public unsafe void Can_seek_and_read_from_chunked_mmap_file(int totalSize, int chunkSize, int seed)
{
var random = new Random(seed);
var buffer = new byte[totalSize];
random.NextBytes(buffer);
fixed(byte *ptr = buffer)
{
var ptrSize = new List <PtrSize>();
var numberOfBuffers = totalSize / chunkSize + (totalSize % chunkSize != 0 ? 1 : 0);
for (int i = 0; i < numberOfBuffers; i++)
{
ptrSize.Add(PtrSize.Create(
ptr + (i * chunkSize),
i == numberOfBuffers - 1 ? totalSize % chunkSize : chunkSize));
}
var sut = new ChunkedMmapStream(ptrSize.ToArray(), chunkSize);
// read all bytes
var allBytes = sut.ReadEntireBlock(totalSize);
Assert.Equal(buffer, allBytes);
// seek to beginning, read to end
sut.Position = 0;
allBytes = sut.ReadData();
Assert.Equal(buffer, allBytes);
// read all bytes one by one
sut.Position = 0;
for (int i = 0; i < allBytes.Length; i++)
{
Assert.Equal(allBytes[i], sut.ReadByte());
}
// random seeks
for (int i = 0; i < 1000; i++)
{
var pos = random.Next(0, totalSize - 1);
sut.Position = pos;
var result = new byte[Math.Min(totalSize - pos, random.Next(1, totalSize))];
sut.ReadEntireBlock(result, 0, result.Length);
Assert.Equal(buffer.Skip(pos).Take(result.Length).ToArray(), result);
}
}
}
private void OpenInternal()
{
var fileTree = _currentTransaction.Value.ReadTree(_name);
if (fileTree == null)
{
throw new FileNotFoundException("Could not find index input", _name);
}
var numberOfChunks = fileTree.State.NumberOfEntries;
_ptrs = new PtrSize[numberOfChunks];
int index = 0;
using (var it = fileTree.Iterate(prefetch: false))
{
if (it.Seek(Slices.BeforeAllKeys) == false)
{
throw new InvalidDataException("Could not seek to any chunk of this file");
}
do
{
var readResult = fileTree.Read(it.CurrentKey);
_ptrs[index] = PtrSize.Create(readResult.Reader.Base, readResult.Reader.Length);
index++;
} while (it.MoveNext());
}
if (numberOfChunks != index)
{
throw new InvalidDataException($"Read invalid number of file chunks. Expected {numberOfChunks}, read {index}.");
}
_stream = new ChunkedMmapStream(_ptrs, VoronIndexOutput.MaxFileChunkSize);
}