/// <summary>
/// Remove a mapping from a document GUID.
/// The page chain is not affected.
/// If no such document id is bound, nothing happens
/// </summary>
public void UnbindIndex(Guid documentId)
{
lock (_fslock)
{
var indexLink = GetIndexPageLink();
if (!indexLink.TryGetLink(0, out var indexTopPageId))
{
return; // no index to unbind
}
// Search for the binding, and remove if found
var currentPage = GetRawPage(indexTopPageId);
while (currentPage != null)
{
var indexSnap = new IndexPage();
indexSnap.Defrost(currentPage.BodyStream());
var found = indexSnap.Remove(documentId);
if (found)
{
var stream = indexSnap.Freeze();
currentPage.Write(stream, 0, stream.Length);
CommitPage(currentPage);
Flush();
return;
}
currentPage = GetRawPage(currentPage.PrevPageId);
}
}
}
/// <summary>
/// Map a document GUID to a page ID.
/// If the document has an existing page, the versions will be incremented.
/// If a version expires, the page ID will be returned in `expiredPageId`
/// </summary>
/// <param name="documentId">Unique ID for the document</param>
/// <param name="newPageId">top page id for most recent version of the document</param>
/// <param name="expiredPageId">an expired version of the document, or `-1` if no versions have expired</param>
public void BindIndex(Guid documentId, int newPageId, out int expiredPageId)
{
lock (_fslock)
{
var indexLink = GetIndexPageLink();
if (!indexLink.TryGetLink(0, out var indexTopPageId))
{
indexTopPageId = -1;
}
// Try to update an existing document
var currentPage = GetRawPage(indexTopPageId);
while (currentPage != null)
{
var indexSnap = new IndexPage();
indexSnap.Defrost(currentPage.BodyStream());
var found = indexSnap.Update(documentId, newPageId, out expiredPageId);
if (found)
{
var stream = indexSnap.Freeze();
currentPage.Write(stream, 0, stream.Length);
CommitPage(currentPage);
return;
}
currentPage = GetRawPage(currentPage.PrevPageId);
}
// Try to insert a new link in an existing index page
expiredPageId = -1;
currentPage = GetRawPage(indexTopPageId);
while (currentPage != null)
{
var indexSnap = new IndexPage();
indexSnap.Defrost(currentPage.BodyStream());
var found = indexSnap.TryInsert(documentId, newPageId);
if (found)
{
var stream = indexSnap.Freeze();
currentPage.Write(stream, 0, stream.Length);
CommitPage(currentPage);
return;
}
currentPage = GetRawPage(currentPage.PrevPageId);
}
// need to extend into a new index, and write to a new version of the head
var newIndex = new IndexPage();
var ok = newIndex.TryInsert(documentId, newPageId);
if (!ok)
{
throw new Exception("Failed to write index to blank index page");
}
var slot = new int[1];
AllocatePageBlock(slot);
var newPage = GetRawPage(slot[0]) ?? throw new Exception("Failed to read newly allocated page");
newPage.PrevPageId = indexTopPageId;
var newStream = newIndex.Freeze();
newPage.Write(newStream, 0, newStream.Length);
CommitPage(newPage);
// set new head link
indexLink.WriteNewLink(newPage.PageId, out _); // Index is always extended, we never clean it up
SetIndexPageLink(indexLink);
Flush();
}
}