/// <summary>
/// Serialize the block into the given stream.
/// </summary>
/// <param name="stream">Stream to write to.</param>
/// <param name="serializer"></param>
public static async Task <BlockHandle> WriteBlockAsync(Stream stream, Action <BinaryWriter> serializer)
{
using (var memoryStream = new MemoryStream(DefaultMemoryStreamSize))
using (var memoryWriter = new BinaryWriter(memoryStream))
{
// Serialize the table section.
serializer.Invoke(memoryWriter);
var blockSize = checked ((int)memoryStream.Position);
// Calculate the checksum.
var checksum = CRC64.ToCRC64(memoryStream.GetBuffer(), 0, blockSize);
// Get the position and size of this section within the stream.
var sectionHandle = new BlockHandle(stream.Position, blockSize);
// Write the checksum.
memoryWriter.Write(checksum);
var blockSizeWithChecksum = checked ((int)memoryStream.Position);
//Utility.Assert((blockSizeWithChecksum - blockSize) == 8, "unexpected block size.");
// Write the buffer and checksum to the stream.
await stream.WriteAsync(memoryStream.GetBuffer(), 0, blockSizeWithChecksum).ConfigureAwait(false);
return(sectionHandle);
}
}
/// <summary>
/// Deserialize a block from the given stream.
/// </summary>
/// <param name="stream">Stream to read from.</param>
/// <param name="blockHandle"></param>
/// <param name="deserializer"></param>
/// <returns>The block read from the stream.</returns>
public static async Task <TBlock> ReadBlockAsync <TBlock>(
Stream stream,
BlockHandle blockHandle,
Func <BinaryReader, BlockHandle, TBlock> deserializer)
{
// Data validation.
if (blockHandle.Offset < 0)
{
throw new InvalidDataException(string.Format(CultureInfo.CurrentCulture, SR.Error_FileBlock_Corrupt, SR.Error_Negative_StreamOffset));
}
if (blockHandle.Size < 0)
{
throw new InvalidDataException(string.Format(CultureInfo.CurrentCulture, SR.Error_FileBlock_Corrupt, SR.Error_Negative_BlockSize));
}
if (blockHandle.EndOffset + sizeof(ulong) > stream.Length)
{
throw new InvalidDataException(string.Format(CultureInfo.CurrentCulture, SR.Error_FileBlock_Corrupt, SR.Error_Block_Beyond_Stream));
}
// Move the stream to the block's position within the stream.
stream.Position = blockHandle.Offset;
var blockSize = checked ((int)blockHandle.Size);
var blockSizeWithChecksum = blockSize + sizeof(ulong);
// Read the bytes for the block, to calculate the checksum.
var blockBytes = new byte[blockSizeWithChecksum];
await stream.ReadAsync(blockBytes, 0, blockBytes.Length).ConfigureAwait(false);
// Calculate the checksum.
var blockChecksum = CRC64.ToCRC64(blockBytes, 0, blockSize);
// Read the actual checksum (checksum is after the block bytes).
var checksum = BitConverter.ToUInt64(blockBytes, blockSize);
// Verify the checksum.
if (checksum != blockChecksum)
{
throw new InvalidDataException(string.Format(CultureInfo.CurrentCulture, SR.Error_FileBlock_Corrupt, SR.Error_Checksum_Mismatch));
}
// Deserialize the actual file block.
using (var memoryStream = new MemoryStream(blockBytes, 0, blockSize, writable: false))
using (var memoryReader = new BinaryReader(memoryStream))
{
return(deserializer.Invoke(memoryReader, new BlockHandle(0, blockHandle.Size)));
}
}
