fix: Custom stick and switch names were being mangled internally (#1770)

* followup to PR1754

* Cleanup

* Formatting

* Long comment

radio/src/lua/api_general.cpp

@@ -91,6 +91,10 @@
   { "EVT_"#xxx"_LONG", EVT_KEY_LONG(yyy) }, \
   { "EVT_"#xxx"_REPT", EVT_KEY_REPT(yyy) }
 
+// see strhelpers.cpp for pre-instantiation of function-template
+// getSourceString() for this parametrization
+static constexpr uint8_t maxSourceNameLength{16};
+
 // Note:
 // - luaRxFifo & luaReceiveData are used only for USB serial
 // - otherwise, the AUX serial buffer is used directly
@@ -2301,22 +2305,23 @@ This function is rather time consuming, and should not be used repeatedly in a s
 @status current Introduced in 2.6
 */
 
-static int luaGetSourceIndex(lua_State * L)
+static int luaGetSourceIndex(lua_State* const L)
 {
-  const char * name = luaL_checkstring(L, 1);
+  const char* const name = luaL_checkstring(L, 1);
   bool found = false;
   mixsrc_t idx;
-  
+
   for (idx = MIXSRC_NONE; idx <= MIXSRC_LAST_TELEM; idx++) {
     if (isSourceAvailable(idx)) {
-      char* s = getSourceString(idx);
-      if (!strncasecmp(s, name, 31)) {
+      char srcName[maxSourceNameLength];
+      getSourceString(srcName, idx);
+      if (!strncasecmp(srcName, name)) {
         found = true;
         break;
       }
     }
   }
-  
+
   if (found)
     lua_pushinteger(L, idx);
   else
@@ -2341,11 +2346,12 @@ static int luaGetSourceName(lua_State * L)
 {
   mixsrc_t idx = luaL_checkinteger(L, 1);
   if (idx <= MIXSRC_LAST_TELEM && isSourceAvailable(idx)) {
-    char* name = getSourceString(idx);
-    lua_pushstring(L, name);
-  }
-  else
+    char srcName[maxSourceNameLength];
+    getSourceString(srcName, idx);
+    lua_pushstring(L, srcName);
+  } else {
     lua_pushnil(L);
+  }
   return 1;
 }
 
@@ -2368,9 +2374,10 @@ static int luaNextSource(lua_State * L)
 
   while (++idx <= last) {
     if (isSourceAvailable(idx)) {
-      char* name = getSourceString(idx);
+      char srcName[maxSourceNameLength];
+      getSourceString(srcName, idx);
       lua_pushinteger(L, idx);
-      lua_pushstring(L, name);
+      lua_pushstring(L, srcName);
       return 2;
     }
   }

radio/src/strhelpers.cpp

@@ -512,9 +512,8 @@ char *getSwitchPositionName(char *dest, swsrc_t idx)
   else if (idx <= SWSRC_LAST_MULTIPOS_SWITCH) {
     div_t swinfo =
         div(int(idx - SWSRC_FIRST_MULTIPOS_SWITCH), XPOTS_MULTIPOS_COUNT);
-    char temp[LEN_ANA_NAME + 1];
+    char temp[LEN_ANA_NAME + 2];
     getSourceString(temp, MIXSRC_FIRST_POT + swinfo.quot);
-    temp[LEN_ANA_NAME] = '\0';
     strAppendStringWithIndex(s, temp, swinfo.rem + 1);
   }
 #endif
@@ -611,10 +610,8 @@ char *getSourceString(char (&dest)[L], mixsrc_t idx)
         dest[0] = CHAR_POT;
 #endif
       }
-
       idx -= MIXSRC_Rud;
-      memcpy(dest + 1, g_eeGeneral.anaNames[idx], L - 1);
-      dest[L - 1] = '\0';
+      copyToTerminated(dest, g_eeGeneral.anaNames[idx], offset_t<1>{});
     } else {
       idx -= MIXSRC_Rud;
       getStringAtIndex(dest, STR_VSRCRAW, idx + 1);
@@ -625,8 +622,7 @@ char *getSourceString(char (&dest)[L], mixsrc_t idx)
   } else if (idx <= MIXSRC_LAST_SWITCH) {
     idx -= MIXSRC_FIRST_SWITCH;
     if (g_eeGeneral.switchNames[idx][0] != '\0') {
-      strncpy(dest, g_eeGeneral.switchNames[idx], LEN_SWITCH_NAME);
-      dest[LEN_SWITCH_NAME] = '\0';
+      copyToTerminated(dest, g_eeGeneral.switchNames[idx], offset_t<1>{});
     } else {
       getStringAtIndex(dest, STR_VSRCRAW,
                        idx + MIXSRC_FIRST_SWITCH - MIXSRC_Rud + 1);
@@ -647,9 +643,8 @@ char *getSourceString(char (&dest)[L], mixsrc_t idx)
                          MAX_GVARS);
   } else if (idx <= MIXSRC_LAST_TIMER) {
     if (g_model.timers[idx - MIXSRC_FIRST_TIMER].name[0] != '\0') {
-      strncpy(dest, g_model.timers[idx - MIXSRC_FIRST_TIMER].name,
-              L - 1);
-      dest[L - 1] = '\0';
+      copyToTerminated(dest, g_model.timers[idx - MIXSRC_FIRST_TIMER].name,
+                       offset_t<1>{});
     } else {
       getStringAtIndex(dest, STR_VSRCRAW,
                        idx - MIXSRC_Rud + 1 - MAX_LOGICAL_SWITCHES -

radio/src/strhelpers.h

@@ -78,7 +78,7 @@ char *getSwitchPositionName(char *dest, swsrc_t idx);
 char *getSwitchName(char *dest, swsrc_t idx);
 
 template<size_t L>
-char *getSourceString(char (&dest)[L], mixsrc_t idx);
+char* getSourceString(char (&dest)[L], mixsrc_t idx);
 
 int  getRawSwitchIdx(char sw);
 char getRawSwitchFromIdx(int sw);
@@ -113,4 +113,35 @@ template<typename S>
 void clearStruct(S& s) {
     memset((void*) &s, 0, sizeof(S));
 }
+
+template <size_t N>
+using offset_t = std::integral_constant<size_t, N>;
+
+template <size_t DL, size_t SL, size_t O = 0>
+void copyToTerminated(char (&dest)[DL], const char (&src)[SL],
+                      const offset_t<O> = offset_t<0>{})
+{
+  // unfortinately std::min() isn't constexpr in C++11
+  // static constexpr size_t len = std::min(DL - O - 1, SL);
+  static constexpr size_t dl{DL - O - 1};
+  static_assert(dl > 0, "wrong sizes or offset");
+  static constexpr size_t len = (dl < SL) ? dl : SL;
+  strncpy(&dest[O], &src[0], len);
+  static_assert((len + O) < DL);
+  dest[len + O] = '\0';
+}
+
+template <size_t L1, size_t L2>
+int strncasecmp(char (&s1)[L1], const char (&s2)[L2])
+{
+  static constexpr size_t len = (L1 < L2) ? L1 : L2;
+  return strncasecmp(s1, s2, len);
+}
+
+template <size_t L1>
+int strncasecmp(char (&s1)[L1], const char *const s2)
+{
+  return strncasecmp(s1, s2, L1);
+}
+
 #endif  // _STRHELPERS_H_