org.tinfour.edge

Class EdgePool

java.lang.Object

org.tinfour.edge.EdgePool

All Implemented Interfaces:

Iterable<IQuadEdge>

public class EdgePool
extends Object
implements Iterable<IQuadEdge>

Provides an object-pool implementation that the manages the allocation, deletion, and reuse of Edges.

This class is written using a very old-school approach as a way of minimizing the frequency with which objects are garbage collected. Edges are extensively allocated and freed as the TIN is built. Were they simply constructed and put out-of-scope, the resulting garbage collection could degrade performance.

Note that this class is not thread safe.

For performance reasons, many of the methods in this class make the assumption that any edges passed into the method are under the management of the current instance. If this assumption is violated, serious errors could occur. For example, if an application uses one edge pool to allocate an edge and then passes it to the deallocEdge method another edge pool instance, both instances could become seriously corrupted.

Constructor Summary

Constructors

Constructor and Description
EdgePool() Construct a QuadEdge manager allocating a small number of initial edges.

Method Summary

Modifier and Type	Method and Description
QuadEdge	allocateEdge(Vertex a, Vertex b)
void	clear() Deallocates all Edges, returning them to the free list.
void	deallocateEdge(QuadEdge e) Deallocates the QuadEdge returning it to the QuadEdge pool.
void	dispose() Puts all references used in the collection out-of-scope as a way of simplifying and expediting garbage collection.
int	getEdgeCount()
List<IQuadEdge>	getEdges() Get a list of the Edges currently stored in the collection
Iterator<IQuadEdge>	getIterator(boolean includeGhostEdges) Constructs an iterator that will optionally skip ghost edges.
int	getMaximumAllocationIndex() Gets the maximum value of an edge index that is currently allocated within the edge pool.
QuadEdge	getStartingEdge() Get first valid, non-ghost QuadEdge in collection
QuadEdge	getStartingGhostEdge()
Iterator<IQuadEdge>	iterator()
void	preAllocateEdges(int n) Pre-allocates the specified number of edges.
void	printDiagnostics(PrintStream ps) Prints diagnostic information about the manager to the specified print stream.
int	size() Get the number of Edges currently stored in the collection
QuadEdge	splitEdge(QuadEdge e, Vertex m) Split the edge e into two by inserting a new vertex m into the edge.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

EdgePool

public EdgePool()

Construct a QuadEdge manager allocating a small number of initial edges.

Method Detail

preAllocateEdges

public void preAllocateEdges(int n)

Pre-allocates the specified number of edges. For a Delaunay Triangulation with n vertices, there should be 3*n edges.

Parameters:

n - the number of edge (not vertices) to be allocated.

allocateEdge

public QuadEdge allocateEdge(Vertex a,
                             Vertex b)

deallocateEdge

public void deallocateEdge(QuadEdge e)

Deallocates the QuadEdge returning it to the QuadEdge pool.

Parameters:

e - a valid QuadEdge

size

public int size()

Get the number of Edges currently stored in the collection

Returns:

an integer value of zero or more

getStartingEdge

public QuadEdge getStartingEdge()

Get first valid, non-ghost QuadEdge in collection

Returns:

for a non-empty collection, a valid QuadEdge; otherwise a null

getStartingGhostEdge

public QuadEdge getStartingGhostEdge()

getEdges

public List<IQuadEdge> getEdges()

Get a list of the Edges currently stored in the collection

Returns:

a valid, potentially empty list of edges

getEdgeCount

public int getEdgeCount()

dispose

public void dispose()

Puts all references used in the collection out-of-scope as a way of simplifying and expediting garbage collection.

clear

public void clear()

Deallocates all Edges, returning them to the free list. Does not delete any existing objects.

toString

public String toString()

Overrides:

toString in class Object

printDiagnostics

public void printDiagnostics(PrintStream ps)

Prints diagnostic information about the manager to the specified print stream.

Parameters:

ps - a valid print stream.

iterator

public Iterator<IQuadEdge> iterator()

Specified by:

iterator in interface Iterable<IQuadEdge>

getIterator

public Iterator<IQuadEdge> getIterator(boolean includeGhostEdges)

Constructs an iterator that will optionally skip ghost edges.

Parameters:

includeGhostEdges - indicates that ghost edges are to be included in the iterator production.

Returns:

a valid instance of an iterator

getMaximumAllocationIndex

public int getMaximumAllocationIndex()

Gets the maximum value of an edge index that is currently allocated within the edge pool.

Returns:

a positive number or zero if the pool is currently unallocated.

splitEdge

public QuadEdge splitEdge(QuadEdge e,
                          Vertex m)

Split the edge e into two by inserting a new vertex m into the edge. The insertion point does not necessarily have to lie on the segment. This method splits the segment into two segments so that edge e(a,b) becomes edges p(a,m) and and e(m,b), with forward and reverse links for both segments being adjusted accordingly. The new segment p(a,m) is returned and the input segment e is adjusted with new vertices (m,b).

The split edge method preserves constraint flags and other attributes associated with the edge.

Parameters:

e - the input segment

m - the insertion vertex

Returns:

a valid instance of a QuadEdge or QuadEdgePartner (depending on the class of the input)