/// <inheritdoc />
public int Optimize()
{
return(_storageOperationLocker.GlobalLock(() =>
{
_logger.Information("Start optimization process");
var dataItemsMoved = 0;
var initialDataSize = _filesystemDescriptorAccessor.Value.FilesDataLength;
// 1. Get all descriptors
var descriptors = _entryDescriptorRepository.ReadAll();
_logger.Information($"There is {descriptors.Count} descriptors found");
// 2. Sort by offset, filter zero-sized data because it is not necessary to move empty data
var orderedDescriptors = descriptors
.Where(descriptor => descriptor.Value.DataLength > 0)
.OrderBy(descriptor => descriptor.Value.DataOffset)
.ToArray();
// 3a. Move first
if (orderedDescriptors.Length > 0 && orderedDescriptors[0].Value.DataOffset != 0)
{
ProcessGap(orderedDescriptors, 0, 0);
dataItemsMoved++;
}
// 3b. Iterate over all descriptors to find gaps
for (var i = 0; i < orderedDescriptors.Length - 1; i++)
{
var current = orderedDescriptors[i];
var next = orderedDescriptors[i + 1];
var currentEnd = current.Value.DataOffset + current.Value.DataLength;
var nextStart = next.Value.DataOffset;
// 4. Found a gap, write data of second right after first
if (nextStart - currentEnd > 0)
{
ProcessGap(orderedDescriptors, i + 1, currentEnd);
dataItemsMoved++;
}
}
// 4. Update new size of file data in descriptor.
var allEntriesDataLength = orderedDescriptors.Select(descriptor => descriptor.Value.DataLength).Sum();
_filesystemDescriptorAccessor.Update(filesDataLengthUpdater: _ => allEntriesDataLength);
var bytesOptimized = initialDataSize - allEntriesDataLength;
_logger.Information(
$"Optimization process completed, {dataItemsMoved} items moved, {bytesOptimized} bytes optimized");
return bytesOptimized;
}));
}
private bool TryFindGap(int size, out Cursor cursor)
{
_logger.Information($"Trying to find existing gap of {size} bytes");
cursor = default;
// 1. Get all descriptors
var descriptors = _entryDescriptorRepository.ReadAll();
// 2. Sort by offset
var orderedDescriptors = descriptors
.Where(descriptor => descriptor.Value.DataLength > 0)
.OrderBy(descriptor => descriptor.Value.DataOffset).ToArray();
// 3. Check first gap
if (orderedDescriptors.Length > 0 && orderedDescriptors[0].Value.DataOffset >= size)
{
// Start of storage is our gap
cursor = new Cursor(0, SeekOrigin.Begin);
_logger.Information($"Found gap of size {size} bytes at offset {cursor.Offset}");
return(true);
}
// 4. Check other gaps
// We should find minimal gap but bigger or equals in size
var minimalGapSize = int.MaxValue;
var minimalGapCursor = default(Cursor);
var found = false;
for (var i = 0; i < orderedDescriptors.Length - 1; i++)
{
var current = orderedDescriptors[i];
var next = orderedDescriptors[i + 1];
var currentEnd = current.Value.DataOffset + current.Value.DataLength;
var nextStart = next.Value.DataOffset;
// If we have gap with specific size or between files
var currentGapSize = nextStart - currentEnd;
if (currentGapSize >= size && currentGapSize < minimalGapSize)
{
minimalGapSize = currentGapSize;
minimalGapCursor = new Cursor(currentEnd, SeekOrigin.Begin);
// We should know that we found at least one correct gap
found = true;
}
}
if (found)
{
cursor = minimalGapCursor;
_logger.Information($"Found gap of size {size} bytes at offset {cursor.Offset}");
return(true);
}
_logger.Information($"Gap of size {size} bytes not found");
return(false);
}