Sdl backend (#670)

* [audio] added sdl audio backend and in-tree atrac9 decoder

* [input] replaced per-platform pad readers with sdl gamepad input

* [video] added sdl window and host display plumbing

* [gui] added host display options and per-game render settings

* [bink] synced host movie playback to the guest audio clock

* [cpu] hooked windows write faults into guest image tracking

* [perf] added guest and render profiling, reserved host cpu lanes

* [kernel] fixed stale pthread mutex handle alias

* [host] wired the sdl session, save-data paths and project references

* [audio] hoisted ajm trace stackalloc out of its loop

* [video] Add guest image sync setting

* [build] Strip native symbols

* reuse

src/SharpEmu.LibAtrac9/Utilities/BitReader.cs

@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: MIT
+#nullable disable
+using System;
+using System.Diagnostics;
+
+namespace LibAtrac9.Utilities
+{
+    internal class BitReader
+    {
+        private byte[] Buffer { get; set; }
+        private int LengthBits { get; set; }
+        public int Position { get; set; }
+        private int Remaining => LengthBits - Position;
+
+        public BitReader(byte[] buffer) => SetBuffer(buffer);
+
+        public void SetBuffer(byte[] buffer)
+        {
+            Buffer = buffer;
+            LengthBits = Buffer?.Length * 8 ?? 0;
+            Position = 0;
+        }
+
+        public int ReadInt(int bitCount)
+        {
+            int value = PeekInt(bitCount);
+            Position += bitCount;
+            return value;
+        }
+
+        public int ReadSignedInt(int bitCount)
+        {
+            int value = PeekInt(bitCount);
+            Position += bitCount;
+            return Bit.SignExtend32(value, bitCount);
+        }
+
+        public bool ReadBool() => ReadInt(1) == 1;
+
+        public int ReadOffsetBinary(int bitCount, OffsetBias bias)
+        {
+            int offset = (1 << (bitCount - 1)) - (int)bias;
+            int value = PeekInt(bitCount) - offset;
+            Position += bitCount;
+            return value;
+        }
+
+        public void AlignPosition(int multiple)
+        {
+            Position = Helpers.GetNextMultiple(Position, multiple);
+        }
+
+        public int PeekInt(int bitCount)
+        {
+            Debug.Assert(bitCount >= 0 && bitCount <= 32);
+
+            if (bitCount > Remaining)
+            {
+                if (Position >= LengthBits) return 0;
+
+                int extraBits = bitCount - Remaining;
+                return PeekIntFallback(Remaining) << extraBits;
+            }
+
+            int byteIndex = Position / 8;
+            int bitIndex = Position % 8;
+
+            if (bitCount <= 9 && Remaining >= 16)
+            {
+                int value = Buffer[byteIndex] << 8 | Buffer[byteIndex + 1];
+                value &= 0xFFFF >> bitIndex;
+                value >>= 16 - bitCount - bitIndex;
+                return value;
+            }
+
+            if (bitCount <= 17 && Remaining >= 24)
+            {
+                int value = Buffer[byteIndex] << 16 | Buffer[byteIndex + 1] << 8 | Buffer[byteIndex + 2];
+                value &= 0xFFFFFF >> bitIndex;
+                value >>= 24 - bitCount - bitIndex;
+                return value;
+            }
+
+            if (bitCount <= 25 && Remaining >= 32)
+            {
+                int value = Buffer[byteIndex] << 24 | Buffer[byteIndex + 1] << 16 | Buffer[byteIndex + 2] << 8 | Buffer[byteIndex + 3];
+                value &= (int)(0xFFFFFFFF >> bitIndex);
+                value >>= 32 - bitCount - bitIndex;
+                return value;
+            }
+            return PeekIntFallback(bitCount);
+        }
+
+        private int PeekIntFallback(int bitCount)
+        {
+            int value = 0;
+            int byteIndex = Position / 8;
+            int bitIndex = Position % 8;
+
+            while (bitCount > 0)
+            {
+                if (bitIndex >= 8)
+                {
+                    bitIndex = 0;
+                    byteIndex++;
+                }
+
+                int bitsToRead = Math.Min(bitCount, 8 - bitIndex);
+                int mask = 0xFF >> bitIndex;
+                int currentByte = (mask & Buffer[byteIndex]) >> (8 - bitIndex - bitsToRead);
+
+                value = (value << bitsToRead) | currentByte;
+                bitIndex += bitsToRead;
+                bitCount -= bitsToRead;
+            }
+            return value;
+        }
+
+        /// <summary>
+        /// Specifies the bias of an offset binary value. A positive bias can represent one more
+        /// positive value than negative value, and a negative bias can represent one more
+        /// negative value than positive value.
+        /// </summary>
+        /// <remarks>Example:
+        /// A 4-bit offset binary value with a positive bias can store
+        /// the values 8 through -7 inclusive.
+        /// A 4-bit offset binary value with a positive bias can store
+        /// the values 7 through -8 inclusive.</remarks>
+        public enum OffsetBias
+        {
+            Negative = 0
+        }
+    }
+}