text: /*
  ** $Id: liolib.c $
  ** Standard I/O (and system) library
  ** See Copyright Notice in lua.h
  */
  
  #define liolib_c
  #define LUA_LIB
  
  #include "lprefix.h"
  
  
  #include <ctype.h>
  #include <errno.h>
  #include <locale.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  
  #include "lua.h"
  
  #include "lauxlib.h"
  #include "lualib.h"
  
  
  
  
  /*
  ** Change this macro to accept other modes for 'fopen' besides
  ** the standard ones.
  */
  #if !defined(l_checkmode)
  
  /* accepted extensions to 'mode' in 'fopen' */
  #if !defined(L_MODEEXT)
  #define L_MODEEXT	"b"
  #endif
  
  /* Check whether 'mode' matches '[rwa]%+?[L_MODEEXT]*' */
  static int l_checkmode (const char *mode) {
    return (*mode != '\0' && strchr("rwa", *(mode++)) != NULL &&
           (*mode != '+' || ((void)(++mode), 1)) &&  /* skip if char is '+' */
           (strspn(mode, L_MODEEXT) == strlen(mode)));  /* check extensions */
  }
  
  #endif
  
  /*
  ** {======================================================
  ** l_popen spawns a new process connected to the current
  ** one through the file streams.
  ** =======================================================
  */
  
  #if !defined(l_checkmodep)
  /* By default, Lua accepts only "r" or "w" as mode */
  #define l_checkmodep(m)	((m[0] == 'r' || m[0] == 'w') && m[1] == '\0')
  #endif
  
  
  #if !defined(l_popen)		/* { */
  
  #if defined(LUA_USE_POSIX)	/* { */
  
  #define l_popen(L,c,m)		(fflush(NULL), popen(c,m))
  #define l_pclose(L,file)	(pclose(file))
  
  #elif defined(LUA_USE_WINDOWS)	/* }{ */
  
  #define l_popen(L,c,m)		(_popen(c,m))
  #define l_pclose(L,file)	(_pclose(file))
  
  #else				/* }{ */
  
  /* ISO C definitions */
  #define l_popen(L,c,m)  \
  	  ((void)c, (void)m, \
  	  luaL_error(L, "'popen' not supported"), \
  	  (FILE*)0)
  #define l_pclose(L,file)		((void)L, (void)file, -1)
  
  #endif				/* } */
  
  #endif				/* } */
  
  /* }====================================================== */
  
  
  #if !defined(l_getc)		/* { */
  
  #if defined(LUA_USE_POSIX)
  #define l_getc(f)		getc_unlocked(f)
  #define l_lockfile(f)		flockfile(f)
  #define l_unlockfile(f)		funlockfile(f)
  #else
  #define l_getc(f)		getc(f)
  #define l_lockfile(f)		((void)0)
  #define l_unlockfile(f)		((void)0)
  #endif
  
  #endif				/* } */
  
  
  /*
  ** {======================================================
  ** l_fseek: configuration for longer offsets
  ** =======================================================
  */
  
  #if !defined(l_fseek)		/* { */
  
  #if defined(LUA_USE_POSIX)	/* { */
  
  #include <sys/types.h>
  
  #define l_fseek(f,o,w)		fseeko(f,o,w)
  #define l_ftell(f)		ftello(f)
  #define l_seeknum		off_t
  
  #elif defined(LUA_USE_WINDOWS) && !defined(_CRTIMP_TYPEINFO) \
     && defined(_MSC_VER) && (_MSC_VER >= 1400)	/* }{ */
  
  /* Windows (but not DDK) and Visual C++ 2005 or higher */
  #define l_fseek(f,o,w)		_fseeki64(f,o,w)
  #define l_ftell(f)		_ftelli64(f)
  #define l_seeknum		__int64
  
  #else				/* }{ */
  
  /* ISO C definitions */
  #define l_fseek(f,o,w)		fseek(f,o,w)
  #define l_ftell(f)		ftell(f)
  #define l_seeknum		long
  
