Add Chunked Audio Clip Store

Util/Audio/Clip/MemoryPCMReader.cs

@@ -0,0 +1,83 @@
+using System;
+using System.Collections.Generic;
+
+namespace ADOFAIRenderer.Util.Audio.Clip;
+
+/// <summary>
+/// Forward-only <see cref="IPCMReader"/> over PCM held in memory as a list of blocks.
+/// Block b holds frames [b * FramesPerBlock, (b + 1) * FramesPerBlock) interleaved; the last block may be shorter.
+/// Each block is released (passed to the release callback and dropped) as soon as the read position passes its end,
+/// and all remaining blocks are released on <see cref="Dispose"/>.
+/// </summary>
+internal sealed class MemoryPCMReader : IPCMReader
+{
+    private readonly float[]?[] _blocks;
+    private readonly Action<float[]>? _onBlockReleased;
+    private int _releasedCount; // Blocks [0, _releasedCount) are released
+
+    public int Channels { get; }
+    public int SampleRate { get; }
+    public long TotalFrames { get; }
+    public bool IsForwardOnly => true;
+    public long Position { get; private set; }
+
+    /// <summary>Frames per block (all blocks except the last).</summary>
+    public int FramesPerBlock { get; }
+
+    public MemoryPCMReader(IReadOnlyList<float[]> blocks, int framesPerBlock, int channels, int sampleRate, long totalFrames,
+        Action<float[]>? onBlockReleased)
+    {
+        if (channels <= 0) throw new ArgumentOutOfRangeException(nameof(channels));
+        if (framesPerBlock <= 0) throw new ArgumentOutOfRangeException(nameof(framesPerBlock));
+        if (totalFrames > (long)blocks.Count * framesPerBlock) throw new ArgumentException("Blocks hold fewer frames than totalFrames.", nameof(blocks));
+
+        _blocks = new float[blocks.Count][];
+        for (var i = 0; i < blocks.Count; i++) _blocks[i] = blocks[i];
+        _onBlockReleased = onBlockReleased;
+        FramesPerBlock = framesPerBlock;
+        Channels = channels;
+        SampleRate = sampleRate;
+        TotalFrames = totalFrames;
+    }
+
+    public void Seek(long frame)
+    {
+        if (frame < 0 || frame > TotalFrames) throw new ArgumentOutOfRangeException(nameof(frame));
+        if (frame < (long)_releasedCount * FramesPerBlock)
+            throw new InvalidOperationException($"Frame {frame} was already released by the forward-only reader.");
+        Position = frame;
+    }
+
+    public int Read(float[] buffer, int frameCount)
+    {
+        var total = (int)Math.Min(frameCount, TotalFrames - Position);
+        if (total <= 0) return 0;
+
+        var written = 0;
+        while (written < total)
+        {
+            var blockIndex = (int)(Position / FramesPerBlock);
+            var block = _blocks[blockIndex] ?? throw new InvalidOperationException($"Block {blockIndex} was already released.");
+            var offset = (int)(Position - (long)blockIndex * FramesPerBlock);
+            var count = Math.Min(total - written, FramesPerBlock - offset);
+            Array.Copy(block, offset * Channels, buffer, written * Channels, count * Channels);
+            written += count;
+            Position += count;
+            ReleaseBlocksBefore((int)(Position / FramesPerBlock));
+        }
+        return written;
+    }
+
+    private void ReleaseBlocksBefore(int blockIndex)
+    {
+        while (_releasedCount < blockIndex && _releasedCount < _blocks.Length)
+        {
+            var block = _blocks[_releasedCount];
+            _blocks[_releasedCount] = null;
+            _releasedCount++;
+            if (block != null) _onBlockReleased?.Invoke(block);
+        }
+    }
+
+    public void Dispose() => ReleaseBlocksBefore(_blocks.Length);
+}