text: /*
  ** $Id: lua.c $
  ** Lua stand-alone interpreter
  ** See Copyright Notice in lua.h
  */
  
  #define lua_c
  
  #include "lprefix.h"
  
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  
  #include <signal.h>
  
  #include "lua.h"
  
  #include "lauxlib.h"
  #include "lualib.h"
  
  
  #if !defined(LUA_PROGNAME)
  #define LUA_PROGNAME		"lua"
  #endif
  
  #if !defined(LUA_INIT_VAR)
  #define LUA_INIT_VAR		"LUA_INIT"
  #endif
  
  #define LUA_INITVARVERSION	LUA_INIT_VAR LUA_VERSUFFIX
  
  
  static lua_State *globalL = NULL;
  
  static const char *progname = LUA_PROGNAME;
  
  
  #if defined(LUA_USE_POSIX)   /* { */
  
  /*
  ** Use 'sigaction' when available.
  */
  static void setsignal (int sig, void (*handler)(int)) {
    struct sigaction sa;
    sa.sa_handler = handler;
    sa.sa_flags = 0;
    sigemptyset(&sa.sa_mask);  /* do not mask any signal */
    sigaction(sig, &sa, NULL);
  }
  
  #else           /* }{ */
  
  #define setsignal            signal
  
  #endif                               /* } */
  
  
  /*
  ** Hook set by signal function to stop the interpreter.
  */
  static void lstop (lua_State *L, lua_Debug *ar) {
    (void)ar;  /* unused arg. */
    lua_sethook(L, NULL, 0, 0);  /* reset hook */
    luaL_error(L, "interrupted!");
  }
  
  
  /*
  ** Function to be called at a C signal. Because a C signal cannot
  ** just change a Lua state (as there is no proper synchronization),
  ** this function only sets a hook that, when called, will stop the
  ** interpreter.
  */
  static void laction (int i) {
    int flag = LUA_MASKCALL | LUA_MASKRET | LUA_MASKLINE | LUA_MASKCOUNT;
    setsignal(i, SIG_DFL); /* if another SIGINT happens, terminate process */
    lua_sethook(globalL, lstop, flag, 1);
  }
  
  
  static void print_usage (const char *badoption) {
    lua_writestringerror("%s: ", progname);
    if (badoption[1] == 'e' || badoption[1] == 'l')
      lua_writestringerror("'%s' needs argument\n", badoption);
    else
      lua_writestringerror("unrecognized option '%s'\n", badoption);
    lua_writestringerror(
    "usage: %s [options] [script [args]]\n"
    "Available options are:\n"
    "  -e stat   execute string 'stat'\n"
    "  -i        enter interactive mode after executing 'script'\n"
    "  -l mod    require library 'mod' into global 'mod'\n"
    "  -l g=mod  require library 'mod' into global 'g'\n"
    "  -v        show version information\n"
    "  -E        ignore environment variables\n"
    "  -W        turn warnings on\n"
    "  --        stop handling options\n"
    "  -         stop handling options and execute stdin\n"
    ,
    progname);
  }
  
  
  /*
  ** Prints an error message, adding the program name in front of it
  ** (if present)
  */
  static void l_message (const char *pname, const char *msg) {
    if (pname) lua_writestringerror("%s: ", pname);
    lua_writestringerror("%s\n", msg);
  }
  
  
  /*
  ** Check whether 'status' is not OK and, if so, prints the error
  ** message on the top of the stack. It assumes that the error object
  ** is a string, as it was either generated by Lua or by 'msghandler'.
  */
  static int report (lua_State *L, int status) {
    if (status != LUA_OK) {
      const char *msg = lua_tostring(L, -1);
      l_message(progname, msg);
      lua_pop(L, 1);  /* remove message */
    }
    return status;
  }
  
  
  /*
  ** Message handler used to run all chunks
  */
  static int msghandler (lua_State *L) {
    const char *msg = lua_tostring(L, 1);
    if (msg == NULL) {  /* is error object not a string? */
      if (luaL_callmeta(L, 1, "__tostring") &&  /* does it have a metamethod */
          lua_type(L, -1) == LUA_TSTRING)  /* that produces a string? */
        return 1;  /* that is the message */
      else
        msg = lua_pushfstring(L, "(error object is a %s value)",
                                 luaL_typename(L, 1));
    }
    luaL_traceback(L, L, msg, 1);  /* append a standard traceback */
    return 1;  /* return the traceback */
  }
  
