From 9b123a28f2c4bcabe11594cf76934a68f1228e79 Mon Sep 17 00:00:00 2001
From: Stefano D'Angelo <s@dangelo.audio>
Date: Thu, 21 Sep 2023 12:10:21 +0200
Subject: [PATCH] finalized bw_src_int

---
 include/bw_src_int.h | 365 ++++++++++++++++++++++++++++++++++++-------
 1 file changed, 309 insertions(+), 56 deletions(-)

diff --git a/include/bw_src_int.h b/include/bw_src_int.h
index fadae80..47a8824 100644
--- a/include/bw_src_int.h
+++ b/include/bw_src_int.h
@@ -35,7 +35,12 @@
  *    <ul>
  *      <li>Version <strong>1.0.0</strong>:
  *        <ul>
- *          <li><code>Fixed frequency response and improved speed.</code></li>
+ *          <li>Added <code>bw_src_int_reset_state_multi()</code> and updated
+ *              C++ API in this regard.</li>
+ *          <li>Now <code>bw_src_int_reset_state()</code> returns the initial
+ *              output value.</li>
+ *          <li>Added overloaded C++ <code>reset()</code> functions taking
+ *              arrays as arguments.</li>
  *          <li><code>bw_src_int_lim_process()</code> and
  *              <code>bw_src_int_lim_process_multi()</code> now use
  *              <code>size_t</code> to count samples and channels.</li>
@@ -44,9 +49,11 @@
  *          <li>Moved C++ code to C header.</li>
  *          <li>Added overloaded C++ <code>process()</code> function taking
  *              C-style arrays as arguments.</li>
+ *          <li>Fixed frequency response and improved speed.</li>
  *          <li>Removed usage of reserved identifiers.</li>
  *          <li>Clarified that the same buffer cannot be used for both input and
  *              output.</li>
+ *          <li>Added debugging code.</li>
  *        </ul>
  *      </li>
  *      <li>Version <strong>0.6.0</strong>:
@@ -93,26 +100,55 @@ typedef struct bw_src_int_state bw_src_int_state;
  *
  *    #### bw_src_int_init()
  *  ```>>> */
-static inline void bw_src_int_init(bw_src_int_coeffs *BW_RESTRICT coeffs, int ratio);
+static inline void bw_src_int_init(
+	bw_src_int_coeffs * BW_RESTRICT coeffs,
+	int                             ratio);
 /*! <<<```
  *    Initializes `coeffs` using the given resampling `ratio`.
  *
  *    If `ratio` is positive, then the sample rate of the output signal will be
  *    `ratio` times the sample rate of the input signal, otherwise, if it is
  *    negative, then the sample rate of the output signal will be equal to the
- *    sample rate of the input signal divided by `-ratio`. `ratio` *MUST NOT* be
- *    in [`-1`, `1`].
+ *    sample rate of the input signal divided by `-ratio`.
+ *
+ *    `ratio` must not be `0`.
  *
  *    #### bw_src_int_reset_state()
  *  ```>>> */
-static inline void bw_src_int_reset_state(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT state, float x_0);
+static inline float bw_src_int_reset_state(
+	const bw_src_int_coeffs * BW_RESTRICT coeffs,
+	bw_src_int_state * BW_RESTRICT        state,
+	float                                 x_0);
 /*! <<<```
  *    Resets the given `state` to its initial values using the given `coeffs`
- *    and the quiescent/initial input value `x_0`.
+ *    and the initial input value `x_0`.
+ *
+ *    Returns the corresponding initial output value.
+ *
+ *    #### bw_src_int_reset_state_multi()
+ *  ```>>> */
+static inline void bw_src_int_reset_state_multi(
+	const bw_src_int_coeffs * BW_RESTRICT              coeffs,
+	bw_src_int_state * BW_RESTRICT const * BW_RESTRICT state,
+	const float *                                      x_0,
+	float *                                            y_0,
+	size_t                                             n_channels);
+/*! <<<```
+ *    Resets each of the `n_channels` `state`s to its initial values using the
+ *    given `coeffs` and the corresponding initial input value in the `x_0`
+ *    array.
