example.c

// Copyright https://github.com/tilkinsc/ MIT

// handles line by line interpretation (REPL)
static int lua_main_postexist(lua_State* L) {
    input = malloc(PRIMARY_REPL_BUFFER_SIZE);
    retfmt = malloc(SECONDARY_REPL_BUFFER_SIZE);
    check_error_OOM(input == NULL || retfmt == NULL, __LINE__);

    int base = 0;
    int status = 0;
    unsigned int ch = 0;
    size_t i = 0;
    while(should_close != 1) {
retry:
        // 1. reset
        status = 0;
        i = 0;

        // 2. read
        lfprint("%c", '>');
        while((ch = fgetc(stdin)) != '\n') {
            if(ch == -1) // sigint
                // TODO: might crash utf16 multichar string
                return luaL_error(L, "SIGINT");
            if(i == PRIMARY_REPL_BUFFER_SIZE - 1) { // if max input reached
                //lferror(_(REPL_LINE_ERROR));
                lferror("Repl line error");
                fflush(stdin);
                goto retry;
            }
            input[i++] = ch;
        }
        input[i++] = '\0'; // ensure c-string format

        // 2.1 exit if requested
        if(memcmp(input, "return", 6 + 1) == 0) { // return\0 returns if without arguments
            should_close = 1;
            return 0;
        }

        // 3. return %s; test
        snprintf(retfmt, SECONDARY_REPL_BUFFER_SIZE, "return %s;", input);
        status = luaL_loadbuffer(L, retfmt, strlen(retfmt), "REPL return");
        if(status != 0) {
            lua_pop(L, 1); // err msg
        } else {
            // attempt first test, return seems to work
            int top = lua_gettop(L);
            status = lua_pcall(L, 0, LUA_MULTRET, 0);
            if(status == 0) { // on success
                top = lua_gettop(L) - top + 1; // + 1 = ignore pushed function
                if(top > 0) { // more than 0 arguments returned
                    lua_getglobal(L, "print");
                    if(lua_isnil(L, -1) != 1) { // check even if no_libraries == 1
                        lua_insert(L, lua_gettop(L)-top);
                        lua_call(L, top, 0);
                    } else
                        lua_pop(L, 1 + top); // nil, anything returned
                }
                continue;
            } else lua_pop(L, 1); // err msg, also ignore it - no relevance
        }

        // 4. load and execute originally inserted code with error handler
        lua_pushcclosure(L, lua_print_error, 0);
        base = lua_gettop(L);
        if((status = luaL_loadbuffer(L, input, strlen(input), "REPL")) != 0) {
            print_error(SYNTAX_ERROR, 1);
            lua_pop(L, 2); // err msg, err handler
        } else {
            if((status = lua_pcall(L, 0, LUA_MULTRET, base)) != 0)
                lua_pop(L, 2); // err msg, err handler, also ignore it - no relevance
        }
    }

    return 0;
}