xref: /freebsd/contrib/lua/src/liolib.c (revision 85f87cf491bec6f90948a85b10f5523ea24db9e3)
1 /*
2 ** $Id: liolib.c,v 2.151.1.1 2017/04/19 17:29:57 roberto Exp $
3 ** Standard I/O (and system) library
4 ** See Copyright Notice in lua.h
5 */
6 
7 #define liolib_c
8 #define LUA_LIB
9 
10 #include "lprefix.h"
11 
12 
13 #include <ctype.h>
14 #include <errno.h>
15 #include <locale.h>
16 #include <stdio.h>
17 #include <stdlib.h>
18 #include <string.h>
19 
20 #include "lua.h"
21 
22 #include "lauxlib.h"
23 #include "lualib.h"
24 
25 
26 
27 
28 /*
29 ** Change this macro to accept other modes for 'fopen' besides
30 ** the standard ones.
31 */
32 #if !defined(l_checkmode)
33 
34 /* accepted extensions to 'mode' in 'fopen' */
35 #if !defined(L_MODEEXT)
36 #define L_MODEEXT	"b"
37 #endif
38 
39 /* Check whether 'mode' matches '[rwa]%+?[L_MODEEXT]*' */
40 static int l_checkmode (const char *mode) {
41   return (*mode != '\0' && strchr("rwa", *(mode++)) != NULL &&
42          (*mode != '+' || (++mode, 1)) &&  /* skip if char is '+' */
43          (strspn(mode, L_MODEEXT) == strlen(mode)));  /* check extensions */
44 }
45 
46 #endif
47 
48 /*
49 ** {======================================================
50 ** l_popen spawns a new process connected to the current
51 ** one through the file streams.
52 ** =======================================================
53 */
54 
55 #if !defined(l_popen)		/* { */
56 
57 #if defined(LUA_USE_POSIX)	/* { */
58 
59 #define l_popen(L,c,m)		(fflush(NULL), popen(c,m))
60 #define l_pclose(L,file)	(pclose(file))
61 
62 #elif defined(LUA_USE_WINDOWS)	/* }{ */
63 
64 #define l_popen(L,c,m)		(_popen(c,m))
65 #define l_pclose(L,file)	(_pclose(file))
66 
67 #else				/* }{ */
68 
69 /* ISO C definitions */
70 #define l_popen(L,c,m)  \
71 	  ((void)((void)c, m), \
72 	  luaL_error(L, "'popen' not supported"), \
73 	  (FILE*)0)
74 #define l_pclose(L,file)		((void)L, (void)file, -1)
75 
76 #endif				/* } */
77 
78 #endif				/* } */
79 
80 /* }====================================================== */
81 
82 
83 #if !defined(l_getc)		/* { */
84 
85 #if defined(LUA_USE_POSIX)
86 #define l_getc(f)		getc_unlocked(f)
87 #define l_lockfile(f)		flockfile(f)
88 #define l_unlockfile(f)		funlockfile(f)
89 #else
90 #define l_getc(f)		getc(f)
91 #define l_lockfile(f)		((void)0)
92 #define l_unlockfile(f)		((void)0)
93 #endif
94 
95 #endif				/* } */
96 
97 
98 /*
99 ** {======================================================
100 ** l_fseek: configuration for longer offsets
101 ** =======================================================
102 */
103 
104 #if !defined(l_fseek)		/* { */
105 
106 #if defined(LUA_USE_POSIX)	/* { */
107 
108 #include <sys/types.h>
109 
110 #define l_fseek(f,o,w)		fseeko(f,o,w)
111 #define l_ftell(f)		ftello(f)
112 #define l_seeknum		off_t
113 
114 #elif defined(LUA_USE_WINDOWS) && !defined(_CRTIMP_TYPEINFO) \
115    && defined(_MSC_VER) && (_MSC_VER >= 1400)	/* }{ */
116 
117 /* Windows (but not DDK) and Visual C++ 2005 or higher */
118 #define l_fseek(f,o,w)		_fseeki64(f,o,w)
119 #define l_ftell(f)		_ftelli64(f)
120 #define l_seeknum		__int64
121 
122 #else				/* }{ */
123 
124 /* ISO C definitions */
125 #define l_fseek(f,o,w)		fseek(f,o,w)
126 #define l_ftell(f)		ftell(f)
127 #define l_seeknum		long
128 
129 #endif				/* } */
130 
131 #endif				/* } */
132 
133 /* }====================================================== */
134 
135 
136 #define IO_PREFIX	"_IO_"
137 #define IOPREF_LEN	(sizeof(IO_PREFIX)/sizeof(char) - 1)
