From e7ee0fdac4c3ab94bc345e17356879487fdcf195 Mon Sep 17 00:00:00 2001
From: Dmitry Pentin <riotbr3aker@gmail.com>
Date: Sat, 8 Jan 2022 11:49:47 +0300
Subject: [PATCH] [WIP] outer scope memory propagation

---
 .../Jpeg/Components/Decoder/HuffmanScanDecoder.cs        | 4 ++--
 .../Formats/Jpeg/Components/Decoder/HuffmanTable.cs      | 9 +++++----
 src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs           | 3 ++-
 3 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanScanDecoder.cs b/src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanScanDecoder.cs
index 20c5d4a9b7..c06f3f2a04 100644
--- a/src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanScanDecoder.cs
+++ b/src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanScanDecoder.cs
@@ -728,10 +728,10 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// <param name="codeLengths">Code lengths.</param>
         /// <param name="values">Code values.</param>
         [MethodImpl(InliningOptions.ShortMethod)]
-        public void BuildHuffmanTable(int type, int index, ReadOnlySpan<byte> codeLengths, ReadOnlySpan<byte> values)
+        public void BuildHuffmanTable(int type, int index, ReadOnlySpan<byte> codeLengths, ReadOnlySpan<byte> values, Span<uint> workspace)
         {
             HuffmanTable[] tables = type == 0 ? this.dcHuffmanTables : this.acHuffmanTables;
-            tables[index] = new HuffmanTable(codeLengths, values);
+            tables[index] = new HuffmanTable(codeLengths, values, workspace);
         }
     }
 }
diff --git a/src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanTable.cs b/src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanTable.cs
index c69949de48..7e69c4d94f 100644
--- a/src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanTable.cs
+++ b/src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanTable.cs
@@ -51,13 +51,14 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// <summary>
         /// Initializes a new instance of the <see cref="HuffmanTable"/> struct.
         /// </summary>
-        /// <param name="codeLengths">The code lengths</param>
-        /// <param name="values">The huffman values</param>
-        public HuffmanTable(ReadOnlySpan<byte> codeLengths, ReadOnlySpan<byte> values)
+        /// <param name="codeLengths">The code lengths.</param>
+        /// <param name="values">The huffman values.</param>
+        /// <param name="workspace">The spare workspace memory, must be provided by the caller.</param>
+        public HuffmanTable(ReadOnlySpan<byte> codeLengths, ReadOnlySpan<byte> values, Span<uint> workspace)
         {
             Unsafe.CopyBlockUnaligned(ref this.Values[0], ref MemoryMarshal.GetReference(values), (uint)values.Length);
 
-            Span<uint> huffCode = stackalloc uint[257];
+            Span<uint> huffCode = workspace;
 
             // Generate codes
             uint code = 0;
diff --git a/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs b/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
index 08d1aa1468..adb0ad4b08 100644
--- a/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
+++ b/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
@@ -1150,7 +1150,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                                 tableType,
                                 tableIndex,
                                 codeLengthsSpan,
-                                huffmanValuesSpan);
+                                huffmanValuesSpan,
+                                stackalloc uint[257]);
                         }
                     }
                 }