Merge branch 'master' into sw/fake-async-codecs

README.md

@@ -35,7 +35,7 @@ Please visit https://sixlabors.com/pricing for details.
 ## Documentation
 
 - [Detailed documentation](https://sixlabors.github.io/docs/) for the ImageSharp API is available. This includes additional conceptual documentation to help you get started.
-- Our [Samples Repository](https://github.com/SixLabors/Samples/tree/master/ImageSharp) is also available containing buildable code samples demonstrating commmon activities.
+- Our [Samples Repository](https://github.com/SixLabors/Samples/tree/master/ImageSharp) is also available containing buildable code samples demonstrating common activities.
 
 ## Questions
 
@@ -95,4 +95,4 @@ Please... Spread the word, contribute algorithms, submit performance improvement
 - [Dirk Lemstra](https://github.com/dlemstra)
 - [Anton Firsov](https://github.com/antonfirsov)
 - [Scott Williams](https://github.com/tocsoft)
-- [Brian Popow](https://github.com/brianpopow)
+- [Brian Popow](https://github.com/brianpopow)

src/ImageSharp/Formats/Png/PngDecoderCore.cs

@@ -30,11 +30,6 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// </summary>
         private readonly byte[] buffer = new byte[4];
 
-        /// <summary>
-        /// Reusable CRC for validating chunks.
-        /// </summary>
-        private readonly Crc32 crc = new Crc32();
-
         /// <summary>
         /// The global configuration.
         /// </summary>
@@ -1210,18 +1205,17 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// <param name="chunk">The <see cref="PngChunk"/>.</param>
         private void ValidateChunk(in PngChunk chunk)
         {
-            uint crc = this.ReadChunkCrc();
+            uint inputCrc = this.ReadChunkCrc();
 
             if (chunk.IsCritical)
             {
                 Span<byte> chunkType = stackalloc byte[4];
                 BinaryPrimitives.WriteUInt32BigEndian(chunkType, (uint)chunk.Type);
 
-                this.crc.Reset();
-                this.crc.Update(chunkType);
-                this.crc.Update(chunk.Data.GetSpan());
+                uint validCrc = Crc32.Calculate(chunkType);
+                validCrc = Crc32.Calculate(validCrc, chunk.Data.GetSpan());
 
-                if (this.crc.Value != crc)
+                if (validCrc != inputCrc)
                 {
                     string chunkTypeName = Encoding.ASCII.GetString(chunkType);
                     PngThrowHelper.ThrowInvalidChunkCrc(chunkTypeName);

src/ImageSharp/Formats/Png/PngEncoderCore.cs

@@ -48,11 +48,6 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// </summary>
         private readonly byte[] chunkDataBuffer = new byte[16];
 
-        /// <summary>
-        /// Reusable CRC for validating chunks.
-        /// </summary>
-        private readonly Crc32 crc = new Crc32();
-
         /// <summary>
         /// The encoder options
         /// </summary>
@@ -1145,18 +1140,16 @@ namespace SixLabors.ImageSharp.Formats.Png
 
             stream.Write(this.buffer, 0, 8);
 
-            this.crc.Reset();
-
-            this.crc.Update(this.buffer.AsSpan(4, 4)); // Write the type buffer
+            uint crc = Crc32.Calculate(this.buffer.AsSpan(4, 4)); // Write the type buffer
 
             if (data != null && length > 0)
             {
                 stream.Write(data, offset, length);
 
-                this.crc.Update(data.AsSpan(offset, length));
+                crc = Crc32.Calculate(crc, data.AsSpan(offset, length));
             }
 
-            BinaryPrimitives.WriteUInt32BigEndian(this.buffer, (uint)this.crc.Value);
+            BinaryPrimitives.WriteUInt32BigEndian(this.buffer, crc);
 
             stream.Write(this.buffer, 0, 4); // write the crc
         }

src/ImageSharp/Formats/Png/Zlib/Adler32.cs

@@ -3,146 +3,258 @@
 
 using System;
 using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
+#if SUPPORTS_RUNTIME_INTRINSICS
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.X86;
+#endif
 
+#pragma warning disable IDE0007 // Use implicit type
 namespace SixLabors.ImageSharp.Formats.Png.Zlib
 {
     /// <summary>
-    /// Computes Adler32 checksum for a stream of data. An Adler32
-    /// checksum is not as reliable as a CRC32 checksum, but a lot faster to
-    /// compute.
+    /// Calculates the 32 bit Adler checksum of a given buffer according to
+    /// RFC 1950. ZLIB Compressed Data Format Specification version 3.3)
     /// </summary>
-    /// <remarks>
-    /// The specification for Adler32 may be found in RFC 1950.
-    /// ZLIB Compressed Data Format Specification version 3.3)
-    ///
-    ///
-    /// From that document:
-    ///
-    ///      "ADLER32 (Adler-32 checksum)
-    ///       This contains a checksum value of the uncompressed data
-    ///       (excluding any dictionary data) computed according to Adler-32
-    ///       algorithm. This algorithm is a 32-bit extension and improvement
-    ///       of the Fletcher algorithm, used in the ITU-T X.224 / ISO 8073
-    ///       standard.
-    ///
-    ///       Adler-32 is composed of two sums accumulated per byte: s1 is
-    ///       the sum of all bytes, s2 is the sum of all s1 values. Both sums
-    ///       are done modulo 65521. s1 is initialized to 1, s2 to zero.  The
-    ///       Adler-32 checksum is stored as s2*65536 + s1 in most-
-    ///       significant-byte first (network) order."
-    ///
-    ///  "8.2. The Adler-32 algorithm
-    ///
-    ///    The Adler-32 algorithm is much faster than the CRC32 algorithm yet
-    ///    still provides an extremely low probability of undetected errors.
-    ///
-    ///    The modulo on unsigned long accumulators can be delayed for 5552
-    ///    bytes, so the modulo operation time is negligible.  If the bytes
-    ///    are a, b, c, the second sum is 3a + 2b + c + 3, and so is position
-    ///    and order sensitive, unlike the first sum, which is just a
-    ///    checksum.  That 65521 is prime is important to avoid a possible
-    ///    large class of two-byte errors that leave the check unchanged.
-    ///    (The Fletcher checksum uses 255, which is not prime and which also
-    ///    makes the Fletcher check insensitive to single byte changes 0 -
-    ///    255.)
-    ///
-    ///    The sum s1 is initialized to 1 instead of zero to make the length
-    ///    of the sequence part of s2, so that the length does not have to be
-    ///    checked separately. (Any sequence of zeroes has a Fletcher
-    ///    checksum of zero.)"
-    /// </remarks>
-    /// <see cref="ZlibInflateStream"/>
-    /// <see cref="ZlibDeflateStream"/>
-    internal sealed class Adler32 : IChecksum
+    internal static class Adler32
     {
         /// <summary>
-        /// largest prime smaller than 65536
+        /// The default initial seed value of a Adler32 checksum calculation.
         /// </summary>
-        private const uint Base = 65521;
+        public const uint SeedValue = 1U;
 
