/// <summary>
/// Get a new empty page - can be a reused page (EmptyPage) or a clean one (extend datafile)
/// </summary>
public T NewPage <T>(BasePage prevPage = null)
where T : BasePage
{
// get header
var header = this.GetPage <HeaderPage>(0);
var pageID = (uint)0;
var diskData = new byte[0];
// try get page from Empty free list
if (header.FreeEmptyPageID != uint.MaxValue)
{
var free = this.GetPage <BasePage>(header.FreeEmptyPageID);
// remove page from empty list
this.AddOrRemoveToFreeList(false, free, header, ref header.FreeEmptyPageID);
pageID = free.PageID;
// if used page has original disk data, copy to my new page
if (free.DiskData.Length > 0)
{
diskData = free.DiskData;
}
}
else
{
pageID = ++header.LastPageID;
// set header page as dirty after increment LastPageID
this.SetDirty(header);
}
var page = BasePage.CreateInstance <T>(pageID);
// copy disk data from re-used page (or be an empty)
page.DiskData = diskData;
// add page to cache with correct T type (could be an old Empty page type)
this.SetDirty(page);
// if there a page before, just fix NextPageID pointer
if (prevPage != null)
{
page.PrevPageID = prevPage.PageID;
prevPage.NextPageID = page.PageID;
this.SetDirty(prevPage);
}
return(page);
}
/// <summary>
/// Get a new empty page - can be a reused page (EmptyPage) or a clean one (extend datafile)
/// Set as Dirty
/// </summary>
public T NewPage <T>(BasePage prevPage = null)
where T : BasePage
{
// get header and mark as dirty
var header = this.GetPage <HeaderPage>(0, true);
var pageID = (uint)0;
// try get page from Empty free list
if (header.FreeEmptyPageID != uint.MaxValue)
{
var free = this.GetPage <BasePage>(header.FreeEmptyPageID);
// remove page from empty list
this.AddOrRemoveToFreeList(false, free, header, ref header.FreeEmptyPageID);
pageID = free.PageID;
}
else
{
pageID = ++header.LastPageID;
}
var page = BasePage.CreateInstance <T>(pageID);
// mark new page as dirty as soon as possible
this.SetDirty(page);
// if there a page before, just fix NextPageID pointer
if (prevPage != null)
{
this.SetDirty(prevPage);
page.PrevPageID = prevPage.PageID;
prevPage.NextPageID = page.PageID;
}
return(page);
}
