void ReadFilter(Slice filterHandleValue)
{
Slice v = filterHandleValue;
BlockHandle filterHandle = new BlockHandle();
if (!filterHandle.DecodeFrom(ref v).IsOk)
{
return;
}
// We might want to unify with ReadBlock() if we start
// requiring checksum verification in Table::Open.
ReadOptions opt = ReadOptions.Default;
BlockContents block;
if (!FormatHelper.ReadBlock(rep_.File, opt, filterHandle, out block).IsOk)
{
return;
}
if (block.HeapAllocated)
{
rep_.FilterData = block.Data.Data; // Will need to delete later
}
rep_.Filter = new FilterBlockReader(rep_.Options.FilterPolicy, block.Data);
}
private static Iterator BlockReader(object arg, ReadOptions options, Slice indexValue)
{
Table table = (Table)arg;
Cache blockCache = table.rep_.Options.BlockCache;
Block block = null;
Cache.Handle cacheHandle = null;
BlockHandle handle = new BlockHandle();
Slice input = indexValue;
Status s = handle.DecodeFrom(ref input);
// We intentionally allow extra stuff in index_value so that we
// can add more features in the future.
if (s.IsOk)
{
BlockContents contents;
if (blockCache != null)
{
ByteArrayPointer cacheKeyBuffer = new ByteArrayPointer(16);
Coding.EncodeFixed64(cacheKeyBuffer, table.rep_.CacheId);
Coding.EncodeFixed64(cacheKeyBuffer + 8, handle.Offset);
Slice key = new Slice(cacheKeyBuffer, cacheKeyBuffer.Length);
cacheHandle = blockCache.Lookup(key);
if (cacheHandle != null)
{
block = (Block)(blockCache.Value(cacheHandle));
}
else
{
s = FormatHelper.ReadBlock(table.rep_.File, options, handle, out contents);
if (s.IsOk)
{
block = new Block(contents);
if (contents.Cachable && options.FillCache)
{
cacheHandle = blockCache.Insert(key, block, block.Size);
}
}
}
}
else
{
s = FormatHelper.ReadBlock(table.rep_.File, options, handle, out contents);
if (s.IsOk)
{
block = new Block(contents);
}
}
}
Iterator iter;
if (block != null)
{
iter = block.NewIterator(table.rep_.Options.Comparator);
if (cacheHandle != null)
{
iter.RegisterCleanup(ReleaseBlock, blockCache, cacheHandle);
}
}
else
{
iter = Iterator.NewErrorIterator(s);
}
return iter;
}
/// <summary>
/// Given a key, return an approximate byte offset in the file where
/// the data for that key begins (or would begin if the key were
/// present in the file). The returned value is in terms of file
/// bytes, and so includes effects like compression of the underlying data.
/// E.g., the approximate offset of the last key in the table will
/// be close to the file length.
/// </summary>
public UInt64 ApproximateOffsetOf(Slice key)
{
Iterator index_iter =
rep_.IndexBlock.NewIterator(rep_.Options.Comparator);
index_iter.Seek(key);
UInt64 result;
if (index_iter.Valid)
{
BlockHandle handle = new BlockHandle();
Slice input = index_iter.Value;
Status s = handle.DecodeFrom(ref input);
if (s.IsOk)
{
result = handle.Offset;
}
else
{
// Strange: we can't decode the block handle in the index block.
// We'll just return the offset of the metaindex block, which is
// close to the whole file size for this case.
result = rep_.MetaindexHandle.Offset;
}
}
else
{
// key is past the last key in the file. Approximate the offset
// by returning the offset of the metaindex block (which is
// right near the end of the file).
result = rep_.MetaindexHandle.Offset;
}
return result;
}
internal Status InternalGet(
ReadOptions options, Slice k,
object arg, HandleResultDelegate saver)
{
Status s = new Status();
Iterator iiter = rep_.IndexBlock.NewIterator(rep_.Options.Comparator);
iiter.Seek(k);
if (iiter.Valid)
{
Slice handle_value = iiter.Value;
FilterBlockReader filter = rep_.Filter;
BlockHandle handle = new BlockHandle();
if (filter != null &&
handle.DecodeFrom(ref handle_value).IsOk &&
!filter.KeyMayMatch(handle.Offset, k))
{
// Not found
}
else
{
Slice tempHandle = iiter.Value;
Iterator blockIter = BlockReader(this, options, iiter.Value);
blockIter.Seek(k);
if (blockIter.Valid)
{
saver(arg, blockIter.Key, blockIter.Value);
}
s = blockIter.Status;
}
}
if (s.IsOk)
{
s = iiter.Status;
}
return s;
}
public static Status ReadBlock(RandomAccessFile file, ReadOptions options, BlockHandle handle, out BlockContents result)
{
result.Data = new Slice();
result.Cachable = false;
result.HeapAllocated = false;
// Read the block contents as well as the type/crc footer.
// See table_builder.cc for the code that built this structure.
int n = (int)handle.Size;
ByteArrayPointer buf = new ByteArrayPointer(n + kBlockTrailerSize);
Slice contents;
Status s = file.Read(handle.Offset, n + kBlockTrailerSize, out contents, buf);
if (!s.IsOk)
{
return s;
}
if (contents.Size != n + kBlockTrailerSize)
{
return Status.Corruption("truncated block read");
}
// Check the crc of the type and the block contents
ByteArrayPointer data = contents.Data; // Pointer to where Read put the data
if (options.VerifyChecksums)
{
// const uint32_t crc = crc32c::Unmask(DecodeFixed32(data + n + 1));
//const uint32_t actual = crc32c::Value(data, n + 1);
//if (actual != crc) {
// delete[] buf;
// s = Status::Corruption("block checksum mismatch");
// return s;
//}
throw new NotSupportedException("CRC is not supported yet");
}
switch ((CompressionType)data[n])
{
case CompressionType.kNoCompression:
if (data != buf)
{
// File implementation gave us pointer to some other data.
// Use it directly under the assumption that it will be live
// while the file is open.
result.Data = new Slice(data, n);
result.HeapAllocated = false;
result.Cachable = false; // Do not double-cache
}
else
{
result.Data = new Slice(buf, n);
result.HeapAllocated = true;
result.Cachable = true;
}
// Ok
break;
case CompressionType.kSnappyCompression:
throw new NotSupportedException("snappy not supported");
// {
// int ulength = 0;
// if (!port::Snappy_GetUncompressedLength(data, n, &ulength)) {
// delete[] buf;
// return Status::Corruption("corrupted compressed block contents");
// }
// char* ubuf = new char[ulength];
// if (!port::Snappy_Uncompress(data, n, ubuf)) {
// delete[] buf;
// delete[] ubuf;
// return Status::Corruption("corrupted compressed block contents");
// }
// delete[] buf;
// result->data = Slice(ubuf, ulength);
// result->heap_allocated = true;
// result->cachable = true;
// break;
//}
default:
return Status.Corruption("bad block type");
}
return Status.OK;
}