-        /// <summary>
-        /// The checksum calculated to far.
-        /// </summary>
-        private uint checksum;
+        // Largest prime smaller than 65536
+        private const uint BASE = 65521;
 
-        /// <summary>
-        /// Initializes a new instance of the <see cref="Adler32"/> class.
-        /// The checksum starts off with a value of 1.
-        /// </summary>
-        public Adler32()
-        {
-            this.Reset();
-        }
+        // NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
+        private const uint NMAX = 5552;
 
-        /// <inheritdoc/>
-        public long Value
-        {
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            get => this.checksum;
-        }
+#if SUPPORTS_RUNTIME_INTRINSICS
+        private const int MinBufferSize = 64;
 
-        /// <inheritdoc/>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public void Reset()
+        // The C# compiler emits this as a compile-time constant embedded in the PE file.
+        private static ReadOnlySpan<byte> Tap1Tap2 => new byte[]
         {
-            this.checksum = 1;
-        }
+            32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, // tap1
+            16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 // tap2
+        };
+#endif
+
+        /// <summary>
+        /// Calculates the Adler32 checksum with the bytes taken from the span.
+        /// </summary>
+        /// <param name="buffer">The readonly span of bytes.</param>
+        /// <returns>The <see cref="uint"/>.</returns>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public static uint Calculate(ReadOnlySpan<byte> buffer)
+            => Calculate(SeedValue, buffer);
 
         /// <summary>
-        /// Updates the checksum with a byte value.
+        /// Calculates the Adler32 checksum with the bytes taken from the span and seed.
         /// </summary>
-        /// <param name="value">
-        /// The data value to add. The high byte of the int is ignored.
-        /// </param>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public void Update(int value)
+        /// <param name="adler">The input Adler32 value.</param>
+        /// <param name="buffer">The readonly span of bytes.</param>
+        /// <returns>The <see cref="uint"/>.</returns>
+        [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
+        public static uint Calculate(uint adler, ReadOnlySpan<byte> buffer)
         {
-            // We could make a length 1 byte array and call update again, but I
-            // would rather not have that overhead
-            uint s1 = this.checksum & 0xFFFF;
-            uint s2 = this.checksum >> 16;
+            if (buffer.IsEmpty)
+            {
+                return adler;
+            }
 
-            s1 = (s1 + ((uint)value & 0xFF)) % Base;
-            s2 = (s1 + s2) % Base;
+#if SUPPORTS_RUNTIME_INTRINSICS
+            if (Sse3.IsSupported && buffer.Length >= MinBufferSize)
+            {
+                return CalculateSse(adler, buffer);
+            }
 
-            this.checksum = (s2 << 16) + s1;
+            return CalculateScalar(adler, buffer);
+#else
+            return CalculateScalar(adler, buffer);
+#endif
         }
 
-        /// <inheritdoc/>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public void Update(ReadOnlySpan<byte> data)
+        // Based on https://github.com/chromium/chromium/blob/master/third_party/zlib/adler32_simd.c
+#if SUPPORTS_RUNTIME_INTRINSICS
+        [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
+        private static unsafe uint CalculateSse(uint adler, ReadOnlySpan<byte> buffer)
         {
-            ref byte dataRef = ref MemoryMarshal.GetReference(data);
-            uint s1 = this.checksum & 0xFFFF;
-            uint s2 = this.checksum >> 16;
+            uint s1 = adler & 0xFFFF;
+            uint s2 = (adler >> 16) & 0xFFFF;
 
-            int count = data.Length;
-            int offset = 0;
+            // Process the data in blocks.
+            const int BLOCK_SIZE = 1 << 5;
 