138 #define IO_INPUT	(IO_PREFIX "input")
139 #define IO_OUTPUT	(IO_PREFIX "output")
140 
141 
142 typedef luaL_Stream LStream;
143 
144 
145 #define tolstream(L)	((LStream *)luaL_checkudata(L, 1, LUA_FILEHANDLE))
146 
147 #define isclosed(p)	((p)->closef == NULL)
148 
149 
150 static int io_type (lua_State *L) {
151   LStream *p;
152   luaL_checkany(L, 1);
153   p = (LStream *)luaL_testudata(L, 1, LUA_FILEHANDLE);
154   if (p == NULL)
155     lua_pushnil(L);  /* not a file */
156   else if (isclosed(p))
157     lua_pushliteral(L, "closed file");
158   else
159     lua_pushliteral(L, "file");
160   return 1;
161 }
162 
163 
164 static int f_tostring (lua_State *L) {
165   LStream *p = tolstream(L);
166   if (isclosed(p))
167     lua_pushliteral(L, "file (closed)");
168   else
169     lua_pushfstring(L, "file (%p)", p->f);
170   return 1;
171 }
172 
173 
174 static FILE *tofile (lua_State *L) {
175   LStream *p = tolstream(L);
176   if (isclosed(p))
177     luaL_error(L, "attempt to use a closed file");
178   lua_assert(p->f);
179   return p->f;
180 }
181 
182 
183 /*
184 ** When creating file handles, always creates a 'closed' file handle
185 ** before opening the actual file; so, if there is a memory error, the
186 ** handle is in a consistent state.
187 */
188 static LStream *newprefile (lua_State *L) {
189   LStream *p = (LStream *)lua_newuserdata(L, sizeof(LStream));
190   p->closef = NULL;  /* mark file handle as 'closed' */
191   luaL_setmetatable(L, LUA_FILEHANDLE);
192   return p;
193 }
194 
195 
196 /*
197 ** Calls the 'close' function from a file handle. The 'volatile' avoids
198 ** a bug in some versions of the Clang compiler (e.g., clang 3.0 for
199 ** 32 bits).
200 */
201 static int aux_close (lua_State *L) {
202   LStream *p = tolstream(L);
203   volatile lua_CFunction cf = p->closef;
204   p->closef = NULL;  /* mark stream as closed */
205   return (*cf)(L);  /* close it */
206 }
207 
208 
209 static int f_close (lua_State *L) {
210   tofile(L);  /* make sure argument is an open stream */
211   return aux_close(L);
212 }
213 
214 
215 static int io_close (lua_State *L) {
216   if (lua_isnone(L, 1))  /* no argument? */
217     lua_getfield(L, LUA_REGISTRYINDEX, IO_OUTPUT);  /* use standard output */
218   return f_close(L);
219 }
220 
221 
222 static int f_gc (lua_State *L) {
223   LStream *p = tolstream(L);
224   if (!isclosed(p) && p->f != NULL)
225     aux_close(L);  /* ignore closed and incompletely open files */
226   return 0;
227 }
228 
229 
230 /*
231 ** function to close regular files
232 */
233 static int io_fclose (lua_State *L) {
234   LStream *p = tolstream(L);
235   int res = fclose(p->f);
236   return luaL_fileresult(L, (res == 0), NULL);
237 }
238 
239 
240 static LStream *newfile (lua_State *L) {
241   LStream *p = newprefile(L);
242   p->f = NULL;
243   p->closef = &io_fclose;
244   return p;
245 }
246 
247 
248 static void opencheck (lua_State *L, const char *fname, const char *mode) {
249   LStream *p = newfile(L);
250   p->f = fopen(fname, mode);
251   if (p->f == NULL)
252     luaL_error(L, "cannot open file '%s' (%s)", fname, strerror(errno));
253 }
254 
255 
256 static int io_open (lua_State *L) {
257   const char *filename = luaL_checkstring(L, 1);
258   const char *mode = luaL_optstring(L, 2, "r");
259   LStream *p = newfile(L);
260   const char *md = mode;  /* to traverse/check mode */
261   luaL_argcheck(L, l_checkmode(md), 2, "invalid mode");
262   p->f = fopen(filename, mode);
263   return (p->f == NULL) ? luaL_fileresult(L, 0, filename) : 1;
