private Task <ShapefileRecordInfoCollection> BuildShapeIndexData(IRandomAccessStream stream, CancellationTokenSource cancellationTokenSource)
{
var token = cancellationTokenSource.Token;
var task = Task.Factory.StartNew(
async() =>
{
if (cancellationTokenSource.IsCancellationRequested)
{
return(null);
}
using (var shapeStream = stream.CloneStream())
{
int offset = 36;
shapeStream.Seek((ulong)offset);
byte[] boundingBox = new byte[32];
await shapeStream.ReadAsync(boundingBox.AsBuffer(), 32u, InputStreamOptions.Partial);
var recordInfos = new ShapefileRecordInfoCollection();
recordInfos.BoundingRect = GetBoundingRect(boundingBox, this.CoordinateValueConverter);
offset = 100;
shapeStream.Seek((ulong)offset);
while (shapeStream.Position < shapeStream.Size)
{
if (cancellationTokenSource.IsCancellationRequested)
{
return(null);
}
byte[] recordHeader = new byte[8];
await shapeStream.ReadAsync(recordHeader.AsBuffer(), 8u, InputStreamOptions.Partial);
// The content length for a record is the length of the record contents section measured in 16-bit words.
int contentLength = ToInt32BigEndian(recordHeader, 4) * 2;
offset += 8;
recordInfos.Add(new ShapefileRecordInfo()
{
ContentOffset = offset, ContentLength = contentLength
});
offset += contentLength;
shapeStream.Seek((ulong)offset);
}
return(recordInfos);
}
},
token).Unwrap();
return(task);
}
private MapShapeModelCollection ProcessItems(IRandomAccessStream shapeStream, ShapefileRecordInfoCollection recordInfos, CancellationTokenSource cancellationTokenSource)
{
if (cancellationTokenSource.IsCancellationRequested)
{
return(null);
}
int itemCount = recordInfos.Count;
int maxDegreeOfParallelism = Environment.ProcessorCount;
if (itemCount < maxDegreeOfParallelism)
{
maxDegreeOfParallelism = itemCount;
}
int remainder = itemCount % maxDegreeOfParallelism;
int multiplier = (itemCount / maxDegreeOfParallelism) + (remainder > 0 ? 1 : 0);
var token = cancellationTokenSource.Token;
List <Task <MapShapeModelCollection> > tasks = new List <Task <MapShapeModelCollection> >();
for (int i = 0; i < maxDegreeOfParallelism; i++)
{
int start = i * multiplier;
int end = Math.Min((i + 1) * multiplier, itemCount);
ParseShapeTaskState taskState = new ParseShapeTaskState()
{
Start = start,
End = end,
Records = recordInfos,
Stream = shapeStream,
CancellationTokenSource = cancellationTokenSource,
CoordinateConverter = this.CoordinateValueConverter
};
var task = Task.Factory.StartNew <Task <MapShapeModelCollection> >(ParseShapes, taskState, token, TaskCreationOptions.AttachedToParent, TaskScheduler.Current).Unwrap();
tasks.Add(task);
}
Task.WaitAll(tasks.ToArray());
MapShapeModelCollection models = tasks[0].Result;
for (int i = 1; i < maxDegreeOfParallelism; i++)
{
var modelsToMerge = tasks[i].Result;
if (modelsToMerge == null)
{
continue;
}
foreach (var model in modelsToMerge)
{
models.Add(model);
}
}
models.BoundingRect = recordInfos.BoundingRect;
return(models);
}