  #endif				/* } */
  
  #endif				/* } */
  
  /* }====================================================== */
  
  
  
  #define IO_PREFIX	"_IO_"
  #define IOPREF_LEN	(sizeof(IO_PREFIX)/sizeof(char) - 1)
  #define IO_INPUT	(IO_PREFIX "input")
  #define IO_OUTPUT	(IO_PREFIX "output")
  
  
  typedef luaL_Stream LStream;
  
  
  #define tolstream(L)	((LStream *)luaL_checkudata(L, 1, LUA_FILEHANDLE))
  
  #define isclosed(p)	((p)->closef == NULL)
  
  
  static int io_type (lua_State *L) {
    LStream *p;
    luaL_checkany(L, 1);
    p = (LStream *)luaL_testudata(L, 1, LUA_FILEHANDLE);
    if (p == NULL)
      luaL_pushfail(L);  /* not a file */
    else if (isclosed(p))
      lua_pushliteral(L, "closed file");
    else
      lua_pushliteral(L, "file");
    return 1;
  }
  
  
  static int f_tostring (lua_State *L) {
    LStream *p = tolstream(L);
    if (isclosed(p))
      lua_pushliteral(L, "file (closed)");
    else
      lua_pushfstring(L, "file (%p)", p->f);
    return 1;
  }
  
  
  static FILE *tofile (lua_State *L) {
    LStream *p = tolstream(L);
    if (isclosed(p))
      luaL_error(L, "attempt to use a closed file");
    lua_assert(p->f);
    return p->f;
  }
  
  
  /*
  ** When creating file handles, always creates a 'closed' file handle
  ** before opening the actual file; so, if there is a memory error, the
  ** handle is in a consistent state.
  */
  static LStream *newprefile (lua_State *L) {
    LStream *p = (LStream *)lua_newuserdatauv(L, sizeof(LStream), 0);
    p->closef = NULL;  /* mark file handle as 'closed' */
    luaL_setmetatable(L, LUA_FILEHANDLE);
    return p;
  }
  
  
  /*
  ** Calls the 'close' function from a file handle. The 'volatile' avoids
  ** a bug in some versions of the Clang compiler (e.g., clang 3.0 for
  ** 32 bits).
  */
  static int aux_close (lua_State *L) {
    LStream *p = tolstream(L);
    volatile lua_CFunction cf = p->closef;
    p->closef = NULL;  /* mark stream as closed */
    return (*cf)(L);  /* close it */
  }
  
  
  static int f_close (lua_State *L) {
    tofile(L);  /* make sure argument is an open stream */
    return aux_close(L);
  }
  
  
  static int io_close (lua_State *L) {
    if (lua_isnone(L, 1))  /* no argument? */
      lua_getfield(L, LUA_REGISTRYINDEX, IO_OUTPUT);  /* use default output */
    return f_close(L);
  }
  
  
  static int f_gc (lua_State *L) {
    LStream *p = tolstream(L);
    if (!isclosed(p) && p->f != NULL)
      aux_close(L);  /* ignore closed and incompletely open files */
    return 0;
  }
  
  
  /*
  ** function to close regular files
  */
  static int io_fclose (lua_State *L) {
    LStream *p = tolstream(L);
    int res = fclose(p->f);
    return luaL_fileresult(L, (res == 0), NULL);
  }
  
  
  static LStream *newfile (lua_State *L) {
    LStream *p = newprefile(L);
    p->f = NULL;
    p->closef = &io_fclose;
    return p;
  }
  
  
  static void opencheck (lua_State *L, const char *fname, const char *mode) {
    LStream *p = newfile(L);
    p->f = fopen(fname, mode);
    if (p->f == NULL)
      luaL_error(L, "cannot open file '%s' (%s)", fname, strerror(errno));
  }
  
  
  static int io_open (lua_State *L) {
    const char *filename = luaL_checkstring(L, 1);
    const char *mode = luaL_optstring(L, 2, "r");
    LStream *p = newfile(L);
    const char *md = mode;  /* to traverse/check mode */
    luaL_argcheck(L, l_checkmode(md), 2, "invalid mode");
    p->f = fopen(filename, mode);
    return (p->f == NULL) ? luaL_fileresult(L, 0, filename) : 1;
  }
  
