Add WindowSize property to BrotliCompressionOptions

src/libraries/System.IO.Compression.Brotli/ref/System.IO.Compression.Brotli.cs

@@ -10,6 +10,7 @@ public sealed partial class BrotliCompressionOptions
     {
         public BrotliCompressionOptions() { }
         public int Quality { get { throw null; } set { } }
+        public int WindowSize { get { throw null; } set { } }
     }
     public partial struct BrotliDecoder : System.IDisposable
     {

src/libraries/System.IO.Compression.Brotli/src/System/IO/Compression/enc/BrotliCompressionOptions.cs

@@ -9,6 +9,7 @@ namespace System.IO.Compression
     public sealed class BrotliCompressionOptions
     {
         private int _quality = BrotliUtils.Quality_Default;
+        private int _windowSize = BrotliUtils.WindowBits_Default;
 
         /// <summary>
         /// Gets or sets the compression quality for a Brotli compression stream.
@@ -28,5 +29,24 @@ public int Quality
                 _quality = value;
             }
         }
+
+        /// <summary>
+        /// Gets or sets the window size for a Brotli compression stream.
+        /// </summary>
+        /// <exception cref="ArgumentOutOfRangeException" accessor="set">The value is less than 10 or greater than 24.</exception>
+        /// <remarks>
+        /// The window size is the sliding window size in bits used by the LZ77 algorithm. Larger window sizes can improve compression ratio but use more memory. Range is from 10 to 24. The default value is 22.
+        /// </remarks>
+        public int WindowSize
+        {
+            get => _windowSize;
+            set
+            {
+                ArgumentOutOfRangeException.ThrowIfLessThan(value, BrotliUtils.WindowBits_Min, nameof(value));
+                ArgumentOutOfRangeException.ThrowIfGreaterThan(value, BrotliUtils.WindowBits_Max, nameof(value));
+
+                _windowSize = value;
+            }
+        }
     }
 }

src/libraries/System.IO.Compression.Brotli/src/System/IO/Compression/enc/BrotliStream.Compress.cs

@@ -41,6 +41,7 @@ public BrotliStream(Stream stream, BrotliCompressionOptions compressionOptions,
             ArgumentNullException.ThrowIfNull(compressionOptions);
 
             _encoder.SetQuality(compressionOptions.Quality);
+            _encoder.SetWindow(compressionOptions.WindowSize);
         }
 
         /// <summary>Writes compressed bytes to the underlying stream from the specified byte array.</summary>

src/libraries/System.IO.Compression.Brotli/tests/CompressionStreamUnitTests.Brotli.cs

@@ -107,6 +107,52 @@ public void InvalidBrotliCompressionQuality()
             Assert.Throws<ArgumentOutOfRangeException>("value", () => options.Quality = 12);
         }
 
+        [Fact]
+        public void InvalidBrotliCompressionWindowSize()
+        {
+            BrotliCompressionOptions options = new();
+
+            Assert.Equal(22, options.WindowSize); // default value
+            Assert.Throws<ArgumentOutOfRangeException>("value", () => options.WindowSize = -1);
+            Assert.Throws<ArgumentOutOfRangeException>("value", () => options.WindowSize = 9);
+            Assert.Throws<ArgumentOutOfRangeException>("value", () => options.WindowSize = 25);
+        }
+
+        [Theory]
+        [InlineData(10)]
+        [InlineData(15)]
+        [InlineData(22)]
+        [InlineData(24)]
+        public void BrotliCompressionWindowSize_RoundTrip(int windowSize)
+        {
+            byte[] testData = new byte[10000];
+            Random.Shared.NextBytes(testData);
+
+            // Compress with specific window size
+            byte[] compressed;
+            using (var ms = new MemoryStream())
+            {
+                using (var compressor = new BrotliStream(ms, new BrotliCompressionOptions() { WindowSize = windowSize }, leaveOpen: true))
+                {
+                    compressor.Write(testData);
+                }
+                compressed = ms.ToArray();
+            }
+
+            // Decompress and verify
+            byte[] decompressed;
+            using (var ms = new MemoryStream(compressed))
+            using (var decompressor = new BrotliStream(ms, CompressionMode.Decompress))
+            using (var resultStream = new MemoryStream())
+            {
+                decompressor.CopyTo(resultStream);
+                decompressed = resultStream.ToArray();
+            }
+
+            Assert.Equal(testData.Length, decompressed.Length);
+            Assert.Equal<byte>(testData, decompressed);
+        }
+
         [Theory]
         [MemberData(nameof(UncompressedTestFilesBrotli))]
         public async Task BrotliCompressionQuality_SizeInOrder(string testFile)