ListClass.cpp

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/*----------------------------------------------------------------------------*/
/*                                                                            */
/* Copyright (c) 1995, 2004 IBM Corporation. All rights reserved.             */
/* Copyright (c) 2005-2009 Rexx Language Association. All rights reserved.    */
/*                                                                            */
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/* the terms of the Common Public License v1.0 which accompanies this         */
/* distribution. A copy is also available at the following address:           */
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/* without modification, are permitted provided that the following            */
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/* derived from this software without specific prior written permission.      */
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/* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS         */
/* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.               */
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/*----------------------------------------------------------------------------*/
/******************************************************************************/
/* REXX Kernel                                                                */
/*                                                                            */
/* Primitive List Class                                                       */
/*                                                                            */
/******************************************************************************/
#include "RexxCore.h"
#include "IntegerClass.hpp"
#include "ListClass.hpp"
#include "ArrayClass.hpp"
#include "SupplierClass.hpp"
#include "ActivityManager.hpp"
#include "ProtectedObject.hpp"
#include "WeakReferenceClass.hpp"
 
// singleton class instance
RexxClass *RexxList::classInstance = OREF_NULL;
 
 
/**
 * Create initial class object at bootstrap time.
 */
void RexxList::createInstance()
{
    CLASS_CREATE(List, "List", RexxClass);
}
 
 
void RexxList::init(void)
/******************************************************************************/
/* Function:  Initial set up of a list object instance                        */
/******************************************************************************/
{
    this->first = LIST_END;              /* no first element                  */
    this->last = LIST_END;               /* no last element                   */
    this->size = INITIAL_LIST_SIZE;      /* set the buffer upper bound        */
                                         /* chain up the free elements        */
    this->partitionBuffer(0, INITIAL_LIST_SIZE);
}
 
RexxObject *RexxList::copy(void)
/******************************************************************************/
/* Function:   create a copy of a list and the associated table               */
/******************************************************************************/
{
    /* make a copy of ourself (also      */
    /* copies the object variables)      */
    RexxList *newlist = (RexxList *)this->RexxObject::copy();
    ProtectedObject p(newlist);
    /* make a copy of the table          */
    OrefSet(newlist, newlist->table, (RexxListTable *)this->table->copy());
    return(RexxObject *)newlist;        /* return the new list               */
}
 
void RexxList::partitionBuffer(
     size_t  first_entry,              /* first entry location              */
     size_t  entry_count )             /* entries to partition              */
/******************************************************************************/
/* Function:  Partition a buffer up into a chain of free elements and set     */
/*            this up as the free element chain                               */
/******************************************************************************/
{
    this->free = first_entry;            /* set the new free chain head       */
    size_t i = first_entry;                     /* get a loop counter                */
    LISTENTRY *element = ENTRY_POINTER(i);          /* point to the first element        */
    while (entry_count-- > 0)
    {
        /* zero the element value            */
        OrefSet(this->table, element->value, OREF_NULL);
        element->next = ++i;               /* set the next element pointer      */
        element->previous = NOT_ACTIVE;    /* mark as a free element            */
        element++;                         /* step to the next element          */
    }
    element--;                           /* step back to last element         */
    element->next = LIST_END;            /* set the terminator                */
}
 
size_t RexxList::getFree(void)
/******************************************************************************/
/* Function:  Check that we have at least one element on the free chain, and  */
/*            if not, expand our buffer size to add some space.               */
/******************************************************************************/
{
    if (this->free == LIST_END)
    {        /* no free elements?                 */
             /* allocate a larger table           */
        RexxListTable *newLTable = new (this->size * 2) RexxListTable;
        /* copy over to the new buffer       */
        memcpy(newLTable->getData(), this->table->getData(), TABLE_SIZE(this->size));
        /* make this the new buffer          */
        OrefSet(this, this->table, newLTable);
        /* If either of the objects are in   */
        /* OldSpace,  we need to OrefSet     */
        /* each copied element               */
        if (this->isOldSpace() || newLTable->isOldSpace())
        {
            LISTENTRY *element = ENTRY_POINTER(0);      /* point at the first element        */
                                             /* copy each element into new buffer */
            for (size_t i = 0; i < this->size; i++)
            {
                /* do an explicit set operator       */
                OrefSet(this->table, element->value, element->value);
                element++;                     /* step to the next element          */
            }
        }
        /* chain up the free elements        */
        this->partitionBuffer(this->size, this->size);
        this->size += this->size;          /* increase the size                 */
    }
    size_t new_index = this->free;       /* get the free element index        */
                                         /* close up the free chain           */
    this->free = ENTRY_POINTER(new_index)->next;
    return new_index;                    /* return the first free element     */
}
 
void RexxList::live(size_t liveMark)
/******************************************************************************/
/* Function:  Normal garbage collection live marking                          */
/******************************************************************************/
{
    memory_mark(this->table);
    memory_mark(this->objectVariables);
}
 
