Add bit writer

src/ImageSharp/Formats/Jxl/Fields/JxlBitsCoder.cs

@@ -2,6 +2,7 @@
 // Licensed under the Six Labors Split License.
 
 using SixLabors.ImageSharp.Formats.Jxl.Processing.Decoder;
+using SixLabors.ImageSharp.Formats.Jxl.Processing.Encoder;
 
 namespace SixLabors.ImageSharp.Formats.Jxl.Fields;
 

src/ImageSharp/Formats/Jxl/Fields/JxlBundle.cs

@@ -5,6 +5,7 @@ using SixLabors.ImageSharp.Formats.Jxl.IO.FrameHeader;
 using SixLabors.ImageSharp.Formats.Jxl.IO.Metadata;
 using SixLabors.ImageSharp.Formats.Jxl.Processing;
 using SixLabors.ImageSharp.Formats.Jxl.Processing.Decoder;
+using SixLabors.ImageSharp.Formats.Jxl.Processing.Encoder;
 using SixLabors.ImageSharp.Formats.Jxl.Processing.Encoder.AuxiliaryOutput;
 using SixLabors.ImageSharp.Formats.Jxl.Processing.Quantization;
 
@@ -118,7 +119,7 @@ internal static class JxlBundle
             return false;
         }
 
-        return writer.WithMaxBits(totalBits, layer, auxOutput, () =>
+        return writer.WithMaxBits(totalBits, () =>
         {
             JxlWriteVisitor visitor = new(extensionBits, writer);
 

src/ImageSharp/Formats/Jxl/Fields/JxlCanEncodeVisitor.cs

@@ -102,7 +102,7 @@ internal sealed class JxlCanEncodeVisitor : JxlVisitorBase
 
             extensionBits = (int)this.encodedBits - (int)this.posAfterExt;
             int encodedBits = 0;
-            this.OK &= JxlU64Coder.CanEncode(extensionBits, ref encodedBits);
+            this.OK &= JxlU64Coder.CanEncode((ulong)extensionBits, ref encodedBits);
             totalBits += encodedBits;
 
             for (int i = 1; i < BitOperations.PopCount(this.extensions); i++)

src/ImageSharp/Formats/Jxl/Fields/JxlF16Coder.cs

@@ -2,6 +2,7 @@
 // Licensed under the Six Labors Split License.
 
 using SixLabors.ImageSharp.Formats.Jxl.Processing.Decoder;
+using SixLabors.ImageSharp.Formats.Jxl.Processing.Encoder;
 
 namespace SixLabors.ImageSharp.Formats.Jxl.Fields;
 

src/ImageSharp/Formats/Jxl/Fields/JxlU32Coder.cs

@@ -3,6 +3,7 @@
 
 using SixLabors.ImageSharp.Formats.Jxl.Processing;
 using SixLabors.ImageSharp.Formats.Jxl.Processing.Decoder;
+using SixLabors.ImageSharp.Formats.Jxl.Processing.Encoder;
 
 namespace SixLabors.ImageSharp.Formats.Jxl.Fields;
 

src/ImageSharp/Formats/Jxl/Fields/JxlU64Coder.cs

@@ -2,6 +2,7 @@
 // Licensed under the Six Labors Split License.
 
 using SixLabors.ImageSharp.Formats.Jxl.Processing.Decoder;
+using SixLabors.ImageSharp.Formats.Jxl.Processing.Encoder;
 
 namespace SixLabors.ImageSharp.Formats.Jxl.Fields;
 

src/ImageSharp/Formats/Jxl/Processing/Encoder/JxlBitWriter.cs

@@ -0,0 +1,88 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Formats.Jxl.Processing.Encoder;
+
+internal sealed class JxlBitWriter(Stream stream)
+{
+    private const int BitsPerByte = 8;
+
+    private bool isLimited;
+    private ulong bitsLimit;
+
+    private byte currentByte;
+    private int bitsInCurrentByte;
+
+    public long BitsWritten { get; private set; }
+
+    public void Write(int nBits, int bits) => this.Write(nBits, (ulong)bits);
+
+    public void Write(int nBits, ulong bits)
+    {
+        DebugGuard.MustBeGreaterThanOrEqualTo(nBits, 0, nameof(nBits));
+        DebugGuard.MustBeLessThanOrEqualTo(nBits, 64, nameof(nBits));
+
+        if (this.isLimited)
+        {
+            if ((ulong)nBits > this.bitsLimit)
+            {
+                throw new InvalidOperationException("Too many bits were written");
+            }
+
+            this.bitsLimit -= (ulong)nBits;
+        }
+
+        while (nBits > 0)
+        {
+            int bitsAvailable = BitsPerByte - this.bitsInCurrentByte;
+            int count = Math.Min(nBits, bitsAvailable);
+
+            ulong mask = count == 64
+                ? ulong.MaxValue
+                : (1UL << count) - 1;
+
+            this.currentByte |= (byte)((bits & mask) << this.bitsInCurrentByte);
+
+            bits >>= count;
+            nBits -= count;
+            this.bitsInCurrentByte += count;
+            this.BitsWritten += count;
+
+            if (this.bitsInCurrentByte == BitsPerByte)
+            {
+                stream.WriteByte(this.currentByte);
+                this.currentByte = 0;
+                this.bitsInCurrentByte = 0;
+            }
+        }
+    }
+
+    public bool WithMaxBits(ulong maxBits, Func<bool> func)
+    {
+        bool previousIsLimited = this.isLimited;
+        ulong previousLimit = this.bitsLimit;
+
+        this.isLimited = true;
+        this.bitsLimit = maxBits;
+
+        try
+        {
+            return func();
+        }
+        finally
+        {
+            this.isLimited = previousIsLimited;
+            this.bitsLimit = previousLimit;
+        }
+    }
+
+    public void Flush()
+    {
+        if (this.bitsInCurrentByte != 0)
+        {
+            stream.WriteByte(this.currentByte);
+            this.currentByte = 0;
+            this.bitsInCurrentByte = 0;
+        }
+    }
+}