jellyfin/MediaBrowser.Controller/Drawing/ImageManager.cs
2013-09-16 22:44:06 -04:00

806 lines
32 KiB
C#

using MediaBrowser.Common.Extensions;
using MediaBrowser.Common.IO;
using MediaBrowser.Controller.Entities;
using MediaBrowser.Controller.Entities.TV;
using MediaBrowser.Controller.Persistence;
using MediaBrowser.Controller.Providers;
using MediaBrowser.Model.Drawing;
using MediaBrowser.Model.Entities;
using MediaBrowser.Model.Logging;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
namespace MediaBrowser.Controller.Drawing
{
/// <summary>
/// Class ImageManager
/// </summary>
public class ImageManager
{
/// <summary>
/// Gets the list of currently registered image processors
/// Image processors are specialized metadata providers that run after the normal ones
/// </summary>
/// <value>The image enhancers.</value>
public IEnumerable<IImageEnhancer> ImageEnhancers { get; set; }
/// <summary>
/// Gets the image size cache.
/// </summary>
/// <value>The image size cache.</value>
private FileSystemRepository ImageSizeCache { get; set; }
/// <summary>
/// Gets or sets the resized image cache.
/// </summary>
/// <value>The resized image cache.</value>
private FileSystemRepository ResizedImageCache { get; set; }
/// <summary>
/// Gets the cropped image cache.
/// </summary>
/// <value>The cropped image cache.</value>
private FileSystemRepository CroppedImageCache { get; set; }
/// <summary>
/// Gets the cropped image cache.
/// </summary>
/// <value>The cropped image cache.</value>
private FileSystemRepository EnhancedImageCache { get; set; }
/// <summary>
/// The cached imaged sizes
/// </summary>
private readonly ConcurrentDictionary<string, ImageSize> _cachedImagedSizes = new ConcurrentDictionary<string, ImageSize>();
/// <summary>
/// The _logger
/// </summary>
private readonly ILogger _logger;
private readonly IItemRepository _itemRepo;
/// <summary>
/// Initializes a new instance of the <see cref="ImageManager" /> class.
/// </summary>
/// <param name="logger">The logger.</param>
/// <param name="appPaths">The app paths.</param>
/// <param name="itemRepo">The item repo.</param>
public ImageManager(ILogger logger, IServerApplicationPaths appPaths, IItemRepository itemRepo)
{
_logger = logger;
_itemRepo = itemRepo;
ImageSizeCache = new FileSystemRepository(Path.Combine(appPaths.ImageCachePath, "image-sizes"));
ResizedImageCache = new FileSystemRepository(Path.Combine(appPaths.ImageCachePath, "resized-images"));
CroppedImageCache = new FileSystemRepository(Path.Combine(appPaths.ImageCachePath, "cropped-images"));
EnhancedImageCache = new FileSystemRepository(Path.Combine(appPaths.ImageCachePath, "enhanced-images"));
}
/// <summary>
/// Processes an image by resizing to target dimensions
/// </summary>
/// <param name="entity">The entity that owns the image</param>
/// <param name="imageType">The image type</param>
/// <param name="imageIndex">The image index (currently only used with backdrops)</param>
/// <param name="originalImagePath">The original image path.</param>
/// <param name="cropWhitespace">if set to <c>true</c> [crop whitespace].</param>
/// <param name="dateModified">The last date modified of the original image file</param>
/// <param name="toStream">The stream to save the new image to</param>
/// <param name="width">Use if a fixed width is required. Aspect ratio will be preserved.</param>
/// <param name="height">Use if a fixed height is required. Aspect ratio will be preserved.</param>
/// <param name="maxWidth">Use if a max width is required. Aspect ratio will be preserved.</param>
/// <param name="maxHeight">Use if a max height is required. Aspect ratio will be preserved.</param>
/// <param name="quality">Quality level, from 0-100. Currently only applies to JPG. The default value should suffice.</param>
/// <param name="enhancers">The enhancers.</param>
/// <returns>Task.</returns>
/// <exception cref="System.ArgumentNullException">entity</exception>
