private static Task ParseAttributes(object state)
{
var taskState = (ParseDataTaskState)state;
var cancellationTokenSource = taskState.CancellationTokenSource;
var token = cancellationTokenSource.Token;
var task = Task.Factory.StartNew(
async() =>
{
using (var dataStream = taskState.Stream.CloneStream())
{
int start = taskState.Start;
int end = taskState.End;
DbfHeader dbfHeader = taskState.DbfHeader;
var shapeModels = taskState.ShapeModels;
var valueConverter = taskState.ValueConverter;
var attributesToLoad = taskState.AttributesToLoad;
dataStream.Seek((ulong)(dbfHeader.RecordsOffset + start * dbfHeader.RecordLength));
for (int i = start; i < end; i++)
{
if (cancellationTokenSource.IsCancellationRequested)
{
return;
}
var shapeModel = shapeModels[i] as MapShapeModel;
byte[] record = new byte[dbfHeader.RecordLength];
await dataStream.ReadAsync(record.AsBuffer(), (uint)dbfHeader.RecordLength, InputStreamOptions.Partial);
// Data records are preceded by one byte; that is, a space (20H) if the record is not deleted, an asterisk (2AH) if the record is deleted.
int offset = 1;
foreach (var field in dbfHeader.Fields)
{
if (attributesToLoad == null || attributesToLoad.Contains(field.Name))
{
string value = dbfHeader.Encoding.GetString(record, offset, field.Length);
object propertyValue = TransformDbfValue(field, value, valueConverter);
shapeModel.Attributes[field.Name] = propertyValue;
}
offset += field.Length;
}
}
}
},
token).Unwrap();
return(task);
}
private static Task <DbfHeader> BuildDbfHeaderData(IRandomAccessStream stream, Encoding encoding, CancellationTokenSource cancellationTokenSource)
{
var token = cancellationTokenSource.Token;
var task = Task.Factory.StartNew(async() =>
{
if (cancellationTokenSource.IsCancellationRequested)
{
return(null);
}
if (stream.Size < 32)
{
throw new NotSupportedException(InvalidFormat);
}
using (var dataStream = stream.CloneStream())
{
byte[] header = new byte[32];
await dataStream.ReadAsync(header.AsBuffer(), 32u, InputStreamOptions.Partial);
byte fileType = header[0];
if (!AllowedTypes.Contains(fileType))
{
throw new NotSupportedException(InvalidFormat);
}
DbfHeader dbfHeader = new DbfHeader();
dbfHeader.RecordsCount = BitConverter.ToInt32(header, 4);
dbfHeader.RecordsOffset = BitConverter.ToInt16(header, 8);
dbfHeader.RecordLength = BitConverter.ToInt16(header, 10);
if (encoding == null)
{
byte languageDriver = header[29];
encoding = DbfEncoding.GetEncoding(languageDriver);
}
dbfHeader.Encoding = encoding;
// header is 32 bytes + n field descriptors * 32 bytes + carriage return byte (0x0D)
int fieldDescriptorCount = (dbfHeader.RecordsOffset - 32 - 1) / 32;
byte[] fieldDescriptor;
DbfFieldInfo dbfField;
for (int i = 0; i < fieldDescriptorCount; i++)
{
if (cancellationTokenSource.IsCancellationRequested)
{
return(null);
}
fieldDescriptor = new byte[32];
await dataStream.ReadAsync(fieldDescriptor.AsBuffer(), 32u, InputStreamOptions.Partial);
dbfField = new DbfFieldInfo();
dbfField.Name = encoding.GetString(fieldDescriptor, 0, 11).Replace("\0", string.Empty);
dbfField.NativeDbfType = (char)fieldDescriptor[11];
dbfField.Length = fieldDescriptor[16];
dbfField.DecimalCount = fieldDescriptor[17];
dbfHeader.Fields.Add(dbfField);
}
return(dbfHeader);
}
},
token).Unwrap();
return(task);
}
private MapShapeModelCollection ProcessDataItems(MapShapeModelCollection shapeModels, DbfHeader dbfHeader, IRandomAccessStream dataStream, CancellationTokenSource cancellationTokenSource)
{
if (cancellationTokenSource.IsCancellationRequested)
{
return(null);
}
var token = cancellationTokenSource.Token;
int itemCount = dbfHeader.RecordsCount;
int maxDegreeOfParallelism = Environment.ProcessorCount;
if (itemCount < maxDegreeOfParallelism)
{
maxDegreeOfParallelism = itemCount;
}
int remainder = itemCount % maxDegreeOfParallelism;
int multiplier = (itemCount / maxDegreeOfParallelism) + (remainder > 0 ? 1 : 0);
List <Task> tasks = new List <Task>();
for (int i = 0; i < maxDegreeOfParallelism; i++)
{
int start = i * multiplier;
int end = Math.Min((i + 1) * multiplier, itemCount);
var taskState = new ParseDataTaskState()
{
Start = start,
End = end,
DbfHeader = dbfHeader,
Stream = dataStream,
ShapeModels = shapeModels,
CancellationTokenSource = cancellationTokenSource,
ValueConverter = this.AttributeValueConverter,
AttributesToLoad = this.AttributesToLoad
};
var task = Task.Factory.StartNew <Task>(ParseAttributes, taskState, token, TaskCreationOptions.AttachedToParent, TaskScheduler.Current).Unwrap();
tasks.Add(task);
}
Task.WaitAll(tasks.ToArray());
return(shapeModels);
}
