php-src/ext/spl/spl_heap.c

/*
   +----------------------------------------------------------------------+
   | Copyright (c) The PHP Group                                          |
   +----------------------------------------------------------------------+
   | This source file is subject to version 3.01 of the PHP license,      |
   | that is bundled with this package in the file LICENSE, and is        |
   | available through the world-wide-web at the following url:           |
   | https://www.php.net/license/3_01.txt                                 |
   | If you did not receive a copy of the PHP license and are unable to   |
   | obtain it through the world-wide-web, please send a note to          |
   | license@php.net so we can mail you a copy immediately.               |
   +----------------------------------------------------------------------+
   | Authors: Etienne Kneuss <colder@php.net>                             |
   +----------------------------------------------------------------------+
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include "php.h"
#include "zend_exceptions.h"

#include "php_spl.h"
#include "spl_functions.h"
#include "spl_engine.h"
#include "spl_iterators.h"
#include "spl_heap.h"
#include "spl_heap_arginfo.h"
#include "spl_exceptions.h"

#define PTR_HEAP_BLOCK_SIZE 64

#define SPL_HEAP_CORRUPTED       0x00000001

#define SPL_PQUEUE_EXTR_MASK     0x00000003
#define SPL_PQUEUE_EXTR_BOTH     0x00000003
#define SPL_PQUEUE_EXTR_DATA     0x00000001
#define SPL_PQUEUE_EXTR_PRIORITY 0x00000002

zend_object_handlers spl_handler_SplHeap;
zend_object_handlers spl_handler_SplPriorityQueue;

PHPAPI zend_class_entry  *spl_ce_SplHeap;
PHPAPI zend_class_entry  *spl_ce_SplMaxHeap;
PHPAPI zend_class_entry  *spl_ce_SplMinHeap;
PHPAPI zend_class_entry  *spl_ce_SplPriorityQueue;


typedef void (*spl_ptr_heap_dtor_func)(void *);
typedef void (*spl_ptr_heap_ctor_func)(void *);
typedef int  (*spl_ptr_heap_cmp_func)(void *, void *, zval *);

typedef struct _spl_ptr_heap {
	void                   *elements;
	spl_ptr_heap_ctor_func  ctor;
	spl_ptr_heap_dtor_func  dtor;
	spl_ptr_heap_cmp_func   cmp;
	int                     count;
	int                     flags;
	size_t                  max_size;
	size_t                  elem_size;
} spl_ptr_heap;

typedef struct _spl_heap_object spl_heap_object;
typedef struct _spl_heap_it spl_heap_it;

struct _spl_heap_object {
	spl_ptr_heap       *heap;
	int                 flags;
	zend_function      *fptr_cmp;
	zend_function      *fptr_count;
	zend_object         std;
};

/* define an overloaded iterator structure */
struct _spl_heap_it {
	zend_user_iterator  intern;
	int                 flags;
};

typedef struct _spl_pqueue_elem {
	zval data;
	zval priority;
} spl_pqueue_elem;

static inline spl_heap_object *spl_heap_from_obj(zend_object *obj) /* {{{ */ {
	return (spl_heap_object*)((char*)(obj) - XtOffsetOf(spl_heap_object, std));
}
/* }}} */

#define Z_SPLHEAP_P(zv)  spl_heap_from_obj(Z_OBJ_P((zv)))

static zend_always_inline void *spl_heap_elem(spl_ptr_heap *heap, size_t i) {
	return (void *) ((char *) heap->elements + heap->elem_size * i);
}

static zend_always_inline void spl_heap_elem_copy(spl_ptr_heap *heap, void *to, void *from) {
	assert(to != from);

	/* Specialized for cases of heap and priority queue. With the size being
	 * constant known at compile time the compiler can fully inline calls to memcpy. */
	if (heap->elem_size == sizeof(spl_pqueue_elem)) {
		memcpy(to, from, sizeof(spl_pqueue_elem));
	} else {
		ZEND_ASSERT(heap->elem_size == sizeof(zval));
		memcpy(to, from, sizeof(zval));
	}
}

static void spl_ptr_heap_zval_dtor(void *elem) { /* {{{ */
	zval_ptr_dtor((zval *) elem);
}
/* }}} */

static void spl_ptr_heap_zval_ctor(void *elem) { /* {{{ */
	Z_TRY_ADDREF_P((zval *) elem);
}
/* }}} */

static void spl_ptr_heap_pqueue_elem_dtor(void *elem) { /* {{{ */
	spl_pqueue_elem *pq_elem = elem;
	zval_ptr_dtor(&pq_elem->data);
	zval_ptr_dtor(&pq_elem->priority);
}
/* }}} */

static void spl_ptr_heap_pqueue_elem_ctor(void *elem) { /* {{{ */
	spl_pqueue_elem *pq_elem = elem;
	Z_TRY_ADDREF_P(&pq_elem->data);
	Z_TRY_ADDREF_P(&pq_elem->priority);
}
/* }}} */

static int spl_ptr_heap_cmp_cb_helper(zval *object, spl_heap_object *heap_object, zval *a, zval *b, zend_long *result) { /* {{{ */
	zval zresult;