-            while (count > 0)
+            uint length = (uint)buffer.Length;
+            uint blocks = length / BLOCK_SIZE;
+            length -= blocks * BLOCK_SIZE;
+
+            int index = 0;
+            fixed (byte* bufferPtr = buffer)
+            fixed (byte* tapPtr = Tap1Tap2)
             {
-                // We can defer the modulo operation:
-                // s1 maximally grows from 65521 to 65521 + 255 * 3800
-                // s2 maximally grows by 3800 * median(s1) = 2090079800 < 2^31
-                int n = 3800;
-                if (n > count)
+                index += (int)blocks * BLOCK_SIZE;
+                var localBufferPtr = bufferPtr;
+
+                // _mm_setr_epi8 on x86
+                Vector128<sbyte> tap1 = Sse2.LoadVector128((sbyte*)tapPtr);
+                Vector128<sbyte> tap2 = Sse2.LoadVector128((sbyte*)(tapPtr + 0x10));
+                Vector128<byte> zero = Vector128<byte>.Zero;
+                var ones = Vector128.Create((short)1);
+
+                while (blocks > 0)
                 {
-                    n = count;
+                    uint n = NMAX / BLOCK_SIZE;  /* The NMAX constraint. */
+                    if (n > blocks)
+                    {
+                        n = blocks;
+                    }
+
+                    blocks -= n;
+
+                    // Process n blocks of data. At most NMAX data bytes can be
+                    // processed before s2 must be reduced modulo BASE.
+                    Vector128<uint> v_ps = Vector128.CreateScalar(s1 * n);
+                    Vector128<uint> v_s2 = Vector128.CreateScalar(s2);
+                    Vector128<uint> v_s1 = Vector128<uint>.Zero;
+
+                    do
+                    {
+                        // Load 32 input bytes.
+                        Vector128<byte> bytes1 = Sse3.LoadDquVector128(localBufferPtr);
+                        Vector128<byte> bytes2 = Sse3.LoadDquVector128(localBufferPtr + 0x10);
+
+                        // Add previous block byte sum to v_ps.
+                        v_ps = Sse2.Add(v_ps, v_s1);
+
+                        // Horizontally add the bytes for s1, multiply-adds the
+                        // bytes by [ 32, 31, 30, ... ] for s2.
+                        v_s1 = Sse2.Add(v_s1, Sse2.SumAbsoluteDifferences(bytes1, zero).AsUInt32());
+                        Vector128<short> mad1 = Ssse3.MultiplyAddAdjacent(bytes1, tap1);
+                        v_s2 = Sse2.Add(v_s2, Sse2.MultiplyAddAdjacent(mad1, ones).AsUInt32());
+
+                        v_s1 = Sse2.Add(v_s1, Sse2.SumAbsoluteDifferences(bytes2, zero).AsUInt32());
+                        Vector128<short> mad2 = Ssse3.MultiplyAddAdjacent(bytes2, tap2);
+                        v_s2 = Sse2.Add(v_s2, Sse2.MultiplyAddAdjacent(mad2, ones).AsUInt32());
+
+                        localBufferPtr += BLOCK_SIZE;
+                    }
+                    while (--n > 0);
+
+                    v_s2 = Sse2.Add(v_s2, Sse2.ShiftLeftLogical(v_ps, 5));
+
+                    // Sum epi32 ints v_s1(s2) and accumulate in s1(s2).
+                    const byte S2301 = 0b1011_0001;  // A B C D -> B A D C
+                    const byte S1032 = 0b0100_1110;  // A B C D -> C D A B
+
+                    v_s1 = Sse2.Add(v_s1, Sse2.Shuffle(v_s1, S1032));
+
+                    s1 += v_s1.ToScalar();
+
+                    v_s2 = Sse2.Add(v_s2, Sse2.Shuffle(v_s2, S2301));
+                    v_s2 = Sse2.Add(v_s2, Sse2.Shuffle(v_s2, S1032));
+
+                    s2 = v_s2.ToScalar();
+
+                    // Reduce.
+                    s1 %= BASE;
+                    s2 %= BASE;
                 }
 
-                count -= n;
-                while (--n >= 0)
+                if (length > 0)
                 {
-                    s1 += Unsafe.Add(ref dataRef, offset++);
-                    s2 += s1;
+                    if (length >= 16)
+                    {
+                        s2 += s1 += localBufferPtr[0];
+                        s2 += s1 += localBufferPtr[1];
+                        s2 += s1 += localBufferPtr[2];
+                        s2 += s1 += localBufferPtr[3];
+                        s2 += s1 += localBufferPtr[4];
+                        s2 += s1 += localBufferPtr[5];
+                        s2 += s1 += localBufferPtr[6];
+                        s2 += s1 += localBufferPtr[7];
+                        s2 += s1 += localBufferPtr[8];
+                        s2 += s1 += localBufferPtr[9];
+                        s2 += s1 += localBufferPtr[10];
+                        s2 += s1 += localBufferPtr[11];
+                        s2 += s1 += localBufferPtr[12];
+                        s2 += s1 += localBufferPtr[13];
+                        s2 += s1 += localBufferPtr[14];
+                        s2 += s1 += localBufferPtr[15];
+
+                        localBufferPtr += 16;
+                        length -= 16;
+                    }
+
+                    while (length-- > 0)
+                    {
+                        s2 += s1 += *localBufferPtr++;
+                    }
+
+                    if (s1 >= BASE)
+                    {
+                        s1 -= BASE;
+                    }
+
+                    s2 %= BASE;
                 }
 
-                s1 %= Base;
-                s2 %= Base;
+                return s1 | (s2 << 16);
             }
+        }
+#endif
 
-            this.checksum = (s2 << 16) | s1;
+        [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
+        private static unsafe uint CalculateScalar(uint adler, ReadOnlySpan<byte> buffer)
+        {
+            uint s1 = adler & 0xFFFF;
+            uint s2 = (adler >> 16) & 0xFFFF;
+            uint k;
+
+            fixed (byte* bufferPtr = buffer)
+            {
+                var localBufferPtr = bufferPtr;
+                uint length = (uint)buffer.Length;
+
+                while (length > 0)
+                {
+                    k = length < NMAX ? length : NMAX;
+                    length -= k;
+
+                    while (k >= 16)
+                    {
+                        s2 += s1 += localBufferPtr[0];
+                        s2 += s1 += localBufferPtr[1];
+                        s2 += s1 += localBufferPtr[2];
+                        s2 += s1 += localBufferPtr[3];
+                        s2 += s1 += localBufferPtr[4];
+                        s2 += s1 += localBufferPtr[5];
+                        s2 += s1 += localBufferPtr[6];
+                        s2 += s1 += localBufferPtr[7];
+                        s2 += s1 += localBufferPtr[8];
+                        s2 += s1 += localBufferPtr[9];
+                        s2 += s1 += localBufferPtr[10];
+                        s2 += s1 += localBufferPtr[11];
+                        s2 += s1 += localBufferPtr[12];
+                        s2 += s1 += localBufferPtr[13];
+                        s2 += s1 += localBufferPtr[14];
+                        s2 += s1 += localBufferPtr[15];
+
+                        localBufferPtr += 16;
+                        k -= 16;
+                    }
+
+                    while (k-- > 0)
+                    {
+                        s2 += s1 += *localBufferPtr++;
+                    }
+
+                    s1 %= BASE;
+                    s2 %= BASE;
+                }
+
+                return (s2 << 16) | s1;
+            }
         }
     }
 }

src/ImageSharp/Formats/Png/Zlib/Crc32.Lut.cs

@@ -0,0 +1,70 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the GNU Affero General Public License, Version 3.
+
+namespace SixLabors.ImageSharp.Formats.Png.Zlib
+{
+    /// <content>
+    /// Contains precalulated tables for scalar calculations.
+    /// </content>
+    internal static partial class Crc32
+    {
+        /// <summary>
+        /// The table of all possible eight bit values for fast scalar lookup.
+        /// </summary>
+        private static readonly uint[] CrcTable =
+        {
+            0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419,
+            0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4,
+            0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07,
+            0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
+            0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7, 0x136C9856,
+            0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
+            0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4,
+            0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
+            0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3,
+            0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A,
+            0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599,
+            0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
+            0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190,
+            0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F,
+            0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E,
+            0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
+            0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED,
+            0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
+            0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3,
+            0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
+            0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A,
+            0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5,
+            0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010,
+            0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
+            0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17,
+            0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6,
+            0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615,
+            0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
+            0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344,
+            0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
+            0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A,
+            0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
+            0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1,
+            0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C,
+            0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF,
+            0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
+            0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE,
+            0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31,
+            0x2CD99E8B, 0x5BDEAE1D, 0x9B64C2B0, 0xEC63F226, 0x756AA39C,
+            0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
+            0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B,
+            0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242,
+            0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1,
+            0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
+            0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278,
+            0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7,
+            0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66,
+            0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
+            0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605,
+            0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8,
+            0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B,
+            0x2D02EF8D
+        };
+    }
+}

