/// <summary>
/// Get a page from cache or from disk (and put on cache)
/// </summary>
public T GetPage <T>(uint pageID, bool setDirty = false)
where T : BasePage
{
var page = _cache.GetPage(pageID);
// is not on cache? load from disk
if (page == null)
{
var buffer = _disk.ReadPage(pageID);
page = BasePage.ReadPage(buffer);
_cache.AddPage(page);
}
#if DEBUG
// if page is empty, convert to T
if (page.PageType == PageType.Empty && typeof(T) != typeof(BasePage))
{
throw new Exception("Pager.GetPage<T>() never shuld happend");
}
#endif
// set page as dirty if passing by param
if (setDirty)
{
this.SetDirty((T)page);
}
return((T)page);
}
/// <summary>
/// This method must be called before read/write operation to avoid dirty reads.
/// It's occurs when my cache contains pages that was changed in another process
/// </summary>
public bool AvoidDirtyRead()
{
var cache = (HeaderPage)_cache.GetPage(0);
if (cache == null)
{
return(false);
}
// read change direct from disk
var change = _disk.GetChangeID();
// if changeID was changed, file was changed by another process - clear all cache
if (cache.ChangeID != change)
{
_cache.Clear();
return(true);
}
return(false);
}