+ *
+ *    The corresponding initial output values are written into the `y_0` array,
+ *    if not `NULL`.
  *
  *    #### bw_src_int_process()
  *  ```>>> */
-static inline size_t bw_src_int_process(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT state, const float *BW_RESTRICT x, float *BW_RESTRICT y, size_t n_in_samples);
+static inline size_t bw_src_int_process(
+	const bw_src_int_coeffs * BW_RESTRICT coeffs,
+	bw_src_int_state * BW_RESTRICT        state,
+	const float * BW_RESTRICT             x,
+	float * BW_RESTRICT                   y,
+	size_t                                n_in_samples);
 /*! <<<```
  *    Processes the first `n_in_samples` of the input buffer `x` and fills the
  *    output buffer `y` using `coeffs`, while using and updating `state`.
@@ -127,7 +163,14 @@ static inline size_t bw_src_int_process(const bw_src_int_coeffs *BW_RESTRICT coe
  *
  *    #### bw_src_int_process_multi()
  *  ```>>> */
-static inline void bw_src_int_process_multi(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT const *BW_RESTRICT state, const float * const *BW_RESTRICT x, float *BW_RESTRICT const *BW_RESTRICT y, size_t *BW_RESTRICT n, size_t n_channels, size_t n_in_samples);
+static inline void bw_src_int_process_multi(
+	const bw_src_int_coeffs * BW_RESTRICT              coeffs,
+	bw_src_int_state * BW_RESTRICT const * BW_RESTRICT state,
+	const float * const * BW_RESTRICT                  x,
+	float *BW_RESTRICT const * BW_RESTRICT             y,
+	size_t                                             n_channels,
+	size_t                                             n_in_samples,
+	size_t * BW_RESTRICT                               n_out_samples);
 /*! <<<```
  *    Processes the first `n_in_samples` of the `n_channels` input buffers `x`
  *    and fills the `n_channels` output buffers `y` using `coeffs`, while using
@@ -140,8 +183,36 @@ static inline void bw_src_int_process_multi(const bw_src_int_coeffs *BW_RESTRICT
  *
  *    A given buffer cannot be used both as an input and output buffer.
  *
- *    `n` is filled with the number of generated output samples for each output
- *    buffer, if not `NULL`.
+ *    `n_out_samples` is filled with the number of generated output samples for
+ *    each output buffer, if not `NULL`.
+ *
+ *    #### bw_src_int_coeffs_is_valid()
+ *  ```>>> */
+static inline char bw_src_int_coeffs_is_valid(
+	const bw_src_int_coeffs * BW_RESTRICT coeffs);
+/*! <<<```
+ *    Tries to determine whether `coeffs` is valid and returns non-`0` if it
+ *    seems to be the case and `0` if it is certainly not. False positives are
+ *    possible, false negatives are not.
+ *
+ *    `coeffs` must at least point to a readable memory block of size greater
+ *    than or equal to that of `bw_src_int_coeffs`.
+ *
+ *    #### bw_src_int_state_is_valid()
+ *  ```>>> */
+static inline char bw_src_int_state_is_valid(
+	const bw_src_int_coeffs * BW_RESTRICT coeffs,
+	const bw_src_int_state * BW_RESTRICT  state);
+/*! <<<```
+ *    Tries to determine whether `state` is valid and returns non-`0` if it
+ *    seems to be the case and `0` if it is certainly not. False positives are
+ *    possible, false negatives are not.
+ *
+ *    If `coeffs` is not `NULL` extra cross-checks might be performed (`state`
+ *    is supposed to be associated to `coeffs`).
+ *
+ *    `state` must at least point to a readable memory block of size greater
+ *    than or equal to that of `bw_src_int_state`.