	zend_call_method_with_2_params(Z_OBJ_P(object), heap_object->std.ce, &heap_object->fptr_cmp, "compare", &zresult, a, b);

	if (EG(exception)) {
		return FAILURE;
	}

	*result = zval_get_long(&zresult);
	zval_ptr_dtor(&zresult);

	return SUCCESS;
}
/* }}} */

static void spl_pqueue_extract_helper(zval *result, spl_pqueue_elem *elem, int flags) /* {{{ */
{
	if ((flags & SPL_PQUEUE_EXTR_BOTH) == SPL_PQUEUE_EXTR_BOTH) {
		array_init(result);
		Z_TRY_ADDREF(elem->data);
		add_assoc_zval_ex(result, "data", sizeof("data") - 1, &elem->data);
		Z_TRY_ADDREF(elem->priority);
		add_assoc_zval_ex(result, "priority", sizeof("priority") - 1, &elem->priority);
		return;
	}

	if (flags & SPL_PQUEUE_EXTR_DATA) {
		ZVAL_COPY(result, &elem->data);
		return;
	}

	if (flags & SPL_PQUEUE_EXTR_PRIORITY) {
		ZVAL_COPY(result, &elem->priority);
		return;
	}

	ZEND_UNREACHABLE();
}
/* }}} */

static int spl_ptr_heap_zval_max_cmp(void *x, void *y, zval *object) { /* {{{ */
	zval *a = x, *b = y;

	if (EG(exception)) {
		return 0;
	}

	if (object) {
		spl_heap_object *heap_object = Z_SPLHEAP_P(object);
		if (heap_object->fptr_cmp) {
			zend_long lval = 0;
			if (spl_ptr_heap_cmp_cb_helper(object, heap_object, a, b, &lval) == FAILURE) {
				/* exception or call failure */
				return 0;
			}
			return ZEND_NORMALIZE_BOOL(lval);
		}
	}

	return zend_compare(a, b);
}
/* }}} */

static int spl_ptr_heap_zval_min_cmp(void *x, void *y, zval *object) { /* {{{ */
	zval *a = x, *b = y;

	if (EG(exception)) {
		return 0;
	}

	if (object) {
		spl_heap_object *heap_object = Z_SPLHEAP_P(object);
		if (heap_object->fptr_cmp) {
			zend_long lval = 0;
			if (spl_ptr_heap_cmp_cb_helper(object, heap_object, a, b, &lval) == FAILURE) {
				/* exception or call failure */
				return 0;
			}
			return ZEND_NORMALIZE_BOOL(lval);
		}
	}

	return zend_compare(b, a);
}
/* }}} */

static int spl_ptr_pqueue_elem_cmp(void *x, void *y, zval *object) { /* {{{ */
	spl_pqueue_elem *a = x;
	spl_pqueue_elem *b = y;
	zval *a_priority_p = &a->priority;
	zval *b_priority_p = &b->priority;

	if (EG(exception)) {
		return 0;
	}

	if (object) {
		spl_heap_object *heap_object = Z_SPLHEAP_P(object);
		if (heap_object->fptr_cmp) {
			zend_long lval = 0;
			if (spl_ptr_heap_cmp_cb_helper(object, heap_object, a_priority_p, b_priority_p, &lval) == FAILURE) {
				/* exception or call failure */
				return 0;
			}
			return ZEND_NORMALIZE_BOOL(lval);
		}
	}

	return zend_compare(a_priority_p, b_priority_p);
}
/* }}} */

/* Specialized comparator used when we are absolutely sure an instance of the
 * not inherited SplPriorityQueue class contains only priorities as longs. This
 * fact is tracked during insertion into the queue. */
static int spl_ptr_pqueue_elem_cmp_long(void *x, void *y, zval *object) {
	zend_long a = Z_LVAL(((spl_pqueue_elem*) x)->priority);
	zend_long b = Z_LVAL(((spl_pqueue_elem*) y)->priority);
	return a>b ? 1 : (a<b ? -1 : 0);
}

/* same as spl_ptr_pqueue_elem_cmp_long */
static int spl_ptr_pqueue_elem_cmp_double(void *x, void *y, zval *object) {
	double a = Z_DVAL(((spl_pqueue_elem*) x)->priority);
	double b = Z_DVAL(((spl_pqueue_elem*) y)->priority);
	return ZEND_NORMALIZE_BOOL(a - b);
}

static spl_ptr_heap *spl_ptr_heap_init(spl_ptr_heap_cmp_func cmp, spl_ptr_heap_ctor_func ctor, spl_ptr_heap_dtor_func dtor, size_t elem_size) /* {{{ */
{
	spl_ptr_heap *heap = emalloc(sizeof(spl_ptr_heap));

	heap->dtor     = dtor;
	heap->ctor     = ctor;
	heap->cmp      = cmp;
	heap->elements = ecalloc(PTR_HEAP_BLOCK_SIZE, elem_size);
	heap->max_size = PTR_HEAP_BLOCK_SIZE;
	heap->count    = 0;
	heap->flags    = 0;
	heap->elem_size = elem_size;

	return heap;
}
/* }}} */

static void spl_ptr_heap_insert(spl_ptr_heap *heap, void *elem, void *cmp_userdata) { /* {{{ */
	int i;

	if (heap->count+1 > heap->max_size) {
		size_t alloc_size = heap->max_size * heap->elem_size;
		/* we need to allocate more memory */
		heap->elements  = erealloc(heap->elements, 2 * alloc_size);
		memset((char *) heap->elements + alloc_size, 0, alloc_size);
		heap->max_size *= 2;
	}