  
  /*
  ** function to close 'popen' files
  */
  static int io_pclose (lua_State *L) {
    LStream *p = tolstream(L);
    errno = 0;
    return luaL_execresult(L, l_pclose(L, p->f));
  }
  
  
  static int io_popen (lua_State *L) {
    const char *filename = luaL_checkstring(L, 1);
    const char *mode = luaL_optstring(L, 2, "r");
    LStream *p = newprefile(L);
    luaL_argcheck(L, l_checkmodep(mode), 2, "invalid mode");
    p->f = l_popen(L, filename, mode);
    p->closef = &io_pclose;
    return (p->f == NULL) ? luaL_fileresult(L, 0, filename) : 1;
  }
  
  
  static int io_tmpfile (lua_State *L) {
    LStream *p = newfile(L);
    p->f = tmpfile();
    return (p->f == NULL) ? luaL_fileresult(L, 0, NULL) : 1;
  }
  
  
  static FILE *getiofile (lua_State *L, const char *findex) {
    LStream *p;
    lua_getfield(L, LUA_REGISTRYINDEX, findex);
    p = (LStream *)lua_touserdata(L, -1);
    if (isclosed(p))
      luaL_error(L, "default %s file is closed", findex + IOPREF_LEN);
    return p->f;
  }
  
  
  static int g_iofile (lua_State *L, const char *f, const char *mode) {
    if (!lua_isnoneornil(L, 1)) {
      const char *filename = lua_tostring(L, 1);
      if (filename)
        opencheck(L, filename, mode);
      else {
        tofile(L);  /* check that it's a valid file handle */
        lua_pushvalue(L, 1);
      }
      lua_setfield(L, LUA_REGISTRYINDEX, f);
    }
    /* return current value */
    lua_getfield(L, LUA_REGISTRYINDEX, f);
    return 1;
  }
  
  
  static int io_input (lua_State *L) {
    return g_iofile(L, IO_INPUT, "r");
  }
  
  
  static int io_output (lua_State *L) {
    return g_iofile(L, IO_OUTPUT, "w");
  }
  
  
  static int io_readline (lua_State *L);
  
  
  /*
  ** maximum number of arguments to 'f:lines'/'io.lines' (it + 3 must fit
  ** in the limit for upvalues of a closure)
  */
  #define MAXARGLINE	250
  
  /*
  ** Auxiliary function to create the iteration function for 'lines'.
  ** The iteration function is a closure over 'io_readline', with
  ** the following upvalues:
  ** 1) The file being read (first value in the stack)
  ** 2) the number of arguments to read
  ** 3) a boolean, true iff file has to be closed when finished ('toclose')
  ** *) a variable number of format arguments (rest of the stack)
  */
  static void aux_lines (lua_State *L, int toclose) {
    int n = lua_gettop(L) - 1;  /* number of arguments to read */
    luaL_argcheck(L, n <= MAXARGLINE, MAXARGLINE + 2, "too many arguments");
    lua_pushvalue(L, 1);  /* file */
    lua_pushinteger(L, n);  /* number of arguments to read */
    lua_pushboolean(L, toclose);  /* close/not close file when finished */
    lua_rotate(L, 2, 3);  /* move the three values to their positions */
    lua_pushcclosure(L, io_readline, 3 + n);
  }
  
  
  static int f_lines (lua_State *L) {
    tofile(L);  /* check that it's a valid file handle */
    aux_lines(L, 0);
    return 1;
  }
  