  *  }}} */
 
 #ifdef __cplusplus
@@ -160,23 +231,39 @@ extern "C" {
 #endif
 
 struct bw_src_int_coeffs {
-	int	ratio;
-	float	b0;
-	float	ma1;
-	float	ma2;
-	float	ma3;
-	float	ma4;
+#ifdef BW_DEBUG_DEEP
+	uint32_t			hash;
+	uint32_t			reset_id;
+#endif
+
+	// Coefficients
+	int				ratio;
+	float				b0;
+	float				ma1;
+	float				ma2;
+	float				ma3;
+	float				ma4;
 };
 
 struct bw_src_int_state {
-	int	i;
-	float	z1;
-	float	z2;
-	float	z3;
-	float	z4;
+#ifdef BW_DEBUG_DEEP
+	uint32_t	hash;
+	uint32_t	coeffs_reset_id;
+#endif
+
+	// States
+	int		i;
+	float		z1;
+	float		z2;
+	float		z3;
+	float		z4;
 };
 
-static inline void bw_src_int_init(bw_src_int_coeffs *BW_RESTRICT coeffs, int ratio) {
+static inline void bw_src_int_init(
+		bw_src_int_coeffs * BW_RESTRICT coeffs,
+		int ratio) {
+	BW_ASSERT(coeffs != NULL);
+
 	coeffs->ratio = ratio;
 	// 4th-degree Butterworth with cutoff at ratio * Nyquist, using bilinear transform w/ prewarping
 	const float fc = (float)(ratio >= 0 ? ratio : -ratio);
@@ -188,9 +275,23 @@ static inline void bw_src_int_init(bw_src_int_coeffs *BW_RESTRICT coeffs, int ra
 	coeffs->ma2 = k * ((6.82842712474619f - 6.f * T2) * T2 - 6.f);
 	coeffs->ma3 = k * (T * (T2 * (5.226251859505504f - 4.f * T) - 5.226251859505504f) + 4.f);
 	coeffs->ma4 = k * (T * (T * ((2.613125929752753f - T) * T - 3.414213562373095f) + 2.613125929752753f) - 1.f);
+
+#ifdef BW_DEBUG_DEEP
+	coeffs->hash = bw_hash_sdbm("bw_src_int_coeffs");
+	coeffs->reset_id = coeffs->hash + 1;
+#endif
+	BW_ASSERT_DEEP(bw_src_int_coeffs_is_valid(coeffs));
 }
 
-static inline void bw_src_int_reset_state(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT state, float x_0) {
+static inline float bw_src_int_reset_state(
+		const bw_src_int_coeffs * BW_RESTRICT coeffs,
+		bw_src_int_state * BW_RESTRICT        state,
+		float                                 x_0) {
+	BW_ASSERT(coeffs != NULL);
+	BW_ASSERT_DEEP(bw_src_int_coeffs_is_valid(coeffs));
+	BW_ASSERT(state != NULL);
+	BW_ASSERT(bw_is_finite(x_0));
+
 	if (coeffs->ratio < 0) {
 		// DF-II
 		state->z1 = x_0 / (1.f - coeffs->ma1 - coeffs->ma2 - coeffs->ma3 - coeffs->ma4);
@@ -206,9 +307,55 @@ static inline void bw_src_int_reset_state(const bw_src_int_coeffs *BW_RESTRICT c
 		state->z2 = (6.f * coeffs->b0 + coeffs->ma2) * x_0 + state->z3;
 		state->z1 = (k + coeffs->ma1) * x_0 + state->z2;
 	}
+	const float y = x_0;
+
+#ifdef BW_DEBUG_DEEP
+	state->hash = bw_hash_sdbm("bw_src_int_state");
+	state->coeffs_reset_id = coeffs->reset_id;
+#endif
+	BW_ASSERT_DEEP(bw_src_int_coeffs_is_valid(coeffs));
+	BW_ASSERT_DEEP(bw_src_int_state_is_valid(coeffs, state));
+	BW_ASSERT(bw_is_finite(y));
+
+	return y;
 }
 
-static inline size_t bw_src_int_process(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT state, const float *BW_RESTRICT x, float *BW_RESTRICT y, size_t n_in_samples) {