	/* sifting up */
	for (i = heap->count; i > 0 && heap->cmp(spl_heap_elem(heap, (i-1)/2), elem, cmp_userdata) < 0; i = (i-1)/2) {
		spl_heap_elem_copy(heap, spl_heap_elem(heap, i), spl_heap_elem(heap, (i-1)/2));
	}
	heap->count++;

	if (EG(exception)) {
		/* exception thrown during comparison */
		heap->flags |= SPL_HEAP_CORRUPTED;
	}

	spl_heap_elem_copy(heap, spl_heap_elem(heap, i), elem);
}
/* }}} */

static void *spl_ptr_heap_top(spl_ptr_heap *heap) { /* {{{ */
	if (heap->count == 0) {
		return NULL;
	}

	return heap->elements;
}
/* }}} */

static int spl_ptr_heap_delete_top(spl_ptr_heap *heap, void *elem, void *cmp_userdata) { /* {{{ */
	int i, j;
	const int limit = (heap->count-1)/2;
	void *bottom;

	if (heap->count == 0) {
		return FAILURE;
	}

	if (elem) {
		spl_heap_elem_copy(heap, elem, spl_heap_elem(heap, 0));
	} else {
		heap->dtor(spl_heap_elem(heap, 0));
	}

	bottom = spl_heap_elem(heap, --heap->count);

	for (i = 0; i < limit; i = j) {
		/* Find smaller child */
		j = i * 2 + 1;
		if (j != heap->count && heap->cmp(spl_heap_elem(heap, j+1), spl_heap_elem(heap, j), cmp_userdata) > 0) {
			j++; /* next child is bigger */
		}

		/* swap elements between two levels */
		if(heap->cmp(bottom, spl_heap_elem(heap, j), cmp_userdata) < 0) {
			spl_heap_elem_copy(heap, spl_heap_elem(heap, i), spl_heap_elem(heap, j));
		} else {
			break;
		}
	}

	if (EG(exception)) {
		/* exception thrown during comparison */
		heap->flags |= SPL_HEAP_CORRUPTED;
	}

	void *to = spl_heap_elem(heap, i);
	if (to != bottom) {
		spl_heap_elem_copy(heap, to, bottom);
	}
	return SUCCESS;
}
/* }}} */

static spl_ptr_heap *spl_ptr_heap_clone(spl_ptr_heap *from) { /* {{{ */
	int i;

	spl_ptr_heap *heap = emalloc(sizeof(spl_ptr_heap));

	heap->dtor     = from->dtor;
	heap->ctor     = from->ctor;
	heap->cmp      = from->cmp;
	heap->max_size = from->max_size;
	heap->count    = from->count;
	heap->flags    = from->flags;
	heap->elem_size = from->elem_size;

	heap->elements = safe_emalloc(from->elem_size, from->max_size, 0);
	memcpy(heap->elements, from->elements, from->elem_size * from->max_size);

	for (i = 0; i < heap->count; ++i) {
		heap->ctor(spl_heap_elem(heap, i));
	}

	return heap;
}
/* }}} */

static void spl_ptr_heap_destroy(spl_ptr_heap *heap) { /* {{{ */
	int i;

	for (i = 0; i < heap->count; ++i) {
		heap->dtor(spl_heap_elem(heap, i));
	}

	efree(heap->elements);
	efree(heap);
}
/* }}} */

static int spl_ptr_heap_count(spl_ptr_heap *heap) { /* {{{ */
	return heap->count;
}
/* }}} */

static void spl_heap_object_free_storage(zend_object *object) /* {{{ */
{
	spl_heap_object *intern = spl_heap_from_obj(object);

	zend_object_std_dtor(&intern->std);

	spl_ptr_heap_destroy(intern->heap);
}
/* }}} */

static zend_object *spl_heap_object_new_ex(zend_class_entry *class_type, zend_object *orig, int clone_orig) /* {{{ */
{
	spl_heap_object   *intern;
	zend_class_entry  *parent = class_type;
	int                inherited = 0;

	intern = zend_object_alloc(sizeof(spl_heap_object), parent);

	zend_object_std_init(&intern->std, class_type);
	object_properties_init(&intern->std, class_type);

	if (orig) {
		spl_heap_object *other = spl_heap_from_obj(orig);
		intern->std.handlers = other->std.handlers;

		if (clone_orig) {
			intern->heap = spl_ptr_heap_clone(other->heap);
		} else {
			intern->heap = other->heap;
		}

		intern->flags = other->flags;
		intern->fptr_cmp = other->fptr_cmp;
		intern->fptr_count = other->fptr_count;
		return &intern->std;
	}