void RexxList::liveGeneral(int reason)
/******************************************************************************/
/* Function:  Generalized object marking                                      */
/******************************************************************************/
{
    memory_mark_general(this->table);
    memory_mark_general(this->objectVariables);
}
 
void RexxList::flatten(RexxEnvelope *envelope)
/******************************************************************************/
/* Function:  Flatten an object                                               */
/******************************************************************************/
{
  setUpFlatten(RexxList)
 
   flatten_reference(newThis->table, envelope);
   flatten_reference(newThis->objectVariables, envelope);
 
  cleanUpFlatten
}
 
LISTENTRY * RexxList::getEntry(
     RexxObject *_index,               /* list index item                   */
     RexxObject *position)             /* index argument error position     */
/******************************************************************************/
/* Function:  Resolve a list index argument to a list element position        */
/******************************************************************************/
{
    if (_index == OREF_NULL)             /* must have one here                */
    {
        /* else an error                     */
        reportException(Error_Incorrect_method_noarg, OREF_positional, position);
    }
    /* force to integer form             */
    RexxInteger *integer_index = (RexxInteger *)REQUEST_INTEGER(_index);
    if (integer_index == TheNilObject)   /* doesn't exist?                    */
    {
        /* raise an exception                */
        reportException(Error_Incorrect_method_index, _index);
    }
    if (integer_index->getValue() < 0)                  /* not a valid index?                */
    {
        /* raise an exception                */
        reportException(Error_Incorrect_method_index, _index);
    }
    /* get the binary value              */
    size_t item_index = integer_index->getValue();
    if (item_index >= this->size)        /* out of possible range?            */
    {
        return NULL;                       /* not found                         */
    }
    LISTENTRY *element = ENTRY_POINTER(item_index); /* point to the item                 */
    if (element->previous == NOT_ACTIVE) /* not a real item?                  */
    {
        element = NULL;                    /* no element found                  */
    }
    return element;                      /* return this                       */
}
 
 
/**
 * Resolve a low-level index into a list entry value.
 *
 * @param item_index The target index.
 *
 * @return A LISTENTRY value, or NULL if not found.
 */
LISTENTRY * RexxList::getEntry(size_t item_index)
{
    if (item_index >= this->size)        /* out of possible range?            */
    {
        return NULL;                       /* not found                         */
    }
    LISTENTRY *element = ENTRY_POINTER(item_index); /* point to the item                 */
    if (element->previous != NOT_ACTIVE) /* got a real item?                  */
    {
        return element;                  // go for it
    }
    return NULL;                         // not found
}
 
 
 
RexxObject *RexxList::value(
     RexxObject *_index)               /* list index item                   */
/******************************************************************************/
/* Function:  Retrieve the value for a given list index                       */
/******************************************************************************/
{
    /* locate this entry                 */
    LISTENTRY *element = this->getEntry(_index, (RexxObject *)IntegerOne);
    if (element == NULL)                 /* not there?                        */
    {
        return TheNilObject;               /* doesn't exist, return .NIL        */
    }
    RexxObject *result = element->value;             /* get the value                     */
    if (result == OREF_NULL)             /* not there?                        */
    {
        result = TheNilObject;             /* just return NIL                   */
    }
    return result;                       /* return this item                  */
}
 
 
 
/**
 * Primitive level getValue() for a list item.
 *
 * @param _index The decoded index item.
 *
 * @return The value associated with the index.  Returns OREF_NULL if not
 *         there.
 */
RexxObject *RexxList::getValue(size_t _index)
{
    /* locate this entry                 */
    LISTENTRY *element = this->getEntry(_index);
    // return a real NULL if this isn't there
    if (element == NULL)
    {
        return OREF_NULL;
    }
    return element->value;               // return whatever is in this position
}
 
 
RexxObject *RexxList::put(
     RexxObject *_value,                /* new value for the item            */
     RexxObject *_index )               /* index of item to replace          */
/******************************************************************************/
/* Function:  Replace the value of an item already in the list.               */
/******************************************************************************/
{
    /* locate this entry                 */
    LISTENTRY *element = this->getEntry(_index, (RexxObject *)IntegerTwo);
    requiredArgument(_value, OREF_positional, ARG_ONE);           /* must have a value also            */
    if (element == NULL)                 /* not a valid index?                */
    {
        /* raise an error                    */
        reportException(Error_Incorrect_method_index, _index);
    }
    /* replace the value                 */
    OrefSet(this->table, element->value, _value);
    return OREF_NULL;                    /* return nothing at all             */
}
 