src/ImageSharp/Formats/Png/Zlib/Crc32.cs

@@ -4,151 +4,212 @@
 using System;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
+#if SUPPORTS_RUNTIME_INTRINSICS
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.X86;
+#endif
 
 namespace SixLabors.ImageSharp.Formats.Png.Zlib
 {
     /// <summary>
-    /// Generate a table for a byte-wise 32-bit CRC calculation on the polynomial:
-    /// x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1.
+    /// Calculates the 32 bit Cyclic Redundancy Check (CRC) checksum of a given buffer
+    /// according to the IEEE 802.3 specification.
     /// </summary>
-    /// <remarks>
-    /// <para>
-    /// Polynomials over GF(2) are represented in binary, one bit per coefficient,
-    /// with the lowest powers in the most significant bit.  Then adding polynomials
-    /// is just exclusive-or, and multiplying a polynomial by x is a right shift by
-    /// one.  If we call the above polynomial p, and represent a byte as the
-    /// polynomial q, also with the lowest power in the most significant bit (so the
-    /// byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
-    /// where a mod b means the remainder after dividing a by b.
-    /// </para>
-    /// <para>
-    /// This calculation is done using the shift-register method of multiplying and
-    /// taking the remainder.  The register is initialized to zero, and for each
-    /// incoming bit, x^32 is added mod p to the register if the bit is a one (where
-    /// x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
-    /// x (which is shifting right by one and adding x^32 mod p if the bit shifted
-    /// out is a one).  We start with the highest power (least significant bit) of
-    /// q and repeat for all eight bits of q.
-    /// </para>
-    /// <para>
-    /// The table is simply the CRC of all possible eight bit values.  This is all
-    /// the information needed to generate CRC's on data a byte at a time for all
-    /// combinations of CRC register values and incoming bytes.
-    /// </para>
-    /// </remarks>
-    internal sealed class Crc32 : IChecksum
+    internal static partial class Crc32
     {
         /// <summary>
-        /// The cycle redundancy check seed
+        /// The default initial seed value of a Crc32 checksum calculation.
         /// </summary>
-        private const uint CrcSeed = 0xFFFFFFFF;
+        public const uint SeedValue = 0U;
 
-        /// <summary>
-        /// The table of all possible eight bit values for fast lookup.
-        /// </summary>
-        private static readonly uint[] CrcTable =
+#if SUPPORTS_RUNTIME_INTRINSICS
+        private const int MinBufferSize = 64;
+        private const int ChunksizeMask = 15;
+
+        // Definitions of the bit-reflected domain constants k1, k2, k3, etc and
+        // the CRC32+Barrett polynomials given at the end of the paper.
+        private static readonly ulong[] K05Poly =
         {
-            0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419,
-            0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4,
-            0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07,
-            0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
-            0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7, 0x136C9856,
-            0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
-            0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4,
-            0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
-            0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3,
-            0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A,
-            0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599,
-            0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
-            0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190,
-            0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F,
-            0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E,
-            0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
-            0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED,
-            0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
-            0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3,
-            0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
-            0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A,
-            0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5,
-            0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010,
-            0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
-            0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17,
-            0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6,
-            0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615,
-            0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
-            0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344,
-            0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
-            0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A,
-            0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
-            0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1,
-            0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C,
-            0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF,
-            0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
-            0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE,
-            0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31,
-            0x2CD99E8B, 0x5BDEAE1D, 0x9B64C2B0, 0xEC63F226, 0x756AA39C,
-            0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
-            0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B,
-            0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242,
-            0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1,
-            0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
-            0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278,
-            0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7,
-            0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66,
-            0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
-            0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605,
-            0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8,
-            0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B,
-            0x2D02EF8D
+            0x0154442bd4, 0x01c6e41596, // k1, k2
+            0x01751997d0, 0x00ccaa009e, // k3, k4
+            0x0163cd6124, 0x0000000000, // k5, k0
+            0x01db710641, 0x01f7011641 // polynomial
         };
+#endif
 
         /// <summary>
-        /// The data checksum so far.
+        /// Calculates the CRC checksum with the bytes taken from the span.
         /// </summary>
-        private uint crc;
+        /// <param name="buffer">The readonly span of bytes.</param>
+        /// <returns>The <see cref="uint"/>.</returns>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public static uint Calculate(ReadOnlySpan<byte> buffer)
+            => Calculate(SeedValue, buffer);
 
-        /// <inheritdoc/>
-        public long Value
+        /// <summary>
+        /// Calculates the CRC checksum with the bytes taken from the span and seed.
+        /// </summary>
+        /// <param name="crc">The input CRC value.</param>
+        /// <param name="buffer">The readonly span of bytes.</param>
+        /// <returns>The <see cref="uint"/>.</returns>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public static uint Calculate(uint crc, ReadOnlySpan<byte> buffer)
         {
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            get => this.crc;
+            if (buffer.IsEmpty)
+            {
+                return crc;
+            }
 
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            set => this.crc = (uint)value;
+#if SUPPORTS_RUNTIME_INTRINSICS
+            if (Sse41.IsSupported && Pclmulqdq.IsSupported && buffer.Length >= MinBufferSize)
+            {
+                return ~CalculateSse(~crc, buffer);
+            }
+            else
+            {
+                return ~CalculateScalar(~crc, buffer);
+            }
+#else
+            return ~CalculateScalar(~crc, buffer);
+#endif
         }
 
