#include <string.h>
#include "allheaders.h"

Macros
#define	SWAP_ITEMS(i, j)

Functions
static l_int32	lheapExtendArray (L_HEAP *lh)

L_HEAP *	lheapCreate (l_int32 nalloc, l_int32 direction)

void	lheapDestroy (L_HEAP **plh, l_int32 freeflag)

l_ok	lheapAdd (L_HEAP lh, void item)

void *	lheapRemove (L_HEAP *lh)

l_int32	lheapGetCount (L_HEAP *lh)

l_ok	lheapSwapUp (L_HEAP *lh, l_int32 index)

l_ok	lheapSwapDown (L_HEAP *lh)

l_ok	lheapSort (L_HEAP *lh)

l_ok	lheapSortStrictOrder (L_HEAP *lh)

l_ok	lheapPrint (FILE fp, L_HEAP lh)

Variables
static const l_int32	MIN_BUFFER_SIZE = 20

static const l_int32	INITIAL_BUFFER_ARRAYSIZE = 128

Detailed Description

 Create/Destroy L_Heap
     L_HEAP         *lheapCreate()
     void           *lheapDestroy()

 Operations to add/remove to/from the heap
     l_int32         lheapAdd()
     static l_int32  lheapExtendArray()
     void           *lheapRemove()

 Heap operations
     l_int32         lheapSwapUp()
     l_int32         lheapSwapDown()
     l_int32         lheapSort()
     l_int32         lheapSortStrictOrder()

 Accessors
     l_int32         lheapGetCount()

 Debug output
     l_int32         lheapPrint()

   The L_Heap is useful to implement a priority queue, that is sorted
   on a key in each element of the heap.  The heap is an array
   of nearly arbitrary structs, with a l_float32 the first field.
   This field is the key on which the heap is sorted.

   Internally, we keep track of the heap size, n.  The item at the
   root of the heap is at the head of the array.  Items are removed
   from the head of the array and added to the end of the array.
   When an item is removed from the head, the item at the end
   of the array is moved to the head.  When items are either
   added or removed, it is usually necessary to swap array items
   to restore the heap order.  It is guaranteed that the number
   of swaps does not exceed log(n).

   -----------------------—  N.B.  ---------------------------—
   The items on the heap (or, equivalently, in the array) are cast
   to void*.  Their key is a l_float32, and it is REQUIRED that the
   key be the first field in the struct.  That allows us to get the
   key by simply dereferencing the struct.  Alternatively, we could
   choose (but don't) to pass an application-specific comparison
   function into the heap operation functions.
   -----------------------—  N.B.  ---------------------------—

Definition in file heap.c.

Macro Definition Documentation

◆ SWAP_ITEMS

#define SWAP_ITEMS	(	i,
		j
	)

Value:

{ void *tempitem = lh->array[(i)]; \
                                 lh->array[(i)] = lh->array[(j)]; \
                                 lh->array[(j)] = tempitem; }

Definition at line 83 of file heap.c.

Function Documentation

◆ lheapAdd()

l_ok lheapAdd	(	L_HEAP *	lh,
		void *	item
	)

lheapAdd()

Parameters

[in]	lh	heap
[in]	item	to be added to the tail of the heap

Returns: 0 if OK, 1 on error

Definition at line 186 of file heap.c.

References L_Heap::array, lheapExtendArray(), lheapSwapUp(), L_Heap::n, and L_Heap::nalloc.

◆ lheapCreate()

L_HEAP* lheapCreate	(	l_int32	nalloc,
		l_int32	direction
	)

lheapCreate()

Parameters

[in]	nalloc	size of ptr array to be alloc'd 0 for default
[in]	direction	L_SORT_INCREASING, L_SORT_DECREASING

Returns: lheap, or NULL on error

Definition at line 102 of file heap.c.

Referenced by pixSearchGrayMaze(), and wshedApply().

◆ lheapDestroy()

void lheapDestroy	(	L_HEAP **	plh,
		l_int32	freeflag
	)

lheapDestroy()

Parameters

[in,out]	plh	to be nulled
[in]	freeflag	TRUE to free each remaining struct in the array

Returns: void

Notes:
     (1) Use freeflag == TRUE when the items in the array can be
         simply destroyed using free.  If those items require their
         own destroy function, they must be destroyed before
         calling this function, and then this function is called
         with freeflag == FALSE.
     (2) To destroy the lheap, we destroy the ptr array, then
         the lheap, and then null the contents of the input ptr.

Definition at line 145 of file heap.c.

References L_Heap::array, and L_Heap::n.

