/// <summary>
/// Attempt to open the table that is stored in bytes [0..file_size)
/// of "file", and read the metadata entries necessary to allow
/// retrieving data from the table.
///
/// If successful, returns ok and sets "*table" to the newly opened
/// table. The client should delete "*table" when no longer needed.
/// If there was an error while initializing the table, sets "*table"
/// to NULL and returns a non-ok status. Does not take ownership of
/// "*source", but the client must ensure that "source" remains live
/// for the duration of the returned table's lifetime.
///
/// *file must remain live while this Table is in use.
/// </summary>
public static Status Open(Options options, RandomAccessFile file, UInt64 size, out Table table)
{
table = null;
if (size < Footer.kEncodedLength)
{
return Status.InvalidArgument("file is too short to be an sstable");
}
ByteArrayPointer footerSpace = new ByteArrayPointer(Footer.kEncodedLength);
Slice footerInput;
Status s = file.Read(size - Footer.kEncodedLength, Footer.kEncodedLength, out footerInput, footerSpace);
if (!s.IsOk) return s;
Footer footer = new Footer();
s = footer.DecodeFrom(ref footerInput);
if (!s.IsOk) return s;
// Read the index block
BlockContents contents;
Block indexBlock = null;
if (s.IsOk)
{
s = FormatHelper.ReadBlock(file, ReadOptions.Default, footer.IndexHandle, out contents);
if (s.IsOk)
{
indexBlock = new Block(contents);
}
}
if (s.IsOk)
{
// We've successfully read the footer and the index block: we're
// ready to serve requests.
Rep rep = new Rep();
rep.Options = options;
rep.File = file;
rep.MetaindexHandle = footer.MetaindexHandle;
rep.IndexBlock = indexBlock;
rep.CacheId = (options.BlockCache != null ? options.BlockCache.NewId() : 0);
rep.FilterData = ByteArrayPointer.Null;
rep.Filter = null;
table = new Table(rep);
table.ReadMeta(footer);
}
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;
}