-        /// <inheritdoc/>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public void Reset()
+#if SUPPORTS_RUNTIME_INTRINSICS
+        // Based on https://github.com/chromium/chromium/blob/master/third_party/zlib/crc32_simd.c
+        [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
+        private static unsafe uint CalculateSse(uint crc, ReadOnlySpan<byte> buffer)
         {
-            this.crc = 0;
-        }
+            int chunksize = buffer.Length & ~ChunksizeMask;
+            int length = chunksize;
 
-        /// <summary>
-        /// Updates the checksum with the given value.
-        /// </summary>
-        /// <param name="value">The byte is taken as the lower 8 bits of value.</param>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public void Update(int value)
-        {
-            this.crc ^= CrcSeed;
-            this.crc = CrcTable[(this.crc ^ value) & 0xFF] ^ (this.crc >> 8);
-            this.crc ^= CrcSeed;
+            fixed (byte* bufferPtr = buffer)
+            fixed (ulong* k05PolyPtr = K05Poly)
+            {
+                byte* localBufferPtr = bufferPtr;
+                ulong* localK05PolyPtr = k05PolyPtr;
+
+                // There's at least one block of 64.
+                Vector128<ulong> x1 = Sse2.LoadVector128((ulong*)(localBufferPtr + 0x00));
+                Vector128<ulong> x2 = Sse2.LoadVector128((ulong*)(localBufferPtr + 0x10));
+                Vector128<ulong> x3 = Sse2.LoadVector128((ulong*)(localBufferPtr + 0x20));
+                Vector128<ulong> x4 = Sse2.LoadVector128((ulong*)(localBufferPtr + 0x30));
+                Vector128<ulong> x5;
+
+                x1 = Sse2.Xor(x1, Sse2.ConvertScalarToVector128UInt32(crc).AsUInt64());
+
+                // k1, k2
+                Vector128<ulong> x0 = Sse2.LoadVector128(localK05PolyPtr + 0x0);
+
+                localBufferPtr += 64;
+                length -= 64;
+
+                // Parallel fold blocks of 64, if any.
+                while (length >= 64)
+                {
+                    x5 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x00);
+                    Vector128<ulong> x6 = Pclmulqdq.CarrylessMultiply(x2, x0, 0x00);
+                    Vector128<ulong> x7 = Pclmulqdq.CarrylessMultiply(x3, x0, 0x00);
+                    Vector128<ulong> x8 = Pclmulqdq.CarrylessMultiply(x4, x0, 0x00);
+
+                    x1 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x11);
+                    x2 = Pclmulqdq.CarrylessMultiply(x2, x0, 0x11);
+                    x3 = Pclmulqdq.CarrylessMultiply(x3, x0, 0x11);
+                    x4 = Pclmulqdq.CarrylessMultiply(x4, x0, 0x11);
+
+                    Vector128<ulong> y5 = Sse2.LoadVector128((ulong*)(localBufferPtr + 0x00));
+                    Vector128<ulong> y6 = Sse2.LoadVector128((ulong*)(localBufferPtr + 0x10));
+                    Vector128<ulong> y7 = Sse2.LoadVector128((ulong*)(localBufferPtr + 0x20));
+                    Vector128<ulong> y8 = Sse2.LoadVector128((ulong*)(localBufferPtr + 0x30));
+
+                    x1 = Sse2.Xor(x1, x5);
+                    x2 = Sse2.Xor(x2, x6);
+                    x3 = Sse2.Xor(x3, x7);
+                    x4 = Sse2.Xor(x4, x8);
+
+                    x1 = Sse2.Xor(x1, y5);
+                    x2 = Sse2.Xor(x2, y6);
+                    x3 = Sse2.Xor(x3, y7);
+                    x4 = Sse2.Xor(x4, y8);
+
+                    localBufferPtr += 64;
+                    length -= 64;
+                }
+
+                // Fold into 128-bits.
+                // k3, k4
+                x0 = Sse2.LoadVector128(k05PolyPtr + 0x2);
+
+                x5 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x00);
+                x1 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x11);
+                x1 = Sse2.Xor(x1, x2);
+                x1 = Sse2.Xor(x1, x5);
+
+                x5 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x00);
+                x1 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x11);
+                x1 = Sse2.Xor(x1, x3);
+                x1 = Sse2.Xor(x1, x5);
+
+                x5 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x00);
+                x1 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x11);
+                x1 = Sse2.Xor(x1, x4);
+                x1 = Sse2.Xor(x1, x5);
+
+                // Single fold blocks of 16, if any.
+                while (length >= 16)
+                {
+                    x2 = Sse2.LoadVector128((ulong*)localBufferPtr);
+
+                    x5 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x00);
+                    x1 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x11);
+                    x1 = Sse2.Xor(x1, x2);
+                    x1 = Sse2.Xor(x1, x5);
+
+                    localBufferPtr += 16;
+                    length -= 16;
+                }
+
+                // Fold 128 - bits to 64 - bits.
+                x2 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x10);
+                x3 = Vector128.Create(~0, 0, ~0, 0).AsUInt64(); // _mm_setr_epi32 on x86
+                x1 = Sse2.ShiftRightLogical128BitLane(x1, 8);
+                x1 = Sse2.Xor(x1, x2);
+
+                // k5, k0
+                x0 = Sse2.LoadScalarVector128(localK05PolyPtr + 0x4);
+
+                x2 = Sse2.ShiftRightLogical128BitLane(x1, 4);
+                x1 = Sse2.And(x1, x3);
+                x1 = Pclmulqdq.CarrylessMultiply(x1, x0, 0x00);
+                x1 = Sse2.Xor(x1, x2);
+
+                // Barret reduce to 32-bits.
+                // polynomial
+                x0 = Sse2.LoadVector128(localK05PolyPtr + 0x6);
+
+                x2 = Sse2.And(x1, x3);
+                x2 = Pclmulqdq.CarrylessMultiply(x2, x0, 0x10);
+                x2 = Sse2.And(x2, x3);
+                x2 = Pclmulqdq.CarrylessMultiply(x2, x0, 0x00);
+                x1 = Sse2.Xor(x1, x2);
+
+                crc = (uint)Sse41.Extract(x1.AsInt32(), 1);
+                return buffer.Length - chunksize == 0 ? crc : CalculateScalar(crc, buffer.Slice(chunksize));
+            }
         }
+#endif
 
