Save Operations Data Flow

Smart save algorithm with fast path optimization - 100x faster for modifications-only

📋 Table of Contents

Overview
Decision Tree
Fast Path: Modifications Only
Full Rebuild: Insertions/Deletions
Async Save with Progress
Error Handling

📖 Overview

HexEditor V2 uses a smart save algorithm that chooses between two paths based on edit type:

Fast Path: For modifications only (no length change) → 100x faster
Full Rebuild: For insertions/deletions (length change) → Complete file reconstruction

🌳 Decision Tree

Algorithm Selection Flowchart

flowchart TD
    Start([Save Requested]) --> Check{Has Edits?}
    Check -->|No| NoOp[No operation needed]
    Check -->|Yes| CheckType{Edit Type?}

    CheckType -->|Only Modifications| FastPath[Fast Path]
    CheckType -->|Has Insertions/Deletions| FullRebuild[Full Rebuild]

    FastPath --> FastSeek[Seek to positions]
    FastSeek --> FastWrite[Write modified bytes]
    FastWrite --> FastFlush[Flush to disk]
    FastFlush --> FastDone[Done: ~1ms]

    FullRebuild --> CreateTemp[Create temp file]
    CreateTemp --> IterateVirtual[Iterate virtual positions]
    IterateVirtual --> WriteVirtual[Write bytes in virtual order]
    WriteVirtual --> Replace[Replace original with temp]
    Replace --> Reopen[Reopen file]
    Reopen --> FullDone[Done: ~100ms]

    NoOp --> End([Complete])
    FastDone --> End
    FullDone --> End

    style Start fill:#e1f5ff
    style FastPath fill:#c8e6c9
    style FullRebuild fill:#ffccbc
    style End fill:#fff9c4

Decision Logic

public void Save()
{
    if (!HasChanges)
    {
        // No changes: no-op
        return;
    }

    if (_editsManager.HasInsertions || _editsManager.HasDeletions)
    {
        // Full rebuild path
        SaveWithRebuild();
    }
    else
    {
        // Fast path (modifications only)
        SaveFastPath();
    }
}

⚡ Fast Path: Modifications Only

Sequence Diagram

sequenceDiagram
    actor User
    participant HE as HexEditor
    participant VM as ViewModel
    participant BP as ByteProvider
    participant EM as EditsManager
    participant FP as FileProvider
    participant FS as FileSystem

    User->>HE: Save()
    HE->>VM: Save()
    VM->>BP: Save()

    BP->>EM: HasInsertions || HasDeletions?
    EM-->>BP: false (modifications only)

    BP->>EM: GetModifications()
    activate EM
    EM-->>BP: Dictionary<long, byte>
    deactivate EM

    Note over BP: Fast path selected

    loop For each modification
        BP->>FP: Seek(physicalPosition)
        activate FP
        FP->>FS: Seek(position)
        FS-->>FP: OK
        FP-->>BP: Position set

        BP->>FP: WriteByte(value)
        FP->>FS: Write(value)
        FS-->>FP: Written
        FP-->>BP: Byte written
        deactivate FP
    end

    BP->>FP: Flush()
    activate FP
    FP->>FS: Flush()
    FS-->>FP: Flushed
    FP-->>BP: Flushed
    deactivate FP

    BP->>EM: ClearModifications()
    activate EM
    EM-->>BP: Cleared
    deactivate EM

    BP-->>VM: Save complete
    VM-->>HE: Saved
    HE->>User: File saved (fast)

Fast Path Implementation

private void SaveFastPath()
{
    // Get all modifications
    var modifications = _editsManager.GetModifications();

    Console.WriteLine($"Fast path: {modifications.Count} modifications");

    // Apply each modification
    foreach (var (position, value) in modifications)
    {
        // Seek to position
        _fileProvider.Seek(position);

        // Write byte
        _fileProvider.WriteByte(value);
    }

    // Flush to disk
    _fileProvider.Flush();

    // Clear modifications (now saved)
    _editsManager.ClearModifications();

    // Raise event
    OnFileSaved();
}

Performance Characteristics

File Size	Modifications	Fast Path Time	Full Rebuild Time	Speedup
1 MB	10	<1ms	100ms	100x
10 MB	100	5ms	500ms	100x
100 MB	1,000	50ms	5000ms	100x

Key Insight: Time is proportional to modification count, not file size!

