public bool Contains(Lockey key)
{
// 需要sync，get不是线程安全的
lock (this)
{
return(locks.get(key) != null);
}
}
private CheckResult _lock_and_check_(KeyValuePair <TableKey, RecordAccessed> e)
{
Lockey lockey = Locks.Instance.Get(e.Key);
bool writeLock = e.Value.Dirty;
lockey.EnterLock(writeLock);
holdLocks.Add(lockey);
return(_check_(writeLock, e.Value));
}
public Lockey Get(Lockey key)
{
lock (this)
{
Lockey exist = locks.get(key);
if (null != exist)
{
return(exist);
}
locks.add(key);
return(key.Alloc());
}
}
// under lockey.writelock
/*
* internal bool RemoeIfNotDirty(K key)
* {
* var storage = Table.Storage;
* if (null == storage)
* return false; // 内存表不该发生Reduce.
*
* if (storage.IsRecordChanged(key)) // 在记录里面维持一个 Dirty 标志是可行的，但是由于 Cache.CleanNow 执行的不频繁，无所谓了。
* return false;
*
* return map.TryRemove(key, out var _);
* }
*/
private bool TryRemoveRecord(KeyValuePair <K, Record <K, V> > p)
{
TableKey tkey = new TableKey(this.Table.Id, p.Key);
Lockey lockey = Locks.Instance.Get(tkey);
if (false == lockey.TryEnterWriteLock(0))
{
return(false);
}
try
{
var storage = Table.Storage;
if (null == storage)
{
/* 不支持内存表cache同步。
* if (p.Value.Acquire(GlobalCacheManager.StateInvalid) != GlobalCacheManager.StateInvalid)
* return false;
*/
return(Remove(p));
}
if (storage.IsRecordChanged(p.Key)) // 在记录里面维持一个 Dirty 标志是可行的，但是由于 Cache.CleanNow 执行的不频繁，无所谓了。
{
return(false);
}
if (p.Value.State != GlobalCacheManager.StateInvalid)
{
if (p.Value.Acquire(GlobalCacheManager.StateInvalid) != GlobalCacheManager.StateInvalid)
{
return(false);
}
}
return(Remove(p));
}
finally
{
lockey.ExitWriteLock();
}
}
/* ---------------- hash算法和映射规则都是来自 ConcurrentHashMap. -------------- */
/**
* Returns the segment that should be used for key with given hash.
*
* @param lockey the Lockey
* @return the segment
*/
private Segment segmentFor(Lockey lockey)
{
/**
* Applies a supplemental hash function to a given hashCode, which defends
* against poor quality hash functions. This is critical because
* ConcurrentHashMap uses power-of-two length hash tables, that otherwise
* encounter collisions for hashCodes that do not differ in lower or upper bits.
*/
// Spread bits to regularize both segment and index locations,
// using variant of single-word Wang/Jenkins hash.
uint h = (uint)lockey.GetHashCode();
h += (h << 15) ^ 0xffffcd7d;
h ^= (h >> 10);
h += (h << 3);
h ^= (h >> 6);
h += (h << 2) + (h << 14);
uint hash = h ^ (h >> 16);
uint index = (hash >> segmentShift) & segmentMask;
return(segments[index]);
}
private CheckResult _lock_and_check_()
{
if (savepoints.Count > 0)
{
// 全部 Rollback 时 Count 为 0；最后提交时 Count 必须为 1；其他情况属于Begin,Commit,Rollback不匹配。外面检查。
foreach (var log in savepoints[savepoints.Count - 1].Logs.Values)
{
if (log.Bean == null)
{
continue; // 特殊日志。不是 bean 的修改日志，当然也不会修改 Record。现在不会有这种情况，保留给未来扩展需要。
}
TableKey tkey = log.Bean.TableKey;
if (accessedRecords.TryGetValue(tkey, out var record))
{
record.Dirty = true;
}
else
{
logger.Fatal("impossible! record not found."); // 只有测试代码会把非 Managed 的 Bean 的日志加进来。
}
}
}
bool conflict = false; // 冲突了，也继续加锁，为重做做准备！！！
if (holdLocks.Count == 0)
{
foreach (var e in accessedRecords)
{
switch (_lock_and_check_(e))
{
case CheckResult.Success: break;
case CheckResult.Redo: conflict = true; break; // continue lock
case CheckResult.RedoAndReleaseLock: return(CheckResult.RedoAndReleaseLock);
}
}
return(conflict ? CheckResult.Redo : CheckResult.Success);
}
int index = 0;
int n = holdLocks.Count;
foreach (var e in accessedRecords)
{
// 如果 holdLocks 全部被对比完毕，直接锁定它
if (index >= n)
{
switch (_lock_and_check_(e))
{
case CheckResult.Success: break;
case CheckResult.Redo: conflict = true; break; // continue lock
case CheckResult.RedoAndReleaseLock: return(CheckResult.RedoAndReleaseLock);
}
continue;
}
Lockey curLock = holdLocks[index];
int c = curLock.TableKey.CompareTo(e.Key);
// holdlocks a b ...
// needlocks a b ...
if (c == 0)
{
// 这里可能发生读写锁提升
if (e.Value.Dirty && false == curLock.isWriteLockHeld())
{
curLock.EnterLock(true);
switch (_check_(true, e.Value))
{
case CheckResult.Success: break;
case CheckResult.Redo: conflict = true; break; // continue lock
case CheckResult.RedoAndReleaseLock: return(CheckResult.RedoAndReleaseLock);
}
}
// else 已经持有读锁，不可能被修改也不可能降级(reduce)，所以不做检测了。
// 已经锁定了，跳过
++index;
continue;
}
// holdlocks a b ...
// needlocks a c ...
if (c < 0)
{
// 释放掉 比当前锁序小的锁，因为当前事务中不再需要这些锁
int unlockEndIndex = index;
for (; unlockEndIndex < n && holdLocks[unlockEndIndex].TableKey.CompareTo(e.Key) < 0; ++unlockEndIndex)
{
var toUnlockLocker = holdLocks[unlockEndIndex];
toUnlockLocker.ExitLock();
}
holdLocks.RemoveRange(index, unlockEndIndex - index);
n = holdLocks.Count;
continue;
}
// holdlocks a c ...
// needlocks a b ...
// 为了不违背锁序，释放从当前锁开始的所有锁
for (int i = index; i < n; ++i)
{
var toUnlockLocker = holdLocks[i];
toUnlockLocker.ExitLock();
}
holdLocks.RemoveRange(index, n - index);
n = holdLocks.Count;
}
return(conflict ? CheckResult.Redo : CheckResult.Success);
}
public Lockey Get(Lockey lockey)
{
return(this.segmentFor(lockey).Get(lockey));
}
public bool Contains(Lockey lockey)
{
return(this.segmentFor(lockey).Contains(lockey));
}