	while (parent) {
		if (parent == spl_ce_SplPriorityQueue) {
			intern->heap = spl_ptr_heap_init(spl_ptr_pqueue_elem_cmp, spl_ptr_heap_pqueue_elem_ctor, spl_ptr_heap_pqueue_elem_dtor, sizeof(spl_pqueue_elem));
			intern->std.handlers = &spl_handler_SplPriorityQueue;
			intern->flags = SPL_PQUEUE_EXTR_DATA;
			break;
		}

		if (parent == spl_ce_SplMinHeap || parent == spl_ce_SplMaxHeap
				|| parent == spl_ce_SplHeap) {
			intern->heap = spl_ptr_heap_init(
				parent == spl_ce_SplMinHeap ? spl_ptr_heap_zval_min_cmp : spl_ptr_heap_zval_max_cmp,
				spl_ptr_heap_zval_ctor, spl_ptr_heap_zval_dtor, sizeof(zval));
			intern->std.handlers = &spl_handler_SplHeap;
			break;
		}

		parent = parent->parent;
		inherited = 1;
	}

	ZEND_ASSERT(parent);

	if (inherited) {
		intern->fptr_cmp = zend_hash_str_find_ptr(&class_type->function_table, "compare", sizeof("compare") - 1);
		if (intern->fptr_cmp->common.scope == parent) {
			intern->fptr_cmp = NULL;
		}
		intern->fptr_count = zend_hash_str_find_ptr(&class_type->function_table, "count", sizeof("count") - 1);
		if (intern->fptr_count->common.scope == parent) {
			intern->fptr_count = NULL;
		}
	}

	return &intern->std;
}
/* }}} */

static zend_object *spl_heap_object_new(zend_class_entry *class_type) /* {{{ */
{
	return spl_heap_object_new_ex(class_type, NULL, 0);
}
/* }}} */

static zend_object *spl_heap_object_clone(zend_object *old_object) /* {{{ */
{
	zend_object *new_object = spl_heap_object_new_ex(old_object->ce, old_object, 1);

	zend_objects_clone_members(new_object, old_object);

	return new_object;
}
/* }}} */

static int spl_heap_object_count_elements(zend_object *object, zend_long *count) /* {{{ */
{
	spl_heap_object *intern = spl_heap_from_obj(object);

	if (intern->fptr_count) {
		zval rv;
		zend_call_method_with_0_params(object, intern->std.ce, &intern->fptr_count, "count", &rv);
		if (!Z_ISUNDEF(rv)) {
			*count = zval_get_long(&rv);
			zval_ptr_dtor(&rv);
			return SUCCESS;
		}
		*count = 0;
		return FAILURE;
	}

	*count = spl_ptr_heap_count(intern->heap);

	return SUCCESS;
}
/* }}} */

static inline HashTable* spl_heap_object_get_debug_info(zend_class_entry *ce, zend_object *obj) { /* {{{ */
	spl_heap_object *intern = spl_heap_from_obj(obj);
	zval tmp, heap_array;
	zend_string *pnstr;
	HashTable *debug_info;
	int  i;

	if (!intern->std.properties) {
		rebuild_object_properties(&intern->std);
	}

	debug_info = zend_new_array(zend_hash_num_elements(intern->std.properties) + 1);
	zend_hash_copy(debug_info, intern->std.properties, (copy_ctor_func_t) zval_add_ref);

	pnstr = spl_gen_private_prop_name(ce, "flags", sizeof("flags")-1);
	ZVAL_LONG(&tmp, intern->flags);
	zend_hash_update(debug_info, pnstr, &tmp);
	zend_string_release_ex(pnstr, 0);

	pnstr = spl_gen_private_prop_name(ce, "isCorrupted", sizeof("isCorrupted")-1);
	ZVAL_BOOL(&tmp, intern->heap->flags&SPL_HEAP_CORRUPTED);
	zend_hash_update(debug_info, pnstr, &tmp);
	zend_string_release_ex(pnstr, 0);

	array_init(&heap_array);

	for (i = 0; i < intern->heap->count; ++i) {
		if (ce == spl_ce_SplPriorityQueue) {
			spl_pqueue_elem *pq_elem = spl_heap_elem(intern->heap, i);
			zval elem;
			spl_pqueue_extract_helper(&elem, pq_elem, SPL_PQUEUE_EXTR_BOTH);
			add_index_zval(&heap_array, i, &elem);
		} else {
			zval *elem = spl_heap_elem(intern->heap, i);
			add_index_zval(&heap_array, i, elem);
			Z_TRY_ADDREF_P(elem);
		}
	}

	pnstr = spl_gen_private_prop_name(ce, "heap", sizeof("heap")-1);
	zend_hash_update(debug_info, pnstr, &heap_array);
	zend_string_release_ex(pnstr, 0);

	return debug_info;
}
/* }}} */

static HashTable *spl_heap_object_get_gc(zend_object *obj, zval **gc_data, int *gc_data_count) /* {{{ */
{
	spl_heap_object *intern = spl_heap_from_obj(obj);
	*gc_data = (zval *) intern->heap->elements;
	*gc_data_count = intern->heap->count;

	return zend_std_get_properties(obj);
}
/* }}} */

static HashTable *spl_pqueue_object_get_gc(zend_object *obj, zval **gc_data, int *gc_data_count) /* {{{ */
{
	spl_heap_object *intern = spl_heap_from_obj(obj);
	*gc_data = (zval *) intern->heap->elements;
	/* Two zvals (value and priority) per pqueue entry */
	*gc_data_count = 2 * intern->heap->count;

	return zend_std_get_properties(obj);
}
/* }}} */

/* {{{ Return the number of elements in the heap. */
PHP_METHOD(SplHeap, count)
{
	zend_long count;
	spl_heap_object *intern = Z_SPLHEAP_P(ZEND_THIS);

