	Cudd_RecursiveDeref(dd, T);
	return(NULL);
    }
    cuddRef(E);

    /* No need to check for T == E, because it is guaranteed not to happen. */
    res = cuddUniqueInter(dd, (int) Cudd_Regular(B)->index, T, E);
    if (res == NULL) {
	Cudd_RecursiveDeref(dd ,T);
	Cudd_RecursiveDeref(dd ,E);
	return(NULL);
    }
    cuddDeref(T);
    cuddDeref(E);

    if (complement) {
	cuddRef(res);
	res1 = cuddAddCmplRecur(dd, res);
	if (res1 == NULL) {
	    Cudd_RecursiveDeref(dd, res);
	    return(NULL);
	}
	cuddRef(res1);
	Cudd_RecursiveDeref(dd, res);
	res = res1;
	cuddDeref(res);
    }

    /* Store result. */
    cuddCacheInsert1(dd,ddBddToAddRecur,B,res);

    return(res);

} /* end of ddBddToAddRecur */


/**
  @brief Performs the recursive step of Cudd_bddTransfer.

  @return a pointer to the result if successful; NULL otherwise.

  @sideeffect None

  @see cuddBddTransfer

*/
static DdNode *
cuddBddTransferRecur(
  DdManager * ddS,
  DdManager * ddD,
  DdNode * f,
  st_table * table)
{
    DdNode *ft, *fe, *t, *e, *var, *res;
    DdNode *one, *zero;
    unsigned int index;
    int comple = 0;

    statLine(ddD);
    one = DD_ONE(ddD);
    comple = Cudd_IsComplement(f);

    /* Trivial cases. */
    if (Cudd_IsConstantInt(f)) return(Cudd_NotCond(one, comple));

    /* Make canonical to increase the utilization of the cache. */
    f = Cudd_NotCond(f,comple);
    /* Now f is a regular pointer to a non-constant node. */

    /* Check the cache. */
    if (st_lookup(table, f, (void **) &res))
	return(Cudd_NotCond(res,comple));
    
    /* Recursive step. */
    index = f->index;
    ft = cuddT(f); fe = cuddE(f);

    t = cuddBddTransferRecur(ddS, ddD, ft, table);
    if (t == NULL) {
    	return(NULL);
    }
    cuddRef(t);

    e = cuddBddTransferRecur(ddS, ddD, fe, table);
    if (e == NULL) {
    	Cudd_RecursiveDeref(ddD, t);
    	return(NULL);
    }
    cuddRef(e);

    zero = Cudd_Not(one);
    var = cuddUniqueInter(ddD,index,one,zero);
    if (var == NULL) {
	Cudd_RecursiveDeref(ddD, t);
	Cudd_RecursiveDeref(ddD, e);
    	return(NULL);
    }
    res = cuddBddIteRecur(ddD,var,t,e);
    if (res == NULL) {
	Cudd_RecursiveDeref(ddD, t);
	Cudd_RecursiveDeref(ddD, e);
	return(NULL);
    }
    cuddRef(res);
    Cudd_RecursiveDeref(ddD, t);
    Cudd_RecursiveDeref(ddD, e);

    if (st_add_direct(table, f, res) == ST_OUT_OF_MEM) {
	Cudd_RecursiveDeref(ddD, res);
	return(NULL);
    }
    return(Cudd_NotCond(res,comple));

} /* end of cuddBddTransferRecur */