-        /// <inheritdoc/>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public void Update(ReadOnlySpan<byte> data)
+        [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
+        private static uint CalculateScalar(uint crc, ReadOnlySpan<byte> buffer)
         {
-            this.crc ^= CrcSeed;
-
             ref uint crcTableRef = ref MemoryMarshal.GetReference(CrcTable.AsSpan());
-            for (int i = 0; i < data.Length; i++)
+            ref byte bufferRef = ref MemoryMarshal.GetReference(buffer);
+
+            for (int i = 0; i < buffer.Length; i++)
             {
-                this.crc = Unsafe.Add(ref crcTableRef, (int)((this.crc ^ data[i]) & 0xFF)) ^ (this.crc >> 8);
+                crc = Unsafe.Add(ref crcTableRef, (int)((crc ^ Unsafe.Add(ref bufferRef, i)) & 0xFF)) ^ (crc >> 8);
             }
 
-            this.crc ^= CrcSeed;
+            return crc;
         }
     }
 }

src/ImageSharp/Formats/Png/Zlib/IChecksum.cs

@@ -1,43 +0,0 @@
-// Copyright (c) Six Labors and contributors.
-// Licensed under the GNU Affero General Public License, Version 3.
-
-using System;
-
-namespace SixLabors.ImageSharp.Formats.Png.Zlib
-{
-    /// <summary>
-    /// Interface to compute a data checksum used by checked input/output streams.
-    /// A data checksum can be updated by one byte or with a byte array. After each
-    /// update the value of the current checksum can be returned by calling
-    /// <code>Value</code>. The complete checksum object can also be reset
-    /// so it can be used again with new data.
-    /// </summary>
-    internal interface IChecksum
-    {
-        /// <summary>
-        /// Gets the data checksum computed so far.
-        /// </summary>
-        long Value { get; }
-
-        /// <summary>
-        /// Resets the data checksum as if no update was ever called.
-        /// </summary>
-        void Reset();
-
-        /// <summary>
-        /// Adds one byte to the data checksum.
-        /// </summary>
-        /// <param name = "value">
-        /// The data value to add. The high byte of the integer is ignored.
-        /// </param>
-        void Update(int value);
-
-        /// <summary>
-        /// Updates the data checksum with the bytes taken from the span.
-        /// </summary>
-        /// <param name="data">
-        /// buffer an array of bytes
-        /// </param>
-        void Update(ReadOnlySpan<byte> data);
-    }
-}

src/ImageSharp/Formats/Png/Zlib/README.md

@@ -1,5 +1,11 @@
-Deflatestream implementation adapted from
+DeflateStream implementation adapted from
 
 https://github.com/icsharpcode/SharpZipLib
 
-LIcensed under MIT
+Licensed under MIT
+
+Crc32 and Adler32 SIMD implementation adapted from
+
+https://github.com/chromium/chromium
+
+Licensed under BSD 3-Clause "New" or "Revised" License

src/ImageSharp/Formats/Png/Zlib/ZlibDeflateStream.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.IO;
+using System.Runtime.CompilerServices;
 using SixLabors.ImageSharp.Memory;
 
 namespace SixLabors.ImageSharp.Formats.Png.Zlib
@@ -20,7 +21,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
         /// <summary>
         /// Computes the checksum for the data stream.
         /// </summary>
-        private readonly Adler32 adler32 = new Adler32();
+        private uint adler = Adler32.SeedValue;
 
         /// <summary>
         /// A value indicating whether this instance of the given entity has been disposed.
@@ -133,10 +134,11 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
         public override void SetLength(long value) => throw new NotSupportedException();
 
         /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
         public override void Write(byte[] buffer, int offset, int count)
         {
             this.deflateStream.Write(buffer, offset, count);
-            this.adler32.Update(buffer.AsSpan(offset, count));
+            this.adler = Adler32.Calculate(this.adler, buffer.AsSpan(offset, count));
         }
 
         /// <inheritdoc/>
@@ -153,7 +155,7 @@ namespace SixLabors.ImageSharp.Formats.Png.Zlib
                 this.deflateStream.Dispose();
 
                 // Add the crc
-                uint crc = (uint)this.adler32.Value;
+                uint crc = this.adler;
                 this.rawStream.WriteByte((byte)((crc >> 24) & 0xFF));
                 this.rawStream.WriteByte((byte)((crc >> 16) & 0xFF));
                 this.rawStream.WriteByte((byte)((crc >> 8) & 0xFF));

tests/Directory.Build.targets

@@ -34,6 +34,7 @@
     <PackageReference Update="Microsoft.NET.Test.Sdk" Version="16.5.0-preview-20200116-01" />
     <PackageReference Update="Moq" Version="4.10.0" />
     <PackageReference Update="Pfim" Version="0.9.1" />
+    <PackageReference Update="SharpZipLib" Version="1.2.0" />
     <PackageReference Update="System.Drawing.Common" Version="4.7.0" />
     <PackageReference Update="xunit" Version="2.4.1" />
     <PackageReference Update="xunit.runner.visualstudio" Version="2.4.1" />

