Bitmap.cs

using System;
using System.IO;

namespace NewProject
{
    public class FileSystemBitmap
    {
        private readonly byte[] bitmap;
        private readonly int totalBlocks;

        public FileSystemBitmap(long totalBlocks)
        {
            this.totalBlocks = (int)totalBlocks;

            int sizeInBytes = (int)Math.Ceiling(this.totalBlocks / 8.0);
            bitmap = new byte[sizeInBytes];
        }

        public void LoadBitmap(FileStream fs, int blockSize)
        {
            fs.Seek(1L * blockSize, SeekOrigin.Begin);
            fs.Read(bitmap, 0, bitmap.Length);
        }

        public bool IsOccupied(int blockIndex)
        {
            // извън диска -> третираме като "заето" (невалидно)
            if (blockIndex < 0 || blockIndex >= totalBlocks) return true;

            int byteIndex = blockIndex / 8;
            int bitOffset = blockIndex % 8;

            return (bitmap[byteIndex] & (1 << bitOffset)) != 0;
        }

        public void OccupyBlock(int blockIndex)
        {
            if (blockIndex < 0 || blockIndex >= totalBlocks) return;

            int byteIndex = blockIndex / 8;
            int bitOffset = blockIndex % 8;

            bitmap[byteIndex] |= (byte)(1 << bitOffset);
        }

        public void FreeBlock(int blockIndex)
        {
            if (blockIndex < 0 || blockIndex >= totalBlocks) return;

            int byteIndex = blockIndex / 8;
            int bitOffset = blockIndex % 8;

            bitmap[byteIndex] &= (byte)~(1 << bitOffset);
        }

        public void WriteBitmap(FileStream fs, int blockSize)
        {
            fs.Seek(1L * blockSize, SeekOrigin.Begin);

            // изчистваме целия блок 1 (както ти беше)
            byte[] empty = new byte[blockSize];
            fs.Write(empty, 0, empty.Length);

            fs.Seek(1L * blockSize, SeekOrigin.Begin);
            fs.Write(bitmap, 0, bitmap.Length);
            fs.Flush();
        }

        public int FindFirstFreeBlock()
        {
            // ТЪРСИМ САМО в [0..totalBlocks-1]
            for (int block = 0; block < totalBlocks; block++)
            {
                if (!IsOccupied(block))
                    return block;
            }
            return -1;
        }
    }
}