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	count = spl_ptr_heap_count(intern->heap);
	RETURN_LONG(count);
}
/* }}} */

/* {{{ Return true if the heap is empty. */
PHP_METHOD(SplHeap, isEmpty)
{
	spl_heap_object *intern = Z_SPLHEAP_P(ZEND_THIS);

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	RETURN_BOOL(spl_ptr_heap_count(intern->heap) == 0);
}
/* }}} */

/* {{{ Push $value on the heap */
PHP_METHOD(SplHeap, insert)
{
	zval *value;
	spl_heap_object *intern;

	ZEND_PARSE_PARAMETERS_START(1, 1)
		Z_PARAM_ZVAL(value);
	ZEND_PARSE_PARAMETERS_END();

	intern = Z_SPLHEAP_P(ZEND_THIS);

	if (intern->heap->flags & SPL_HEAP_CORRUPTED) {
		zend_throw_exception(spl_ce_RuntimeException, "Heap is corrupted, heap properties are no longer ensured.", 0);
		RETURN_THROWS();
	}

	Z_TRY_ADDREF_P(value);
	spl_ptr_heap_insert(intern->heap, value, ZEND_THIS);

	RETURN_TRUE;
}
/* }}} */

/* {{{ extract the element out of the top of the heap */
PHP_METHOD(SplHeap, extract)
{
	spl_heap_object *intern;

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	intern = Z_SPLHEAP_P(ZEND_THIS);

	if (intern->heap->flags & SPL_HEAP_CORRUPTED) {
		zend_throw_exception(spl_ce_RuntimeException, "Heap is corrupted, heap properties are no longer ensured.", 0);
		RETURN_THROWS();
	}

	if (spl_ptr_heap_delete_top(intern->heap, return_value, ZEND_THIS) == FAILURE) {
		zend_throw_exception(spl_ce_RuntimeException, "Can't extract from an empty heap", 0);
		RETURN_THROWS();
	}
}
/* }}} */

/* {{{ Push $value with the priority $priodiry on the priorityqueue */
PHP_METHOD(SplPriorityQueue, insert)
{
	zval *data, *priority;
	spl_heap_object *intern;
	spl_pqueue_elem elem;

	ZEND_PARSE_PARAMETERS_START(2, 2)
		Z_PARAM_ZVAL(data);
		Z_PARAM_ZVAL(priority);
	ZEND_PARSE_PARAMETERS_END();

	intern = Z_SPLHEAP_P(ZEND_THIS);

	if (intern->heap->flags & SPL_HEAP_CORRUPTED) {
		zend_throw_exception(spl_ce_RuntimeException, "Heap is corrupted, heap properties are no longer ensured.", 0);
		RETURN_THROWS();
	}

	ZVAL_COPY(&elem.data, data);
	ZVAL_COPY(&elem.priority, priority);

	/* If we know this call came from non inherited SplPriorityQueue it's
	 * possible to do specialization on the type of the priority parameter. */
	if (!intern->fptr_cmp) {
		int type = Z_TYPE(elem.priority);
		spl_ptr_heap_cmp_func new_cmp =
			(type == IS_LONG) ? spl_ptr_pqueue_elem_cmp_long :
			((type == IS_DOUBLE) ? spl_ptr_pqueue_elem_cmp_double : spl_ptr_pqueue_elem_cmp);

		if (intern->heap->count == 0) { /* Specialize empty queue */
			intern->heap->cmp = new_cmp;
		} else if (new_cmp != intern->heap->cmp) { /* Despecialize on type conflict. */
			intern->heap->cmp = spl_ptr_pqueue_elem_cmp;
		}
	}

	spl_ptr_heap_insert(intern->heap, &elem, ZEND_THIS);

	RETURN_TRUE;
}
/* }}} */

/* {{{ extract the element out of the top of the priority queue */
PHP_METHOD(SplPriorityQueue, extract)
{
	spl_pqueue_elem elem;
	spl_heap_object *intern;

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	intern = Z_SPLHEAP_P(ZEND_THIS);

	if (intern->heap->flags & SPL_HEAP_CORRUPTED) {
		zend_throw_exception(spl_ce_RuntimeException, "Heap is corrupted, heap properties are no longer ensured.", 0);
		RETURN_THROWS();
	}

	if (spl_ptr_heap_delete_top(intern->heap, &elem, ZEND_THIS) == FAILURE) {
		zend_throw_exception(spl_ce_RuntimeException, "Can't extract from an empty heap", 0);
		RETURN_THROWS();
	}

	spl_pqueue_extract_helper(return_value, &elem, intern->flags);
	spl_ptr_heap_pqueue_elem_dtor(&elem);
}
/* }}} */