RexxObject *RexxList::section(
     RexxObject *_index,                /* index of starting item            */
     RexxObject *_count )               /* count of items to return          */
/******************************************************************************/
/* Function:  Create a sublist of this list                                   */
/******************************************************************************/
{
    size_t counter;                      /* object counter                    */
                                         /* locate this entry                 */
    LISTENTRY *element = this->getEntry(_index, (RexxObject *)IntegerOne);
    if (_count != OREF_NULL)
    {           /* have a count?                     */
                /* Make sure it's a good integer     */
        counter = _count->requiredNonNegative(OREF_positional, ARG_TWO);
    }
    else
    {
        counter = 999999999;               /* just use largest possible count   */
    }
    if (element == NULL)                 /* index doesn't exist?              */
                                         /* raise an error                    */
        reportException(Error_Incorrect_method_index, _index);
    if (!isOfClass(List, this))              /* actually a list subclass?         */
    {
        /* need to do this the slow way      */
        return this->sectionSubclass(element, counter);
    }
    RexxList *result = new RexxList;     /* create a new list                 */
    ProtectedObject p(result);
    /* while still more to go and not at */
    /* the end of the list               */
    while (counter--> 0)
    {               /* while still more items            */
                    /* add the this item to new list     */
        result->addLast(element->value);
        if (element->next == LIST_END)     /* this the last one?                */
        {
            break;                           /* done sectioning                   */
        }
                                             /* step to the next item             */
        element = ENTRY_POINTER(element->next);
    }
    return result;                       /* return the sectioned list         */
}
 
RexxObject *RexxList::sectionSubclass(
    LISTENTRY *element,                /* starting element                  */
    size_t     counter)                /* count of elements                 */
/******************************************************************************/
/* Function:  Rexx level section method                                       */
/******************************************************************************/
{
    ProtectedObject r;
    /* create a new list                 */
    this->behaviour->getOwningClass()->sendMessage(OREF_NEW, r);
    RexxList *newList = (RexxList *)(RexxObject *)r;
    /* while still more to go and not at */
    /* the end of the list               */
    while (counter-- > 0)                /* while still more items            */
    {
        /* add the this item to new list     */
        newList->sendMessage(OREF_INSERT, element->value);
        if (element->next == LIST_END)     /* this the last one?                */
        {
            break;                           /* done sectioning                   */
        }
                                             /* step to the next item             */
        element = ENTRY_POINTER(element->next);
    }
    return newList;                      /* return the sectioned list         */
}
 
RexxObject *RexxList::add(
     RexxObject *_value,                /* new value to add                  */
     RexxObject *_index)                /* addition insertion index          */
/******************************************************************************/
/* Function:  Add a new element to the list at the given insertion point.     */
/*            TheNilObject indicates it should be added to the list end       */
/******************************************************************************/
{
    LISTENTRY *element;                  /* list element                      */
 
                                         /* make sure we have room to insert  */
    size_t new_index = this->getFree();
    /* point to the actual element       */
    LISTENTRY *new_element = ENTRY_POINTER(new_index);
    if (_index == TheNilObject)          /* inserting at the end?             */
    {
        element = NULL;                    /* flag this as new                  */
    }
    else
    {
        /* locate this entry                 */
        element = this->getEntry(_index, (RexxObject *)IntegerOne);
        if (element == NULL)               /* index doesn't exist?              */
        {
            /* raise an error                    */
            reportException(Error_Incorrect_method_index, _index);
        }
    }
    this->count++;                       /* increase our count                */
                                         /* set the value                     */
    OrefSet(this->table, new_element->value, _value);
    if (element == NULL)
    {               /* adding at the end                 */
        if (this->last == LIST_END)
        {      /* first element added?              */
            this->first = new_index;         /* set this as the first             */
            this->last = new_index;          /* and the last                      */
            new_element->next = LIST_END;    /* this is the last element          */
            new_element->previous = LIST_END;/* in both directions                */
        }
        else
        {                             /* adding at the end                 */
                                      /* previous is current last          */
            new_element->previous = this->last;
            new_element->next = LIST_END;    /* nothing after this                */
                                             /* point to the end element          */
            element = ENTRY_POINTER(this->last);
            element->next = new_index;       /* point it at the new entry         */
            this->last = new_index;          /* this is the new last element      */
        }
    }
    else
    {                               /* have a real insertion point       */
                                    /* set the next pointer              */
        new_element->next = ENTRY_INDEX(element);
 
        if (element->previous == LIST_END) /* inserting at the front?           */
        {
            this->first = new_index;         /* new first element                 */
        }
        else                               /* fudge the previous element        */
        {
            ENTRY_POINTER(element->previous)->next = new_index;
        }
        /* insert before this element        */
        new_element->previous = element->previous;
        element->previous = new_index;     /* new previous one                  */
                                           /* point at the insertion point      */
        new_element->next = ENTRY_INDEX(element);
    }
    /* return this index item            */
    return new_integer(new_index);
}
 