public async Task ProcessImage(BaseItem entity, ImageType imageType, int imageIndex, string originalImagePath, bool cropWhitespace, DateTime dateModified, Stream toStream, int? width, int? height, int? maxWidth, int? maxHeight, int? quality, List<IImageEnhancer> enhancers)
{
if (entity == null)
{
throw new ArgumentNullException("entity");
}
if (toStream == null)
{
throw new ArgumentNullException("toStream");
}
if (cropWhitespace)
{
originalImagePath = await GetCroppedImage(originalImagePath, dateModified).ConfigureAwait(false);
}
// No enhancement - don't cache
if (enhancers.Count > 0)
{
try
{
// Enhance if we have enhancers
var ehnancedImagePath = await GetEnhancedImage(originalImagePath, dateModified, entity, imageType, imageIndex, enhancers).ConfigureAwait(false);
// If the path changed update dateModified
if (!ehnancedImagePath.Equals(originalImagePath, StringComparison.OrdinalIgnoreCase))
{
dateModified = File.GetLastWriteTimeUtc(ehnancedImagePath);
originalImagePath = ehnancedImagePath;
}
}
catch (Exception ex)
{
_logger.Error("Error enhancing image", ex);
}
}
var originalImageSize = GetImageSize(originalImagePath, dateModified);
// Determine the output size based on incoming parameters
var newSize = DrawingUtils.Resize(originalImageSize, width, height, maxWidth, maxHeight);
if (!quality.HasValue)
{
quality = 90;
}
var cacheFilePath = GetCacheFilePath(originalImagePath, newSize, quality.Value, dateModified);
try
{
using (var fileStream = new FileStream(cacheFilePath, FileMode.Open, FileAccess.Read, FileShare.Read, StreamDefaults.DefaultFileStreamBufferSize, FileOptions.Asynchronous))
{
await fileStream.CopyToAsync(toStream).ConfigureAwait(false);
return;
}
}
catch (IOException)
{
// Cache file doesn't exist or is currently being written ro
}
var semaphore = GetLock(cacheFilePath);
await semaphore.WaitAsync().ConfigureAwait(false);
// Check again in case of lock contention
if (File.Exists(cacheFilePath))
{
try
{
using (var fileStream = new FileStream(cacheFilePath, FileMode.Open, FileAccess.Read, FileShare.Read, StreamDefaults.DefaultFileStreamBufferSize, FileOptions.Asynchronous))
{
await fileStream.CopyToAsync(toStream).ConfigureAwait(false);
return;
}
}
finally
{
semaphore.Release();
}
}
try
{
using (var fileStream = new FileStream(originalImagePath, FileMode.Open, FileAccess.Read, FileShare.Read, StreamDefaults.DefaultFileStreamBufferSize, true))
{
// Copy to memory stream to avoid Image locking file
using (var memoryStream = new MemoryStream())
{
await fileStream.CopyToAsync(memoryStream).ConfigureAwait(false);
using (var originalImage = Image.FromStream(memoryStream, true, false))
{
var newWidth = Convert.ToInt32(newSize.Width);
var newHeight = Convert.ToInt32(newSize.Height);
// Graphics.FromImage will throw an exception if the PixelFormat is Indexed, so we need to handle that here
using (var thumbnail = !ImageExtensions.IsPixelFormatSupportedByGraphicsObject(originalImage.PixelFormat) ? new Bitmap(originalImage, newWidth, newHeight) : new Bitmap(newWidth, newHeight, originalImage.PixelFormat))
{
// Preserve the original resolution
thumbnail.SetResolution(originalImage.HorizontalResolution, originalImage.VerticalResolution);
using (var thumbnailGraph = Graphics.FromImage(thumbnail))
{
thumbnailGraph.CompositingQuality = CompositingQuality.HighQuality;
thumbnailGraph.SmoothingMode = SmoothingMode.HighQuality;
thumbnailGraph.InterpolationMode = InterpolationMode.HighQualityBicubic;
thumbnailGraph.PixelOffsetMode = PixelOffsetMode.HighQuality;
thumbnailGraph.CompositingMode = CompositingMode.SourceOver;
thumbnailGraph.DrawImage(originalImage, 0, 0, newWidth, newHeight);
var outputFormat = originalImage.RawFormat;
using (var outputMemoryStream = new MemoryStream())
{
// Save to the memory stream
thumbnail.Save(outputFormat, outputMemoryStream, quality.Value);
var bytes = outputMemoryStream.ToArray();
var outputTask = toStream.WriteAsync(bytes, 0, bytes.Length);
// kick off a task to cache the result
var cacheTask = CacheResizedImage(cacheFilePath, bytes);
await Task.WhenAll(outputTask, cacheTask).ConfigureAwait(false);
}
}
}
}
}
}
}
finally
{
semaphore.Release();
}
}
/// <summary>
/// Caches the resized image.