+static inline void bw_src_int_reset_state_multi(
+		const bw_src_int_coeffs * BW_RESTRICT              coeffs,
+		bw_src_int_state * BW_RESTRICT const * BW_RESTRICT state,
+		const float *                                      x_0,
+		float *                                            y_0,
+		size_t                                             n_channels) {
+	BW_ASSERT(coeffs != NULL);
+	BW_ASSERT_DEEP(bw_src_int_coeffs_is_valid(coeffs));
+	BW_ASSERT(state != NULL);
+	BW_ASSERT(x_0 != NULL);
+
+	if (y_0 != NULL)
+		for (size_t i = 0; i < n_channels; i++)
+			y_0[i] = bw_src_int_reset_state(coeffs, state[i], x_0[i]);
+	else
+		for (size_t i = 0; i < n_channels; i++)
+			bw_src_int_reset_state(coeffs, state[i], x_0[i]);
+
+	BW_ASSERT_DEEP(bw_src_int_coeffs_is_valid(coeffs));
+	BW_ASSERT_DEEP(y_0 != NULL ? bw_has_only_finite(y_0, n_channels) : 1);
+}
+
+static inline size_t bw_src_int_process(
+		const bw_src_int_coeffs * BW_RESTRICT coeffs,
+		bw_src_int_state * BW_RESTRICT        state,
+		const float * BW_RESTRICT             x,
+		float * BW_RESTRICT                   y,
+		size_t                                n_in_samples) {
+	BW_ASSERT(coeffs != NULL);
+	BW_ASSERT_DEEP(bw_src_int_coeffs_is_valid(coeffs));
+	BW_ASSERT(state != NULL);
+	BW_ASSERT_DEEP(bw_src_int_state_is_valid(coeffs, state));
+	BW_ASSERT(x != NULL);
+	BW_ASSERT_DEEP(bw_has_only_finite(x, n_in_samples));
+	BW_ASSERT(y != NULL);
+
 	size_t n = 0;
 	if (coeffs->ratio < 0) {
 		for (size_t i = 0; i < n_in_samples; i++) {
@@ -250,16 +397,76 @@ static inline size_t bw_src_int_process(const bw_src_int_coeffs *BW_RESTRICT coe
 			}
 		}
 	}
+
+	BW_ASSERT_DEEP(bw_src_int_coeffs_is_valid(coeffs));
+	BW_ASSERT_DEEP(bw_src_int_state_is_valid(coeffs, state));
+	BW_ASSERT(n <= (coeffs->ratio > 0 ? coeffs->ratio * n_in_samples : n_in_samples / (-coeffs->ratio)) + 1);
+
 	return n;
 }
 
-static inline void bw_src_int_process_multi(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT const *BW_RESTRICT state, const float * const *BW_RESTRICT x, float *BW_RESTRICT const *BW_RESTRICT y, size_t *BW_RESTRICT n, size_t n_channels, size_t n_in_samples) {
-	if (n != NULL)
+static inline void bw_src_int_process_multi(
+		const bw_src_int_coeffs * BW_RESTRICT              coeffs,
+		bw_src_int_state * BW_RESTRICT const * BW_RESTRICT state,
+		const float * const * BW_RESTRICT                  x,
+		float *BW_RESTRICT const * BW_RESTRICT             y,
+		size_t                                             n_channels,
+		size_t                                             n_in_samples,
+		size_t * BW_RESTRICT                               n_out_samples) {
+	BW_ASSERT(coeffs != NULL);
+	BW_ASSERT_DEEP(bw_src_int_coeffs_is_valid(coeffs));
+	BW_ASSERT(state != NULL);
