st235 · January 4, 2025 15:08
diff --git a/Lua.Exercise30.1.cpp b/Lua.Exercise30.1.cpp
 // 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
 for fname in dir.open(".") do
    print(fname)
 end
diff --git a/output.txt b/output.txt
 .
 ..
 CMakeFiles
 Makefile
 cmake_install.cmake
 deps
 CMakeCache.txt
 lua-test
	// 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;
	}
	.
	..
	CMakeFiles
	Makefile
	cmake_install.cmake
	deps
	CMakeCache.txt
	lua-test