void RexxList::addLast(
     RexxObject *_value )              /* new value to add                  */
/******************************************************************************/
/* Function:  Add a new element to the tail of a list                         */
/******************************************************************************/
{
    /* make sure we have room to insert  */
    size_t new_index = this->getFree();
    /* point to the actual element       */
    LISTENTRY *new_element = ENTRY_POINTER(new_index);
    this->count++;                       /* increase our count                */
                                         /* set the value                     */
    OrefSet(this->table, new_element->value, _value);
    if (this->last == LIST_END)
    {        /* first element added?              */
        this->first = new_index;           /* set this as the first             */
        this->last = new_index;            /* and the last                      */
        new_element->next = LIST_END;      /* this is the last element          */
        new_element->previous = LIST_END;  /* in both directions                */
    }
    else
    {                               /* adding at the end                 */
        new_element->previous = this->last;/* previous is current last          */
        new_element->next = LIST_END;      /* nothing after this                */
                                           /* point to the end element          */
        new_element = ENTRY_POINTER(this->last);
        new_element->next = new_index;     /* point it at the new entry         */
        this->last = new_index;            /* this is the new last element      */
    }
}
 
void RexxList::addFirst(
     RexxObject *_value)               /* new value to add                  */
/******************************************************************************/
/* Function:  Insert an element at the front of the list                      */
/******************************************************************************/
{
    size_t new_index = this->getFree();         /* make sure we have room to insert  */
    /* point to the actual element       */
    LISTENTRY *new_element = ENTRY_POINTER(new_index);
    this->count++;                       /* increase our count                */
                                         /* set the value                     */
    OrefSet(this->table, new_element->value, _value);
    if (this->last == LIST_END)
    {        /* first element added?              */
        this->first = new_index;           /* set this as the first             */
        this->last = new_index;            /* and the last                      */
        new_element->next = LIST_END;      /* this is the last element          */
        new_element->previous = LIST_END;  /* in both directions                */
    }
    else
    {                               /* adding at the front               */
 
        new_element->next = this->first;   /* previous is current first         */
        new_element->previous = LIST_END;  /* nothing before this               */
                                           /* point to the first element        */
        LISTENTRY *element = ENTRY_POINTER(this->first);
        element->previous = new_index;     /* point it at the new entry         */
        this->first = new_index;           /* this is the new first element     */
    }
}
 
 
RexxObject *RexxList::insertRexx(
     RexxObject *_value,               /* new value to add                  */
     RexxObject *_index)               /* addition insertion index          */
/******************************************************************************/
/* Function:  Publicly accessible version of the list insert function.        */
/******************************************************************************/
{
    requiredArgument(_value, OREF_positional, ARG_ONE);           /* must have a value to insert       */
                                         /* go do the real insert             */
    return this->insert(_value, _index);
}
 
 
/**
 * Append an item after the last item in the list.
 *
 * @param value  The value to append.
 *
 * @return The index of the appended item.
 */
RexxObject *RexxList::append(RexxObject *_value)
{
    requiredArgument(_value, OREF_positional, ARG_ONE);
    // this is just an insertion operation with an ommitted index.
    return insert(_value, OREF_NULL);
}
 
 
RexxObject *RexxList::insert(
     RexxObject *_value,               /* new value to add                  */
     RexxObject *_index)               /* addition insertion index          */
/******************************************************************************/
/* Function:  Add a new element to the list at the given insertion point.     */
/*            TheNilObject indicates it should be added to the list fron      */
/******************************************************************************/
{
    LISTENTRY *element;                  /* list element                      */
 
                                         /* make sure we have room to insert  */
    size_t new_index = this->getFree();
    /* point to the actual element       */
    LISTENTRY *new_element = ENTRY_POINTER(new_index);
    if (_index == TheNilObject)          /* inserting at the front?           */
    {
        element = NULL;                    /* flag this as new                  */
    }
    else if (_index == OREF_NULL)
    {      /* inserting at the end?             */
        if (this->last == LIST_END)        /* currently empty?                  */
        {
            element = NULL;                  /* just use the front insert code    */
        }
        else                               /* insert after the last element     */
        {
            element = ENTRY_POINTER(this->last);
        }
    }
    else
    {
        /* locate this entry                 */
        element = this->getEntry(_index, (RexxObject *)IntegerOne);
        if (element == NULL)               /* index doesn't exist?              */
        {
            /* raise an error                    */
            reportException(Error_Incorrect_method_index, _index);
        }
    }
    this->count++;                       /* increase our count                */
                                         /* set the value                     */
    OrefSet(this->table, new_element->value, _value);
    if (element == NULL)
    {               /* adding at the front               */
        if (this->last == LIST_END)
        {      /* first element added?              */
            this->first = new_index;         /* set this as the first             */
            this->last = new_index;          /* and the last                      */
            new_element->next = LIST_END;    /* this is the last element          */
            new_element->previous = LIST_END;/* in both directions                */
        }
        else
        {                             /* adding at the front               */
 
            new_element->next = this->first; /* previous is current first         */
            new_element->previous = LIST_END;/* nothing before this               */
                                             /* point to the first element        */
            element = ENTRY_POINTER(this->first);
            element->previous = new_index;   /* point it at the new entry         */
            this->first = new_index;         /* this is the new first element     */
        }
    }
    else
    {                               /* have a real insertion point       */
                                    /* set the next pointer              */
        new_element->previous = ENTRY_INDEX(element);
 
        if (element->next == LIST_END)     /* inserting at the end?             */
        {
            this->last = new_index;          /* new first element                 */
        }
        else                               /* fudge the next element            */
        {
            ENTRY_POINTER(element->next)->previous = new_index;
        }
        new_element->next = element->next; /* insert after this element         */
        element->next = new_index;         /* new following one                 */
                                           /* point at the insertion point      */
        new_element->previous = ENTRY_INDEX(element);
    }
    /* return this index item            */
    return new_integer(new_index);
}
 
