[FEAT] substr

ascii.cpp

@@ -423,9 +423,9 @@ int rnd(int x) {
     srand(x);
 }*/
 
-char tostr_tmp[256];
+char str_tmp[256];
 const char* tostr(float val) {
-    return SDL_itoa(val, tostr_tmp, 10);
+    return SDL_itoa(val, str_tmp, 10);
 }
 
 void debug_set_prompt() {
@@ -489,6 +489,12 @@ const char* chr(uint8_t ascii) {
     return chr_trans;
 }
 
+const char* substr(const char* str, uint8_t start, uint8_t length) {
+    memcpy(str_tmp, &str[start], length);
+    str_tmp[length] = '\0';
+    return str_tmp;
+}
+
 void setchar(uint8_t index, uint8_t b0, uint8_t b1, uint8_t b2, uint8_t b3, uint8_t b4, uint8_t b5, uint8_t b6, uint8_t b7) {
     mem[MEM_CHAR_OFFSET+index*8] = b0;
     mem[MEM_CHAR_OFFSET+index*8+1] = b1;

ascii.h

@@ -163,6 +163,7 @@ void debug_get_cmd();
 
 uint8_t ascii(const char *str, uint8_t index);
 const char* chr(uint8_t ascii);
+const char* substr(const char* str, uint8_t start, uint8_t length);
 
 void setchar(uint8_t index, uint8_t b0, uint8_t b1, uint8_t b2, uint8_t b3, uint8_t b4, uint8_t b5, uint8_t b6, uint8_t b7);
 uint8_t peek(uint16_t addr);

lua.cpp

@@ -183,6 +183,13 @@ extern "C" {
         lua_pushinteger(L, strlen(str));
         return 1;
     }
+    static int cpp_substr(lua_State *L) {
+        const char* str = luaL_checkstring(L, 1);
+        int start = luaL_checknumber(L, 2);
+        int length = luaL_checknumber(L, 3);
+        lua_pushstring(L, substr(str, start, length));
+        return 1;
+    }
     
     static int cpp_setchar(lua_State *L) {
         int index = luaL_checkinteger(L, 1);
@@ -346,6 +353,7 @@ void lua_init(const char* filename, const bool start_playing) {
     lua_pushcfunction(L,cpp_ascii);     lua_setglobal(L, "ascii");
     lua_pushcfunction(L,cpp_chr);     lua_setglobal(L, "chr");
     lua_pushcfunction(L,cpp_strlen);     lua_setglobal(L, "strlen");
+    lua_pushcfunction(L,cpp_substr);     lua_setglobal(L, "substr");
 
     lua_pushcfunction(L,cpp_setchar);     lua_setglobal(L, "setchar");
     lua_pushcfunction(L,cpp_peek);     lua_setglobal(L, "peek");