list.cxx

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/*[]---------------------------------------------------[]*/
/*|                                                     |*/
/*|     list.c - bidirectional list class               |*/
/*|                                                     |*/
/*|                                                     |*/
/*|  Author: Alexander Gelfenbain                       |*/
/*[]---------------------------------------------------[]*/

#include <assert.h>
#include <cstdlib>

#include "list.h"

namespace {

/*- private data types */
struct lnode {
    struct lnode *next;
    struct lnode *prev;

    void *value;

};

}

struct list_ {
    lnode *head, *tail, *cptr;
    size_t aCount;
    list_destructor eDtor;
};

/*- private methods */

static lnode *newNode(void *el)
{
    lnode *ptr = static_cast<lnode *>(std::malloc(sizeof(lnode)));
    assert(ptr != nullptr);

    ptr->value = el;

    return ptr;
}

static lnode *appendPrim(list pThis, void *el)
{
    lnode *ptr = newNode(el);
    lnode **flink, *blink;

    if (pThis->tail != nullptr) {
        flink = &(pThis->tail->next);
        blink = pThis->tail;
    } else {
        flink = &pThis->head;
        blink = nullptr;
        pThis->cptr = ptr;                         /*- list was empty - set current to this element */
    }

    *flink  = ptr;
    pThis->tail = ptr;

    ptr->prev = blink;
    ptr->next = nullptr;

    pThis->aCount++;
    return ptr;
}

/*- public methods  */
list listNewEmpty()                           /*- default ctor */
{
    list pThis = static_cast<list>(std::malloc(sizeof(struct list_)));
    assert(pThis != nullptr);

    pThis->aCount = 0;
    pThis->eDtor = nullptr;
    pThis->head = pThis->tail = pThis->cptr = nullptr;

    return pThis;
}

void listDispose(list pThis)                       /*- dtor */
{
    assert(pThis != nullptr);
    listClear(pThis);
    std::free(pThis);
}

void listSetElementDtor(list pThis, list_destructor f)
{
    assert(pThis != nullptr);
    pThis->eDtor = f;
}

/* calling this function on an empty list is a run-time error */
void *listCurrent(list pThis)
{
    assert(pThis != nullptr);
    assert(pThis->cptr != nullptr);
    return pThis->cptr->value;
}

int   listCount(list pThis)
{
    assert(pThis != nullptr);
    return pThis->aCount;
}

int   listIsEmpty(list pThis)
{
    assert(pThis != nullptr);
    return pThis->aCount == 0;
}

int    listNext(list pThis)
{
    return listSkipForward(pThis, 1);
}

int    listSkipForward(list pThis, int n)
{
    int m = 0;
    assert(pThis != nullptr);

    if (pThis->cptr == nullptr) return 0;

    while (n != 0) {
        if (pThis->cptr->next == nullptr) break;
        pThis->cptr = pThis->cptr->next;
        n--;
        m++;
    }
    return m;
}

int    listToFirst(list pThis)
{
    assert(pThis != nullptr);

    if (pThis->cptr != pThis->head) {
        pThis->cptr = pThis->head;
        return 1;
    }
    return 0;
}

int    listToLast(list pThis)
{
    assert(pThis != nullptr);

    if (pThis->cptr != pThis->tail) {
        pThis->cptr = pThis->tail;
        return 1;
    }
    return 0;
}

list   listAppend(list pThis, void *el)
{
    assert(pThis != nullptr);

    appendPrim(pThis, el);
    return pThis;
}

list   listRemove(list pThis)
{
    lnode *ptr = nullptr;
    if (pThis->cptr == nullptr) return pThis;

    if (pThis->cptr->next != nullptr) {
        ptr  = pThis->cptr->next;
        pThis->cptr->next->prev = pThis->cptr->prev;
    } else {
        pThis->tail = pThis->cptr->prev;
    }

    if (pThis->cptr->prev != nullptr) {
        if (ptr == nullptr) ptr = pThis->cptr->prev;
        pThis->cptr->prev->next = pThis->cptr->next;
    } else {
        pThis->head = pThis->cptr->next;
    }

    if (pThis->eDtor) pThis->eDtor(pThis->cptr->value);        /* call the dtor callback */

    std::free(pThis->cptr);
    pThis->aCount--;
    pThis->cptr = ptr;
    return pThis;
}

list   listClear(list pThis)
{
    lnode *node = pThis->head, *ptr;

    while (node) {
        ptr = node->next;
        if (pThis->eDtor) pThis->eDtor(node->value);           /* call the dtor callback */
        std::free(node);
        pThis->aCount--;
        node = ptr;
    }

    pThis->head = pThis->tail = pThis->cptr = nullptr;
    assert(pThis->aCount == 0);
    return pThis;
}

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