tests/ImageSharp.Benchmarks/General/Adler32Benchmark.cs

@@ -0,0 +1,72 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the GNU Affero General Public License, Version 3.
+
+using System;
+using BenchmarkDotNet.Attributes;
+using SixLabors.ImageSharp.Formats.Png.Zlib;
+using SharpAdler32 = ICSharpCode.SharpZipLib.Checksum.Adler32;
+
+namespace SixLabors.ImageSharp.Benchmarks.General
+{
+    [Config(typeof(Config.ShortClr))]
+    public class Adler32Benchmark
+    {
+        private byte[] data;
+        private readonly SharpAdler32 adler = new SharpAdler32();
+
+        [Params(1024, 2048, 4096)]
+        public int Count { get; set; }
+
+        [GlobalSetup]
+        public void SetUp()
+        {
+            this.data = new byte[this.Count];
+            new Random(1).NextBytes(this.data);
+        }
+
+        [Benchmark(Baseline = true)]
+        public long SharpZipLibCalculate()
+        {
+            this.adler.Reset();
+            this.adler.Update(this.data);
+            return this.adler.Value;
+        }
+
+        [Benchmark]
+        public uint SixLaborsCalculate()
+        {
+            return Adler32.Calculate(this.data);
+        }
+    }
+
+    // ########## 17/05/2020 ##########
+    //
+    // |               Method |       Runtime | Count |        Mean |       Error |    StdDev | Ratio | RatioSD | Gen 0 | Gen 1 | Gen 2 | Allocated |
+    // |--------------------- |-------------- |------ |------------:|------------:|----------:|------:|--------:|------:|------:|------:|----------:|
+    // | SharpZipLibCalculate |    .NET 4.7.2 |  1024 |   793.18 ns |   775.66 ns | 42.516 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate |    .NET 4.7.2 |  1024 |   384.86 ns |    15.64 ns |  0.857 ns |  0.49 |    0.03 |     - |     - |     - |         - |
+    // |                      |               |       |             |             |           |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 2.1 |  1024 |   790.31 ns |   353.34 ns | 19.368 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 2.1 |  1024 |   465.28 ns |   652.41 ns | 35.761 ns |  0.59 |    0.03 |     - |     - |     - |         - |
+    // |                      |               |       |             |             |           |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 3.1 |  1024 |   877.25 ns |    97.89 ns |  5.365 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 3.1 |  1024 |    45.60 ns |    13.28 ns |  0.728 ns |  0.05 |    0.00 |     - |     - |     - |         - |
+    // |                      |               |       |             |             |           |       |         |       |       |       |           |
+    // | SharpZipLibCalculate |    .NET 4.7.2 |  2048 | 1,537.04 ns |   428.44 ns | 23.484 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate |    .NET 4.7.2 |  2048 |   849.76 ns | 1,066.34 ns | 58.450 ns |  0.55 |    0.04 |     - |     - |     - |         - |
+    // |                      |               |       |             |             |           |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 2.1 |  2048 | 1,616.97 ns |   276.70 ns | 15.167 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 2.1 |  2048 |   790.77 ns |   691.71 ns | 37.915 ns |  0.49 |    0.03 |     - |     - |     - |         - |
+    // |                      |               |       |             |             |           |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 3.1 |  2048 | 1,735.11 ns | 1,374.22 ns | 75.325 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 3.1 |  2048 |    87.80 ns |    56.84 ns |  3.116 ns |  0.05 |    0.00 |     - |     - |     - |         - |
+    // |                      |               |       |             |             |           |       |         |       |       |       |           |
+    // | SharpZipLibCalculate |    .NET 4.7.2 |  4096 | 3,054.53 ns |   796.41 ns | 43.654 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate |    .NET 4.7.2 |  4096 | 1,538.90 ns |   487.02 ns | 26.695 ns |  0.50 |    0.01 |     - |     - |     - |         - |
+    // |                      |               |       |             |             |           |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 2.1 |  4096 | 3,223.48 ns |    32.32 ns |  1.771 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 2.1 |  4096 | 1,547.60 ns |   309.72 ns | 16.977 ns |  0.48 |    0.01 |     - |     - |     - |         - |
+    // |                      |               |       |             |             |           |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 3.1 |  4096 | 3,672.33 ns | 1,095.81 ns | 60.065 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 3.1 |  4096 |   159.44 ns |    36.31 ns |  1.990 ns |  0.04 |    0.00 |     - |     - |     - |         - |
+}

tests/ImageSharp.Benchmarks/General/Crc32Benchmark.cs

@@ -0,0 +1,72 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the GNU Affero General Public License, Version 3.
+
+using System;
+using BenchmarkDotNet.Attributes;
+using SixLabors.ImageSharp.Formats.Png.Zlib;
+using SharpCrc32 = ICSharpCode.SharpZipLib.Checksum.Crc32;
+
+namespace SixLabors.ImageSharp.Benchmarks.General
+{
+    [Config(typeof(Config.ShortClr))]
+    public class Crc32Benchmark
+    {
+        private byte[] data;
+        private readonly SharpCrc32 crc = new SharpCrc32();
+
+        [Params(1024, 2048, 4096)]
+        public int Count { get; set; }
+
+        [GlobalSetup]
+        public void SetUp()
+        {
+            this.data = new byte[this.Count];
+            new Random(1).NextBytes(this.data);
+        }
+
+        [Benchmark(Baseline = true)]
+        public long SharpZipLibCalculate()
+        {
+            this.crc.Reset();
+            this.crc.Update(this.data);
+            return this.crc.Value;
+        }
+
+        [Benchmark]
+        public long SixLaborsCalculate()
+        {
+            return Crc32.Calculate(this.data);
+        }
+    }
+
+    // ########## 17/05/2020 ##########
+    //
+    // |               Method |       Runtime | Count |         Mean |        Error |     StdDev | Ratio | RatioSD | Gen 0 | Gen 1 | Gen 2 | Allocated |
+    // |--------------------- |-------------- |------ |-------------:|-------------:|-----------:|------:|--------:|------:|------:|------:|----------:|
+    // | SharpZipLibCalculate |    .NET 4.7.2 |  1024 |  2,797.77 ns |   278.697 ns |  15.276 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate |    .NET 4.7.2 |  1024 |  2,275.56 ns |   216.100 ns |  11.845 ns |  0.81 |    0.01 |     - |     - |     - |         - |
+    // |                      |               |       |              |              |            |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 2.1 |  1024 |  2,923.43 ns | 2,656.882 ns | 145.633 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 2.1 |  1024 |  2,257.79 ns |    75.081 ns |   4.115 ns |  0.77 |    0.04 |     - |     - |     - |         - |
+    // |                      |               |       |              |              |            |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 3.1 |  1024 |  2,764.14 ns |    86.281 ns |   4.729 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 3.1 |  1024 |     49.32 ns |     1.813 ns |   0.099 ns |  0.02 |    0.00 |     - |     - |     - |         - |
+    // |                      |               |       |              |              |            |       |         |       |       |       |           |
+    // | SharpZipLibCalculate |    .NET 4.7.2 |  2048 |  5,603.71 ns |   427.240 ns |  23.418 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate |    .NET 4.7.2 |  2048 |  4,525.02 ns |    33.931 ns |   1.860 ns |  0.81 |    0.00 |     - |     - |     - |         - |
+    // |                      |               |       |              |              |            |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 2.1 |  2048 |  5,563.32 ns |    49.337 ns |   2.704 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 2.1 |  2048 |  4,519.61 ns |    29.837 ns |   1.635 ns |  0.81 |    0.00 |     - |     - |     - |         - |
+    // |                      |               |       |              |              |            |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 3.1 |  2048 |  5,543.37 ns |   518.551 ns |  28.424 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 3.1 |  2048 |     89.07 ns |     3.312 ns |   0.182 ns |  0.02 |    0.00 |     - |     - |     - |         - |
+    // |                      |               |       |              |              |            |       |         |       |       |       |           |
+    // | SharpZipLibCalculate |    .NET 4.7.2 |  4096 | 11,396.95 ns |   373.450 ns |  20.470 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate |    .NET 4.7.2 |  4096 |  9,070.35 ns |   271.083 ns |  14.859 ns |  0.80 |    0.00 |     - |     - |     - |         - |
+    // |                      |               |       |              |              |            |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 2.1 |  4096 | 11,127.81 ns |   239.177 ns |  13.110 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 2.1 |  4096 |  9,050.46 ns |   230.916 ns |  12.657 ns |  0.81 |    0.00 |     - |     - |     - |         - |
+    // |                      |               |       |              |              |            |       |         |       |       |       |           |
+    // | SharpZipLibCalculate | .NET Core 3.1 |  4096 | 11,098.62 ns |   687.978 ns |  37.710 ns |  1.00 |    0.00 |     - |     - |     - |         - |
+    // |   SixLaborsCalculate | .NET Core 3.1 |  4096 |    168.11 ns |     3.633 ns |   0.199 ns |  0.02 |    0.00 |     - |     - |     - |         - |
+}

