/// <inheritdoc />
public IObservable <string> Get(Tile tile)
{
// TODO tile can cross more than one srtm cell: need load more.
var prefix = GetFileNamePrefix(tile.BoundingBox.Center());
var filePath = Path.Combine(_elePath, prefix);
if (_fileSystemService.Exists(filePath))
{
return(Observable.Return(filePath));
}
return(Download(prefix).Select(bytes =>
{
lock (_lock)
{
if (!_fileSystemService.Exists(filePath))
{
_trace.Info(TraceCategory, "Unzipping {0} bytes", bytes.Length.ToString());
var hgtData = CompressionUtils.Unzip(bytes).Single().Value;
using (var stream = _fileSystemService.WriteStream(filePath))
stream.Write(hgtData, 0, hgtData.Length);
}
}
return filePath;
}));
}
/// <inheritdoc />
protected override void WriteBytes(Stream stream, byte[] bytes)
{
_trace.Info(TraceCategory, "Unzipping {0} bytes", bytes.Length.ToString());
var hgtData = CompressionUtils.Unzip(bytes).Single().Value;
stream.Write(hgtData, 0, hgtData.Length);
}
private IObservable <Unit> Download(GeoCoordinate coordinate)
{
_trace.Info(TraceCategory, "downloading data for {0}", coordinate.ToString());
return(_downloader.Download(coordinate).SelectMany(bytes =>
{
_trace.Info(TraceCategory, "downloaded {0} bytes", bytes.Length.ToString());
_hgtData = CompressionUtils.Unzip(bytes).Single().Value;
InitData((int)coordinate.Latitude, (int)coordinate.Longitude);
// store data to disk
var path = GetFilePath(_srtmLat, _srtmLon);
_trace.Info(TraceCategory, "storing as {0}", path);
using (var stream = _fileSystemService.WriteStream(path))
stream.Write(_hgtData, 0, _hgtData.Length);
return Observable.Return <Unit>(Unit.Default);
}));
}