/* {{{ Peek at the top element of the priority queue */
PHP_METHOD(SplPriorityQueue, top)
{
	spl_heap_object *intern;
	spl_pqueue_elem *elem;

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	intern = Z_SPLHEAP_P(ZEND_THIS);

	if (intern->heap->flags & SPL_HEAP_CORRUPTED) {
		zend_throw_exception(spl_ce_RuntimeException, "Heap is corrupted, heap properties are no longer ensured.", 0);
		RETURN_THROWS();
	}

	elem = spl_ptr_heap_top(intern->heap);

	if (!elem) {
		zend_throw_exception(spl_ce_RuntimeException, "Can't peek at an empty heap", 0);
		RETURN_THROWS();
	}

	spl_pqueue_extract_helper(return_value, elem, intern->flags);
}
/* }}} */


/* {{{ Set the flags of extraction*/
PHP_METHOD(SplPriorityQueue, setExtractFlags)
{
	zend_long value;
	spl_heap_object *intern;

	if (zend_parse_parameters(ZEND_NUM_ARGS(), "l", &value) == FAILURE) {
		RETURN_THROWS();
	}

	value &= SPL_PQUEUE_EXTR_MASK;
	if (!value) {
		zend_throw_exception(spl_ce_RuntimeException, "Must specify at least one extract flag", 0);
		RETURN_THROWS();
	}

	intern = Z_SPLHEAP_P(ZEND_THIS);
	intern->flags = value;
	RETURN_LONG(intern->flags);
}
/* }}} */

/* {{{ Get the flags of extraction*/
PHP_METHOD(SplPriorityQueue, getExtractFlags)
{
	spl_heap_object *intern;

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	intern = Z_SPLHEAP_P(ZEND_THIS);

	RETURN_LONG(intern->flags);
}
/* }}} */

/* {{{ Recover from a corrupted state*/
PHP_METHOD(SplHeap, recoverFromCorruption)
{
	spl_heap_object *intern;

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	intern = Z_SPLHEAP_P(ZEND_THIS);

	intern->heap->flags = intern->heap->flags & ~SPL_HEAP_CORRUPTED;

	RETURN_TRUE;
}
/* }}} */

/* {{{ Tells if the heap is in a corrupted state*/
PHP_METHOD(SplHeap, isCorrupted)
{
	spl_heap_object *intern;

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	intern = Z_SPLHEAP_P(ZEND_THIS);

	RETURN_BOOL(intern->heap->flags & SPL_HEAP_CORRUPTED);
}
/* }}} */

/* {{{ compare the priorities */
PHP_METHOD(SplPriorityQueue, compare)
{
	zval *a, *b;

	if (zend_parse_parameters(ZEND_NUM_ARGS(), "zz", &a, &b) == FAILURE) {
		RETURN_THROWS();
	}

	RETURN_LONG(spl_ptr_heap_zval_max_cmp(a, b, NULL));
}
/* }}} */

/* {{{ Peek at the top element of the heap */
PHP_METHOD(SplHeap, top)
{
	zval *value;
	spl_heap_object *intern;

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	intern = Z_SPLHEAP_P(ZEND_THIS);

	if (intern->heap->flags & SPL_HEAP_CORRUPTED) {
		zend_throw_exception(spl_ce_RuntimeException, "Heap is corrupted, heap properties are no longer ensured.", 0);
		RETURN_THROWS();
	}

	value = spl_ptr_heap_top(intern->heap);

	if (!value) {
		zend_throw_exception(spl_ce_RuntimeException, "Can't peek at an empty heap", 0);
		RETURN_THROWS();
	}

	RETURN_COPY_DEREF(value);
}
/* }}} */

/* {{{ compare the values */
PHP_METHOD(SplMinHeap, compare)
{
	zval *a, *b;

	if (zend_parse_parameters(ZEND_NUM_ARGS(), "zz", &a, &b) == FAILURE) {
		RETURN_THROWS();
	}

	RETURN_LONG(spl_ptr_heap_zval_min_cmp(a, b, NULL));
}
/* }}} */

/* {{{ compare the values */
PHP_METHOD(SplMaxHeap, compare)
{
	zval *a, *b;

	if (zend_parse_parameters(ZEND_NUM_ARGS(), "zz", &a, &b) == FAILURE) {
		RETURN_THROWS();
	}