  
  /*
  ** Return an iteration function for 'io.lines'. If file has to be
  ** closed, also returns the file itself as a second result (to be
  ** closed as the state at the exit of a generic for).
  */
  static int io_lines (lua_State *L) {
    int toclose;
    if (lua_isnone(L, 1)) lua_pushnil(L);  /* at least one argument */
    if (lua_isnil(L, 1)) {  /* no file name? */
      lua_getfield(L, LUA_REGISTRYINDEX, IO_INPUT);  /* get default input */
      lua_replace(L, 1);  /* put it at index 1 */
      tofile(L);  /* check that it's a valid file handle */
      toclose = 0;  /* do not close it after iteration */
    }
    else {  /* open a new file */
      const char *filename = luaL_checkstring(L, 1);
      opencheck(L, filename, "r");
      lua_replace(L, 1);  /* put file at index 1 */
      toclose = 1;  /* close it after iteration */
    }
    aux_lines(L, toclose);  /* push iteration function */
    if (toclose) {
      lua_pushnil(L);  /* state */
      lua_pushnil(L);  /* control */
      lua_pushvalue(L, 1);  /* file is the to-be-closed variable (4th result) */
      return 4;
    }
    else
      return 1;
  }
  
  
  /*
  ** {======================================================
  ** READ
  ** =======================================================
  */
  
  
  /* maximum length of a numeral */
  #if !defined (L_MAXLENNUM)
  #define L_MAXLENNUM     200
  #endif
  
  
  /* auxiliary structure used by 'read_number' */
  typedef struct {
    FILE *f;  /* file being read */
    int c;  /* current character (look ahead) */
    int n;  /* number of elements in buffer 'buff' */
    char buff[L_MAXLENNUM + 1];  /* +1 for ending '\0' */
  } RN;
  
  
  /*
  ** Add current char to buffer (if not out of space) and read next one
  */
  static int nextc (RN *rn) {
    if (rn->n >= L_MAXLENNUM) {  /* buffer overflow? */
      rn->buff[0] = '\0';  /* invalidate result */
      return 0;  /* fail */
    }
    else {
      rn->buff[rn->n++] = rn->c;  /* save current char */
      rn->c = l_getc(rn->f);  /* read next one */
      return 1;
    }
  }
  
  
  /*
  ** Accept current char if it is in 'set' (of size 2)
  */
  static int test2 (RN *rn, const char *set) {
    if (rn->c == set[0] || rn->c == set[1])
      return nextc(rn);
    else return 0;
  }
  
  
  /*
  ** Read a sequence of (hex)digits
  */
  static int readdigits (RN *rn, int hex) {
    int count = 0;
    while ((hex ? isxdigit(rn->c) : isdigit(rn->c)) && nextc(rn))
      count++;
    return count;
  }
  
  
  /*
  ** Read a number: first reads a valid prefix of a numeral into a buffer.
  ** Then it calls 'lua_stringtonumber' to check whether the format is
  ** correct and to convert it to a Lua number.
  */
  static int read_number (lua_State *L, FILE *f) {
    RN rn;
    int count = 0;
    int hex = 0;
    char decp[2];
    rn.f = f; rn.n = 0;
    decp[0] = lua_getlocaledecpoint();  /* get decimal point from locale */
    decp[1] = '.';  /* always accept a dot */
    l_lockfile(rn.f);
    do { rn.c = l_getc(rn.f); } while (isspace(rn.c));  /* skip spaces */
    test2(&rn, "-+");  /* optional sign */
    if (test2(&rn, "00")) {
      if (test2(&rn, "xX")) hex = 1;  /* numeral is hexadecimal */
      else count = 1;  /* count initial '0' as a valid digit */
    }
    count += readdigits(&rn, hex);  /* integral part */
    if (test2(&rn, decp))  /* decimal point? */
      count += readdigits(&rn, hex);  /* fractional part */
    if (count > 0 && test2(&rn, (hex ? "pP" : "eE"))) {  /* exponent mark? */
      test2(&rn, "-+");  /* exponent sign */
      readdigits(&rn, 0);  /* exponent digits */
    }
    ungetc(rn.c, rn.f);  /* unread look-ahead char */
    l_unlockfile(rn.f);
    rn.buff[rn.n] = '\0';  /* finish string */
    if (lua_stringtonumber(L, rn.buff))  /* is this a valid number? */
      return 1;  /* ok */
    else {  /* invalid format */
     lua_pushnil(L);  /* "result" to be removed */
     return 0;  /* read fails */
    }
  }
  
