|
public AccessRangeUncached ( long offset, uint size, MemoryMappedFileAccess access = MemoryMappedFileAccess.ReadWrite ) : |
||
| offset | long | The offset within the stream, relative to the end of the stream header. |
| size | uint | The size of the range to access, in bytes. |
| access | MemoryMappedFileAccess | |
| return | ||
private void EnsureFreelistExists()
{
var pHeader = (BTreeHeader *)_HeaderRange.Pointer;
if (EnableFreelist)
{
long oldOffset = 0;
if (pHeader->FreelistIndexOffset == 0)
{
uint size = FreelistIndex.Size;
long?offset = AllocateDataSpace(ref size);
if (!offset.HasValue)
{
throw new OutOfMemoryException("Unable to allocate space for freelist index in data stream.");
}
oldOffset = Interlocked.Exchange(ref pHeader->FreelistIndexOffset, offset.Value);
}
_FreelistIndexRange = DataStream.AccessRangeUncached(pHeader->FreelistIndexOffset, FreelistIndex.Size, MemoryMappedFileAccess.ReadWrite);
Native.memset(_FreelistIndexRange.Pointer, 0, new UIntPtr(FreelistIndex.Size / 4));
if (oldOffset != 0)
{
FreelistPut(oldOffset, FreelistIndex.Size);
}
}
else
{
pHeader->FreelistIndexOffset = 0;
}
}
public BTree(StreamSource storage, string prefix)
{
Storage = storage;
Prefix = prefix;
IndexStream = Storage.Open(prefix + "index");
KeyStream = Storage.Open(prefix + "keys");
DataStream = Storage.Open(prefix + "data");
VersionCheck(IndexStream);
VersionCheck(KeyStream);
VersionCheck(DataStream);
bool needInit = IndexStream.Length < BTreeHeader.Size;
IndexStream.LengthChanging += IndexStream_LengthChanging;
IndexStream.LengthChanged += IndexStream_LengthChanged;
DataStream.LengthChanging += DataStream_LengthChanging;
DataStream.LengthChanged += DataStream_LengthChanged;
_GetKeyOfEntry = ReadKey;
_HeaderRange = IndexStream.AccessRangeUncached(0, BTreeHeader.Size);
if (needInit)
{
InitializeBTree();
}
_FreelistBucketLocks = new object[FreelistIndex.BucketCount];
for (int i = 0; i < _FreelistBucketLocks.Length; i++)
{
_FreelistBucketLocks[i] = new object();
}
EnsureFreelistExists();
}
void IndexStream_LengthChanged(object sender, EventArgs e)
{
_HeaderRange = IndexStream.AccessRangeUncached(0, BTreeHeader.Size);
}