	RETURN_LONG(spl_ptr_heap_zval_max_cmp(a, b, NULL));
}
/* }}} */

static void spl_heap_it_dtor(zend_object_iterator *iter) /* {{{ */
{
	spl_heap_it *iterator = (spl_heap_it *)iter;

	zend_user_it_invalidate_current(iter);
	zval_ptr_dtor(&iterator->intern.it.data);
}
/* }}} */

static void spl_heap_it_rewind(zend_object_iterator *iter) /* {{{ */
{
	/* do nothing, the iterator always points to the top element */
}
/* }}} */

static int spl_heap_it_valid(zend_object_iterator *iter) /* {{{ */
{
	return ((Z_SPLHEAP_P(&iter->data))->heap->count != 0 ? SUCCESS : FAILURE);
}
/* }}} */

static zval *spl_heap_it_get_current_data(zend_object_iterator *iter) /* {{{ */
{
	spl_heap_object *object = Z_SPLHEAP_P(&iter->data);

	if (object->heap->flags & SPL_HEAP_CORRUPTED) {
		zend_throw_exception(spl_ce_RuntimeException, "Heap is corrupted, heap properties are no longer ensured.", 0);
		return NULL;
	}

	if (object->heap->count == 0) {
		return NULL;
	} else {
		return spl_heap_elem(object->heap, 0);
	}
}
/* }}} */

static zval *spl_pqueue_it_get_current_data(zend_object_iterator *iter) /* {{{ */
{
	zend_user_iterator *user_it = (zend_user_iterator *) iter;
	spl_heap_object *object = Z_SPLHEAP_P(&iter->data);

	if (object->heap->flags & SPL_HEAP_CORRUPTED) {
		zend_throw_exception(spl_ce_RuntimeException, "Heap is corrupted, heap properties are no longer ensured.", 0);
		return NULL;
	}

	if (object->heap->count == 0) {
		return NULL;
	}

	if (Z_ISUNDEF(user_it->value)) {
		spl_pqueue_elem *elem = spl_heap_elem(object->heap, 0);
		spl_pqueue_extract_helper(&user_it->value, elem, object->flags);
	}
	return &user_it->value;
}
/* }}} */

static void spl_heap_it_get_current_key(zend_object_iterator *iter, zval *key) /* {{{ */
{
	spl_heap_object *object = Z_SPLHEAP_P(&iter->data);

	ZVAL_LONG(key, object->heap->count - 1);
}
/* }}} */

static void spl_heap_it_move_forward(zend_object_iterator *iter) /* {{{ */
{
	spl_heap_object *object = Z_SPLHEAP_P(&iter->data);

	if (object->heap->flags & SPL_HEAP_CORRUPTED) {
		zend_throw_exception(spl_ce_RuntimeException, "Heap is corrupted, heap properties are no longer ensured.", 0);
		return;
	}

	spl_ptr_heap_delete_top(object->heap, NULL, &iter->data);
	zend_user_it_invalidate_current(iter);
}
/* }}} */

/* {{{ Return current array key */
PHP_METHOD(SplHeap, key)
{
	spl_heap_object *intern = Z_SPLHEAP_P(ZEND_THIS);

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	RETURN_LONG(intern->heap->count - 1);
}
/* }}} */

/* {{{ Move to next entry */
PHP_METHOD(SplHeap, next)
{
	spl_heap_object *intern = Z_SPLHEAP_P(ZEND_THIS);

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	spl_ptr_heap_delete_top(intern->heap, NULL, ZEND_THIS);
}
/* }}} */

/* {{{ Check whether the datastructure contains more entries */
PHP_METHOD(SplHeap, valid)
{
	spl_heap_object *intern = Z_SPLHEAP_P(ZEND_THIS);

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	RETURN_BOOL(intern->heap->count != 0);
}
/* }}} */

/* {{{ Rewind the datastructure back to the start */
PHP_METHOD(SplHeap, rewind)
{
	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}
	/* do nothing, the iterator always points to the top element */
}
/* }}} */

/* {{{ Return current datastructure entry */
PHP_METHOD(SplHeap, current)
{
	spl_heap_object *intern  = Z_SPLHEAP_P(ZEND_THIS);

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	if (!intern->heap->count) {
		RETURN_NULL();
	} else {
		zval *element = spl_heap_elem(intern->heap, 0);
		RETURN_COPY_DEREF(element);
	}
}
/* }}} */

/* {{{ Return current datastructure entry */
PHP_METHOD(SplPriorityQueue, current)
{
	spl_heap_object  *intern  = Z_SPLHEAP_P(ZEND_THIS);

	if (zend_parse_parameters_none() == FAILURE) {
		RETURN_THROWS();
	}

	if (!intern->heap->count) {
		RETURN_NULL();
	} else {
		spl_pqueue_elem *elem = spl_heap_elem(intern->heap, 0);
		spl_pqueue_extract_helper(return_value, elem, intern->flags);
	}
}
/* }}} */

/* {{{ */
PHP_METHOD(SplHeap, __debugInfo)
{
	if (zend_parse_parameters_none() == FAILURE) {
		return;
	}

	RETURN_ARR(spl_heap_object_get_debug_info(spl_ce_SplHeap, Z_OBJ_P(ZEND_THIS)));
} /* }}} */

/* {{{ */
PHP_METHOD(SplPriorityQueue, __debugInfo)
{
	if (zend_parse_parameters_none() == FAILURE) {
		return;
	}

	RETURN_ARR(spl_heap_object_get_debug_info(spl_ce_SplPriorityQueue, Z_OBJ_P(ZEND_THIS)));
} /* }}} */

