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EmptyDirectoryConstraint doesn't need to enumerate entire directory contents #3622
Description
EmptyDirectoryConstraint currently tries to read in and instantiate all content in a directory in order to determine if the directory is empty or not empty.
An alternative could be to use one call to EnumerateFileSystemInfos().Any() to detect existence of either files or subdirectories without instantiating a whole array of them. Unfortunately, this API isn't available in .NET 35, so some sort of fallback would be required to go this route. A fallback could be either the currently implementation, or using GetFileSystemInfos().Any(). Example:
- files = dirInfo.GetFiles().Length;
- subdirs = dirInfo.GetDirectories().Length;
- bool hasSucceeded = files == 0 && subdirs == 0;
+ bool hasSucceeded;
+ #if !NET35
+ hasSucceeded = !dirInfo.EnumerateFileSystemInfos().Any();
+ #else
+ hasSucceeded = !dirInfo.GetFileSystemInfos().Any();
+ #endifI've done a quick verification via BenchmarkDotNet, and it seems promising (N = number of files, N/2 = number of subdirectories)
| Method | N | Mean | Error | StdDev | Gen 0 | Gen 1 | Gen 2 | Allocated |
|----------------- |----- |------------:|-------------:|----------:|---------:|--------:|------:|----------:|
| IsEmpty_Original | 0 | 44.18 us | 11.016 us | 0.604 us | 0.1221 | - | - | 592 B |
| IsEmpty_New | 0 | 21.05 us | 2.992 us | 0.164 us | 0.0610 | - | - | 296 B |
| IsEmpty_Original | 100 | 115.95 us | 3.041 us | 0.167 us | 11.9629 | 0.1221 | - | 50216 B |
| IsEmpty_New | 100 | 61.05 us | 153.207 us | 8.398 us | 0.1221 | - | - | 600 B |
| IsEmpty_Original | 1024 | 1,447.30 us | 1,445.389 us | 79.227 us | 105.4688 | 33.2031 | - | 508424 B |
| IsEmpty_New | 1024 | 79.75 us | 31.172 us | 1.709 us | 0.1221 | - | - | 600 B |
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