internal bool hasSharedCacheTableLock(Pgno rootID, bool isIndex, LOCK eLockType)
{
// If this database is not shareable, or if the client is reading and has the read-uncommitted flag set, then no lock is required. Return true immediately.
if (!Sharable || (eLockType == LOCK.READ && (DB.flags & sqlite3b.SQLITE.ReadUncommitted) != 0))
return true;
// If the client is reading or writing an index and the schema is not loaded, then it is too difficult to actually check to see if
// the correct locks are held. So do not bother - just return true. This case does not come up very often anyhow.
var schema = Shared.Schema;
if (isIndex && (schema == null || (schema.flags & SchemaFlags.SchemaLoaded) == 0))
return true;
// Figure out the root-page that the lock should be held on. For table b-trees, this is just the root page of the b-tree being read or
// written. For index b-trees, it is the root page of the associated table.
Pgno tableID = 0;
if (isIndex)
throw new NotImplementedException();
//for (var p = schema.idxHash.first; p != null; p = p.next)
//{
// var pIdx = (IIndex)p.data;
// if (pIdx.tnum == (int)rootID)
// tableID = pIdx.pTable.tnum;
//}
else
tableID = rootID;
// Search for the required lock. Either a write-lock on root-page iTab, a write-lock on the schema table, or (if the client is reading) a
// read-lock on tableID will suffice. Return 1 if any of these are found.
for (var @lock = Shared.Locks; @lock != null; @lock = @lock.Next)
if (@lock.Tree == this && (@lock.TableID == tableID || (@lock.Lock == LOCK.WRITE && @lock.TableID == 1)) && @lock.Lock >= eLockType)
return true;
// Failed to find the required lock.
return false;
}
internal bool hasSharedCacheTableLock(Pgno rootID, bool isIndex, LOCK eLockType)
{
// If this database is not shareable, or if the client is reading and has the read-uncommitted flag set, then no lock is required. Return true immediately.
if (!Sharable || (eLockType == LOCK.READ && (DB.flags & sqlite3b.SQLITE.ReadUncommitted) != 0))
{
return(true);
}
// If the client is reading or writing an index and the schema is not loaded, then it is too difficult to actually check to see if
// the correct locks are held. So do not bother - just return true. This case does not come up very often anyhow.
var schema = Shared.Schema;
if (isIndex && (schema == null || (schema.flags & SchemaFlags.SchemaLoaded) == 0))
{
return(true);
}
// Figure out the root-page that the lock should be held on. For table b-trees, this is just the root page of the b-tree being read or
// written. For index b-trees, it is the root page of the associated table.
Pgno tableID = 0;
if (isIndex)
{
throw new NotImplementedException();
}
//for (var p = schema.idxHash.first; p != null; p = p.next)
//{
// var pIdx = (IIndex)p.data;
// if (pIdx.tnum == (int)rootID)
// tableID = pIdx.pTable.tnum;
//}
else
{
tableID = rootID;
}
// Search for the required lock. Either a write-lock on root-page iTab, a write-lock on the schema table, or (if the client is reading) a
// read-lock on tableID will suffice. Return 1 if any of these are found.
for (var @lock = Shared.Locks; @lock != null; @lock = @lock.Next)
{
if (@lock.Tree == this && (@lock.TableID == tableID || (@lock.Lock == LOCK.WRITE && @lock.TableID == 1)) && @lock.Lock >= eLockType)
{
return(true);
}
}
// Failed to find the required lock.
return(false);
}
internal RC querySharedCacheTableLock(Pgno tableID, LOCK eLock)
{
Debug.Assert(sqlite3BtreeHoldsMutex());
Debug.Assert(eLock == LOCK.READ || eLock == LOCK.WRITE);
Debug.Assert(DB != null);
Debug.Assert((DB.flags & sqlite3b.SQLITE.ReadUncommitted) == 0 || eLock == LOCK.WRITE || tableID == 1);
// If requesting a write-lock, then the Btree must have an open write transaction on this file. And, obviously, for this to be so there
// must be an open write transaction on the file itself.
