point_list.c

#include <stdio.h>  /* stderr fprintf */

#include "point.h"
#include "point_list.h"

void bg_point_list_print(
        struct bg_point_list * plist) {
    fprintf(stderr, "bg_point_list @ %p: ", plist);
    for (struct bg_point * p=plist->head_p;
            p<plist->head_p+plist->length; 
            ++p) {
        fprintf(stderr, "(%d, %d) -> ", p->x, p->y);
    }
    fprintf(stderr, "\n");
    return;
}

/* bg_point_list_append()
 * Allocate a new list and it is {sizeof(struct bg_point)} bytes bigger than olds,
 * then copy the content from olds to news. The old list would be freed.
 */
void 
bg_point_list_append(
        struct bg_point_list * point_list_p,
        struct bg_point * new_point_p) {
    /* allocate for new list*/
    unsigned int
        new_head_size=(point_list_p->length+1)*sizeof(struct bg_point);
    struct bg_point * 
        new_head_p=(struct bg_point *)malloc(new_head_size);

    /* copy */
    if (NULL != point_list_p->head_p) {
        memcpy(new_head_p, 
                point_list_p->head_p, 
                sizeof(struct bg_point)*point_list_p->length);
    }

    /* append */
    *(new_head_p + point_list_p->length) = *new_point_p;

    /* update point list size value */
    point_list_p->length += 1;

    /* free old list */
    if (NULL != point_list_p->head_p)
    {
        free(point_list_p->head_p);
        point_list_p->head_p = NULL;
    }

    /* replace head pointer */
    point_list_p->head_p = new_head_p;

    return;
}

void
bg_point_list_clear(
        struct bg_point_list * point_list_p) {
    point_list_p->length = 0;
    if (NULL != point_list_p->head_p) {
        free(point_list_p->head_p);
        point_list_p->head_p = NULL;
    }
    return;
}

void bg_point_list_removeback(
        struct bg_point_list * point_list_p) {
    /* allocate for new list*/
    unsigned int
        new_head_size=(point_list_p->length-1)*sizeof(struct bg_point);
    struct bg_point * 
        new_head_p=(struct bg_point *)malloc(new_head_size);

    /* copy */
    if (NULL != point_list_p->head_p) {
        memcpy(new_head_p, 
                point_list_p->head_p, 
                sizeof(struct bg_point)*(point_list_p->length-1));
    }

    /* update point list size value */
    point_list_p->length -= 1;

    /* free old list */
    if (NULL != point_list_p->head_p) {
        free(point_list_p->head_p);
        point_list_p->head_p = NULL;
    }

    /* replace head pointer */
    point_list_p->head_p = new_head_p;

    return;
}