Merge pull request #197 from Eizock/add-MinChunkSize

Add MinimumChunkSize to set minimum size a single chunk should have

Author: bezzad

src/Downloader/ChunkHub.cs

@@ -1,4 +1,5 @@
-using System.Linq;
+using System;
+using System.Linq;
 
 namespace Downloader;
 
@@ -69,6 +70,16 @@ private void Validate(DownloadPackage package)
             _chunkCount = 1;
         }
 
+        if (_config.MinimumChunkSize > 0)
+        {
+            int maxChunksByMinSize = (int)(package.TotalFileSize / _config.MinimumChunkSize);
+            if (maxChunksByMinSize < 1)
+                maxChunksByMinSize = 1;
+
+            // Respect both ChunkCount and MinChunkSize constraints
+            _chunkCount = Math.Min(_config.ChunkCount, maxChunksByMinSize);
+        }
+        
         _chunkSize = package.TotalFileSize / _chunkCount;
     }
 

src/Downloader/DownloadConfiguration.cs

@@ -29,6 +29,9 @@ public class DownloadConfiguration : ICloneable, INotifyPropertyChanged
     // minimum size of chunking to download a file in multiple parts
     private long _minimumSizeOfChunking = 512;
 
+    // minimum size of a single chunk
+    private long _minimumChunkSize = 0;
+
     // Before starting the download, reserve the storage space of the file as file size.
     private bool _reserveStorageSpaceBeforeStartingDownload;
 
@@ -218,6 +221,18 @@ public long MinimumSizeOfChunking
         set => OnPropertyChanged(ref _minimumSizeOfChunking, value);
     }
 
+    /// <summary>
+    /// Gets or sets the minimum size of a single chunk
+    /// If it is not 0 it dynamically reduces the chunk count to keep the chunk size above this value
+    /// Keeps ChunkCount as a Maximum
+    /// Default value is 0
+    /// </summary>
+    public long MinimumChunkSize
+    {
+        get => _minimumChunkSize;
+        set => OnPropertyChanged(ref _minimumChunkSize, value);
+    }
+
     /// <summary>
     /// Gets or sets a value indicating whether to reserve the storage space of the file as file size before starting the download.
     /// Default value is false.

src/Samples/Downloader.Sample/Program.Config.cs

@@ -24,6 +24,7 @@ private static DownloadConfiguration GetDownloadConfiguration()
             RangeHigh = 0,              // ceiling offset of download range of a large file
             ClearPackageOnCompletionWithFailure = true, // Clear package and downloaded data when download completed with failure, default value is false
             MinimumSizeOfChunking = 1024, // minimum size of chunking to download a file in multiple parts, default value is 512                                              
+            MinimumChunkSize = 0, // minimum size of a single chunk, 0 disables this, default is 0
             ReserveStorageSpaceBeforeStartingDownload = false, // Before starting the download, reserve the storage space of the file as file size, default value is false
             EnableLiveStreaming = false, // Get on demand downloaded data with ReceivedBytes on downloadProgressChanged event 
             RequestConfiguration =