  
  /*
  ** Interface to 'lua_pcall', which sets appropriate message function
  ** and C-signal handler. Used to run all chunks.
  */
  static int docall (lua_State *L, int narg, int nres) {
    int status;
    int base = lua_gettop(L) - narg;  /* function index */
    lua_pushcfunction(L, msghandler);  /* push message handler */
    lua_insert(L, base);  /* put it under function and args */
    globalL = L;  /* to be available to 'laction' */
    setsignal(SIGINT, laction);  /* set C-signal handler */
    status = lua_pcall(L, narg, nres, base);
    setsignal(SIGINT, SIG_DFL); /* reset C-signal handler */
    lua_remove(L, base);  /* remove message handler from the stack */
    return status;
  }
  
  
  static void print_version (void) {
    lua_writestring(LUA_COPYRIGHT, strlen(LUA_COPYRIGHT));
    lua_writeline();
  }
  
  
  /*
  ** Create the 'arg' table, which stores all arguments from the
  ** command line ('argv'). It should be aligned so that, at index 0,
  ** it has 'argv[script]', which is the script name. The arguments
  ** to the script (everything after 'script') go to positive indices;
  ** other arguments (before the script name) go to negative indices.
  ** If there is no script name, assume interpreter's name as base.
  */
  static void createargtable (lua_State *L, char **argv, int argc, int script) {
    int i, narg;
    if (script == argc) script = 0;  /* no script name? */
    narg = argc - (script + 1);  /* number of positive indices */
    lua_createtable(L, narg, script + 1);
    for (i = 0; i < argc; i++) {
      lua_pushstring(L, argv[i]);
      lua_rawseti(L, -2, i - script);
    }
    lua_setglobal(L, "arg");
  }
  
  
  static int dochunk (lua_State *L, int status) {
    if (status == LUA_OK) status = docall(L, 0, 0);
    return report(L, status);
  }
  
  
  static int dofile (lua_State *L, const char *name) {
    return dochunk(L, luaL_loadfile(L, name));
  }
  
  
  static int dostring (lua_State *L, const char *s, const char *name) {
    return dochunk(L, luaL_loadbuffer(L, s, strlen(s), name));
  }
  
  
  /*
  ** Receives 'globname[=modname]' and runs 'globname = require(modname)'.
  */
  static int dolibrary (lua_State *L, char *globname) {
    int status;
    char *modname = strchr(globname, '=');
    if (modname == NULL)  /* no explicit name? */
      modname = globname;  /* module name is equal to global name */
    else {
      *modname = '\0';  /* global name ends here */
      modname++;  /* module name starts after the '=' */
    }
    lua_getglobal(L, "require");
    lua_pushstring(L, modname);
    status = docall(L, 1, 1);  /* call 'require(modname)' */
    if (status == LUA_OK)
      lua_setglobal(L, globname);  /* globname = require(modname) */
    return report(L, status);
  }
  
  
  /*
  ** Push on the stack the contents of table 'arg' from 1 to #arg
  */
  static int pushargs (lua_State *L) {
    int i, n;
    if (lua_getglobal(L, "arg") != LUA_TTABLE)
      luaL_error(L, "'arg' is not a table");
    n = (int)luaL_len(L, -1);
    luaL_checkstack(L, n + 3, "too many arguments to script");
    for (i = 1; i <= n; i++)
      lua_rawgeti(L, -i, i);
    lua_remove(L, -i);  /* remove table from the stack */
    return n;
  }
  
  
  static int handle_script (lua_State *L, char **argv) {
    int status;
    const char *fname = argv[0];
    if (strcmp(fname, "-") == 0 && strcmp(argv[-1], "--") != 0)
      fname = NULL;  /* stdin */
    status = luaL_loadfile(L, fname);
    if (status == LUA_OK) {
      int n = pushargs(L);  /* push arguments to script */
      status = docall(L, n, LUA_MULTRET);
    }
    return report(L, status);
  }
  
  
  /* bits of various argument indicators in 'args' */
  #define has_error	1	/* bad option */
  #define has_i		2	/* -i */
  #define has_v		4	/* -v */
  #define has_e		8	/* -e */
  #define has_E		16	/* -E */
  