264 }
265 
266 
267 /*
268 ** function to close 'popen' files
269 */
270 static int io_pclose (lua_State *L) {
271   LStream *p = tolstream(L);
272   return luaL_execresult(L, l_pclose(L, p->f));
273 }
274 
275 
276 static int io_popen (lua_State *L) {
277   const char *filename = luaL_checkstring(L, 1);
278   const char *mode = luaL_optstring(L, 2, "r");
279   LStream *p = newprefile(L);
280   p->f = l_popen(L, filename, mode);
281   p->closef = &io_pclose;
282   return (p->f == NULL) ? luaL_fileresult(L, 0, filename) : 1;
283 }
284 
285 
286 static int io_tmpfile (lua_State *L) {
287   LStream *p = newfile(L);
288   p->f = tmpfile();
289   return (p->f == NULL) ? luaL_fileresult(L, 0, NULL) : 1;
290 }
291 
292 
293 static FILE *getiofile (lua_State *L, const char *findex) {
294   LStream *p;
295   lua_getfield(L, LUA_REGISTRYINDEX, findex);
296   p = (LStream *)lua_touserdata(L, -1);
297   if (isclosed(p))
298     luaL_error(L, "standard %s file is closed", findex + IOPREF_LEN);
299   return p->f;
300 }
301 
302 
303 static int g_iofile (lua_State *L, const char *f, const char *mode) {
304   if (!lua_isnoneornil(L, 1)) {
305     const char *filename = lua_tostring(L, 1);
306     if (filename)
307       opencheck(L, filename, mode);
308     else {
309       tofile(L);  /* check that it's a valid file handle */
310       lua_pushvalue(L, 1);
311     }
312     lua_setfield(L, LUA_REGISTRYINDEX, f);
313   }
314   /* return current value */
315   lua_getfield(L, LUA_REGISTRYINDEX, f);
316   return 1;
317 }
318 
319 
320 static int io_input (lua_State *L) {
321   return g_iofile(L, IO_INPUT, "r");
322 }
323 
324 
325 static int io_output (lua_State *L) {
326   return g_iofile(L, IO_OUTPUT, "w");
327 }
328 
329 
330 static int io_readline (lua_State *L);
331 
332 
333 /*
334 ** maximum number of arguments to 'f:lines'/'io.lines' (it + 3 must fit
335 ** in the limit for upvalues of a closure)
336 */
337 #define MAXARGLINE	250
338 
339 static void aux_lines (lua_State *L, int toclose) {
340   int n = lua_gettop(L) - 1;  /* number of arguments to read */
341   luaL_argcheck(L, n <= MAXARGLINE, MAXARGLINE + 2, "too many arguments");
342   lua_pushinteger(L, n);  /* number of arguments to read */
343   lua_pushboolean(L, toclose);  /* close/not close file when finished */
344   lua_rotate(L, 2, 2);  /* move 'n' and 'toclose' to their positions */
345   lua_pushcclosure(L, io_readline, 3 + n);
346 }
347 
348 
349 static int f_lines (lua_State *L) {
350   tofile(L);  /* check that it's a valid file handle */
351   aux_lines(L, 0);
352   return 1;
353 }
354 
355 
356 static int io_lines (lua_State *L) {
357   int toclose;
358   if (lua_isnone(L, 1)) lua_pushnil(L);  /* at least one argument */
359   if (lua_isnil(L, 1)) {  /* no file name? */
360     lua_getfield(L, LUA_REGISTRYINDEX, IO_INPUT);  /* get default input */
361     lua_replace(L, 1);  /* put it at index 1 */
362     tofile(L);  /* check that it's a valid file handle */
363     toclose = 0;  /* do not close it after iteration */
364   }
365   else {  /* open a new file */
366     const char *filename = luaL_checkstring(L, 1);
367     opencheck(L, filename, "r");
368     lua_replace(L, 1);  /* put file at index 1 */
369     toclose = 1;  /* close it after iteration */
370   }
371   aux_lines(L, toclose);
372   return 1;
373 }
374 
375 
376 /*
377 ** {======================================================
378 ** READ
379 ** =======================================================