  
  static int test_eof (lua_State *L, FILE *f) {
    int c = getc(f);
    ungetc(c, f);  /* no-op when c == EOF */
    lua_pushliteral(L, "");
    return (c != EOF);
  }
  
  
  static int read_line (lua_State *L, FILE *f, int chop) {
    luaL_Buffer b;
    int c;
    luaL_buffinit(L, &b);
    do {  /* may need to read several chunks to get whole line */
      char *buff = luaL_prepbuffer(&b);  /* preallocate buffer space */
      int i = 0;
      l_lockfile(f);  /* no memory errors can happen inside the lock */
      while (i < LUAL_BUFFERSIZE && (c = l_getc(f)) != EOF && c != '\n')
        buff[i++] = c;  /* read up to end of line or buffer limit */
      l_unlockfile(f);
      luaL_addsize(&b, i);
    } while (c != EOF && c != '\n');  /* repeat until end of line */
    if (!chop && c == '\n')  /* want a newline and have one? */
      luaL_addchar(&b, c);  /* add ending newline to result */
    luaL_pushresult(&b);  /* close buffer */
    /* return ok if read something (either a newline or something else) */
    return (c == '\n' || lua_rawlen(L, -1) > 0);
  }
  
  
  static void read_all (lua_State *L, FILE *f) {
    size_t nr;
    luaL_Buffer b;
    luaL_buffinit(L, &b);
    do {  /* read file in chunks of LUAL_BUFFERSIZE bytes */
      char *p = luaL_prepbuffer(&b);
      nr = fread(p, sizeof(char), LUAL_BUFFERSIZE, f);
      luaL_addsize(&b, nr);
    } while (nr == LUAL_BUFFERSIZE);
    luaL_pushresult(&b);  /* close buffer */
  }
  
  
  static int read_chars (lua_State *L, FILE *f, size_t n) {
    size_t nr;  /* number of chars actually read */
    char *p;
    luaL_Buffer b;
    luaL_buffinit(L, &b);
    p = luaL_prepbuffsize(&b, n);  /* prepare buffer to read whole block */
    nr = fread(p, sizeof(char), n, f);  /* try to read 'n' chars */
    luaL_addsize(&b, nr);
    luaL_pushresult(&b);  /* close buffer */
    return (nr > 0);  /* true iff read something */
  }
  
  
  static int g_read (lua_State *L, FILE *f, int first) {
    int nargs = lua_gettop(L) - 1;
    int n, success;
    clearerr(f);
    if (nargs == 0) {  /* no arguments? */
      success = read_line(L, f, 1);
      n = first + 1;  /* to return 1 result */
    }
    else {
      /* ensure stack space for all results and for auxlib's buffer */
      luaL_checkstack(L, nargs+LUA_MINSTACK, "too many arguments");
      success = 1;
      for (n = first; nargs-- && success; n++) {
        if (lua_type(L, n) == LUA_TNUMBER) {
          size_t l = (size_t)luaL_checkinteger(L, n);
          success = (l == 0) ? test_eof(L, f) : read_chars(L, f, l);
        }
        else {
          const char *p = luaL_checkstring(L, n);
          if (*p == '*') p++;  /* skip optional '*' (for compatibility) */
          switch (*p) {
            case 'n':  /* number */
              success = read_number(L, f);
              break;
            case 'l':  /* line */
              success = read_line(L, f, 1);
              break;
            case 'L':  /* line with end-of-line */
              success = read_line(L, f, 0);
              break;
            case 'a':  /* file */
              read_all(L, f);  /* read entire file */
              success = 1; /* always success */
              break;
            default:
              return luaL_argerror(L, n, "invalid format");
          }
        }
      }
    }
    if (ferror(f))
      return luaL_fileresult(L, 0, NULL);
    if (!success) {
      lua_pop(L, 1);  /* remove last result */
      luaL_pushfail(L);  /* push nil instead */
    }
    return n - first;
  }
  