/// </summary>
/// <param name="cacheFilePath">The cache file path.</param>
/// <param name="bytes">The bytes.</param>
private async Task CacheResizedImage(string cacheFilePath, byte[] bytes)
{
var parentPath = Path.GetDirectoryName(cacheFilePath);
if (!Directory.Exists(parentPath))
{
Directory.CreateDirectory(parentPath);
}
// Save to the cache location
using (var cacheFileStream = new FileStream(cacheFilePath, FileMode.Create, FileAccess.Write, FileShare.Read, StreamDefaults.DefaultFileStreamBufferSize, FileOptions.Asynchronous))
{
// Save to the filestream
await cacheFileStream.WriteAsync(bytes, 0, bytes.Length).ConfigureAwait(false);
}
}
/// <summary>
/// Gets the cache file path based on a set of parameters
/// </summary>
/// <param name="originalPath">The path to the original image file</param>
/// <param name="outputSize">The size to output the image in</param>
/// <param name="quality">Quality level, from 0-100. Currently only applies to JPG. The default value should suffice.</param>
/// <param name="dateModified">The last modified date of the image</param>
/// <returns>System.String.</returns>
private string GetCacheFilePath(string originalPath, ImageSize outputSize, int quality, DateTime dateModified)
{
var filename = originalPath;
filename += "width=" + outputSize.Width;
filename += "height=" + outputSize.Height;
filename += "quality=" + quality;
filename += "datemodified=" + dateModified.Ticks;
return ResizedImageCache.GetResourcePath(filename, Path.GetExtension(originalPath));
}
/// <summary>
/// Gets image dimensions
/// </summary>
/// <param name="imagePath">The image path.</param>
/// <param name="dateModified">The date modified.</param>
/// <returns>Task{ImageSize}.</returns>
/// <exception cref="System.ArgumentNullException">imagePath</exception>
public ImageSize GetImageSize(string imagePath, DateTime dateModified)
{
if (string.IsNullOrEmpty(imagePath))
{
throw new ArgumentNullException("imagePath");
}
var name = imagePath + "datemodified=" + dateModified.Ticks;
ImageSize size;
if (!_cachedImagedSizes.TryGetValue(name, out size))
{
size = GetImageSize(name, imagePath);
_cachedImagedSizes.AddOrUpdate(name, size, (keyName, oldValue) => size);
}
return size;
}
protected readonly CultureInfo UsCulture = new CultureInfo("en-US");
/// <summary>
/// Gets the size of the image.
/// </summary>
/// <param name="keyName">Name of the key.</param>
/// <param name="imagePath">The image path.</param>
/// <returns>ImageSize.</returns>
private ImageSize GetImageSize(string keyName, string imagePath)
{
// Now check the file system cache
var fullCachePath = ImageSizeCache.GetResourcePath(keyName, ".txt");
try
{
var result = File.ReadAllText(fullCachePath).Split('|').Select(i => double.Parse(i, UsCulture)).ToArray();
return new ImageSize { Width = result[0], Height = result[1] };
}
catch (IOException)
{
// Cache file doesn't exist or is currently being written to
}
var syncLock = GetObjectLock(fullCachePath);
lock (syncLock)
{
try
{
var result = File.ReadAllText(fullCachePath)
.Split('|')
.Select(i => double.Parse(i, UsCulture))
.ToArray();
return new ImageSize { Width = result[0], Height = result[1] };
}
catch (FileNotFoundException)
{
// Cache file doesn't exist no biggie
}
catch (DirectoryNotFoundException)
{
// Cache file doesn't exist no biggie
}
var size = ImageHeader.GetDimensions(imagePath, _logger);
var parentPath = Path.GetDirectoryName(fullCachePath);
if (!Directory.Exists(parentPath))
{
Directory.CreateDirectory(parentPath);
}
// Update the file system cache
File.WriteAllText(fullCachePath, size.Width.ToString(UsCulture) + @"|" + size.Height.ToString(UsCulture));
return new ImageSize { Width = size.Width, Height = size.Height };
}
}
/// <summary>
/// Gets the image path.