380 */
381 
382 
383 /* maximum length of a numeral */
384 #if !defined (L_MAXLENNUM)
385 #define L_MAXLENNUM     200
386 #endif
387 
388 
389 /* auxiliary structure used by 'read_number' */
390 typedef struct {
391   FILE *f;  /* file being read */
392   int c;  /* current character (look ahead) */
393   int n;  /* number of elements in buffer 'buff' */
394   char buff[L_MAXLENNUM + 1];  /* +1 for ending '\0' */
395 } RN;
396 
397 
398 /*
399 ** Add current char to buffer (if not out of space) and read next one
400 */
401 static int nextc (RN *rn) {
402   if (rn->n >= L_MAXLENNUM) {  /* buffer overflow? */
403     rn->buff[0] = '\0';  /* invalidate result */
404     return 0;  /* fail */
405   }
406   else {
407     rn->buff[rn->n++] = rn->c;  /* save current char */
408     rn->c = l_getc(rn->f);  /* read next one */
409     return 1;
410   }
411 }
412 
413 
414 /*
415 ** Accept current char if it is in 'set' (of size 2)
416 */
417 static int test2 (RN *rn, const char *set) {
418   if (rn->c == set[0] || rn->c == set[1])
419     return nextc(rn);
420   else return 0;
421 }
422 
423 
424 /*
425 ** Read a sequence of (hex)digits
426 */
427 static int readdigits (RN *rn, int hex) {
428   int count = 0;
429   while ((hex ? isxdigit(rn->c) : isdigit(rn->c)) && nextc(rn))
430     count++;
431   return count;
432 }
433 
434 
435 /*
436 ** Read a number: first reads a valid prefix of a numeral into a buffer.
437 ** Then it calls 'lua_stringtonumber' to check whether the format is
438 ** correct and to convert it to a Lua number
439 */
440 static int read_number (lua_State *L, FILE *f) {
441   RN rn;
442   int count = 0;
443   int hex = 0;
444   char decp[2];
445   rn.f = f; rn.n = 0;
446   decp[0] = lua_getlocaledecpoint();  /* get decimal point from locale */
447   decp[1] = '.';  /* always accept a dot */
448   l_lockfile(rn.f);
449   do { rn.c = l_getc(rn.f); } while (isspace(rn.c));  /* skip spaces */
450   test2(&rn, "-+");  /* optional signal */
451   if (test2(&rn, "00")) {
452     if (test2(&rn, "xX")) hex = 1;  /* numeral is hexadecimal */
453     else count = 1;  /* count initial '0' as a valid digit */
454   }
455   count += readdigits(&rn, hex);  /* integral part */
456   if (test2(&rn, decp))  /* decimal point? */
457     count += readdigits(&rn, hex);  /* fractional part */
458   if (count > 0 && test2(&rn, (hex ? "pP" : "eE"))) {  /* exponent mark? */
459     test2(&rn, "-+");  /* exponent signal */
460     readdigits(&rn, 0);  /* exponent digits */
461   }
462   ungetc(rn.c, rn.f);  /* unread look-ahead char */
463   l_unlockfile(rn.f);
464   rn.buff[rn.n] = '\0';  /* finish string */
465   if (lua_stringtonumber(L, rn.buff))  /* is this a valid number? */
466     return 1;  /* ok */
467   else {  /* invalid format */
468    lua_pushnil(L);  /* "result" to be removed */
469    return 0;  /* read fails */
470   }
471 }
472 
473 
474 static int test_eof (lua_State *L, FILE *f) {
475   int c = getc(f);
476   ungetc(c, f);  /* no-op when c == EOF */
477   lua_pushliteral(L, "");
478   return (c != EOF);
479 }
480 
481 
482 static int read_line (lua_State *L, FILE *f, int chop) {
483   luaL_Buffer b;
484   int c = '\0';
485   luaL_buffinit(L, &b);
486   while (c != EOF && c != '\n') {  /* repeat until end of line */
487     char *buff = luaL_prepbuffer(&b);  /* preallocate buffer */
488     int i = 0;
489     l_lockfile(f);  /* no memory errors can happen inside the lock */
490     while (i < LUAL_BUFFERSIZE && (c = l_getc(f)) != EOF && c != '\n')