🏗️ Full Rebuild: Insertions/Deletions

Sequence Diagram

sequenceDiagram
    actor User
    participant HE as HexEditor
    participant VM as ViewModel
    participant BP as ByteProvider
    participant EM as EditsManager
    participant PM as PositionMapper
    participant FP as FileProvider
    participant FS as FileSystem

    User->>HE: Save()
    HE->>VM: Save()
    VM->>BP: Save()

    BP->>EM: HasInsertions || HasDeletions?
    EM-->>BP: true (has structural changes)

    Note over BP: Full rebuild selected

    BP->>FP: CreateTempFile()
    activate FP
    FP->>FS: Create("temp.tmp")
    FS-->>FP: Temp stream
    FP-->>BP: Temp file created
    deactivate FP

    BP->>BP: Calculate virtual length
    Note over BP: VirtualLength = Original + Insertions - Deletions

    loop For each virtual position
        BP->>EM: IsInsertion(virtualPos)?
        activate EM

        alt Is insertion
            EM-->>BP: true, value=insertedByte
            BP->>FP: WriteByte(temp, insertedByte)
            activate FP
            FP->>FS: Write(insertedByte)
            FS-->>FP: Written
            FP-->>BP: Written
            deactivate FP

        else Not insertion
            EM-->>BP: false
            deactivate EM

            BP->>PM: VirtualToPhysical(virtualPos)
            activate PM
            PM-->>BP: physicalPosition
            deactivate PM

            BP->>EM: IsDeleted(physicalPosition)?
            activate EM

            alt Is deleted
                EM-->>BP: true
                Note over BP: Skip this byte
                deactivate EM

            else Not deleted
                EM-->>BP: false
                deactivate EM

                BP->>FP: ReadByte(original, physicalPos)
                activate FP
                FP->>FS: Read from original
                FS-->>FP: Original byte
                FP-->>BP: originalByte
                deactivate FP

                BP->>EM: IsModified(physicalPos)?
                activate EM

                alt Is modified
                    EM-->>BP: true, value=modifiedByte
                    BP->>FP: WriteByte(temp, modifiedByte)
                else Not modified
                    EM-->>BP: false
                    deactivate EM
                    BP->>FP: WriteByte(temp, originalByte)
                end

                activate FP
                FP->>FS: Write to temp
                FS-->>FP: Written
                FP-->>BP: Written
                deactivate FP
            end
        end
    end

    BP->>FP: FlushTemp()
    activate FP
    FP->>FS: Flush temp file
    FS-->>FP: Flushed
    FP-->>BP: Flushed
    deactivate FP

    BP->>FP: CloseOriginal()
    activate FP
    FP->>FS: Close original stream
    FS-->>FP: Closed
    FP-->>BP: Closed
    deactivate FP

    BP->>FP: ReplaceOriginalWithTemp()
    activate FP
    FP->>FS: Delete(original)
    FS-->>FP: Deleted
    FP->>FS: Move(temp → original)
    FS-->>FP: Moved
    FP-->>BP: Replaced
    deactivate FP

    BP->>FP: ReopenOriginal()
    activate FP
    FP->>FS: Open(original)
    FS-->>FP: Stream handle
    FP-->>BP: Reopened
    deactivate FP

    BP->>EM: ClearAll()
    activate EM
    EM-->>BP: All edits cleared
    deactivate EM

    BP->>PM: Reset()
    activate PM
    PM-->>BP: Mapper reset
    deactivate PM

    BP-->>VM: Save complete
    VM-->>HE: Saved
    HE->>User: File saved (rebuild)

Full Rebuild Implementation

private void SaveWithRebuild()
{
    string tempFile = Path.GetTempFileName();

    try
    {
        // Create temp file
        using (var tempStream = File.Create(tempFile))
        {
            long virtualLength = CalculateVirtualLength();

            Console.WriteLine($"Rebuild: {virtualLength} bytes");

            // Write bytes in virtual order
            for (long virtualPos = 0; virtualPos < virtualLength; virtualPos++)
            {
                byte value = ReadVirtualByte(virtualPos);
                tempStream.WriteByte(value);
            }

            tempStream.Flush();
        }

        // Close original file
        _fileProvider.Close();

        // Replace original with temp
        File.Delete(_fileName);
        File.Move(tempFile, _fileName);

