st235 · January 4, 2025 15:08 · Jan 4, 2025
diff --git a/Lua.Exercise30.1.cpp b/Lua.Exercise30.1.cpp
@@ -0,0 +1,119 @@
+// Exercise 30.1: 
+// Modify the dir_iter function in the directory example
+// so that it closes the DIR structure when it reaches
+// the end of the traversal.
+// With this change,
+// the program does not need to wait for a garbage collection
+// to release a resource that it knows it will not need anymore.
+
+// (When you close the directory,
+// you should set the address stored in the userdatum to NULL,
+// to signal to the finalizer that the directory is already closed.
+// Also, function dir_iter will have to check whether the directory
+// is not closed before using it.)
+
+#define LUA_COMPAT_APIINTCASTS
+
+#include <cmath>
+#include <cstdint>
+#include <dirent.h>
+#include <exception>
+#include <iomanip>
+#include <iostream>
+#include <limits>
+#include <string>
+#include <vector>
+#include <stack>
+#include <unordered_set>
+
+#include "lua.hpp"
+
+namespace {
+
+bool AbortWithMessage(const char* message) {
+    std::cout << message << std::endl;
+    std::abort();
+}
+
+bool LoadFile(lua_State* state, const std::string& filename) {
+    return !(luaL_loadfile(state, filename.c_str()) || lua_pcall(state, 0, 0, 0));
+}
+
+int dir_iter(lua_State *L) {
+    DIR** dir_ptr = (DIR**) lua_touserdata(L, lua_upvalueindex(1));
+
+    struct dirent* entry;
+    if (*dir_ptr && (entry = readdir(*dir_ptr)) != NULL) {
+        lua_pushstring(L, entry->d_name);
+        return 1;
+    }
+
+    // Directory is empty.
+    if (*dir_ptr) {
+        closedir(*dir_ptr);
+        *dir_ptr = nullptr;
+    }
+
+    return 0;
+}
+
+int l_dir(lua_State *L) {
+    const char *path = luaL_checkstring(L, 1);
+
+    DIR** d = (DIR**) lua_newuserdata(L, sizeof(DIR*));
+
+    luaL_getmetatable(L, "LuaBook.dir");
+    lua_setmetatable(L, -2);
+
+    *d = opendir(path);
+    if (*d == NULL) {
+        luaL_error(L, "cannot open %s: %s", path, strerror(errno));
+    }
+
+    lua_pushcclosure(L, dir_iter, 1);
+    return 1;
+}
+
+int dir_gc(lua_State *L) {
+    DIR* d = *(DIR**) lua_touserdata(L, 1);
+    if (d) {
+        closedir(d);
+    }
+    return 0;
+}
+
+const struct luaL_Reg dirlib[] = {
+    {"open", l_dir},
+    {NULL, NULL}
+};
+
+int luaopen_dir(lua_State *L) {
+    luaL_newmetatable(L, "LuaBook.dir");
+
+    lua_pushcfunction(L, dir_gc);
+    lua_setfield(L, -2, "__gc");
+
+    luaL_newlib(L, dirlib);
+    lua_setglobal(L, "dir");
+    return 0;
+}
+
+}  // namespace
+
+int main(int argc, char* argv[]) {
+    if (argc < 2) {
+        std::cout << "Please, specify lua script file to run." << std::endl;
+        return 0;
+    }
+
+    lua_State* L = luaL_newstate();
+    luaL_openlibs(L);
+    luaopen_dir(L);
+
+    if (!LoadFile(L, std::string(argv[1]))) {
+        AbortWithMessage(lua_tostring(L, -1));
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/main.lua b/main.lua
@@ -0,0 +1,3 @@
+for fname in dir.open(".") do
+    print(fname)
+end
diff --git a/output.txt b/output.txt
@@ -0,0 +1,8 @@
+.
+..
+CMakeFiles
+Makefile
+cmake_install.cmake
+deps
+CMakeCache.txt
+lua-test