491       buff[i++] = c;
492     l_unlockfile(f);
493     luaL_addsize(&b, i);
494   }
495   if (!chop && c == '\n')  /* want a newline and have one? */
496     luaL_addchar(&b, c);  /* add ending newline to result */
497   luaL_pushresult(&b);  /* close buffer */
498   /* return ok if read something (either a newline or something else) */
499   return (c == '\n' || lua_rawlen(L, -1) > 0);
500 }
501 
502 
503 static void read_all (lua_State *L, FILE *f) {
504   size_t nr;
505   luaL_Buffer b;
506   luaL_buffinit(L, &b);
507   do {  /* read file in chunks of LUAL_BUFFERSIZE bytes */
508     char *p = luaL_prepbuffer(&b);
509     nr = fread(p, sizeof(char), LUAL_BUFFERSIZE, f);
510     luaL_addsize(&b, nr);
511   } while (nr == LUAL_BUFFERSIZE);
512   luaL_pushresult(&b);  /* close buffer */
513 }
514 
515 
516 static int read_chars (lua_State *L, FILE *f, size_t n) {
517   size_t nr;  /* number of chars actually read */
518   char *p;
519   luaL_Buffer b;
520   luaL_buffinit(L, &b);
521   p = luaL_prepbuffsize(&b, n);  /* prepare buffer to read whole block */
522   nr = fread(p, sizeof(char), n, f);  /* try to read 'n' chars */
523   luaL_addsize(&b, nr);
524   luaL_pushresult(&b);  /* close buffer */
525   return (nr > 0);  /* true iff read something */
526 }
527 
528 
529 static int g_read (lua_State *L, FILE *f, int first) {
530   int nargs = lua_gettop(L) - 1;
531   int success;
532   int n;
533   clearerr(f);
534   if (nargs == 0) {  /* no arguments? */
535     success = read_line(L, f, 1);
536     n = first+1;  /* to return 1 result */
537   }
538   else {  /* ensure stack space for all results and for auxlib's buffer */
539     luaL_checkstack(L, nargs+LUA_MINSTACK, "too many arguments");
540     success = 1;
541     for (n = first; nargs-- && success; n++) {
542       if (lua_type(L, n) == LUA_TNUMBER) {
543         size_t l = (size_t)luaL_checkinteger(L, n);
544         success = (l == 0) ? test_eof(L, f) : read_chars(L, f, l);
545       }
546       else {
547         const char *p = luaL_checkstring(L, n);
548         if (*p == '*') p++;  /* skip optional '*' (for compatibility) */
549         switch (*p) {
550           case 'n':  /* number */
551             success = read_number(L, f);
552             break;
553           case 'l':  /* line */
554             success = read_line(L, f, 1);
555             break;
556           case 'L':  /* line with end-of-line */
557             success = read_line(L, f, 0);
558             break;
559           case 'a':  /* file */
560             read_all(L, f);  /* read entire file */
561             success = 1; /* always success */
562             break;
563           default:
564             return luaL_argerror(L, n, "invalid format");
565         }
566       }
567     }
568   }
569   if (ferror(f))
570     return luaL_fileresult(L, 0, NULL);
571   if (!success) {
572     lua_pop(L, 1);  /* remove last result */
573     lua_pushnil(L);  /* push nil instead */
574   }
575   return n - first;
576 }
577 
578 
579 static int io_read (lua_State *L) {
580   return g_read(L, getiofile(L, IO_INPUT), 1);
581 }
582 
583 
584 static int f_read (lua_State *L) {
585   return g_read(L, tofile(L), 2);
586 }
587 
588 
589 static int io_readline (lua_State *L) {
590   LStream *p = (LStream *)lua_touserdata(L, lua_upvalueindex(1));
591   int i;
592   int n = (int)lua_tointeger(L, lua_upvalueindex(2));
593   if (isclosed(p))  /* file is already closed? */
594     return luaL_error(L, "file is already closed");
