Add benchmarks for Apple ADC decompression.

Aaru6.Compression/ADC.cs

@@ -0,0 +1,164 @@
+//
+// ADC.cs
+//
+// Author:
+//       Natalia Portillo <claunia@claunia.com>
+//
+// Copyright (c) 2016 © Claunia.com
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace Aaru6.Compression
+{
+    /// <summary>Implements the Apple version of RLE</summary>
+    public class ADC
+    {
+        const int PLAIN      = 1;
+        const int TWO_BYTE   = 2;
+        const int THREE_BYTE = 3;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        static int GetChunkType(byte byt) => (byt & 0x80) == 0x80
+                                                 ? PLAIN
+                                                 : (byt & 0x40) == 0x40
+                                                     ? THREE_BYTE
+                                                     : TWO_BYTE;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        static int GetChunkSize(byte byt) => GetChunkType(byt) switch
+        {
+            PLAIN      => (byt & 0x7F)        + 1,
+            TWO_BYTE   => ((byt & 0x3F) >> 2) + 3,
+            THREE_BYTE => (byt & 0x3F)        + 4,
+            _          => -1
+        };
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        static int GetOffset(ReadOnlySpan<byte> chunk) => GetChunkType(chunk[0]) switch
+        {
+            PLAIN      => 0,
+            TWO_BYTE   => ((chunk[0] & 0x03) << 8) + chunk[1],
+            THREE_BYTE => (chunk[1]          << 8) + chunk[2],
+            _          => -1
+        };
+
+        /// <summary>Decompresses a byte buffer that's compressed with ADC</summary>
+        /// <param name="source">Compressed buffer</param>
+        /// <param name="destination">Buffer to hold decompressed data</param>
+        /// <returns>How many bytes are stored on <paramref name="destination" /></returns>
+        [MethodImpl(MethodImplOptions.AggressiveOptimization)]
+        public static int DecodeBuffer(byte[] source, byte[] destination)
+        {
+            int        inputPosition = 0;
+            int        chunkSize;
+            int        offset;
+            int        chunkType;
+            int        outPosition = 0;
+            Span<byte> temp        = stackalloc byte[3];
+
+            while(inputPosition < source.Length)
+            {
+                byte readByte = source[inputPosition++];
+
+                chunkType = GetChunkType(readByte);
+
+                switch(chunkType)
+                {
+                    case PLAIN:
+                        chunkSize = GetChunkSize(readByte);
+
+                        if(outPosition + chunkSize > destination.Length)
+                            goto finished;
+
+                        Array.Copy(source, inputPosition, destination, outPosition, chunkSize);
+                        outPosition   += chunkSize;
+                        inputPosition += chunkSize;
+
+                        break;
+                    case TWO_BYTE:
+                        chunkSize = GetChunkSize(readByte);
+                        temp[0]   = readByte;
+                        temp[1]   = source[inputPosition++];
+                        offset    = GetOffset(temp);
+
+                        if(outPosition + chunkSize > destination.Length)
+                            goto finished;
+
+                        if(offset == 0)
+                        {
+                            byte lastByte = destination[outPosition - 1];
+
+                            for(int i = 0; i < chunkSize; i++)
+                            {
+                                destination[outPosition] = lastByte;
+                                outPosition++;
+                            }
+                        }
+                        else
+                        {
+                            for(int i = 0; i < chunkSize; i++)
+                            {
+                                destination[outPosition] = destination[outPosition - offset - 1];
+                                outPosition++;
+                            }
+                        }
+
+                        break;
+                    case THREE_BYTE:
+                        chunkSize = GetChunkSize(readByte);
+                        temp[0]   = readByte;
+                        temp[1]   = source[inputPosition++];
+                        temp[2]   = source[inputPosition++];
+                        offset    = GetOffset(temp);
+
+                        if(outPosition + chunkSize > destination.Length)
+                            goto finished;
+
+                        if(offset == 0)
+                        {
+                            byte lastByte = destination[outPosition - 1];
+
+                            for(int i = 0; i < chunkSize; i++)
+                            {
+                                destination[outPosition] = lastByte;
+                                outPosition++;
+                            }
+                        }
+                        else
+                        {
+                            for(int i = 0; i < chunkSize; i++)
+                            {
+                                destination[outPosition] = destination[outPosition - offset - 1];
+                                outPosition++;
+                            }
+                        }
+
+                        break;
+                }
+            }
+
+            finished:
+
+            return outPosition;
+        }
+    }
+}