        // Reopen original
        _fileProvider.Open(_fileName);

        // Clear all edits (now saved)
        _editsManager.ClearAll();
        _positionMapper.Reset();

        // Raise event
        OnFileSaved();
    }
    catch
    {
        // Clean up temp file on error
        if (File.Exists(tempFile))
            File.Delete(tempFile);

        throw;
    }
}

private byte ReadVirtualByte(long virtualPosition)
{
    // Check if insertion
    if (_editsManager.IsInsertion(virtualPosition, out byte insertedValue))
        return insertedValue;

    // Convert to physical
    long physicalPos = _positionMapper.VirtualToPhysical(virtualPosition);

    // Check if deleted
    if (_editsManager.IsDeleted(physicalPos))
        throw new InvalidOperationException("Deleted byte in virtual view");

    // Check if modified
    if (_editsManager.IsModified(physicalPos, out byte modifiedValue))
        return modifiedValue;

    // Return original
    return _fileProvider.ReadByte(physicalPos);
}

Rebuild Example

Original file: [41 42 43 44 45 46 47 48]  (8 bytes)

Edits:
- Modify position 1: 42 → FF
- Insert 3 bytes at position 3: [AA BB CC]
- Delete 2 bytes at position 6-7 (physical)

Virtual view: [41 FF 43 AA BB CC 44 45]  (8 bytes)

Rebuild process:
Pos 0: Not insertion, physical=0, not deleted, not modified → Write 41
Pos 1: Not insertion, physical=1, not deleted, IS modified → Write FF
Pos 2: Not insertion, physical=2, not deleted, not modified → Write 43
Pos 3: IS insertion → Write AA
Pos 4: IS insertion → Write BB
Pos 5: IS insertion → Write CC
Pos 6: Not insertion, physical=3, not deleted, not modified → Write 44
Pos 7: Not insertion, physical=4, not deleted, not modified → Write 45
(Physical positions 5-6 were deleted, skipped)

Result file: [41 FF 43 AA BB CC 44 45]  (8 bytes)

⚡ Async Save with Progress

Sequence Diagram

sequenceDiagram
    actor User
    participant HE as HexEditor
    participant VM as ViewModel
    participant BP as ByteProvider
    participant BG as Background Thread
    participant Progress
    participant UI as UI Thread

    User->>HE: SaveAsync(progress)
    HE->>VM: SaveAsync(progress)

    VM->>BP: SaveAsync(progress)
    activate BP

    BP->>BG: Task.Run(() => Save())
    activate BG

    loop Save progress
        BG->>BG: Process bytes
        BG->>Progress: Report(percentComplete)
        activate Progress
        Progress->>UI: Invoke progress callback
        activate UI
        UI->>User: Update progress bar
        deactivate UI
        deactivate Progress
    end

    BG-->>BP: Save complete
    deactivate BG

    BP-->>VM: Task complete
    deactivate BP

    VM-->>HE: Saved
    HE->>User: File saved

Async Implementation

public async Task SaveAsync(string fileName, IProgress<double> progress = null)
{
    await Task.Run(() =>
    {
        if (_editsManager.HasInsertions || _editsManager.HasDeletions)
        {
            SaveWithRebuildAsync(fileName, progress);
        }
        else
        {
            SaveFastPathAsync(fileName, progress);
        }
    });
}

private void SaveWithRebuildAsync(string fileName, IProgress<double> progress)
{
    string tempFile = Path.GetTempFileName();

    using (var tempStream = File.Create(tempFile))
    {
        long virtualLength = CalculateVirtualLength();
        long processedBytes = 0;

        for (long virtualPos = 0; virtualPos < virtualLength; virtualPos++)
        {
            // Read and write byte
            byte value = ReadVirtualByte(virtualPos);
            tempStream.WriteByte(value);

            // Report progress every 1000 bytes
            processedBytes++;
            if (processedBytes % 1000 == 0)
            {
                double percent = (double)processedBytes / virtualLength * 100.0;
                progress?.Report(percent);
            }
        }

        tempStream.Flush();
    }

    // Replace file
    File.Delete(fileName);
    File.Move(tempFile, fileName);

