/* handle<->ptr conversion. */

#include <assert.h>
#include <stdlib.h>
#include "handle.h"

typedef struct _node node;
struct _node {
    void *ptr;
    int   handle;
    node *prev, *next;
};

static node *head = NULL;
static int nexthandle;

void INITIALIZE()
{
    if (head == NULL) {
	head = malloc(sizeof(node));
	head->next = head;
	head->prev = head;
    }
}


int newhandle(void *ptr)
{
    node *newnode;
    node *prevnode, *nextnode;

    INITIALIZE();
    
    /* Create new node */
    newnode = malloc(sizeof(node));
    newnode->handle = nexthandle++;
    newnode->ptr    = ptr;

    /* Insert into doubly-linked list */
    prevnode = head;
    nextnode = head->next;

    prevnode->next = newnode;
    nextnode->prev = newnode;

    newnode->next  = nextnode;
    newnode->prev  = prevnode;
}


void deletehandle(int handle)
{
    node *cur = head->next;
    node *prevnode, *nextnode;
    
    INITIALIZE();

    while ((cur != head) && (cur->handle != handle)) 
	cur = cur->next;

    assert(cur != head);
    assert(cur->handle == handle);
    
    /* Remove node from the doubly-linked list */
    
    prevnode = cur->prev;
    nextnode = cur->next;
    
    prevnode->next = nextnode;
    nextnode->prev = prevnode;

    free(cur);
}

int handletoptr(int   h,   void **ptr)
{
    node *cur = head->next;

    INITIALIZE();

    while (cur != head) {
	if (cur->handle == h) {
	    *ptr = cur->ptr;
	    return 1;
	}
	cur = cur->next;
    }
    
    return 0;
}

int ptrtohandle(void *ptr, int   *h)
{
    node *cur = head->next;

    INITIALIZE();

    while (cur != head) {
	if (cur->ptr == ptr) {
	    *h = cur->handle;
	    return 1;
	}
	cur = cur->next;
    }
    
    return 0;
}