  
  static int io_read (lua_State *L) {
    return g_read(L, getiofile(L, IO_INPUT), 1);
  }
  
  
  static int f_read (lua_State *L) {
    return g_read(L, tofile(L), 2);
  }
  
  
  /*
  ** Iteration function for 'lines'.
  */
  static int io_readline (lua_State *L) {
    LStream *p = (LStream *)lua_touserdata(L, lua_upvalueindex(1));
    int i;
    int n = (int)lua_tointeger(L, lua_upvalueindex(2));
    if (isclosed(p))  /* file is already closed? */
      return luaL_error(L, "file is already closed");
    lua_settop(L , 1);
    luaL_checkstack(L, n, "too many arguments");
    for (i = 1; i <= n; i++)  /* push arguments to 'g_read' */
      lua_pushvalue(L, lua_upvalueindex(3 + i));
    n = g_read(L, p->f, 2);  /* 'n' is number of results */
    lua_assert(n > 0);  /* should return at least a nil */
    if (lua_toboolean(L, -n))  /* read at least one value? */
      return n;  /* return them */
    else {  /* first result is false: EOF or error */
      if (n > 1) {  /* is there error information? */
        /* 2nd result is error message */
        return luaL_error(L, "%s", lua_tostring(L, -n + 1));
      }
      if (lua_toboolean(L, lua_upvalueindex(3))) {  /* generator created file? */
        lua_settop(L, 0);  /* clear stack */
        lua_pushvalue(L, lua_upvalueindex(1));  /* push file at index 1 */
        aux_close(L);  /* close it */
      }
      return 0;
    }
  }
  
  /* }====================================================== */
  
  
  static int g_write (lua_State *L, FILE *f, int arg) {
    int nargs = lua_gettop(L) - arg;
    int status = 1;
    for (; nargs--; arg++) {
      if (lua_type(L, arg) == LUA_TNUMBER) {
        /* optimization: could be done exactly as for strings */
        int len = lua_isinteger(L, arg)
                  ? fprintf(f, LUA_INTEGER_FMT,
                               (LUAI_UACINT)lua_tointeger(L, arg))
                  : fprintf(f, LUA_NUMBER_FMT,
                               (LUAI_UACNUMBER)lua_tonumber(L, arg));
        status = status && (len > 0);
      }
      else {
        size_t l;
        const char *s = luaL_checklstring(L, arg, &l);
        status = status && (fwrite(s, sizeof(char), l, f) == l);
      }
    }
    if (status) return 1;  /* file handle already on stack top */
    else return luaL_fileresult(L, status, NULL);
  }
  
  
  static int io_write (lua_State *L) {
    return g_write(L, getiofile(L, IO_OUTPUT), 1);
  }
  
  
  static int f_write (lua_State *L) {
    FILE *f = tofile(L);
    lua_pushvalue(L, 1);  /* push file at the stack top (to be returned) */
    return g_write(L, f, 2);
  }
  
  
  static int f_seek (lua_State *L) {
    static const int mode[] = {SEEK_SET, SEEK_CUR, SEEK_END};
    static const char *const modenames[] = {"set", "cur", "end", NULL};
    FILE *f = tofile(L);
    int op = luaL_checkoption(L, 2, "cur", modenames);
    lua_Integer p3 = luaL_optinteger(L, 3, 0);
    l_seeknum offset = (l_seeknum)p3;
    luaL_argcheck(L, (lua_Integer)offset == p3, 3,
                    "not an integer in proper range");
    op = l_fseek(f, offset, mode[op]);
    if (op)
      return luaL_fileresult(L, 0, NULL);  /* error */
    else {
      lua_pushinteger(L, (lua_Integer)l_ftell(f));
      return 1;
    }
  }
  