/* iterator handler table */
static const zend_object_iterator_funcs spl_heap_it_funcs = {
	spl_heap_it_dtor,
	spl_heap_it_valid,
	spl_heap_it_get_current_data,
	spl_heap_it_get_current_key,
	spl_heap_it_move_forward,
	spl_heap_it_rewind,
	NULL,
	NULL, /* get_gc */
};

static const zend_object_iterator_funcs spl_pqueue_it_funcs = {
	spl_heap_it_dtor,
	spl_heap_it_valid,
	spl_pqueue_it_get_current_data,
	spl_heap_it_get_current_key,
	spl_heap_it_move_forward,
	spl_heap_it_rewind,
	NULL,
	NULL, /* get_gc */
};

zend_object_iterator *spl_heap_get_iterator(zend_class_entry *ce, zval *object, int by_ref) /* {{{ */
{
	spl_heap_it     *iterator;
	spl_heap_object *heap_object = Z_SPLHEAP_P(object);

	if (by_ref) {
		zend_throw_error(NULL, "An iterator cannot be used with foreach by reference");
		return NULL;
	}

	iterator = emalloc(sizeof(spl_heap_it));

	zend_iterator_init(&iterator->intern.it);

	Z_ADDREF_P(object);
	ZVAL_OBJ(&iterator->intern.it.data, Z_OBJ_P(object));
	iterator->intern.it.funcs = &spl_heap_it_funcs;
	iterator->intern.ce       = ce;
	iterator->flags           = heap_object->flags;
	ZVAL_UNDEF(&iterator->intern.value);

	return &iterator->intern.it;
}
/* }}} */

zend_object_iterator *spl_pqueue_get_iterator(zend_class_entry *ce, zval *object, int by_ref) /* {{{ */
{
	spl_heap_it     *iterator;
	spl_heap_object *heap_object = Z_SPLHEAP_P(object);

	if (by_ref) {
		zend_throw_error(NULL, "An iterator cannot be used with foreach by reference");
		return NULL;
	}

	iterator = emalloc(sizeof(spl_heap_it));

	zend_iterator_init((zend_object_iterator*)iterator);

	Z_ADDREF_P(object);
	ZVAL_OBJ(&iterator->intern.it.data, Z_OBJ_P(object));
	iterator->intern.it.funcs = &spl_pqueue_it_funcs;
	iterator->intern.ce       = ce;
	iterator->flags           = heap_object->flags;

	ZVAL_UNDEF(&iterator->intern.value);

	return &iterator->intern.it;
}
/* }}} */

PHP_MINIT_FUNCTION(spl_heap) /* {{{ */
{
	spl_ce_SplHeap = register_class_SplHeap(zend_ce_iterator, zend_ce_countable);
	spl_ce_SplHeap->create_object = spl_heap_object_new;
	spl_ce_SplHeap->get_iterator = spl_heap_get_iterator;

	memcpy(&spl_handler_SplHeap, &std_object_handlers, sizeof(zend_object_handlers));

	spl_handler_SplHeap.offset         = XtOffsetOf(spl_heap_object, std);
	spl_handler_SplHeap.clone_obj      = spl_heap_object_clone;
	spl_handler_SplHeap.count_elements = spl_heap_object_count_elements;
	spl_handler_SplHeap.get_gc         = spl_heap_object_get_gc;
	spl_handler_SplHeap.free_obj = spl_heap_object_free_storage;

	spl_ce_SplMinHeap = register_class_SplMinHeap(spl_ce_SplHeap);
	spl_ce_SplMinHeap->create_object = spl_heap_object_new;
	spl_ce_SplMinHeap->get_iterator = spl_heap_get_iterator;

	spl_ce_SplMaxHeap = register_class_SplMaxHeap(spl_ce_SplHeap);
	spl_ce_SplMaxHeap->create_object = spl_heap_object_new;
	spl_ce_SplMaxHeap->get_iterator = spl_heap_get_iterator;

	spl_ce_SplPriorityQueue = register_class_SplPriorityQueue(zend_ce_iterator, zend_ce_countable);
	spl_ce_SplPriorityQueue->create_object = spl_heap_object_new;
	spl_ce_SplPriorityQueue->get_iterator = spl_pqueue_get_iterator;

	memcpy(&spl_handler_SplPriorityQueue, &std_object_handlers, sizeof(zend_object_handlers));

	spl_handler_SplPriorityQueue.offset         = XtOffsetOf(spl_heap_object, std);
	spl_handler_SplPriorityQueue.clone_obj      = spl_heap_object_clone;
	spl_handler_SplPriorityQueue.count_elements = spl_heap_object_count_elements;
	spl_handler_SplPriorityQueue.get_gc         = spl_pqueue_object_get_gc;
	spl_handler_SplPriorityQueue.free_obj = spl_heap_object_free_storage;

	REGISTER_SPL_CLASS_CONST_LONG(SplPriorityQueue, "EXTR_BOTH",      SPL_PQUEUE_EXTR_BOTH);
	REGISTER_SPL_CLASS_CONST_LONG(SplPriorityQueue, "EXTR_PRIORITY",  SPL_PQUEUE_EXTR_PRIORITY);
	REGISTER_SPL_CLASS_CONST_LONG(SplPriorityQueue, "EXTR_DATA",      SPL_PQUEUE_EXTR_DATA);

	return SUCCESS;
}
/* }}} */