private static unsafe void FindFieldFromMvccRaw(ushort id, IntPtr vp, int vs, ulong ts, ref KVField found)
{
ushort *countPtr = (ushort *)vp.ToPointer();
ushort count = (ushort)(*countPtr >> 1);
uint offsetToEnd = 0;
int to = GetVersionLessOrEqual(vp, count, ts, &offsetToEnd);
int from = GetNearestFullVersionIndex(to);
byte * dataPtr = (byte *)vp + vs - offsetToEnd;
uint dataSize = GetDataSizeAt(vp, to);
KVField temp = new KVField();
for (int i = to; i >= from; i--) //注意倒序
{
FindField(id, dataPtr, dataSize, ref temp);
if (temp.Id == id)
{
found = temp;
break; //因为倒序找到即是最新版本
}
if (i > from)
{
dataSize = GetDataSizeAt(vp, i - 1);
dataPtr -= dataSize;
}
}
}
/// <summary>
/// Only for test
/// </summary>
public static unsafe bool CompareRaw(ushort id, IntPtr vp, int vs, byte[] target)
{
KVField found = KVField.Invalid;
FindFieldFromMvccRaw(id, vp, vs, ulong.MaxValue, ref found);
var span = new ReadOnlySpan <byte>(found.DataPtr.ToPointer(), found.DataSize);
return(span.SequenceEqual(target));
}
static KVField GetField(Type type)
{
KVField kvField;
if (!_typeToField.TryGetValue(type, out kvField))
{
_typeToField[type] = kvField = new KVField()
{
keyField = type.GetField("key"),
valueField = type.GetField("_value")
};
}
return kvField;
}
public static unsafe byte?GetByte(ushort id, IntPtr vp, int vs, bool mv, ulong ts)
{
KVField found = KVField.Invalid;
if (mv)
{
FindFieldFromMvccRaw(id, vp, vs, ts, ref found);
}
else
{
FindField(id, (byte *)vp.ToPointer(), (uint)vs, ref found);
}
return(found.IsInvalid() ? null : found.GetByte());
}
private static unsafe void FindField(ushort id, byte *dataPtr, uint dataSize, ref KVField found)
{
byte *cur = dataPtr;
byte *end = cur + dataSize;
while (cur < end)
{
found.ReadFrom(&cur);
if (found.Id == id)
{
break;
}
cur += found.DataSize;
}
}
