Oversampler and Resampler

modules/yup_dsp/resampling/yup_CircularBuffer.h

@@ -0,0 +1,95 @@
+/*
+  ==============================================================================
+
+   This file is part of the YUP library.
+   Copyright (c) 2026 - kunitoki@gmail.com
+
+   YUP is an open source library subject to open-source licensing.
+
+   The code included in this file is provided under the terms of the ISC license
+   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
+   to use, copy, modify, and/or distribute this software for any purpose with or
+   without fee is hereby granted provided that the above copyright notice and
+   this permission notice appear in all copies.
+
+   YUP IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
+   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
+   DISCLAIMED.
+
+  ==============================================================================
+*/
+
+#pragma once
+
+namespace yup
+{
+
+//==============================================================================
+/**
+    Fixed-size circular (ring) buffer for efficient sample history access.
+
+    Provides O(1) push and random-read operations. Logically, index 0 refers to
+    the oldest element and index BufferSize - 1 to the most recently pushed one.
+
+    Intended as a building block for block-based DSP algorithms that require a
+    sliding window of sample history, such as polyphase resampling and FIR
+    convolution.
+
+    @tparam SampleType  Element type stored in the buffer.
+    @tparam BufferSize  Compile-time capacity (must be > 0).
+*/
+template <typename SampleType, int BufferSize>
+class CircularBuffer
+{
+public:
+    static_assert (BufferSize > 0, "CircularBuffer BufferSize must be greater than zero");
+
+    //==============================================================================
+    /** Default constructor. */
+    CircularBuffer() noexcept
+    {
+        buffer.fill (SampleType {});
+    }
+
+    /** Constructs a buffer with all entries initialised to initValue. */
+    explicit CircularBuffer (SampleType initValue) noexcept
+    {
+        buffer.fill (initValue);
+    }
+
+    //==============================================================================
+    /** Inserts value, overwriting the oldest entry and advancing the write pointer. */
+    forcedinline void push (SampleType value) noexcept
+    {
+        buffer[static_cast<std::size_t> (oldestIndex)] = value;
+
+        if (++oldestIndex == BufferSize)
+            oldestIndex = 0;
+    }
+
+    /** Returns the element at logical index (0 = oldest, BufferSize-1 = newest). */
+    forcedinline SampleType& operator[] (int index) noexcept
+    {
+        return buffer[static_cast<std::size_t> ((oldestIndex + index) % BufferSize)];
+    }
+
+    /** Returns the element at logical index (0 = oldest, BufferSize-1 = newest). */
+    const forcedinline SampleType& operator[] (int index) const noexcept
+    {
+        return buffer[static_cast<std::size_t> ((oldestIndex + index) % BufferSize)];
+    }
+
+    //==============================================================================
+    /** Resets all entries to zero and rewinds the write pointer. */
+    void clear() noexcept
+    {
+        buffer.fill (SampleType {});
+        oldestIndex = 0;
+    }
+
+private:
+    std::array<SampleType, static_cast<std::size_t> (BufferSize)> buffer {};
+    int oldestIndex = 0;
+};
+
+} // namespace yup