RexxObject *RexxList::remove(
     RexxObject *_index)               /* index of item to remove           */
/******************************************************************************/
/* Function:  Remove a list item from the list                                */
/******************************************************************************/
{
                                       /* just remove the given index       */
    return this->primitiveRemove(this->getEntry(_index, (RexxObject *)IntegerOne));
}
 
RexxObject *RexxList::primitiveRemove(
     LISTENTRY *element)               /* element to remove                 */
/******************************************************************************/
/* Function:  Remove a list item from the list                                */
/******************************************************************************/
{
    LISTENTRY *_previous;                /* previous entry                    */
    LISTENTRY *_next;                    /* next entry                        */
 
    if (element == NULL)                 /* not a valid index?                */
        return TheNilObject;               /* just return .nil                  */
 
    RexxObject *_value = element->value; /* copy the value                    */
    if (element->next != LIST_END)
    {     /* not end of the list?              */
          /* point to the next entry           */
        _next = ENTRY_POINTER(element->next);
        _next->previous = element->previous;/* update the previous pointer       */
    }
    else
    {
        this->last = element->previous;    /* need to update the last pointer   */
    }
    if (element->previous != LIST_END)
    { /* not end of the list?              */
      /* point to the next entry           */
        _previous = ENTRY_POINTER(element->previous);
        _previous->next = element->next;   /* remove this from the chain        */
    }
    else
    {
        this->first = element->next;       /* need to update the last pointer   */
    }
 
    this->count--;                       /* "forget" we had this              */
    element->previous = NOT_ACTIVE;      /* no longer a good element          */
    element->next = this->free;          /* new head of the free chain        */
    this->free = ENTRY_INDEX(element);   /* this is the first free element    */
 
    return _value;                       /* return the old value              */
}
 
RexxObject *RexxList::firstItem(void)
/******************************************************************************/
/* Function:  Return first item (value part) in the list                      */
/******************************************************************************/
{
    if (this->first == LIST_END)         /* empty list?                       */
    {
        return TheNilObject;               /* give the empty indicator          */
    }
    else                                 /* return the first value            */
    {
        return ENTRY_POINTER(this->first)->value;
    }
}
 
RexxObject *RexxList::lastItem(void)
/******************************************************************************/
/* Function:  Return last item (value part) in the list                       */
/******************************************************************************/
{
    if (this->last == LIST_END)          /* empty list?                       */
    {
        return TheNilObject;               /* give the empty indicator          */
    }
    else                                 /* return the first value            */
    {
        return ENTRY_POINTER(this->last)->value;
    }
}
 
RexxObject *RexxList::firstRexx(void)
/******************************************************************************/
/* Function:  Return index of the first list item                             */
/******************************************************************************/
{
    if (this->first == LIST_END)         /* no first item?                    */
    {
        return TheNilObject;               /* just return a .nil index          */
    }
    else
    {
        /* return the index as an integer    */
        return new_integer(this->first);
    }
}
 
RexxObject *RexxList::lastRexx(void)
/******************************************************************************/
/* Function:  Return index of the last list item                              */
/******************************************************************************/
{
    if (this->last == LIST_END)          /* no first item?                    */
    {
        return TheNilObject;               /* just return a .nil index          */
    }
    else
    {
        /* return the index as an integer    */
        return new_integer(this->last);
    }
}
 
RexxObject *RexxList::next(
     RexxObject *_index)               /* index of the target item          */
/******************************************************************************/
/* Function:  Return the next item after the given indexed item               */
/******************************************************************************/
{
    /* locate this entry                 */
    LISTENTRY *element = this->getEntry(_index, (RexxObject *)IntegerOne);
    if (element == NULL)                 /* not a valid index?                */
    {
        /* raise an error                    */
        reportException(Error_Incorrect_method_index, _index);
    }
 
    if (element->next == LIST_END)       /* no next item?                     */
    {
        return TheNilObject;               /* just return .nil                  */
    }
    else
    {
        /* return the next item              */
        return new_integer(element->next);
    }
}
 
RexxObject *RexxList::previous(
     RexxObject *_index)                /* index of the target item          */
/******************************************************************************/
/* Function:  Return the item previous to the indexed item                    */
/******************************************************************************/
{
    /* locate this entry                 */
    LISTENTRY *element = this->getEntry(_index, (RexxObject *)IntegerOne);
    if (element == NULL)                 /* not a valid index?                */
    {
        /* raise an error                    */
        reportException(Error_Incorrect_method_index, _index);
    }
 
    if (element->previous == LIST_END)   /* no previous item?                 */
    {
        return TheNilObject;               /* just return .nil                  */
    }
    else
    {                               /* return the previous item index    */
        return new_integer(element->previous);
    }
}
 
