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

2026-07-31 15:09:42 +08:00 · 2026-07-28 01:05:42 +03:00
parent b4cc5f88ca
commit 8987fc396e
35 changed files with 3060 additions and 146 deletions
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: MIT
+#nullable disable
+namespace LibAtrac9.Utilities
+{
+    internal static class Bit
+    {
+        private static uint BitReverse32(uint value)
+        {
+            value = ((value & 0xaaaaaaaa) >> 1) | ((value & 0x55555555) << 1);
+            value = ((value & 0xcccccccc) >> 2) | ((value & 0x33333333) << 2);
+            value = ((value & 0xf0f0f0f0) >> 4) | ((value & 0x0f0f0f0f) << 4);
+            value = ((value & 0xff00ff00) >> 8) | ((value & 0x00ff00ff) << 8);
+            return (value >> 16) | (value << 16);
+        }
+        private static uint BitReverse32(uint value, int bitCount) => BitReverse32(value) >> (32 - bitCount);
+        public static int BitReverse32(int value, int bitCount) => (int) BitReverse32((uint) value, bitCount);
+
+        public static int SignExtend32(int value, int bits)
+        {
+            int shift = 8 * sizeof(int) - bits;
+            return (value << shift) >> shift;
+        }
+    }
+}