var shared = this.Shared;
Debug.Assert(eLock == LOCK.READ || (shared.Writer == this && InTransaction == TRANS.WRITE));
Debug.Assert(eLock == LOCK.READ || shared.InTransaction == TRANS.WRITE);
// This routine is a no-op if the shared-cache is not enabled
if (!Sharable)
{
return(RC.OK);
}
// If some other connection is holding an exclusive lock, the requested lock may not be obtained.
if (shared.Writer != this && shared.IsExclusive)
{
sqlite3b.sqlite3ConnectionBlocked(DB, shared.Writer.DB);
return(RC.LOCKED_SHAREDCACHE);
}
for (var @lock = shared.Locks; @lock != null; @lock = @lock.Next)
{
// The condition (pIter.eLock!=eLock) in the following if(...) statement is a simplification of:
// (eLock==WRITE_LOCK || pIter.eLock==WRITE_LOCK)
// since we know that if eLock==WRITE_LOCK, then no other connection may hold a WRITE_LOCK on any table in this file (since there can
// only be a single writer).
Debug.Assert(@lock.Lock == LOCK.READ || @lock.Lock == LOCK.WRITE);
Debug.Assert(eLock == LOCK.READ || @lock.Tree == this || @lock.Lock == LOCK.READ);
if (@lock.Tree != this && @lock.TableID == tableID && @lock.Lock != eLock)
{
sqlite3b.sqlite3ConnectionBlocked(DB, @lock.Tree.DB);
if (eLock == LOCK.WRITE)
{
Debug.Assert(shared.Writer == this);
shared.IsPending = true;
}
return(RC.LOCKED_SHAREDCACHE);
}
}
return(RC.OK);
}
internal RC setSharedCacheTableLock(Pgno tableID, LOCK eLock)
{
Debug.Assert(sqlite3BtreeHoldsMutex());
Debug.Assert(eLock == LOCK.READ || eLock == LOCK.WRITE);
Debug.Assert(DB != null);
// A connection with the read-uncommitted flag set will never try to obtain a read-lock using this function. The only read-lock obtained
// by a connection in read-uncommitted mode is on the sqlite_master table, and that lock is obtained in BtreeBeginTrans().
Debug.Assert((DB.flags & sqlite3b.SQLITE.ReadUncommitted) == 0 || eLock == LOCK.WRITE);
// This function should only be called on a sharable b-tree after it has been determined that no other b-tree holds a conflicting lock.
Debug.Assert(Sharable);
Debug.Assert(querySharedCacheTableLock(tableID, eLock) == RC.OK);
// First search the list for an existing lock on this table.
BtreeLock pLock = null;
for (var @lock = Shared.Locks; @lock != null; @lock = @lock.Next)
{
if (@lock.TableID == tableID && @lock.Tree == this)
{
pLock = @lock;
break;
}
}
// If the above search did not find a BtLock struct associating Btree p with table iTable, allocate one and link it into the list.
if (pLock == null)
{
var shared = Shared;
pLock = new BtreeLock();
pLock.TableID = tableID;
pLock.Tree = this;
pLock.Next = shared.Locks;
shared.Locks = pLock;
}
// Set the BtLock.eLock variable to the maximum of the current lock and the requested lock. This means if a write-lock was already held
// and a read-lock requested, we don't incorrectly downgrade the lock.
Debug.Assert(LOCK.WRITE > LOCK.READ);
if (eLock > pLock.Lock)
{
pLock.Lock = eLock;
}
return(RC.OK);
}
internal bool hasSharedCacheTableLock(Pgno b, bool c, LOCK d)
{
return(true);
}
internal bool hasSharedCacheTableLock(Pgno b, bool c, LOCK d)
{
return true;
}
internal RC setSharedCacheTableLock(Pgno tableID, LOCK eLock)
{
Debug.Assert(sqlite3BtreeHoldsMutex());
Debug.Assert(eLock == LOCK.READ || eLock == LOCK.WRITE);
Debug.Assert(DB != null);
// A connection with the read-uncommitted flag set will never try to obtain a read-lock using this function. The only read-lock obtained
// by a connection in read-uncommitted mode is on the sqlite_master table, and that lock is obtained in BtreeBeginTrans().