    // Final progress
    progress?.Report(100.0);
}

Usage Example

// Async save with progress UI
var progress = new Progress<double>(percent =>
{
    progressBar.Value = percent;
    statusLabel.Text = $"Saving: {percent:F1}%";
});

try
{
    await hexEditor.SaveAsync("output.bin", progress);
    MessageBox.Show("File saved successfully");
}
catch (Exception ex)
{
    MessageBox.Show($"Save failed: {ex.Message}");
}

❌ Error Handling

Error Scenarios

1. Disk Full

try
{
    Save();
}
catch (IOException ex) when (ex.HResult == -2147024784)  // Disk full
{
    MessageBox.Show("Disk is full. Cannot save file.");
}

2. File In Use

try
{
    Save();
}
catch (IOException ex) when (ex.Message.Contains("being used"))
{
    MessageBox.Show("File is in use by another process.");
}

3. Temp File Creation Failed

private void SaveWithRebuild()
{
    string tempFile = null;

    try
    {
        tempFile = Path.GetTempFileName();

        // Save logic...
    }
    catch (IOException ex)
    {
        MessageBox.Show($"Cannot create temp file: {ex.Message}");
    }
    finally
    {
        // Clean up temp file
        if (tempFile != null && File.Exists(tempFile))
        {
            try
            {
                File.Delete(tempFile);
            }
            catch
            {
                // Ignore cleanup errors
            }
        }
    }
}

4. Transaction Rollback

private void SaveWithRebuild()
{
    string backupFile = _fileName + ".backup";
    string tempFile = Path.GetTempFileName();

    // Create backup
    File.Copy(_fileName, backupFile, overwrite: true);

    try
    {
        // Perform save...
        SaveToTempFile(tempFile);
        ReplaceOriginalFile(tempFile);

        // Delete backup on success
        File.Delete(backupFile);
    }
    catch
    {
        // Restore from backup on failure
        if (File.Exists(backupFile))
        {
            File.Copy(backupFile, _fileName, overwrite: true);
            File.Delete(backupFile);
        }

        throw;
    }
}

📊 Performance Comparison

Fast Path vs Full Rebuild

File Size	Edit Type	Fast Path	Full Rebuild	Speedup
1 MB	10 mods	0.5ms	100ms	200x
1 MB	10 mods + 1 insertion	N/A	100ms	N/A
10 MB	100 mods	5ms	500ms	100x
10 MB	100 mods + 1 insertion	N/A	500ms	N/A
100 MB	1,000 mods	50ms	5000ms	100x
100 MB	1,000 mods + 1 insertion	N/A	5000ms	N/A

Key Takeaways:

✅ Fast path is 100x faster for modifications-only edits
⚠️ Single insertion/deletion forces full rebuild
📝 Full rebuild time is proportional to file size
⚡ Fast path time is proportional to modification count

🔗 See Also

File Operations - Open, close sequences
Edit Operations - Modify, insert, delete sequences
ByteProvider System - Data access coordination

Last Updated: 2026-02-19 Version: V2.0

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Save Operations Data Flow

📋 Table of Contents

📖 Overview

🌳 Decision Tree

Algorithm Selection Flowchart

Decision Logic

⚡ Fast Path: Modifications Only

Sequence Diagram

Fast Path Implementation

Performance Characteristics

🏗️ Full Rebuild: Insertions/Deletions

Sequence Diagram

Full Rebuild Implementation

Rebuild Example

⚡ Async Save with Progress

Sequence Diagram

Async Implementation

Usage Example

❌ Error Handling

Error Scenarios

1. Disk Full

2. File In Use

3. Temp File Creation Failed

4. Transaction Rollback

📊 Performance Comparison

Fast Path vs Full Rebuild

🔗 See Also

FilesExpand file tree

save-operations.md

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save-operations.md

File metadata and controls

Save Operations Data Flow

📋 Table of Contents

📖 Overview

🌳 Decision Tree

Algorithm Selection Flowchart

Decision Logic

⚡ Fast Path: Modifications Only

Sequence Diagram

Fast Path Implementation

Performance Characteristics

🏗️ Full Rebuild: Insertions/Deletions

Sequence Diagram

Full Rebuild Implementation

Rebuild Example

⚡ Async Save with Progress

Sequence Diagram

Async Implementation

Usage Example

❌ Error Handling

Error Scenarios

1. Disk Full

2. File In Use

3. Temp File Creation Failed

4. Transaction Rollback

📊 Performance Comparison

Fast Path vs Full Rebuild

🔗 See Also