/// <summary>
/// Creates block and reads its contents from index file
/// </summary>
/// <param name="offset">Offset of block in index file</param>
/// <param name="length">Length of block in index file</param>
/// <returns>New block instance</returns>
/// <exception cref="IOException">not enough data in index file to fill the block</exception>
public static T Read <T>(this IIndexFileBlockProvider blockProvider, long offset, int length) where T : ISerializableIndexData, new()
{
var result = new T();
blockProvider.Read(result, offset, length);
return(result);
}
/// <summary>
/// Adds metadata of written stream to index file
/// </summary>
/// <param name="streamMetadata">stream metadata to be added to index</param>
/// <exception cref="System.ArgumentException">An element with the same key already exists</exception>
public void Set(StreamMetadata streamMetadata)
{
streamMetadata.ThrowIfNull(nameof(streamMetadata));
var key = streamMetadata.Key;
if (Contains(key))
{
throw new ArgumentException(nameof(key));
}
var blockInfo = header.Get(key);
var block = new IndexBlock();
var oldLength = 0;
if (blockInfo.Offset > 0)
{
if (blockInfo.Length + streamMetadata.SerializedLength < MaxIndexBlockLength)
{
blockProvider.Read(block, blockInfo.Offset, blockInfo.Length);
oldLength = blockInfo.Length;
}
else
{
block = new IndexBlock(blockInfo);
}
}
block.Add(streamMetadata);
var offset = blockProvider.Write(block);
var length = block.SerializedLength;
blockInfo = new BlockInfo()
{
Offset = offset, Length = length
};
header.Set(key, blockInfo);
header.IndexWrittenLength += length - oldLength;
header.StorageWrittenLength += streamMetadata.Length;
}
/// <summary>
/// Initializes new instance of <see cref="StorageFileReader"/> class.
/// </summary>
/// <param name="streamFactory"><see cref="IStreamFactory"/> object used to create file streams</param>
/// <exception cref="ArgumentNullException">factory is null</exception>
public BinaryStorageIndex(IIndexFileBlockProvider blockProvider)
{
this.blockProvider = blockProvider.ThrowIfNull(nameof(blockProvider));
if (blockProvider.Length == 0)
{
header = new IndexHeader();
blockProvider.Write(header, 0);
}
else
{
header = blockProvider.Read <IndexHeader>(0, IndexHeader.FullHeaderSize);
}
}