Debug.Assert((DB.flags & sqlite3b.SQLITE.ReadUncommitted) == 0 || eLock == LOCK.WRITE);
// This function should only be called on a sharable b-tree after it has been determined that no other b-tree holds a conflicting lock.
Debug.Assert(Sharable);
Debug.Assert(querySharedCacheTableLock(tableID, eLock) == RC.OK);
// First search the list for an existing lock on this table.
BtreeLock pLock = null;
for (var @lock = Shared.Locks; @lock != null; @lock = @lock.Next)
if (@lock.TableID == tableID && @lock.Tree == this)
{
pLock = @lock;
break;
}
// If the above search did not find a BtLock struct associating Btree p with table iTable, allocate one and link it into the list.
if (pLock == null)
{
var shared = Shared;
pLock = new BtreeLock();
pLock.TableID = tableID;
pLock.Tree = this;
pLock.Next = shared.Locks;
shared.Locks = pLock;
}
// Set the BtLock.eLock variable to the maximum of the current lock and the requested lock. This means if a write-lock was already held
// and a read-lock requested, we don't incorrectly downgrade the lock.
Debug.Assert(LOCK.WRITE > LOCK.READ);
if (eLock > pLock.Lock)
pLock.Lock = eLock;
return RC.OK;
}
internal RC querySharedCacheTableLock(Pgno tableID, LOCK eLock)
{
Debug.Assert(sqlite3BtreeHoldsMutex());
Debug.Assert(eLock == LOCK.READ || eLock == LOCK.WRITE);
Debug.Assert(DB != null);
Debug.Assert((DB.flags & sqlite3b.SQLITE.ReadUncommitted) == 0 || eLock == LOCK.WRITE || tableID == 1);
// If requesting a write-lock, then the Btree must have an open write transaction on this file. And, obviously, for this to be so there
// must be an open write transaction on the file itself.
var shared = this.Shared;
Debug.Assert(eLock == LOCK.READ || (shared.Writer == this && InTransaction == TRANS.WRITE));
Debug.Assert(eLock == LOCK.READ || shared.InTransaction == TRANS.WRITE);
// This routine is a no-op if the shared-cache is not enabled
if (!Sharable)
return RC.OK;
// If some other connection is holding an exclusive lock, the requested lock may not be obtained.
if (shared.Writer != this && shared.IsExclusive)
{
sqlite3b.sqlite3ConnectionBlocked(DB, shared.Writer.DB);
return RC.LOCKED_SHAREDCACHE;
}
for (var @lock = shared.Locks; @lock != null; @lock = @lock.Next)
{
// The condition (pIter.eLock!=eLock) in the following if(...) statement is a simplification of:
// (eLock==WRITE_LOCK || pIter.eLock==WRITE_LOCK)
// since we know that if eLock==WRITE_LOCK, then no other connection may hold a WRITE_LOCK on any table in this file (since there can
// only be a single writer).
Debug.Assert(@lock.Lock == LOCK.READ || @lock.Lock == LOCK.WRITE);
Debug.Assert(eLock == LOCK.READ || @lock.Tree == this || @lock.Lock == LOCK.READ);
if (@lock.Tree != this && @lock.TableID == tableID && @lock.Lock != eLock)
{
sqlite3b.sqlite3ConnectionBlocked(DB, @lock.Tree.DB);
if (eLock == LOCK.WRITE)
{
Debug.Assert(shared.Writer == this);
shared.IsPending = true;
}
return RC.LOCKED_SHAREDCACHE;
}
}
return RC.OK;
}