  
  static int f_setvbuf (lua_State *L) {
    static const int mode[] = {_IONBF, _IOFBF, _IOLBF};
    static const char *const modenames[] = {"no", "full", "line", NULL};
    FILE *f = tofile(L);
    int op = luaL_checkoption(L, 2, NULL, modenames);
    lua_Integer sz = luaL_optinteger(L, 3, LUAL_BUFFERSIZE);
    int res = setvbuf(f, NULL, mode[op], (size_t)sz);
    return luaL_fileresult(L, res == 0, NULL);
  }
  
  
  
  static int io_flush (lua_State *L) {
    return luaL_fileresult(L, fflush(getiofile(L, IO_OUTPUT)) == 0, NULL);
  }
  
  
  static int f_flush (lua_State *L) {
    return luaL_fileresult(L, fflush(tofile(L)) == 0, NULL);
  }
  
  
  /*
  ** functions for 'io' library
  */
  static const luaL_Reg iolib[] = {
    {"close", io_close},
    {"flush", io_flush},
    {"input", io_input},
    {"lines", io_lines},
    {"open", io_open},
    {"output", io_output},
    {"popen", io_popen},
    {"read", io_read},
    {"tmpfile", io_tmpfile},
    {"type", io_type},
    {"write", io_write},
    {NULL, NULL}
  };
  
  
  /*
  ** methods for file handles
  */
  static const luaL_Reg meth[] = {
    {"read", f_read},
    {"write", f_write},
    {"lines", f_lines},
    {"flush", f_flush},
    {"seek", f_seek},
    {"close", f_close},
    {"setvbuf", f_setvbuf},
    {NULL, NULL}
  };
  
  
  /*
  ** metamethods for file handles
  */
  static const luaL_Reg metameth[] = {
    {"__index", NULL},  /* place holder */
    {"__gc", f_gc},
    {"__close", f_gc},
    {"__tostring", f_tostring},
    {NULL, NULL}
  };
  
  
  static void createmeta (lua_State *L) {
    luaL_newmetatable(L, LUA_FILEHANDLE);  /* metatable for file handles */
    luaL_setfuncs(L, metameth, 0);  /* add metamethods to new metatable */
    luaL_newlibtable(L, meth);  /* create method table */
    luaL_setfuncs(L, meth, 0);  /* add file methods to method table */
    lua_setfield(L, -2, "__index");  /* metatable.__index = method table */
    lua_pop(L, 1);  /* pop metatable */
  }
  
  
  /*
  ** function to (not) close the standard files stdin, stdout, and stderr
  */
  static int io_noclose (lua_State *L) {
    LStream *p = tolstream(L);
    p->closef = &io_noclose;  /* keep file opened */
    luaL_pushfail(L);
    lua_pushliteral(L, "cannot close standard file");
    return 2;
  }
  
  
  static void createstdfile (lua_State *L, FILE *f, const char *k,
                             const char *fname) {
    LStream *p = newprefile(L);
    p->f = f;
    p->closef = &io_noclose;
    if (k != NULL) {
      lua_pushvalue(L, -1);
      lua_setfield(L, LUA_REGISTRYINDEX, k);  /* add file to registry */
    }
    lua_setfield(L, -2, fname);  /* add file to module */
  }
  
  
  LUAMOD_API int luaopen_io (lua_State *L) {
    luaL_newlib(L, iolib);  /* new module */
    createmeta(L);
    /* create (and set) default files */
    createstdfile(L, stdin, IO_INPUT, "stdin");
    createstdfile(L, stdout, IO_OUTPUT, "stdout");
    createstdfile(L, stderr, NULL, "stderr");
    return 1;
  }
  
  