  
  /*
  ** Traverses all arguments from 'argv', returning a mask with those
  ** needed before running any Lua code (or an error code if it finds
  ** any invalid argument). 'first' returns the first not-handled argument
  ** (either the script name or a bad argument in case of error).
  */
  static int collectargs (char **argv, int *first) {
    int args = 0;
    int i;
    for (i = 1; argv[i] != NULL; i++) {
      *first = i;
      if (argv[i][0] != '-')  /* not an option? */
          return args;  /* stop handling options */
      switch (argv[i][1]) {  /* else check option */
        case '-':  /* '--' */
          if (argv[i][2] != '\0')  /* extra characters after '--'? */
            return has_error;  /* invalid option */
          *first = i + 1;
          return args;
        case '\0':  /* '-' */
          return args;  /* script "name" is '-' */
        case 'E':
          if (argv[i][2] != '\0')  /* extra characters? */
            return has_error;  /* invalid option */
          args |= has_E;
          break;
        case 'W':
          if (argv[i][2] != '\0')  /* extra characters? */
            return has_error;  /* invalid option */
          break;
        case 'i':
          args |= has_i;  /* (-i implies -v) *//* FALLTHROUGH */
        case 'v':
          if (argv[i][2] != '\0')  /* extra characters? */
            return has_error;  /* invalid option */
          args |= has_v;
          break;
        case 'e':
          args |= has_e;  /* FALLTHROUGH */
        case 'l':  /* both options need an argument */
          if (argv[i][2] == '\0') {  /* no concatenated argument? */
            i++;  /* try next 'argv' */
            if (argv[i] == NULL || argv[i][0] == '-')
              return has_error;  /* no next argument or it is another option */
          }
          break;
        default:  /* invalid option */
          return has_error;
      }
    }
    *first = i;  /* no script name */
    return args;
  }
  
  
  /*
  ** Processes options 'e' and 'l', which involve running Lua code, and
  ** 'W', which also affects the state.
  ** Returns 0 if some code raises an error.
  */
  static int runargs (lua_State *L, char **argv, int n) {
    int i;
    for (i = 1; i < n; i++) {
      int option = argv[i][1];
      lua_assert(argv[i][0] == '-');  /* already checked */
      switch (option) {
        case 'e':  case 'l': {
          int status;
          char *extra = argv[i] + 2;  /* both options need an argument */
          if (*extra == '\0') extra = argv[++i];
          lua_assert(extra != NULL);
          status = (option == 'e')
                   ? dostring(L, extra, "=(command line)")
                   : dolibrary(L, extra);
          if (status != LUA_OK) return 0;
          break;
        }
        case 'W':
          lua_warning(L, "@on", 0);  /* warnings on */
          break;
      }
    }
    return 1;
  }
  
  
  static int handle_luainit (lua_State *L) {
    const char *name = "=" LUA_INITVARVERSION;
    const char *init = getenv(name + 1);
    if (init == NULL) {
      name = "=" LUA_INIT_VAR;
      init = getenv(name + 1);  /* try alternative name */
    }
    if (init == NULL) return LUA_OK;
    else if (init[0] == '@')
      return dofile(L, init+1);
    else
      return dostring(L, init, name);
  }
  
  
  /*
  ** {==================================================================
  ** Read-Eval-Print Loop (REPL)
  ** ===================================================================
  */
  
  #if !defined(LUA_PROMPT)
  #define LUA_PROMPT		"> "
  #define LUA_PROMPT2		">> "
  #endif
  
  #if !defined(LUA_MAXINPUT)
  #define LUA_MAXINPUT		512
  #endif
  
  
  /*
  ** lua_stdin_is_tty detects whether the standard input is a 'tty' (that
  ** is, whether we're running lua interactively).
  */
  #if !defined(lua_stdin_is_tty)	/* { */
  
  #if defined(LUA_USE_POSIX)	/* { */
  
  #include <unistd.h>
  #define lua_stdin_is_tty()	isatty(0)
  
  #elif defined(LUA_USE_WINDOWS)	/* }{ */
  
  #include <io.h>
  #include <windows.h>
  
  #define lua_stdin_is_tty()	_isatty(_fileno(stdin))
  
  #else				/* }{ */
  
  /* ISO C definition */
  #define lua_stdin_is_tty()	1  /* assume stdin is a tty */
  
  #endif				/* } */
  
  #endif				/* } */
  
  
  /*
  ** lua_readline defines how to show a prompt and then read a line from
  ** the standard input.
  ** lua_saveline defines how to "save" a read line in a "history".
  ** lua_freeline defines how to free a line read by lua_readline.
  */
  #if !defined(lua_readline)	/* { */
  
  #if defined(LUA_USE_READLINE)	/* { */
  
  #include <readline/readline.h>
  #include <readline/history.h>
  #define lua_initreadline(L)	((void)L, rl_readline_name="lua")
  #define lua_readline(L,b,p)	((void)L, ((b)=readline(p)) != NULL)
  #define lua_saveline(L,line)	((void)L, add_history(line))
  #define lua_freeline(L,b)	((void)L, free(b))
  
