Scaled channel ints (#4129)

* test that fails today

* Revert "int32 scaled_channel has float precision #4128"

This reverts commit eb82fbc162.

* fix the problem

* format

* x

* s

firmware/util/scaled_channel.h

@@ -32,19 +32,30 @@ class scaled_channel : scaled_channel_base {
 	using TSelf = scaled_channel<T, mul, div>;
 
 public:
+	struct IncompleteType;
+
 	constexpr scaled_channel() : m_value(static_cast<T>(0)) { }
-	constexpr scaled_channel(float val)
+
-	{
+	// Only allow conversion directly to T when mul/div are both 1, otherwise this constructor doesn't exist and the float conversion is used.
-		val *= float(mul) / div;
+	constexpr scaled_channel(std::conditional_t<mul == 1 && div == 1, T, IncompleteType> val) {
-		if (std::is_integral_v<T>) {
+		m_value = val;
-			m_value = std::roundf(val);
+	}
-		} else {
+
-			m_value = val;
+	// Scale the float in to our scaled channel
-		}
+	constexpr scaled_channel(std::conditional_t<mul != 1 || div != 1, float, IncompleteType> val) {
+		// If there are scale factors, it must NOT be a float. Why would you scale a float?
+		static_assert(std::is_integral_v<T>);
+
+		m_value = std::roundf(val * float(mul) / div);
+	}
+
+	// Only allow conversion directly to T when mul/div are both 1, otherwise this operator doesn't exist and the float conversion is used.
+	constexpr operator typename std::conditional_t<mul == 1 && div == 1, T, IncompleteType>() const {
+		return m_value;
 	}
 
 	// Allow reading back out as a float (note: this may be lossy!)
-	constexpr operator float() const {
+	constexpr operator typename std::conditional_t<mul != 1 || div != 1, float, IncompleteType>() const {
 		return m_value * (float(div) / mul);
 	}
 
@@ -56,7 +67,6 @@ public:
 		static_assert(mul == 1 && div == 1,
 			      "Increment operator only supported for non-scaled integer types");
 		static_assert(std::is_integral_v<T>, "Increment operator only supported for non-scaled integer types");
-	
 
 		m_value++;
 	}

java_console/io/src/test/java/com/rusefi/native_/JniUnitTest.java

@@ -9,7 +9,8 @@ import org.junit.Test;
 
 import java.nio.ByteBuffer;
 
-import static com.rusefi.config.generated.Fields.*;
+import static com.rusefi.config.generated.Fields.TS_FILE_VERSION;
+import static com.rusefi.config.generated.Fields.engine_type_e_MRE_MIATA_NB2_MAP;
 import static com.rusefi.shared.FileUtil.littleEndianWrap;
 import static junit.framework.Assert.*;
 
@@ -24,10 +25,7 @@ public class JniUnitTest {
 
         engineLogic.invokePeriodicCallback();
 
-        /*
-        todo: fix me https://github.com/rusefi/rusefi/issues/4128
         assertEquals(TS_FILE_VERSION, (int) getValue(engineLogic.getOutputs(), Sensor.FIRMWARE_VERSION));
-         */
 
         assertEquals(14.0, getValue(engineLogic.getOutputs(), Sensor.TARGET_AFR));
         double veValue = getValue(engineLogic.getOutputs(), Sensor.veValue);

unit_tests/tests/util/test_scaled_channel.cpp

@@ -32,3 +32,14 @@ TEST(ScaledChannel, Basic) {
 		i2 =  -11; EXPECT_FLOAT_EQ(i2,  -10); // round
 	}
 }
+
+TEST(ScaledChannel, IntegerBehavior) {
+	scaled_channel<uint32_t, 1, 1> test;
+
+	// Check that a round trip thru scaled_channel gets us back the same integer
+	uint32_t a = 20210311;
+	test = a;
+	uint32_t b = test;
+
+	EXPECT_EQ(a, b);
+}