//
// Returns 0 if lock was not acquired because somebody else already holds it
// Else returns > 0
// Does NOT BLOCK
//
public long AcquireLock(string itemID)
{
if (string.IsNullOrEmpty(itemID))
{
throw new ArgumentException("itemID");
}
lock (m_locks)
{
if (this.GetLock(itemID) != null)
{
return(LockNotAcquired);
}
long lockID = this.NextLockID();
Debug.Assert(RecordItemLockTable.IsValidLockID(lockID));
m_locks[itemID] = LockData.Create(lockID);
return(lockID);
}
}
//
// Will only write the item to the local store IF:
// - Can take the write lock on the item (no pending edits in progress)
// - There are no pending changes on the item
//
async Task SafePutItemInLocalStoreAsync(RecordItem item)
{
long lockID = m_itemLocks.AcquireLock(item.ID);
if (!RecordItemLockTable.IsValidLockID(lockID))
{
return; // Item is locked for editing. Don't overrwrite yet
}
try
{
// Make sure there are no pending updates
if (!await m_changeManager.HasChangesForItemAsync(item.ID))
{
await m_localStore.PutItemAsync(item);
}
}
finally
{
m_itemLocks.SafeReleaseLock(item.ID, lockID);
}
}