 
/**
 * A low-level next() method for internal usage.  This works
 * directly off the index values without needing to create
 * object instances.  This is critical for some of the internal
 * data structures implemented as lists.
 *
 * @param _index The target item index.
 *
 * @return The index of the next item, or LIST_END if there is no next item.
 */
size_t RexxList::nextIndex(size_t _index)
{
    LISTENTRY *element = this->getEntry(_index);
    // we're a little less strict when dealing with internal lists.  Just return
    // the end of list marker here
    if (element == NULL)
    {
        return LIST_END;
    }
    // we can just return this value directly...if there is no previous element,
    // the next field contains LIST_END;
    return element->next;
}
 
 
/**
 * A low-level previous() method for internal usage.  This works
 * directly off the index values without needing to create
 * object instances.  This is critical for some of the internal
 * data structures implemented as lists.
 *
 * @param _index The target item index.
 *
 * @return The index of the previous item, or LIST_END if there
 *         is no previous item.
 */
size_t RexxList::previousIndex(size_t _index)
{
    LISTENTRY *element = this->getEntry(_index);
    // we're a little less strict when dealing with internal lists.  Just return
    // the end of list marker here
    if (element == NULL)
    {
        return LIST_END;
    }
    // we can just return this value directly...if there is no previous element,
    // the previous field contains LIST_END;
    return element->previous;
}
 
 
RexxObject *RexxList::hasIndex(
     RexxObject *_index)               /* index of the target item          */
/******************************************************************************/
/* Function:  Return an index existence flag                                  */
/******************************************************************************/
{
    /* locate this entry                 */
    LISTENTRY *element = this->getEntry(_index, (RexxObject *)IntegerOne);
    /* return an existence flag          */
    return(element!= NULL) ? (RexxObject *)TheTrueObject : (RexxObject *)TheFalseObject;
}
 
RexxArray *RexxList::requestArray()
/******************************************************************************/
/* Function:  Primitive level request('ARRAY') fast path                      */
/******************************************************************************/
{
    if (isOfClass(List, this))               /* primitive level object?           */
    {
        return this->makeArray();              /* just do the makearray             */
    }
    else                                     /* need to so full request mechanism */
    {
        return(RexxArray *)this->sendMessage( OREF_REQUEST, OREF_ARRAYSYM);
    }
}
 
 
RexxArray *RexxList::makeArray(void)
/******************************************************************************/
/* Function:  Return all of the list values in an array                       */
/******************************************************************************/
{
    return this->allItems();           // this is just all of the array items.
}
 
 
/**
 * Return an array containing all elements contained in the list,
 * in sorted order.
 *
 * @return An array with the list elements.
 */
RexxArray *RexxList::allItems(void)
{
    // just iterate through the list, copying the elements.
    RexxArray *array = (RexxArray *)new_array(this->count);
    size_t   nextEntry = this->first;
    for (size_t  i = 1; i <= this->count; i++)
    {
        LISTENTRY *element = ENTRY_POINTER(nextEntry);
        array->put(element->value, i);
        nextEntry = element->next;
    }
    return array;
}
 
 
/**
 * Empty all of the items from a list.
 *
 * @return No return value.
 */
RexxObject *RexxList::empty()
{
    while (this->first != LIST_END)
    {
        // get the list entry and remove the value
        LISTENTRY *element = ENTRY_POINTER(this->first);
        primitiveRemove(element);
    }
    return OREF_NULL;
}
 
 
 
/**
 * Test if a list is empty.
 *
 * @return True if the list is empty, false otherwise
 */
RexxObject *RexxList::isEmpty()
{
    return (count == 0) ? TheTrueObject : TheFalseObject;
}
 
 
/**
 * Return an array containing all elements contained in the list,
 * in sorted order.
 *
 * @return An array with the list elements.
 */
RexxArray *RexxList::allIndexes(void)
{
    // just iterate through the list, copying the elements.
    RexxArray *array = (RexxArray *)new_array(this->count);
    // this requires protecting, since we're going to be creating new
    // integer objects.
    ProtectedObject p(array);
    size_t   nextEntry = this->first;
    for (size_t i = 1; i <= this->count; i++)
    {
        LISTENTRY *element = ENTRY_POINTER(nextEntry);
        array->put((RexxObject *)new_integer(nextEntry), i);
        nextEntry = element->next;
    }
    return array;
}
 
 
/**
 * Return the index of the first item with a matching value
 * in the list.  Returns .nil if the object is not found.
 *
 * @param target The target object.
 *
 * @return The index of the item, or .nil.
 */
RexxObject *RexxList::index(RexxObject *target)
{
    // we require the index to be there.
    requiredArgument(target, OREF_positional, ARG_ONE);
 
