//+------------------------------------------------------------------+
//| Simple memory-mapped file simulation for large datasets          |
//+------------------------------------------------------------------+
class CDatasetMapper
{
private:
   int m_fileHandle;
   string m_fileName;
   int m_recordSize;
   int m_recordCount;
   
   // Cache for recently accessed records
   double m_cache[];
   int m_cacheSize;
   int m_cacheStart;
   
public:
   // Constructor
   CDatasetMapper(string fileName, int recordSize, int cacheSize = 1000)
   {
      m_fileName = fileName;
      m_recordSize = recordSize;
      m_cacheSize = cacheSize;
      
      // Open or create the file
      m_fileHandle = FileOpen(m_fileName, FILE_READ|FILE_WRITE|FILE_BIN);
      
      if(m_fileHandle != INVALID_HANDLE)
      {
         // Get file size and calculate record count
         m_recordCount = (int)(FileSize(m_fileHandle) / (m_recordSize * sizeof(double)));
         
         // Initialize cache
         ArrayResize(m_cache, m_cacheSize * m_recordSize);
         m_cacheStart = -1;  // Cache is initially empty
         
         Print("Dataset mapper initialized: ", m_fileName, ", ", m_recordCount, " records");
      }
      else
      {
         Print("Failed to open dataset file: ", m_fileName, ", error: ", GetLastError());
      }
   }
   
   // Add a record to the dataset
   bool AddRecord(double &record[])
   {
      if(m_fileHandle == INVALID_HANDLE || ArraySize(record) != m_recordSize)
         return false;
         
      // Seek to the end of the file
      FileSeek(m_fileHandle, 0, SEEK_END);
      
      // Write the record
      int written = FileWriteArray(m_fileHandle, record, 0, m_recordSize);
      
      if(written == m_recordSize)
      {
         m_recordCount++;
         return true;
      }
      
      return false;
   }
   
   // Get a record from the dataset
   bool GetRecord(int index, double &record[])
   {
      if(m_fileHandle == INVALID_HANDLE || index < 0 || index >= m_recordCount)
         return false;
         
      // Check if the record is in cache
      if(index >= m_cacheStart && index < m_cacheStart + m_cacheSize)
      {
         // Copy from cache
         int cacheOffset = (index - m_cacheStart) * m_recordSize;
         ArrayCopy(record, m_cache, 0, cacheOffset, m_recordSize);
         return true;
      }
      
      // Load a new cache block
      m_cacheStart = (index / m_cacheSize) * m_cacheSize;
      int fileOffset = m_cacheStart * m_recordSize * sizeof(double);
      
      // Seek to the start of the cache block
      FileSeek(m_fileHandle, fileOffset, SEEK_SET);
      
      // Read into cache
      int read = FileReadArray(m_fileHandle, m_cache, 0, m_cacheSize * m_recordSize);
      
      if(read > 0)
      {
         // Copy from cache
         int cacheOffset = (index - m_cacheStart) * m_recordSize;
         ArrayCopy(record, m_cache, 0, cacheOffset, m_recordSize);
         return true;
      }
      
      return false;
   }
   
   // Get record count
   int GetRecordCount()
   {
      return m_recordCount;
   }
   
   // Destructor
   ~CDatasetMapper()
   {
      if(m_fileHandle != INVALID_HANDLE)
      {
         FileClose(m_fileHandle);
         Print("Dataset mapper closed: ", m_fileName);
      }
   }
};