/// </summary>
/// <param name="item">The item.</param>
/// <param name="imageType">Type of the image.</param>
/// <param name="imageIndex">Index of the image.</param>
/// <returns>System.String.</returns>
/// <exception cref="System.ArgumentNullException">item</exception>
/// <exception cref="System.InvalidOperationException"></exception>
public string GetImagePath(BaseItem item, ImageType imageType, int imageIndex)
{
if (item == null)
{
throw new ArgumentNullException("item");
}
if (imageType == ImageType.Backdrop)
{
if (item.BackdropImagePaths == null)
{
throw new InvalidOperationException(string.Format("Item {0} does not have any Backdrops.", item.Name));
}
return item.BackdropImagePaths[imageIndex];
}
if (imageType == ImageType.Screenshot)
{
if (item.ScreenshotImagePaths == null)
{
throw new InvalidOperationException(string.Format("Item {0} does not have any Screenshots.", item.Name));
}
return item.ScreenshotImagePaths[imageIndex];
}
if (imageType == ImageType.Chapter)
{
return _itemRepo.GetChapter(item.Id, imageIndex).ImagePath;
}
return item.GetImage(imageType);
}
/// <summary>
/// Gets the image date modified.
/// </summary>
/// <param name="item">The item.</param>
/// <param name="imageType">Type of the image.</param>
/// <param name="imageIndex">Index of the image.</param>
/// <returns>DateTime.</returns>
/// <exception cref="System.ArgumentNullException">item</exception>
public DateTime GetImageDateModified(BaseItem item, ImageType imageType, int imageIndex)
{
if (item == null)
{
throw new ArgumentNullException("item");
}
var imagePath = GetImagePath(item, imageType, imageIndex);
return GetImageDateModified(item, imagePath);
}
/// <summary>
/// Gets the image date modified.
/// </summary>
/// <param name="item">The item.</param>
/// <param name="imagePath">The image path.</param>
/// <returns>DateTime.</returns>
/// <exception cref="System.ArgumentNullException">item</exception>
public DateTime GetImageDateModified(BaseItem item, string imagePath)
{
if (item == null)
{
throw new ArgumentNullException("item");
}
if (string.IsNullOrEmpty(imagePath))
{
throw new ArgumentNullException("imagePath");
}
var metaFileEntry = item.ResolveArgs.GetMetaFileByPath(imagePath);
// If we didn't the metafile entry, check the Season
if (metaFileEntry == null)
{
var episode = item as Episode;
if (episode != null && episode.Season != null)
{
episode.Season.ResolveArgs.GetMetaFileByPath(imagePath);
}
}
// See if we can avoid a file system lookup by looking for the file in ResolveArgs
return metaFileEntry == null ? File.GetLastWriteTimeUtc(imagePath) : metaFileEntry.LastWriteTimeUtc;
}
/// <summary>
/// Crops whitespace from an image, caches the result, and returns the cached path
/// </summary>
/// <param name="originalImagePath">The original image path.</param>
/// <param name="dateModified">The date modified.</param>
/// <returns>System.String.</returns>
private async Task<string> GetCroppedImage(string originalImagePath, DateTime dateModified)
{
var name = originalImagePath;
name += "datemodified=" + dateModified.Ticks;
var croppedImagePath = CroppedImageCache.GetResourcePath(name, Path.GetExtension(originalImagePath));
var semaphore = GetLock(croppedImagePath);
await semaphore.WaitAsync().ConfigureAwait(false);
// Check again in case of contention
if (File.Exists(croppedImagePath))
{
semaphore.Release();
return croppedImagePath;
}
try
{
using (var fileStream = new FileStream(originalImagePath, FileMode.Open, FileAccess.Read, FileShare.Read, StreamDefaults.DefaultFileStreamBufferSize, true))
{
// Copy to memory stream to avoid Image locking file
using (var memoryStream = new MemoryStream())
{
await fileStream.CopyToAsync(memoryStream).ConfigureAwait(false);
using (var originalImage = (Bitmap)Image.FromStream(memoryStream, true, false))
{
var outputFormat = originalImage.RawFormat;
using (var croppedImage = originalImage.CropWhitespace())
{
var parentPath = Path.GetDirectoryName(croppedImagePath);
if (!Directory.Exists(parentPath))
{
Directory.CreateDirectory(parentPath);
}
using (var outputStream = new FileStream(croppedImagePath, FileMode.Create, FileAccess.Write, FileShare.Read))
{
croppedImage.Save(outputFormat, outputStream, 100);
}
}
}
}
}
}
catch (Exception ex)
{
// We have to have a catch-all here because some of the .net image methods throw a plain old Exception
_logger.ErrorException("Error cropping image {0}", ex, originalImagePath);
return originalImagePath;
}
finally
{
semaphore.Release();
}
return croppedImagePath;
}
/// <summary>
/// Gets the enhanced image.
