param: Add contained-params-bitset export interface to the param layers

Allows for efficient looping over the contained data

src/lib/parameters/ConstLayer.h

@@ -51,6 +51,17 @@ public:
 		return param < PARAM_COUNT;
 	}
 
+	px4::AtomicBitset<PARAM_COUNT> containedAsBitset() const override
+	{
+		px4::AtomicBitset<PARAM_COUNT> set;
+
+		for (int i = 0; i < PARAM_COUNT; i++) {
+			set.set(i);
+		}
+
+		return set;
+	}
+
 	param_value_u get(param_t param) const override
 	{
 		if (param >= PARAM_COUNT) {

src/lib/parameters/DynamicSparseLayer.h

@@ -97,6 +97,19 @@ public:
 		return _getIndex(param) < _next_slot;
 	}
 
+	px4::AtomicBitset<PARAM_COUNT> containedAsBitset() const override
+	{
+		px4::AtomicBitset<PARAM_COUNT> set;
+		const AtomicTransaction transaction;
+		Slot *slots = _slots.load();
+
+		for (int i = 0; i < _next_slot; i++) {
+			set.set(slots[i].param);
+		}
+
+		return set;
+	}
+
 	param_value_u get(param_t param) const override
 	{
 		const AtomicTransaction transaction;

src/lib/parameters/ExhaustiveLayer.h

@@ -67,6 +67,11 @@ public:
 		return param < PARAM_COUNT && _ownership_set[param];
 	}
 
+	px4::AtomicBitset<PARAM_COUNT> containedAsBitset() const override
+	{
+		return _ownership_set;
+	}
+
 	param_value_u get(param_t param) const override
 	{
 		if (param >= PARAM_COUNT) {

src/lib/parameters/ParamLayer.h

@@ -31,9 +31,9 @@
  *
  ****************************************************************************/
 
-#ifndef PX4_PARAMLAYER_H
-#define PX4_PARAMLAYER_H
+#pragma once
 
+#include <px4_platform_common/atomic_bitset.h>
 #include "atomic_transaction.h"
 #include "param.h"
 #include <stdlib.h>
@@ -55,6 +55,8 @@ public:
 
 	virtual bool contains(param_t param) const = 0;
 
+	virtual px4::AtomicBitset<PARAM_COUNT> containedAsBitset() const = 0;
+
 	virtual param_value_u get(param_t param) const = 0;
 
 	virtual void reset(param_t param) = 0;
@@ -68,5 +70,3 @@ public:
 protected:
 	ParamLayer *const _parent;
 };
-
-#endif //PX4_PARAMLAYER_H

src/lib/parameters/StaticSparseLayer.h

@@ -74,6 +74,18 @@ public:
 		return _getIndex(param) < _next_slot;
 	}
 
+	px4::AtomicBitset<PARAM_COUNT> containedAsBitset() const override
+	{
+		px4::AtomicBitset<PARAM_COUNT> set;
+		const AtomicTransaction transaction;
+
+		for (int i = 0; i < _next_slot; i++) {
+			set.set(_slots[i].param);
+		}
+
+		return set;
+	}
+
 	param_value_u get(param_t param) const override
 	{
 		const AtomicTransaction transaction;

src/lib/parameters/flashparams/flashparams.cpp

@@ -84,16 +84,17 @@ param_export_internal(param_filter_func filter)
 	/* Use realloc */
 
 	bson_encoder_init_buf(&encoder, nullptr, 0);
+	auto changed_params = user_config.containedAsBitset();
 
 	for (param_t param = 0; param < user_config.PARAM_COUNT; param++) {
 
-		int32_t i;
-		float   f;
-
-		if (filter && !filter(param)) {
+		if (!changed_params[param] || (filter && !filter(param))) {
 			continue;
 		}
 
+		int32_t i;
+		float   f;
+
 		/* append the appropriate BSON type object */
 
 		switch (param_type(param)) {

src/lib/parameters/parameters.cpp

@@ -1039,6 +1039,7 @@ param_export(const char *filename, param_filter_func filter)
 static int param_export_internal(int fd, param_filter_func filter)
 {
 	PX4_DEBUG("param_export_internal");
+	const auto changed_params = user_config.containedAsBitset();
 
 	int result = -1;
 	bson_encoder_s encoder{};
@@ -1054,7 +1055,7 @@ static int param_export_internal(int fd, param_filter_func filter)
 	}
 
 	for (param_t param = 0; handle_in_range(param); param++) {
-		if (filter && !filter(param)) {
+		if (!changed_params[param] || (filter && !filter(param))) {
 			continue;
 		}