AP_Math: added unsigned versions of constrain functions

sometimes it really does matter that we use constrain_uint32() instead
of constrain_int32(). For example, if we have a value like 0xFFFFFFFF
then the result will be very different

we should use unsigned constrain when dealing with unsigned values

libraries/AP_Math/AP_Math.cpp

@@ -313,9 +313,13 @@ T constrain_value(const T amt, const T low, const T high)
 }
 
 template int constrain_value<int>(const int amt, const int low, const int high);
+template unsigned int constrain_value<unsigned int>(const unsigned int amt, const unsigned int low, const unsigned int high);
 template long constrain_value<long>(const long amt, const long low, const long high);
+template unsigned long constrain_value<unsigned long>(const unsigned long amt, const unsigned long low, const unsigned long high);
 template long long constrain_value<long long>(const long long amt, const long long low, const long long high);
+template unsigned long long constrain_value<unsigned long long>(const unsigned long long amt, const unsigned long long low, const unsigned long long high);
 template short constrain_value<short>(const short amt, const short low, const short high);
+template unsigned short constrain_value<unsigned short>(const unsigned short amt, const unsigned short low, const unsigned short high);
 template float constrain_value<float>(const float amt, const float low, const float high);
 template double constrain_value<double>(const double amt, const double low, const double high);
 

libraries/AP_Math/AP_Math.h

@@ -179,16 +179,31 @@ inline int16_t constrain_int16(const int16_t amt, const int16_t low, const int16
     return constrain_value(amt, low, high);
 }
 
+inline uint16_t constrain_uint16(const uint16_t amt, const uint16_t low, const uint16_t high)
+{
+    return constrain_value(amt, low, high);
+}
+
 inline int32_t constrain_int32(const int32_t amt, const int32_t low, const int32_t high)
 {
     return constrain_value(amt, low, high);
 }
 
+inline uint32_t constrain_uint32(const uint32_t amt, const uint32_t low, const uint32_t high)
+{
+    return constrain_value(amt, low, high);
+}
+
 inline int64_t constrain_int64(const int64_t amt, const int64_t low, const int64_t high)
 {
     return constrain_value(amt, low, high);
 }
 
+inline uint64_t constrain_uint64(const uint64_t amt, const uint64_t low, const uint64_t high)
+{
+    return constrain_value(amt, low, high);
+}
+
 // degrees -> radians
 static inline constexpr ftype radians(ftype deg)
 {

libraries/AP_Math/tests/test_math.cpp

@@ -377,6 +377,10 @@ TEST(MathTest, Constrain)
     EXPECT_EQ(19.9, constrain_value(19.8, 19.9, 20.1));
     EXPECT_EQ(19.9f, constrain_value(19.8f, 19.9f, 20.1f));
 
+    // test that constrain on 32 bit integer works correctly. Note the asymmetry
+    EXPECT_EQ(10,    constrain_int32( 0xFFFFFFFFU, 10U, 1200U));
+    EXPECT_EQ(1200U, constrain_uint32(0xFFFFFFFFU, 10U, 1200U));
+
 #if CONFIG_HAL_BOARD == HAL_BOARD_LINUX
     EXPECT_EQ(1.0f, constrain_float(nanf("0x4152"), 1.0f, 1.0f));
     EXPECT_EQ(1.0f, constrain_value(nanf("0x4152"), 1.0f, 1.0f));