using System;

using System.IO;

namespace SourceGit.Models

{

public class BinaryFile : IDisposable

{

public long Size

{

get => _size;

}

public BinaryFile(string file, bool needDeleteFile = false)

{

_filePath = file;

_needDeleteFile = needDeleteFile;

if (File.Exists(_filePath))

{

_size = new FileInfo(_filePath).Length;

_reader = new FileStream(_filePath, FileMode.Open, FileAccess.Read, FileShare.Read, BUFFER_SIZE, FileOptions.RandomAccess);

_readedStart = 0;

_readedEnd = Math.Min(_size, BUFFER_SIZE);

if (_size > 0)

{

_reader.Seek(_readedStart, SeekOrigin.Begin);

_reader.ReadExactly(_buffer, 0, (int)_readedEnd);

}

}

}

public void Dispose()

{

_reader?.Dispose();

_reader = null;

if (_needDeleteFile && File.Exists(_filePath))

File.Delete(_filePath);

}

public ArraySegment<byte> Read(long offset, long length)

{

if (_reader == null || _size == 0 || offset >= _size)

return Array.Empty<byte>();

if (length > 8192)

length = 8192;

if (offset + length > _size)

length = _size - offset;

if (_readedStart <= offset && _readedEnd >= offset + length)

return new ArraySegment<byte>(_buffer, (int)(offset - _readedStart), (int)length);

_readedStart = (Math.Max(0, offset - 2048) / 1024) * 1024;

_readedEnd = Math.Min(_readedStart + BUFFER_SIZE, _size);

_reader.Seek(_readedStart, SeekOrigin.Begin);

_reader.ReadExactly(_buffer, 0, (int)(_readedEnd - _readedStart));

return new ArraySegment<byte>(_buffer, (int)(offset - _readedStart), (int)length);

}

private const int BUFFER_SIZE = 16384;

private string _filePath = string.Empty;

private bool _needDeleteFile = false;

private FileStream _reader = null;

private long _size = 0;

private long _readedStart = 0;

private long _readedEnd = 0;

private byte[] _buffer = new byte[BUFFER_SIZE];

}

}