public async Task <byte[]> ReadImageBufferAsync(int x, int y, int zoomLevel)
{
byte[] imageBuffer = null;
try
{
using (var command = new SQLiteCommand("select tile_data from tiles where zoom_level=@z and tile_column=@x and tile_row=@y", connection))
{
command.Parameters.AddWithValue("@z", zoomLevel);
command.Parameters.AddWithValue("@x", x);
command.Parameters.AddWithValue("@y", (1 << zoomLevel) - y - 1);
imageBuffer = await command.ExecuteScalarAsync() as byte[];
}
}
catch (Exception ex)
{
Debug.WriteLine("MBTileData: {0}/{1}/{2}: {3}", zoomLevel, x, y, ex.Message);
}
return(imageBuffer);
}
// Some day, Microsoft will deign it useful to add async service initializers and we can
// bring this code back to the light of day.
#if false
private async Task <bool> CheckExistingDbAsync(DbConnection db, CancellationToken cancel)
{
try
{
// Check for correct structure
using (var cmd = new DbCommand(@"SELECT COUNT(*) from sqlite_master", db))
{
var result = (long)await cmd.ExecuteScalarAsync(cancel);
// We are expecting two tables and one additional index
if (result != 3)
{
_logger.LogWarning("Incorrect/incompatible existing cache db structure found!");
return(false);
}
}
// Check for correct version
using (var cmd = new DbCommand(@"SELECT value FROM meta WHERE key = ""version""", db))
{
var result = (long)await cmd.ExecuteScalarAsync(cancel);
if (result != SchemaVersion)
{
_logger.LogWarning("Existing cache db has unsupported schema version {SchemaVersion}",
result);
return(false);
}
}
}
catch (Exception ex)
{
_logger.LogError(ex, "Error while checking compatibilty of existing cache db!");
return(false);
}
return(true);
}
/// <summary>
/// Tests the connection asynchronously.
/// </summary>
/// <returns></returns>
public override async Task TestConnectionAsync()
{
using (var con = await CreateConnectionAsync())
using (var cmd = new SQLiteCommand("SELECT 1", con))
await cmd.ExecuteScalarAsync();
}
/// <summary>
/// Tests the connection asynchronously.
/// </summary>
/// <returns></returns>
public override async Task TestConnectionAsync()
{
using (var con = await CreateConnectionAsync())
using (var cmd = new SQLiteCommand("SELECT 1", con))
await cmd.ExecuteScalarAsync();
}