AP_Scripting: Factor out common range constraints

libraries/AP_Scripting/lua_bindings.cpp

@@ -4,8 +4,21 @@
 
 #include "lua_bindings.h"
 
-int lua_gcs_send_text(lua_State *state) {
-    const char* str = lua_tostring(state, 1);
+int check_arguments(lua_State *L, int expected_arguments, const char *fn_name) {
+    const int args = lua_gettop(L);
+    if (args != expected_arguments) {
+        return luaL_error(L, "%s expected %d arguments got %d", fn_name, expected_arguments, args);
+    }
+    return 0;
+}
+
+// GCS binding
+
+int lua_gcs_send_text(lua_State *L) {
+    check_arguments(L, 1, "send_text");
+
+    const char* str = lua_tostring(L, 1);
+
     gcs().send_text(MAV_SEVERITY_INFO, str);
     return 0;
 }
@@ -16,21 +29,21 @@ static const luaL_Reg gcs_functions[] =
     {NULL, NULL}
 };
 
-int lua_servo_set_output_pwm(lua_State *state) {
-    int servo_function = luaL_checkinteger(state, -2);
-    int output_value = luaL_checknumber(state, -1);
+// servo binding
 
-    // range check the output function
-    if ((servo_function < SRV_Channel::Aux_servo_function_t::k_scripting1) ||
-        (servo_function > SRV_Channel::Aux_servo_function_t::k_scripting16)) {
-        return luaL_error(state, "Servo function (%d) is not a scriptable output", servo_function);
-    }
+int lua_servo_set_output_pwm(lua_State *L) {
+    check_arguments(L, 2, "set_output_pwm");
 
-    if (output_value > (int)UINT16_MAX) {
-        return luaL_error(state, "Servo range (%d) is out of range", output_value);
-    }
+    const SRV_Channel::Aux_servo_function_t servo_function = (SRV_Channel::Aux_servo_function_t)luaL_checkinteger(L, 1);
+    luaL_argcheck(L, ((servo_function >= SRV_Channel::Aux_servo_function_t::k_scripting1) &&
+                      (servo_function <= SRV_Channel::Aux_servo_function_t::k_scripting16)),
+                  2, "function out of range");
+
+    const int output = luaL_checknumber(L, 2);
+    luaL_argcheck(L, ((output >= 0) && (output <= UINT16_MAX)), 2, "output out of range");
+
+    SRV_Channels::set_output_pwm((SRV_Channel::Aux_servo_function_t)servo_function, output);
 
-    SRV_Channels::set_output_pwm((SRV_Channel::Aux_servo_function_t)servo_function, output_value);
     return 0;
 }
 
@@ -40,6 +53,8 @@ static const luaL_Reg servo_functions[] =
     {NULL, NULL}
 };
 
+// all bindings
+
 void load_lua_bindings(lua_State *state) {
     luaL_newlib(state, gcs_functions);
     lua_setglobal(state, "gcs");