#include "list_entry.h"

void InitializeListHead(PLIST_ENTRY ListHead) {
    ListHead->flink = ListHead;
    ListHead->blink = ListHead;
}

int IsListEmpty(const PLIST_ENTRY ListHead) {
    return ListHead->flink == ListHead;
}

void InsertHeadList(PLIST_ENTRY ListHead, PLIST_ENTRY Entry) {
    Entry->flink = ListHead->flink;
    Entry->blink = ListHead;
    ListHead->flink->blink = Entry;
    ListHead->flink = Entry;
}

void InsertTailList(PLIST_ENTRY ListHead, PLIST_ENTRY Entry) {
    Entry->blink = ListHead->blink;
    Entry->flink = ListHead;
    ListHead->blink->flink = Entry;
    ListHead->blink = Entry;
}

void RemoveEntryList(PLIST_ENTRY Entry) {
    Entry->blink->flink = Entry->flink;
    Entry->flink->blink = Entry->blink;
    Entry->flink = Entry;
    Entry->blink = Entry;
}

PLIST_ENTRY RemoveHeadList(PLIST_ENTRY ListHead) {
    if (IsListEmpty(ListHead)) return NULL;
    PLIST_ENTRY first = ListHead->flink;
    RemoveEntryList(first);
    return first;
}

PLIST_ENTRY RemoveTailList(PLIST_ENTRY ListHead) {
    if (IsListEmpty(ListHead)) return NULL;
    PLIST_ENTRY last = ListHead->blink;
    RemoveEntryList(last);
    return last;
}