  #else				/* }{ */
  
  #define lua_initreadline(L)  ((void)L)
  #define lua_readline(L,b,p) \
          ((void)L, fputs(p, stdout), fflush(stdout),  /* show prompt */ \
          fgets(b, LUA_MAXINPUT, stdin) != NULL)  /* get line */
  #define lua_saveline(L,line)	{ (void)L; (void)line; }
  #define lua_freeline(L,b)	{ (void)L; (void)b; }
  
  #endif				/* } */
  
  #endif				/* } */
  
  
  /*
  ** Return the string to be used as a prompt by the interpreter. Leave
  ** the string (or nil, if using the default value) on the stack, to keep
  ** it anchored.
  */
  static const char *get_prompt (lua_State *L, int firstline) {
    if (lua_getglobal(L, firstline ? "_PROMPT" : "_PROMPT2") == LUA_TNIL)
      return (firstline ? LUA_PROMPT : LUA_PROMPT2);  /* use the default */
    else {  /* apply 'tostring' over the value */
      const char *p = luaL_tolstring(L, -1, NULL);
      lua_remove(L, -2);  /* remove original value */
      return p;
    }
  }
  
  /* mark in error messages for incomplete statements */
  #define EOFMARK		"<eof>"
  #define marklen		(sizeof(EOFMARK)/sizeof(char) - 1)
  
  
  /*
  ** Check whether 'status' signals a syntax error and the error
  ** message at the top of the stack ends with the above mark for
  ** incomplete statements.
  */
  static int incomplete (lua_State *L, int status) {
    if (status == LUA_ERRSYNTAX) {
      size_t lmsg;
      const char *msg = lua_tolstring(L, -1, &lmsg);
      if (lmsg >= marklen && strcmp(msg + lmsg - marklen, EOFMARK) == 0) {
        lua_pop(L, 1);
        return 1;
      }
    }
    return 0;  /* else... */
  }
  
  
  /*
  ** Prompt the user, read a line, and push it into the Lua stack.
  */
  static int pushline (lua_State *L, int firstline) {
    char buffer[LUA_MAXINPUT];
    char *b = buffer;
    size_t l;
    const char *prmt = get_prompt(L, firstline);
    int readstatus = lua_readline(L, b, prmt);
    if (readstatus == 0)
      return 0;  /* no input (prompt will be popped by caller) */
    lua_pop(L, 1);  /* remove prompt */
    l = strlen(b);
    if (l > 0 && b[l-1] == '\n')  /* line ends with newline? */
      b[--l] = '\0';  /* remove it */
    if (firstline && b[0] == '=')  /* for compatibility with 5.2, ... */
      lua_pushfstring(L, "return %s", b + 1);  /* change '=' to 'return' */
    else
      lua_pushlstring(L, b, l);
    lua_freeline(L, b);
    return 1;
  }
  
  
  /*
  ** Try to compile line on the stack as 'return <line>;'; on return, stack
  ** has either compiled chunk or original line (if compilation failed).
  */
  static int addreturn (lua_State *L) {
    const char *line = lua_tostring(L, -1);  /* original line */
    const char *retline = lua_pushfstring(L, "return %s;", line);
    int status = luaL_loadbuffer(L, retline, strlen(retline), "=stdin");
    if (status == LUA_OK) {
      lua_remove(L, -2);  /* remove modified line */
      if (line[0] != '\0')  /* non empty? */
        lua_saveline(L, line);  /* keep history */
    }
    else
      lua_pop(L, 2);  /* pop result from 'luaL_loadbuffer' and modified line */
    return status;
  }
  
  
  /*
  ** Read multiple lines until a complete Lua statement
  */
  static int multiline (lua_State *L) {
    for (;;) {  /* repeat until gets a complete statement */
      size_t len;
      const char *line = lua_tolstring(L, 1, &len);  /* get what it has */
      int status = luaL_loadbuffer(L, line, len, "=stdin");  /* try it */
      if (!incomplete(L, status) || !pushline(L, 0)) {
        lua_saveline(L, line);  /* keep history */
        return status;  /* cannot or should not try to add continuation line */
      }
      lua_pushliteral(L, "\n");  /* add newline... */
      lua_insert(L, -2);  /* ...between the two lines */
      lua_concat(L, 3);  /* join them */
    }
  }
  