+	BW_ASSERT(x != NULL);
+	BW_ASSERT(y != NULL);
+
+	if (n_out_samples != NULL)
 		for (size_t i = 0; i < n_channels; i++)
-			n[i] = bw_src_int_process(coeffs, state[i], x[i], y[i], n_in_samples);
+			n_out_samples[i] = bw_src_int_process(coeffs, state[i], x[i], y[i], n_in_samples);
 	else
 		for (size_t i = 0; i < n_channels; i++)
 			bw_src_int_process(coeffs, state[i], x[i], y[i], n_in_samples);
+
+	BW_ASSERT_DEEP(bw_src_int_coeffs_is_valid(coeffs));
+}
+
+static inline char bw_src_int_coeffs_is_valid(
+		const bw_src_int_coeffs * BW_RESTRICT coeffs) {
+	BW_ASSERT(coeffs != NULL);
+
+#ifdef BW_DEBUG_DEEP
+	if (coeffs->hash != bw_hash_sdbm("bw_src_int_coeffs"))
+		return 0;
+#endif
+
+	return coeffs->ratio != 0
+		&& bw_is_finite(coeffs->b0)
+		&& bw_is_finite(coeffs->ma1)
+		&& bw_is_finite(coeffs->ma2)
+		&& bw_is_finite(coeffs->ma3)
+		&& bw_is_finite(coeffs->ma4);
+}
+
+static inline char bw_src_int_state_is_valid(
+		const bw_src_int_coeffs * BW_RESTRICT coeffs,
+		const bw_src_int_state * BW_RESTRICT  state) {
+	BW_ASSERT(state != NULL);
+
+#ifdef BW_DEBUG_DEEP
+	if (state->hash != bw_hash_sdbm("bw_src_int_state"))
+		return 0;
+
+	if (coeffs != NULL && coeffs->reset_id != state->coeffs_reset_id)
+		return 0;
+#endif
+
+	if (coeffs)
+		if (coeffs->ratio < 0 && (state->i < 0 || state->i >= -coeffs->ratio))
+			return 0;
+
+	return bw_is_finite(state->z1)
+		&& bw_is_finite(state->z2)
+		&& bw_is_finite(state->z3)
+		&& bw_is_finite(state->z4);
 }
 
 #ifdef __cplusplus
@@ -278,16 +485,34 @@ template<size_t N_CHANNELS>
 class SRCInt {
 public:
 	SRCInt(int ratio);
-	
-	void reset(float x_0 = 0.f);
-	std::array<size_t, N_CHANNELS> process(
-		const float * const *x,
-		float * const *y,
-		size_t nInSamples);
-	std::array<size_t, N_CHANNELS> process(
-		std::array<const float *, N_CHANNELS> x,
-		std::array<float *, N_CHANNELS> y,
-		size_t nInSamples);
+
+	void reset(
+		float               x0 = 0.f,
+		float * BW_RESTRICT y0 = nullptr);
+
+	void reset(
+		float                                       x0,
+		std::array<float, N_CHANNELS> * BW_RESTRICT y0);
+
+	void reset(
+		const float * x0,
+		float *       y0 = nullptr);
+
+	void reset(
+		std::array<float, N_CHANNELS>               x0,
+		std::array<float, N_CHANNELS> * BW_RESTRICT y0 = nullptr);
+
+	void process(
+		const float * const * BW_RESTRICT x,
+		float * const * BW_RESTRICT       y,
+		size_t                            nInSamples,
+		size_t * BW_RESTRICT              nOutSamples = nullptr);
+
+	void process(
+		std::array<const float * BW_RESTRICT, N_CHANNELS> x,
+		std::array<float * BW_RESTRICT, N_CHANNELS>       y,
+		size_t                                            nInSamples,
+		std::array<size_t, N_CHANNELS> * BW_RESTRICT      nOutSamples = nullptr);
 /*! <<<...