/// </summary>
/// <param name="originalImagePath">The original image path.</param>
/// <param name="dateModified">The date modified.</param>
/// <param name="item">The item.</param>
/// <param name="imageType">Type of the image.</param>
/// <param name="imageIndex">Index of the image.</param>
/// <returns>Task{System.String}.</returns>
/// <exception cref="System.ArgumentNullException">item</exception>
public Task<string> GetEnhancedImage(string originalImagePath, DateTime dateModified, BaseItem item, ImageType imageType, int imageIndex)
{
if (item == null)
{
throw new ArgumentNullException("item");
}
var supportedImageEnhancers = ImageEnhancers.Where(i =>
{
try
{
return i.Supports(item, imageType);
}
catch (Exception ex)
{
_logger.ErrorException("Error in image enhancer: {0}", ex, i.GetType().Name);
return false;
}
}).ToList();
return GetEnhancedImage(originalImagePath, dateModified, item, imageType, imageIndex, supportedImageEnhancers);
}
/// <summary>
/// Runs an image through the image enhancers, caches the result, and returns the cached path
/// </summary>
/// <param name="originalImagePath">The original image path.</param>
/// <param name="dateModified">The date modified of the original image file.</param>
/// <param name="item">The item.</param>
/// <param name="imageType">Type of the image.</param>
/// <param name="imageIndex">Index of the image.</param>
/// <param name="supportedEnhancers">The supported enhancers.</param>
/// <returns>System.String.</returns>
/// <exception cref="System.ArgumentNullException">originalImagePath</exception>
public async Task<string> GetEnhancedImage(string originalImagePath, DateTime dateModified, BaseItem item, ImageType imageType, int imageIndex, List<IImageEnhancer> supportedEnhancers)
{
if (string.IsNullOrEmpty(originalImagePath))
{
throw new ArgumentNullException("originalImagePath");
}
if (item == null)
{
throw new ArgumentNullException("item");
}
var cacheGuid = GetImageCacheTag(originalImagePath, dateModified, supportedEnhancers, item, imageType);
// All enhanced images are saved as png to allow transparency
var enhancedImagePath = EnhancedImageCache.GetResourcePath(cacheGuid + ".png");
var semaphore = GetLock(enhancedImagePath);
await semaphore.WaitAsync().ConfigureAwait(false);
// Check again in case of contention
if (File.Exists(enhancedImagePath))
{
semaphore.Release();
return enhancedImagePath;
}
try
{
using (var fileStream = new FileStream(originalImagePath, FileMode.Open, FileAccess.Read, FileShare.Read, StreamDefaults.DefaultFileStreamBufferSize, true))
{
// Copy to memory stream to avoid Image locking file
using (var memoryStream = new MemoryStream())
{
await fileStream.CopyToAsync(memoryStream).ConfigureAwait(false);
using (var originalImage = Image.FromStream(memoryStream, true, false))
{
//Pass the image through registered enhancers
using (var newImage = await ExecuteImageEnhancers(supportedEnhancers, originalImage, item, imageType, imageIndex).ConfigureAwait(false))
{
var parentDirectory = Path.GetDirectoryName(enhancedImagePath);
if (!Directory.Exists(parentDirectory))
{
Directory.CreateDirectory(parentDirectory);
}
//And then save it in the cache
using (var outputStream = new FileStream(enhancedImagePath, FileMode.Create, FileAccess.Write, FileShare.Read))
{
newImage.Save(ImageFormat.Png, outputStream, 100);
}
}
}
}
}
}
finally
{
semaphore.Release();
}
return enhancedImagePath;
}
/// <summary>
/// Gets the image cache tag.