tests/ImageSharp.Benchmarks/ImageSharp.Benchmarks.csproj

@@ -25,6 +25,7 @@
     <PackageReference Include="BenchmarkDotNet.Diagnostics.Windows" Condition="'$(OS)' == 'Windows_NT'" />
     <PackageReference Include="Colourful" />
     <PackageReference Include="Pfim" />
+    <PackageReference Include="SharpZipLib"  />
     <PackageReference Include="System.Drawing.Common" />
   </ItemGroup>
 

tests/ImageSharp.Tests/Formats/Png/Adler32Tests.cs

@@ -0,0 +1,50 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the GNU Affero General Public License, Version 3.
+
+using System;
+using SixLabors.ImageSharp.Formats.Png.Zlib;
+using Xunit;
+using SharpAdler32 = ICSharpCode.SharpZipLib.Checksum.Adler32;
+
+namespace SixLabors.ImageSharp.Tests.Formats.Png
+{
+    public class Adler32Tests
+    {
+        [Theory]
+        [InlineData(0)]
+        [InlineData(1)]
+        [InlineData(2)]
+        public void ReturnsCorrectWhenEmpty(uint input)
+        {
+            Assert.Equal(input, Adler32.Calculate(input, default));
+        }
+
+        [Theory]
+        [InlineData(0)]
+        [InlineData(8)]
+        [InlineData(215)]
+        [InlineData(1024)]
+        [InlineData(1024 + 15)]
+        [InlineData(2034)]
+        [InlineData(4096)]
+        public void MatchesReference(int length)
+        {
+            var data = GetBuffer(length);
+            var adler = new SharpAdler32();
+            adler.Update(data);
+
+            long expected = adler.Value;
+            long actual = Adler32.Calculate(data);
+
+            Assert.Equal(expected, actual);
+        }
+
+        private static byte[] GetBuffer(int length)
+        {
+            var data = new byte[length];
+            new Random(1).NextBytes(data);
+
+            return data;
+        }
+    }
+}

tests/ImageSharp.Tests/Formats/Png/Crc32Tests.cs

@@ -0,0 +1,50 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the GNU Affero General Public License, Version 3.
+
+using System;
+using SixLabors.ImageSharp.Formats.Png.Zlib;
+using Xunit;
+using SharpCrc32 = ICSharpCode.SharpZipLib.Checksum.Crc32;
+
+namespace SixLabors.ImageSharp.Tests.Formats.Png
+{
+    public class Crc32Tests
+    {
+        [Theory]
+        [InlineData(0)]
+        [InlineData(1)]
+        [InlineData(2)]
+        public void ReturnsCorrectWhenEmpty(uint input)
+        {
+            Assert.Equal(input, Crc32.Calculate(input, default));
+        }
+
+        [Theory]
+        [InlineData(0)]
+        [InlineData(8)]
+        [InlineData(215)]
+        [InlineData(1024)]
+        [InlineData(1024 + 15)]
+        [InlineData(2034)]
+        [InlineData(4096)]
+        public void MatchesReference(int length)
+        {
+            var data = GetBuffer(length);
+            var crc = new SharpCrc32();
+            crc.Update(data);
+
+            long expected = crc.Value;
+            long actual = Crc32.Calculate(data);
+
+            Assert.Equal(expected, actual);
+        }
+
+        private static byte[] GetBuffer(int length)
+        {
+            var data = new byte[length];
+            new Random(1).NextBytes(data);
+
+            return data;
+        }
+    }
+}

tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.Chunks.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the GNU Affero General Public License, Version 3.
 
+using System;
 using System.Buffers.Binary;
 using System.IO;
 using System.Text;
@@ -16,6 +17,9 @@ namespace SixLabors.ImageSharp.Tests.Formats.Png
 {
     public partial class PngDecoderTests
     {
+        // Represents ASCII string of "123456789"
+        private readonly byte[] check = { 49, 50, 51, 52, 53, 54, 55, 56, 57 };
+
         // Contains the png marker, IHDR and pHYs chunks of a 1x1 pixel 32bit png 1 a single black pixel.
         private static readonly byte[] Raw1X1PngIhdrAndpHYs =
             {
@@ -79,20 +83,6 @@ namespace SixLabors.ImageSharp.Tests.Formats.Png
             }
         }
 
-        [Fact]
-        public void CalculateCrc_Works()
-        {
-            // arrange
-            var data = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 };
-            var crc = new Crc32();
-
-            // act
-            crc.Update(data);
-
-            // assert
-            Assert.Equal(0x88AA689F, crc.Value);
-        }
-
         private static string GetChunkTypeName(uint value)
         {
             var data = new byte[4];

tests/ImageSharp.Tests/ImageSharp.Tests.csproj

@@ -21,6 +21,7 @@
     <PackageReference Include="Magick.NET-Q16-AnyCPU" />
     <PackageReference Include="Microsoft.DotNet.RemoteExecutor" />
     <PackageReference Include="Moq" />
+    <PackageReference Include="SharpZipLib"  />
     <PackageReference Include="System.Drawing.Common" />
   </ItemGroup>