◆ lheapExtendArray()

static l_int32 lheapExtendArray ( L_HEAP * lh )

static

lheapExtendArray()

Parameters

[in] lh heap

Returns: 0 if OK, 1 on error

Definition at line 217 of file heap.c.

References L_Heap::array, L_Heap::nalloc, and reallocNew().

Referenced by lheapAdd().

◆ lheapGetCount()

l_int32 lheapGetCount ( L_HEAP * lh )

lheapGetCount()

Parameters

[in] lh heap

Returns: count, or 0 on error

Definition at line 271 of file heap.c.

References L_Heap::n.

Referenced by lheapSwapDown(), and pixcmapGenerateFromMedianCuts().

◆ lheapPrint()

l_ok lheapPrint	(	FILE *	fp,
		L_HEAP *	lh
	)

lheapPrint()

Parameters

[in]	fp	file stream
[in]	lh	heap

Returns: 0 if OK; 1 on error

Definition at line 524 of file heap.c.

References L_Heap::array, L_Heap::n, and L_Heap::nalloc.

◆ lheapRemove()

void* lheapRemove ( L_HEAP * lh )

lheapRemove()

Parameters

[in] lh heap

Returns: ptr to item popped from the root of the heap, or NULL if the heap is empty or on error

Definition at line 242 of file heap.c.

References L_Heap::array, lheapSwapDown(), and L_Heap::n.

Referenced by pixcmapGenerateFromMedianCuts().

◆ lheapSort()

l_ok lheapSort ( L_HEAP * lh )

lheapSort()

Parameters

[in] lh heap, with internal array

Returns: 0 if OK, 1 on error

Notes:
     (1) This sorts an array into heap order.  If the heap is already
         in heap order for the direction given, this has no effect.

Definition at line 453 of file heap.c.

References lheapSwapUp(), and L_Heap::n.

◆ lheapSortStrictOrder()

l_ok lheapSortStrictOrder ( L_HEAP * lh )

lheapSortStrictOrder()

Parameters

[in] lh heap, with internal array

Returns: 0 if OK, 1 on error

Notes:
     (1) This sorts a heap into strict order.
     (2) For each element, starting at the end of the array and
         working forward, the element is swapped with the head
         element and then allowed to swap down onto a heap of
         size reduced by one.  The result is that the heap is
         reversed but in strict order.  The array elements are
         then reversed to put it in the original order.

Definition at line 487 of file heap.c.

References L_Heap::n.

◆ lheapSwapDown()

l_ok lheapSwapDown ( L_HEAP * lh )

lheapSwapDown()

Parameters

[in] lh heap

Returns: 0 if OK, 1 on error

Notes:
     (1) This is called after an item has been popped off the
         root of the heap, and the last item in the heap has
         been placed at the root.
     (2) To regain the heap order, we let it bubble down,
         iteratively swapping with one of its children.  For a
         decreasing sort, it swaps with the largest child; for
         an increasing sort, the smallest.  This continues until
         it either reaches the lowest level in the heap, or the
         parent finds that neither child should swap with it
         (e.g., for a decreasing heap, the parent is larger
         than or equal to both children).

Definition at line 370 of file heap.c.

References L_Heap::array, L_Heap::direction, L_SORT_INCREASING, lheapGetCount(), and L_Heap::n.

Referenced by lheapRemove().

◆ lheapSwapUp()

l_ok lheapSwapUp	(	L_HEAP *	lh,
		l_int32	index
	)

lheapSwapUp()

Parameters

[in]	lh	heap
[in]	index	of array corresponding to node to be swapped up

Returns: 0 if OK, 1 on error

Notes:
     (1) This is called after a new item is put on the heap, at the
         bottom of a complete tree.
     (2) To regain the heap order, we let it bubble up,
         iteratively swapping with its parent, until it either
         reaches the root of the heap or it finds a parent that
         is in the correct position already vis-a-vis the child.

Definition at line 304 of file heap.c.

References L_Heap::array, L_Heap::direction, L_SORT_INCREASING, and L_Heap::n.

Referenced by lheapAdd(), and lheapSort().

Macros

Functions

Variables

Detailed Description

Macro Definition Documentation

◆ SWAP_ITEMS

Function Documentation

◆ lheapAdd()

◆ lheapCreate()

◆ lheapDestroy()

◆ lheapExtendArray()

◆ lheapGetCount()

◆ lheapPrint()

◆ lheapRemove()

◆ lheapSort()

◆ lheapSortStrictOrder()

◆ lheapSwapDown()

◆ lheapSwapUp()