Function setpath

third-party/lua-5.5.0/src/loadlib.c:274–304

** Set a path. (If using the default path, assume it is a string ** literal in C and create it as an external string.) */

** literal in C and create it as an external string.)
*/
static void setpath (lua_State *L, const char *fieldname,
                                   const char *envname,
                                   const char *dft) {
  const char *dftmark;
  const char *nver = lua_pushfstring(L, "%s%s", envname, LUA_VERSUFFIX);
  const char *path = getenv(nver);  /* try versioned name */
  if (path == NULL)  /* no versioned environment variable? */
    path = getenv(envname);  /* try unversioned name */
  if (path == NULL || noenv(L))  /* no environment variable? */
    lua_pushexternalstring(L, dft, strlen(dft), NULL, NULL);  /* use default */
  else if ((dftmark = strstr(path, LUA_PATH_SEP LUA_PATH_SEP)) == NULL)
    lua_pushstring(L, path);  /* nothing to change */
  else {  /* path contains a ";;": insert default path in its place */
    size_t len = strlen(path);
    luaL_Buffer b;
    luaL_buffinit(L, &b);
    if (path < dftmark) {  /* is there a prefix before ';;'? */
      luaL_addlstring(&b, path, ct_diff2sz(dftmark - path));  /* add it */
      luaL_addchar(&b, *LUA_PATH_SEP);
    }
    luaL_addstring(&b, dft);  /* add default */
    if (dftmark < path + len - 2) {  /* is there a suffix after ';;'? */
      luaL_addchar(&b, *LUA_PATH_SEP);
      luaL_addlstring(&b, dftmark + 2, ct_diff2sz((path + len - 2) - dftmark));
    }
    luaL_pushresult(&b);
  }
  setprogdir(L);
  lua_setfield(L, -3, fieldname);  /* package[fieldname] = path value */
  lua_pop(L, 1);  /* pop versioned variable name ('nver') */
}

/* }================================================================== */