  
  /*
  ** Read a line and try to load (compile) it first as an expression (by
  ** adding "return " in front of it) and second as a statement. Return
  ** the final status of load/call with the resulting function (if any)
  ** in the top of the stack.
  */
  static int loadline (lua_State *L) {
    int status;
    lua_settop(L, 0);
    if (!pushline(L, 1))
      return -1;  /* no input */
    if ((status = addreturn(L)) != LUA_OK)  /* 'return ...' did not work? */
      status = multiline(L);  /* try as command, maybe with continuation lines */
    lua_remove(L, 1);  /* remove line from the stack */
    lua_assert(lua_gettop(L) == 1);
    return status;
  }
  
  
  /*
  ** Prints (calling the Lua 'print' function) any values on the stack
  */
  static void l_print (lua_State *L) {
    int n = lua_gettop(L);
    if (n > 0) {  /* any result to be printed? */
      luaL_checkstack(L, LUA_MINSTACK, "too many results to print");
      lua_getglobal(L, "print");
      lua_insert(L, 1);
      if (lua_pcall(L, n, 0, 0) != LUA_OK)
        l_message(progname, lua_pushfstring(L, "error calling 'print' (%s)",
                                               lua_tostring(L, -1)));
    }
  }
  
  
  /*
  ** Do the REPL: repeatedly read (load) a line, evaluate (call) it, and
  ** print any results.
  */
  static void doREPL (lua_State *L) {
    int status;
    const char *oldprogname = progname;
    progname = NULL;  /* no 'progname' on errors in interactive mode */
    lua_initreadline(L);
    while ((status = loadline(L)) != -1) {
      if (status == LUA_OK)
        status = docall(L, 0, LUA_MULTRET);
      if (status == LUA_OK) l_print(L);
      else report(L, status);
    }
    lua_settop(L, 0);  /* clear stack */
    lua_writeline();
    progname = oldprogname;
  }
  
  /* }================================================================== */
  
  
  /*
  ** Main body of stand-alone interpreter (to be called in protected mode).
  ** Reads the options and handles them all.
  */
  static int pmain (lua_State *L) {
    int argc = (int)lua_tointeger(L, 1);
    char **argv = (char **)lua_touserdata(L, 2);
    int script;
    int args = collectargs(argv, &script);
    luaL_checkversion(L);  /* check that interpreter has correct version */
    if (argv[0] && argv[0][0]) progname = argv[0];
    if (args == has_error) {  /* bad arg? */
      print_usage(argv[script]);  /* 'script' has index of bad arg. */
      return 0;
    }
    if (args & has_v)  /* option '-v'? */
      print_version();
    if (args & has_E) {  /* option '-E'? */
      lua_pushboolean(L, 1);  /* signal for libraries to ignore env. vars. */
      lua_setfield(L, LUA_REGISTRYINDEX, "LUA_NOENV");
    }
    luaL_openlibs(L);  /* open standard libraries */
    createargtable(L, argv, argc, script);  /* create table 'arg' */
    lua_gc(L, LUA_GCGEN, 0, 0);  /* GC in generational mode */
    if (!(args & has_E)) {  /* no option '-E'? */
      if (handle_luainit(L) != LUA_OK)  /* run LUA_INIT */
        return 0;  /* error running LUA_INIT */
    }
    if (!runargs(L, argv, script))  /* execute arguments -e and -l */
      return 0;  /* something failed */
    if (script < argc &&  /* execute main script (if there is one) */
        handle_script(L, argv + script) != LUA_OK)
      return 0;
    if (args & has_i)  /* -i option? */
      doREPL(L);  /* do read-eval-print loop */
    else if (script == argc && !(args & (has_e | has_v))) {  /* no arguments? */
      if (lua_stdin_is_tty()) {  /* running in interactive mode? */
        print_version();
        doREPL(L);  /* do read-eval-print loop */
      }
      else dofile(L, NULL);  /* executes stdin as a file */
    }
    lua_pushboolean(L, 1);  /* signal no errors */
    return 1;
  }
  
  
  int main (int argc, char **argv) {
    int status, result;
    lua_State *L = luaL_newstate();  /* create state */
    if (L == NULL) {
      l_message(argv[0], "cannot create state: not enough memory");
      return EXIT_FAILURE;
    }
    lua_pushcfunction(L, &pmain);  /* to call 'pmain' in protected mode */
    lua_pushinteger(L, argc);  /* 1st argument */
    lua_pushlightuserdata(L, argv); /* 2nd argument */
    status = lua_pcall(L, 2, 1, 0);  /* do the call */
    result = lua_toboolean(L, -1);  /* get result */
    report(L, status);
    lua_close(L);
    return (result && status == LUA_OK) ? EXIT_SUCCESS : EXIT_FAILURE;
  }
  
  