diff --git a/src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/PdfJsHuffmanTable.cs b/src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/PdfJsHuffmanTable.cs index 1958de7c65..80cf7d5498 100644 --- a/src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/PdfJsHuffmanTable.cs +++ b/src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/PdfJsHuffmanTable.cs @@ -1,7 +1,8 @@ // Copyright (c) Six Labors and contributors. // Licensed under the Apache License, Version 2.0. -using System; +using System.Runtime.CompilerServices; +using System.Runtime.InteropServices; using SixLabors.ImageSharp.Memory; namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components @@ -39,12 +40,16 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components /// The huffman values public PdfJsHuffmanTable(MemoryManager memoryManager, byte[] lengths, byte[] values) { - using (IBuffer huffsize = memoryManager.Allocate(257)) - using (IBuffer huffcode = memoryManager.Allocate(257)) + const int length = 257; + using (IBuffer huffsize = memoryManager.Allocate(length)) + using (IBuffer huffcode = memoryManager.Allocate(length)) { - GenerateSizeTable(lengths, huffsize.Span); - GenerateCodeTable(huffsize.Span, huffcode.Span); - this.GenerateDecoderTables(lengths, huffcode.Span); + ref short huffsizeRef = ref MemoryMarshal.GetReference(huffsize.Span); + ref short huffcodeRef = ref MemoryMarshal.GetReference(huffcode.Span); + + GenerateSizeTable(lengths, ref huffsizeRef); + GenerateCodeTable(ref huffsizeRef, ref huffcodeRef, length); + this.GenerateDecoderTables(lengths, ref huffcodeRef); this.GenerateLookaheadTables(lengths, values); } @@ -61,8 +66,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components /// Figure C.1: make table of Huffman code length for each symbol /// /// The code lengths - /// The huffman size span - private static void GenerateSizeTable(byte[] lengths, Span huffsize) + /// The huffman size span ref + private static void GenerateSizeTable(byte[] lengths, ref short huffsizeRef) { short index = 0; for (short l = 1; l <= 16; l++) @@ -70,29 +75,30 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components byte i = lengths[l]; for (short j = 0; j < i; j++) { - huffsize[index] = l; + Unsafe.Add(ref huffsizeRef, index) = l; index++; } } - huffsize[index] = 0; + Unsafe.Add(ref huffsizeRef, index) = 0; } /// /// Figure C.2: generate the codes themselves /// - /// The huffman size span - /// The huffman code span - private static void GenerateCodeTable(Span huffsize, Span huffcode) + /// The huffman size span ref + /// The huffman code span ref + /// The length of the huffsize span + private static void GenerateCodeTable(ref short huffsizeRef, ref short huffcodeRef, int length) { short k = 0; - short si = huffsize[0]; + short si = huffsizeRef; short code = 0; - for (short i = 0; i < huffsize.Length; i++) + for (short i = 0; i < length; i++) { - while (huffsize[k] == si) + while (Unsafe.Add(ref huffsizeRef, k) == si) { - huffcode[k] = code; + Unsafe.Add(ref huffcodeRef, k) = code; code++; k++; } @@ -106,8 +112,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components /// Figure F.15: generate decoding tables for bit-sequential decoding /// /// The code lengths - /// The huffman code span - private void GenerateDecoderTables(byte[] lengths, Span huffcode) + /// The huffman code span ref + private void GenerateDecoderTables(byte[] lengths, ref short huffcodeRef) { fixed (short* valOffsetRef = this.ValOffset.Data) fixed (long* maxcodeRef = this.MaxCode.Data) @@ -117,10 +123,10 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components { if (lengths[i] != 0) { - // valOffsetRef[l] = huffval[] index of 1st symbol of code length i, minus the minimum code of length i - valOffsetRef[i] = (short)(bitcount - huffcode[bitcount]); + // valOffsetRef[l] = huffcodeRef[] index of 1st symbol of code length i, minus the minimum code of length i + valOffsetRef[i] = (short)(bitcount - Unsafe.Add(ref huffcodeRef, bitcount)); bitcount += lengths[i]; - maxcodeRef[i] = huffcode[bitcount - 1]; // maximum code of length i + maxcodeRef[i] = Unsafe.Add(ref huffcodeRef, bitcount - 1); // maximum code of length i } else {