    // ok, now run the list looking for the target item
    size_t nextEntry = this->first;
    for (size_t i = 1; i <= this->count; i++)
    {
        LISTENTRY *element = ENTRY_POINTER(nextEntry);
        // if we got a match, return the item
        if (target->equalValue(element->value))
        {
            return new_integer(nextEntry);
        }
        nextEntry = element->next;
    }
    // no match
    return TheNilObject;
}
 
 
/**
 * Tests whether there is an object with the given value in the
 * list.
 *
 * @param target The target value.
 *
 * @return .true if there is a match, .false otherwise.
 */
RexxObject *RexxList::hasItem(RexxObject *target)
{
    // we require the index to be there.
    requiredArgument(target, OREF_positional, ARG_ONE);
 
    // ok, now run the list looking for the target item
    size_t nextEntry = this->first;
    for (size_t i = 1; i <= this->count; i++)
    {
        LISTENTRY *element = ENTRY_POINTER(nextEntry);
        // if we got a match, return the item
        if (target->equalValue(element->value))
        {
            return TheTrueObject;
        }
        nextEntry = element->next;
    }
    // no match
    return TheFalseObject;
}
 
 
/**
 * Removes an item from the collection.
 *
 * @param target The target value.
 *
 * @return The target item.
 */
RexxObject *RexxList::removeItem(RexxObject *target)
{
    // we require the index to be there.
    requiredArgument(target, OREF_positional, ARG_ONE);
 
    // ok, now run the list looking for the target item
    size_t nextEntry = this->first;
 
    for (size_t i = 1; i <= this->count; i++)
    {
        LISTENTRY *element = ENTRY_POINTER(nextEntry);
        // if we got a match, return the item
        if (target->equalValue(element->value))
        {
            // remove this item
            return primitiveRemove(element);
        }
        nextEntry = element->next;
    }
    // no match
    return TheNilObject;
}
 
 
/**
 * Removes an item from the collection using Object identity
 * comparisons.  This is used in some special circumstances when
 * we don't want to have the equals method called, which can
 * cause some exceptions or false positives.  This is used
 * primarily for managing the local reference save lists.
 *
 * @param target The target value.
 *
 * @return The target item.
 */
RexxObject *RexxList::removeObject(RexxObject *target)
{
    // we require the index to be there.
    requiredArgument(target, OREF_positional, ARG_ONE);
 
    // ok, now run the list looking for the target item
    size_t nextEntry = this->first;
 
    for (size_t i = 1; i <= this->count; i++)
    {
        LISTENTRY *element = ENTRY_POINTER(nextEntry);
        // if we got a match, return the item
        if (target == element->value)
        {
            // remove this item
            return primitiveRemove(element);
        }
        nextEntry = element->next;
    }
    // no match
    return TheNilObject;
}
 
 
RexxObject *RexxList::indexOfValue(
     RexxObject *_value)
/*****************************************************************************/
/* Function:  Return the index for the value that was passed in              */
/*            or OREF_NULL                                                   */
/*****************************************************************************/
{
    RexxObject *_index = OREF_NULL;
    RexxObject *this_value = OREF_NULL;
    /* get the last index in the list     */
    RexxObject *last_index = this->lastRexx();
    /* if there was any items in list     */
    if (last_index != TheNilObject)
    {
        /* loop thru the list looking for the */
        /* specified value                    */
        for (_index = this->firstRexx();
            ((this_value = this->value(_index)) != _value) && _index != last_index;
            _index = this->next(_index));
    }
    /* return the index if the value was  */
    /* in the list                        */
    if (this_value == _value)
    {
        return _index;
    }
    /* otherwise return nothing           */
    return OREF_NULL;
}
 
RexxArray  *RexxList::makeArrayIndices()
/******************************************************************************/
/* Function:  Return an array containing all of the list indices              */
/******************************************************************************/
{
                                       /* allocate proper sized array       */
    RexxArray *array = (RexxArray *)new_array(this->count);
    ProtectedObject p(array);
    size_t nextEntry = this->first;             /* point to the first element        */
    for (size_t i = 1; i <= this->count; i++)
    { /* step through the array elements   */
        LISTENTRY *element = ENTRY_POINTER(nextEntry);/* get the next item                 */
        /* create an index item              */
        array->put((RexxObject *)new_integer(nextEntry), i);
        nextEntry = element->next;         /* get the next pointer              */
    }
    return array;                        /* return the array element          */
}
 
RexxSupplier *RexxList::supplier(void)
/******************************************************************************/
/* Function:  Create a supplier object for this list                          */
/******************************************************************************/
{
    RexxArray *values;                   /* array of value items              */
    RexxArray *indices;                  /* array of index items              */
 
                                         /* and all of the indices            */
    indices = this->makeArrayIndices();
    ProtectedObject p_indices(indices);
    values = this->makeArray();          /* get the list values               */
    ProtectedObject p_values(values);
                                         /* return the supplier values        */
    return(RexxSupplier *)new_supplier(values, indices);
}
 
