private async Task <Page> ReadPageAsync(int pageNum, ushort pageSize, CancellationToken cancellationToken)
{
// Sanity checks
if (stream == null)
{
// TODO - create custom exception
throw new Exception("Block store is not open!");
}
// Seek to the proper spot
SeekToPage(pageNum);
// Read the bytes for the page
var bytes = new byte[pageSize];
await stream.ReadAsync(bytes, 0, pageSize);
// Peek at the page type and build the proper page type.
// TODO - a big switch statement is ugly...find a better way.
var pageType = BitConverter.ToUInt16(bytes, 1);
Page page = null;
switch (pageType)
{
case ZeroPage.PageId:
page = new ZeroPage();
break;
case HeaderPage.PageId:
page = new HeaderPage();
break;
default:
throw new Exception($"Unhandled page type: {pageType}.");
}
// Have the page deserialize itself
page.Deserialize(bytes);
// And return whatever we've got.
return(page);
}
