Implement manual border refreshing for BitString (fixes #20)

[konard]

🎯 Summary

This pull request implements the ability to manually control border refreshing in the BitString class, addressing issue #20. Users can now choose when to refresh borders (minimum and maximum non-zero words) for performance optimization.

📋 Issue Reference

Fixes #20

🚀 Key Features

• AutomaticBorderRefreshing property: Enables/disables automatic border updates on every bit change
• RefreshBorders() method: Allows manual border recalculation when needed
• Factory methods: Create() methods for creating BitString instances with custom border behavior
• Backward compatibility: Automatic refreshing remains enabled by default

🔧 Implementation Details

Core Changes

1. BitString.cs:

   • Added _automaticBorderRefreshing field and property
   • Modified RefreshBordersByWord() to respect the automatic refreshing setting
   • Implemented comprehensive RefreshBorders() method that scans the entire array
   • Added static factory methods for creating BitString instances with custom behavior
   • Updated constructors to preserve automatic refreshing settings in copy operations

2. BitStringTests.cs:

   • Added 6 comprehensive unit tests covering all aspects of the new functionality
   • Tests for property behavior, factory methods, manual refresh, and behavioral comparisons
   • Ensures backward compatibility and correct border calculation

Performance Benefits

When automatic border refreshing is disabled, users can:

• Perform bulk bit operations without repeated border calculations
• Call RefreshBorders() once at the end for optimal performance
• Maintain accurate borders when needed while avoiding unnecessary overhead

✅ Testing

All tests pass successfully:

• ✅ 19/19 existing BitString tests (no regressions)
• ✅ 6/6 new tests for manual border refresh functionality
• ✅ Backward compatibility verified

📖 Usage Examples

Default Behavior (Backward Compatible)

var bitString = new BitString(1000);  // AutomaticBorderRefreshing = true
bitString.Set(100, true);             // Borders updated automatically

Manual Border Refreshing for Performance

var bitString = BitString.Create(1000, false);  // Disable automatic refreshing
// Perform bulk operations without border overhead
for (int i = 0; i < 1000; i++)
{
    bitString.Set(i, someValue);  // No border updates
}
bitString.RefreshBorders();  // Update borders once when needed

Runtime Control

var bitString = new BitString(1000);
bitString.AutomaticBorderRefreshing = false;  // Disable for bulk operations
// ... perform operations ...
bitString.RefreshBorders();  // Manual refresh
bitString.AutomaticBorderRefreshing = true;   // Re-enable automatic updates

🔬 Technical Notes

• The RefreshBorders() method performs a complete array scan to find accurate borders
• When automatic refreshing is disabled, methods like GetFirstSetBitIndex() rely on cached border values
• The implementation maintains all existing behavior when automatic refreshing is enabled
• Border states are correctly preserved during copy operations

🤖 Generated with Claude Code