  *  }
  *  ```
@@ -299,40 +524,68 @@ public:
  * change at any time in future versions. Please, do not use it directly. */
 
 private:
-	bw_src_int_coeffs	 coeffs;
-	bw_src_int_state	 states[N_CHANNELS];
-	bw_src_int_state	*BW_RESTRICT statesP[N_CHANNELS];
+	bw_src_int_coeffs		coeffs;
+	bw_src_int_state		states[N_CHANNELS];
+	bw_src_int_state * BW_RESTRICT	statesP[N_CHANNELS];
 };
 
 template<size_t N_CHANNELS>
-inline SRCInt<N_CHANNELS>::SRCInt(int ratio) {
+inline SRCInt<N_CHANNELS>::SRCInt(
+		int ratio) {
 	bw_src_int_init(&coeffs, ratio);
 	for (size_t i = 0; i < N_CHANNELS; i++)
 		statesP[i] = states + i;
 }
 
 template<size_t N_CHANNELS>
-inline void SRCInt<N_CHANNELS>::reset(float x_0) {
-	for (size_t i = 0; i < N_CHANNELS; i++)
-		bw_src_int_reset_state(&coeffs, states + i, x_0);
+inline void SRCInt<N_CHANNELS>::reset(
+		float               x0,
+		float * BW_RESTRICT y0) {
+	if (y0 != nullptr)
+		for (size_t i = 0; i < N_CHANNELS; i++)
+			y0[i] = bw_src_int_reset_state(&coeffs, states + i, x0);
+	else
+		for (size_t i = 0; i < N_CHANNELS; i++)
+			bw_src_int_reset_state(&coeffs, states + i, x0);
 }
 
 template<size_t N_CHANNELS>
-inline std::array<size_t, N_CHANNELS> SRCInt<N_CHANNELS>::process(
-		const float * const *x,
-		float * const *y,
-		size_t nInSamples) {
-	std::array<size_t, N_CHANNELS> ret;
-	bw_src_int_process_multi(&coeffs, statesP, x, y, ret.data(), N_CHANNELS, nInSamples);
-	return ret;
+inline void SRCInt<N_CHANNELS>::reset(
+		float                                       x0,
+		std::array<float, N_CHANNELS> * BW_RESTRICT y0) {
+	reset(x0, y0 != nullptr ? y0->data() : nullptr);
 }
 
 template<size_t N_CHANNELS>
-inline std::array<size_t, N_CHANNELS> SRCInt<N_CHANNELS>::process(
-		std::array<const float *, N_CHANNELS> x,
-		std::array<float *, N_CHANNELS> y,
-		size_t nInSamples) {
-	return process(x.data(), y.data(), nInSamples);
+inline void SRCInt<N_CHANNELS>::reset(
+		const float * x0,
+		float *       y0) {
+	bw_src_int_reset_state_multi(&coeffs, statesP, x0, y0, N_CHANNELS);
+}
+
+template<size_t N_CHANNELS>
+inline void SRCInt<N_CHANNELS>::reset(
+		std::array<float, N_CHANNELS>               x0,
+		std::array<float, N_CHANNELS> * BW_RESTRICT y0) {
+	reset(x0.data(), y0 != nullptr ? y0->data() : nullptr);
+}
+
+template<size_t N_CHANNELS>
+inline void SRCInt<N_CHANNELS>::process(
+		const float * const * BW_RESTRICT x,
+		float * const * BW_RESTRICT       y,
+		size_t                            nInSamples,
+		size_t * BW_RESTRICT              nOutSamples) {
+	bw_src_int_process_multi(&coeffs, statesP, x, y, N_CHANNELS, nInSamples, nOutSamples);
+}
+
+template<size_t N_CHANNELS>
+inline void SRCInt<N_CHANNELS>::process(
+		std::array<const float * BW_RESTRICT, N_CHANNELS> x,
+		std::array<float * BW_RESTRICT, N_CHANNELS>       y,
+		size_t                                            nInSamples,
+		std::array<size_t, N_CHANNELS> * BW_RESTRICT      nOutSamples) {
+	process(x.data(), y.data(), nInSamples, nOutSamples ? nOutSamples->data() : nullptr);
 }
 
 }