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// (c) 1994 Michael E. Stillman
#ifndef _queue_hh_
#define _queue_hh_
#include "newdelete.hpp"
#include <utility>
#include <cassert>
const int block_size = 128;
#define QUEUE(T) queue<T>
template <class T>
class queue;
template <class T>
class queue_block : public our_new_delete
{
friend class queue<T>;
T entries[block_size];
queue_block<T> *next;
queue_block() : next(NULL) {}
};
template <class T>
class queue : public our_new_delete
{
int ephemeral;
queue_block<T> *head;
int head_i;
queue_block<T> *tail;
int tail_i;
int len;
void copy(const queue<T> &q);
void obtain(const queue<T> &qq)
{
queue<T> &q = const_cast<queue<T> &>(qq);
if (q.ephemeral == 0)
copy(q);
else
{
ephemeral = 1;
std::swap(head, q.head);
std::swap(tail, q.tail);
std::swap(head_i, q.head_i);
std::swap(tail_i, q.tail_i);
std::swap(len, q.len);
}
}
void del_list()
{
while (head != NULL)
{
queue_block<T> *temp = head;
head = head->next;
delete temp;
}
}
public:
queue() : ephemeral(0), head(NULL), head_i(0), tail(NULL), tail_i(0), len(0)
{
}
queue(queue<T> &q) { obtain(q); }
~queue() { del_list(); }
void make_ephemeral() { ephemeral = 1; }
queue<T> &operator=(const queue<T> &q)
{
if (&q != this) obtain(q);
return *this;
}
void insert(const T &elem);
bool remove(T &elem);
void flush()
{
del_list();
tail = NULL;
head_i = tail_i = len = 0;
}
int length() const { return len; }
bool operator==(const queue<T> &) const { return false; }
bool operator!=(const queue<T> &) const { return true; }
};
template <class T>
void queue<T>::copy(const queue<T> &q)
{
assert(0);
if (q.len == 0)
{
while (head != NULL)
{
queue_block<T> *tmp = head;
head = head->next;
delete tmp;
}
head_i = tail_i = len = 0;
tail = NULL;
return;
}
}
template <class T>
void queue<T>::insert(const T &elem)
{
if (len == 0)
{
tail = head = new queue_block<T>;
tail_i = head_i = 0;
}
if (tail_i >= block_size)
{
tail = tail->next = new queue_block<T>;
tail_i = 0;
}
tail->entries[tail_i] = elem;
tail_i++;
len++;
}
template <class T>
bool queue<T>::remove(T &elem)
{
if (len == 0) return false;
elem = head->entries[head_i];
head_i++;
len--;
if (head == tail)
{
if (head_i == tail_i)
{
delete head;
head = NULL;
len = head_i = tail_i = 0;
}
}
else if (head_i >= block_size)
{
queue_block<T> *temp = head;
head = head->next;
delete temp;
head_i = 0;
}
return true;
}
#endif
// Local Variables:
// compile-command: "make -C $M2BUILDDIR/Macaulay2/e "
// indent-tabs-mode: nil
// End:
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