Allow scaled_channel to have both multiplier and divisor (#3468)

Disallow scaled_channel for float.  I can't think of a reason to allow it, and it gets in the way
of rounding.

Add separate template param to setTable; let the compiler sort out whether assignment can happen
between TElement and VElement without forcing them to be the same at function call time.

firmware/controllers/algo/rusefi_types.h

@@ -96,7 +96,7 @@ typedef brain_pin_e egt_cs_array_t[EGT_CHANNEL_COUNT];
 
 #if __cplusplus
 #include "scaled_channel.h"
-using ve_table_t = scaled_channel<float, 1>[FUEL_LOAD_COUNT][FUEL_RPM_COUNT];
+using ve_table_t = float[FUEL_LOAD_COUNT][FUEL_RPM_COUNT];
 using lambda_table_t = scaled_channel<uint8_t, PACK_MULT_LAMBDA_CFG>[FUEL_LOAD_COUNT][FUEL_RPM_COUNT];
 #endif
 

firmware/util/containers/table_helper.h

@@ -152,17 +152,8 @@ void setArrayValues(TValue (&array)[TSize], TValue value) {
 	}
 }
 
-template <typename TElement, size_t N, size_t M>
-constexpr void setTable(TElement (&dest)[N][M], const TElement value) {
-	for (size_t n = 0; n < N; n++) {
-		for (size_t m = 0; m < M; m++) {
-			dest[n][m] = value;
-		}
-	}
-}
-
-template <typename TElement, size_t N, size_t M, int mult = 1>
-constexpr void setTable(scaled_channel<TElement, mult> (&dest)[N][M], float value) {
+template <typename TElement, typename VElement, size_t N, size_t M>
+constexpr void setTable(TElement (&dest)[N][M], const VElement value) {
 	for (size_t n = 0; n < N; n++) {
 		for (size_t m = 0; m < M; m++) {
 			dest[n][m] = value;

firmware/util/scaled_channel.h

@@ -11,6 +11,7 @@
 
 #pragma once
 
+#include <cmath>
 #include <cstdint>
 #include <type_traits>
 
@@ -26,20 +27,25 @@ static constexpr bool is_scaled_channel = std::is_base_of_v<scaled_channel_base,
 // scaled_channel<uint8_t, 10> myVar;
 // myVar = 2.4f;	// converts to an int, stores 24
 // float x = myVar; // converts back to float, returns 2.4f
-template <typename T, int mult = 1>
+template <typename T, int mul = 1, int div = 1>
 class scaled_channel : scaled_channel_base {
-	using TSelf = scaled_channel<T, mult>;
+	using TSelf = scaled_channel<T, mul, div>;
 
 public:
 	constexpr scaled_channel() : m_value(static_cast<T>(0)) { }
 	constexpr scaled_channel(float val)
-		: m_value(val * mult)
 	{
+		val *= float(mul) / div;
+		if (std::is_integral_v<T>) {
+			m_value = std::roundf(val);
+		} else {
+			m_value = val;
+		}
 	}
 
 	// Allow reading back out as a float (note: this may be lossy!)
 	constexpr operator float() const {
-		return m_value / (float)mult;
+		return m_value * (float(div) / mul);
 	}
 
 	// Postfix increment operator
@@ -47,9 +53,11 @@ public:
 	//  - base type T is an integral type (integer)
 	//  - multiplier is equal to 1
 	void operator++(int) {
-		static_assert(mult == 1, "Increment operator only supported for non-scaled integer types");
+		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++;
 	}
 

unit_tests/tests/tests.mk

@@ -28,6 +28,7 @@ TESTS_SRC_CPP = \
 	tests/lua/test_lua_hooks.cpp \
 	tests/sensor/test_cj125.cpp \
 	tests/test_change_engine_type.cpp \
+	tests/util/test_scaled_channel.cpp \
 	tests/util/test_timer.cpp \
 	tests/system/test_periodic_thread_controller.cpp \
 	tests/test_util.cpp \
@@ -89,6 +90,3 @@ TESTS_SRC_CPP = \
 	tests/sensor/test_frequency_sensor.cpp \
 	tests/sensor/test_turbocharger_speed_converter.cpp \
 	tests/sensor/test_vehicle_speed_converter.cpp
-
-	
-

unit_tests/tests/util/test_scaled_channel.cpp

@@ -0,0 +1,34 @@
+#include "pch.h"
+
+#include "boost_control.h"
+
+using ::testing::_;
+using ::testing::StrictMock;
+
+TEST(ScaledChannel, Basic) {
+	{
+		scaled_channel<int16_t, 10> i1;
+		i1 = 10;    EXPECT_FLOAT_EQ(i1, 10);
+		i1 =  1;    EXPECT_FLOAT_EQ(i1,  1);
+		i1 =  0.11; EXPECT_FLOAT_EQ(i1,  0.1); // round
+		i1 =  0.1;  EXPECT_FLOAT_EQ(i1,  0.1);
+		i1 =  0.09; EXPECT_FLOAT_EQ(i1,  0.1); // round
+		i1 =  0.01; EXPECT_FLOAT_EQ(i1,  0.); // out of range
+		i1 = -0.09; EXPECT_FLOAT_EQ(i1, -0.1); // round
+		i1 = -0.1;  EXPECT_FLOAT_EQ(i1, -0.1);
+		i1 = -0.11; EXPECT_FLOAT_EQ(i1, -0.1); // round
+	}
+
+	{
+		scaled_channel<int16_t, 1, 10> i2;
+		i2 = 1000; EXPECT_FLOAT_EQ(i2, 1000);
+		i2 =  100; EXPECT_FLOAT_EQ(i2,  100);
+		i2 =   11; EXPECT_FLOAT_EQ(i2,   10); // round
+		i2 =   10; EXPECT_FLOAT_EQ(i2,   10);
+		i2 =    9; EXPECT_FLOAT_EQ(i2,   10); // round
+		i2 =    1; EXPECT_FLOAT_EQ(i2,    0); // out of range
+		i2 =   -9; EXPECT_FLOAT_EQ(i2,  -10); // round
+		i2 =  -10; EXPECT_FLOAT_EQ(i2,  -10);
+		i2 =  -11; EXPECT_FLOAT_EQ(i2,  -10); // round
+	}
+}