/// </summary>
/// <param name="item">The item.</param>
/// <param name="imageType">Type of the image.</param>
/// <param name="imagePath">The image path.</param>
/// <returns>Guid.</returns>
/// <exception cref="System.ArgumentNullException">item</exception>
public Guid GetImageCacheTag(BaseItem item, ImageType imageType, string imagePath)
{
if (item == null)
{
throw new ArgumentNullException("item");
}
if (string.IsNullOrEmpty(imagePath))
{
throw new ArgumentNullException("imagePath");
}
var dateModified = GetImageDateModified(item, imagePath);
var supportedEnhancers = ImageEnhancers.Where(i =>
{
try
{
return i.Supports(item, imageType);
}
catch (Exception ex)
{
_logger.ErrorException("Error in image enhancer: {0}", ex, i.GetType().Name);
return false;
}
}).ToList();
return GetImageCacheTag(imagePath, dateModified, supportedEnhancers, item, imageType);
}
/// <summary>
/// Gets the image cache tag.
/// </summary>
/// <param name="originalImagePath">The original image path.</param>
/// <param name="dateModified">The date modified of the original image file.</param>
/// <param name="imageEnhancers">The image enhancers.</param>
/// <param name="item">The item.</param>
/// <param name="imageType">Type of the image.</param>
/// <returns>Guid.</returns>
/// <exception cref="System.ArgumentNullException">item</exception>
public Guid GetImageCacheTag(string originalImagePath, DateTime dateModified, IEnumerable<IImageEnhancer> imageEnhancers, BaseItem item, ImageType imageType)
{
if (item == null)
{
throw new ArgumentNullException("item");
}
if (imageEnhancers == null)
{
throw new ArgumentNullException("imageEnhancers");
}
if (string.IsNullOrEmpty(originalImagePath))
{
throw new ArgumentNullException("originalImagePath");
}
// Cache name is created with supported enhancers combined with the last config change so we pick up new config changes
var cacheKeys = imageEnhancers.Select(i => i.GetConfigurationCacheKey(item, imageType)).ToList();
cacheKeys.Add(originalImagePath + dateModified.Ticks);
return string.Join("|", cacheKeys.ToArray()).GetMD5();
}
/// <summary>
/// Executes the image enhancers.
/// </summary>
/// <param name="imageEnhancers">The image enhancers.</param>
/// <param name="originalImage">The original image.</param>
/// <param name="item">The item.</param>
/// <param name="imageType">Type of the image.</param>
/// <param name="imageIndex">Index of the image.</param>
/// <returns>Task{EnhancedImage}.</returns>
private async Task<Image> ExecuteImageEnhancers(IEnumerable<IImageEnhancer> imageEnhancers, Image originalImage, BaseItem item, ImageType imageType, int imageIndex)
{
var result = originalImage;
// Run the enhancers sequentially in order of priority
foreach (var enhancer in imageEnhancers)
{
var typeName = enhancer.GetType().Name;
try
{
result = await enhancer.EnhanceImageAsync(item, result, imageType, imageIndex).ConfigureAwait(false);
}
catch (Exception ex)
{
_logger.ErrorException("{0} failed enhancing {1}", ex, typeName, item.Name);
throw;
}
}
return result;
}
/// <summary>
/// The _semaphoreLocks
/// </summary>
private readonly ConcurrentDictionary<string, SemaphoreSlim> _semaphoreLocks = new ConcurrentDictionary<string, SemaphoreSlim>();
/// <summary>
/// Gets the lock.
/// </summary>
/// <param name="filename">The filename.</param>
/// <returns>System.Object.</returns>
private SemaphoreSlim GetLock(string filename)
{
return _semaphoreLocks.GetOrAdd(filename, key => new SemaphoreSlim(1, 1));
}
/// <summary>
/// The _semaphoreLocks
/// </summary>
private readonly ConcurrentDictionary<string, object> _locks = new ConcurrentDictionary<string, object>();
/// <summary>
/// Gets the lock.
/// </summary>
/// <param name="filename">The filename.</param>
/// <returns>System.Object.</returns>
private object GetObjectLock(string filename)
{
return _locks.GetOrAdd(filename, key => new object());
}
}
}