RexxObject *RexxList::itemsRexx(void)
/******************************************************************************/
/* Function:  Return the size of the list as an integer                       */
/******************************************************************************/
{
                                       /* return the item count             */
    return (RexxObject *)new_integer(this->count);
}
 
 
RexxArray *RexxList::weakReferenceArray()
/******************************************************************************/
/* Function:  Scan the list removing all cleared weak reference objects,      */
/*            and return an array of the dereferenced week array objects.     */
/******************************************************************************/
{
    LISTENTRY *element;                  /* current working entry             */
 
    size_t i = this->firstIndex();              /* point to the first element        */
    size_t itemCount = this->count;
    while (itemCount--)                  /* step through the array elements   */
    {
        element = ENTRY_POINTER(i);      /* get the next item                 */
        // step to the next element now, so we can remove this one
        i = element->next;
 
        // get the reference value
        WeakReference *ref = (WeakReference *)element->value;
        // has the referenced object gone out of scope?
        if (ref->get() == OREF_NULL)
        {
            // remove this element from the list...note that this also
            // decrements the count, which will effect the number of
            // loop iterations.
            primitiveRemove(element);
        }
    }
 
    // we've removed the dead references, so make a second pass copying
    // the real values into the returned array
    RexxArray *array = (RexxArray *)new_array(this->count);
    i = this->firstIndex();              /* point to the first element        */
    for (size_t j = 1; j <= this->count; j++) /* step through the array elements   */
    {
        element = ENTRY_POINTER(i);      /* get the next item                 */
                                         /* copy over to the array            */
        // get the reference value
        WeakReference *ref = (WeakReference *)element->value;
        array->put(ref->get(), j);
        i = element->next;               /* get the next pointer              */
    }
    return array;                        /* return the array element          */
}
 
void *RexxList::operator new(size_t size)
/******************************************************************************/
/* Function:  Construct and initialized a new list item                       */
/******************************************************************************/
{
    /* Get new object                    */
    RexxList *newList = (RexxList *)new (INITIAL_LIST_SIZE, size) RexxListTable;
    /* Give new object its behaviour     */
    newList->setBehaviour(TheListBehaviour);
    newList->init();                     /* finish initializing               */
    return newList;                      /* return the new list item          */
}
 
RexxList *RexxList::newRexx(
    RexxObject **init_args,
    size_t       argCount,
    size_t       named_argCount)
/******************************************************************************/
/* Function:  Construct and initialized a new list item                       */
/******************************************************************************/
{
    /* get a new directory               */
    /* NOTE:  this does not use the      */
    /* macro version because the class   */
    /* object might actually be for a    */
    /* subclass                          */
    RexxList *newList = new RexxList;
    ProtectedObject p(newList);
    /* Give new object its behaviour     */
    newList->setBehaviour(((RexxClass *)this)->getInstanceBehaviour());
    if (((RexxClass *)this)->hasUninitDefined())
    {
        newList->hasUninit();
    }
 
    /* Initialize the new list instance  */
    newList->sendMessage(OREF_INIT, init_args, argCount, named_argCount);
    return newList;                      /* return the new list item          */
}
 
RexxList *RexxList::classOf(
     RexxObject **args,                /* array of list items               */
     size_t       argCount,            /* size of the argument array        */
     size_t       named_argCount)
/******************************************************************************/
/* Function:  Create a new list containing the given list items               */
/******************************************************************************/
{
    RexxList *newList;                   /* newly created list                */
 
    if (TheListClass == (RexxClass *)this )
    {         /* creating an internel list item?   */
        size_t _size = argCount;           /* get the array size                */
        newList  = new RexxList;           /* get a new list                    */
        ProtectedObject p(newList);
        for (size_t i = 0; i < _size; i++)
        {       /* step through the array            */
            RexxObject *item = args[i];                  /* get the next item                 */
            if (item == OREF_NULL)
            {         /* omitted item?                     */
                      /* raise an error on this            */
                reportException(Error_Incorrect_method_noarg, OREF_positional, i + 1);
            }
            /* add this to the list end          */
            newList->addLast(item);
        }
    }
    else
    {
        size_t _size = argCount;                   /* get the array size                */
        ProtectedObject p;
        /* get a new list                    */
        this->sendMessage(OREF_NEW, p);
        newList = (RexxList *)(RexxObject *)p;
        for (size_t i = 0; i < _size; i++)
        {       /* step through the array            */
            RexxObject *item = args[i];                  /* get the next item                 */
            if (item == OREF_NULL)
            {         /* omitted item?                     */
                      /* raise an error on this            */
                reportException(Error_Incorrect_method_noarg, OREF_positional, i + 1);
            }
            /* add this to the list end          */
            newList->sendMessage(OREF_INSERT, item);
        }
    }
    return newList;                      /* give back the list                */
}