595   lua_settop(L , 1);
596   luaL_checkstack(L, n, "too many arguments");
597   for (i = 1; i <= n; i++)  /* push arguments to 'g_read' */
598     lua_pushvalue(L, lua_upvalueindex(3 + i));
599   n = g_read(L, p->f, 2);  /* 'n' is number of results */
600   lua_assert(n > 0);  /* should return at least a nil */
601   if (lua_toboolean(L, -n))  /* read at least one value? */
602     return n;  /* return them */
603   else {  /* first result is nil: EOF or error */
604     if (n > 1) {  /* is there error information? */
605       /* 2nd result is error message */
606       return luaL_error(L, "%s", lua_tostring(L, -n + 1));
607     }
608     if (lua_toboolean(L, lua_upvalueindex(3))) {  /* generator created file? */
609       lua_settop(L, 0);
610       lua_pushvalue(L, lua_upvalueindex(1));
611       aux_close(L);  /* close it */
612     }
613     return 0;
614   }
615 }
616 
617 /* }====================================================== */
618 
619 
620 static int g_write (lua_State *L, FILE *f, int arg) {
621   int nargs = lua_gettop(L) - arg;
622   int status = 1;
623   for (; nargs--; arg++) {
624     if (lua_type(L, arg) == LUA_TNUMBER) {
625       /* optimization: could be done exactly as for strings */
626       int len = lua_isinteger(L, arg)
627                 ? fprintf(f, LUA_INTEGER_FMT,
628                              (LUAI_UACINT)lua_tointeger(L, arg))
629                 : fprintf(f, LUA_NUMBER_FMT,
630                              (LUAI_UACNUMBER)lua_tonumber(L, arg));
631       status = status && (len > 0);
632     }
633     else {
634       size_t l;
635       const char *s = luaL_checklstring(L, arg, &l);
636       status = status && (fwrite(s, sizeof(char), l, f) == l);
637     }
638   }
639   if (status) return 1;  /* file handle already on stack top */
640   else return luaL_fileresult(L, status, NULL);
641 }
642 
643 
644 static int io_write (lua_State *L) {
645   return g_write(L, getiofile(L, IO_OUTPUT), 1);
646 }
647 
648 
649 static int f_write (lua_State *L) {
650   FILE *f = tofile(L);
651   lua_pushvalue(L, 1);  /* push file at the stack top (to be returned) */
652   return g_write(L, f, 2);
653 }
654 
655 
656 static int f_seek (lua_State *L) {
657   static const int mode[] = {SEEK_SET, SEEK_CUR, SEEK_END};
658   static const char *const modenames[] = {"set", "cur", "end", NULL};
659   FILE *f = tofile(L);
660   int op = luaL_checkoption(L, 2, "cur", modenames);
661   lua_Integer p3 = luaL_optinteger(L, 3, 0);
662   l_seeknum offset = (l_seeknum)p3;
663   luaL_argcheck(L, (lua_Integer)offset == p3, 3,
664                   "not an integer in proper range");
665   op = l_fseek(f, offset, mode[op]);
666   if (op)
667     return luaL_fileresult(L, 0, NULL);  /* error */
668   else {
669     lua_pushinteger(L, (lua_Integer)l_ftell(f));
670     return 1;
671   }
672 }
673 
674 
675 static int f_setvbuf (lua_State *L) {
676   static const int mode[] = {_IONBF, _IOFBF, _IOLBF};
677   static const char *const modenames[] = {"no", "full", "line", NULL};
678   FILE *f = tofile(L);
679   int op = luaL_checkoption(L, 2, NULL, modenames);
680   lua_Integer sz = luaL_optinteger(L, 3, LUAL_BUFFERSIZE);
681   int res = setvbuf(f, NULL, mode[op], (size_t)sz);
682   return luaL_fileresult(L, res == 0, NULL);
683 }
684 
685 
686 
687 static int io_flush (lua_State *L) {
688   return luaL_fileresult(L, fflush(getiofile(L, IO_OUTPUT)) == 0, NULL);
689 }
690 
691 
692 static int f_flush (lua_State *L) {
693   return luaL_fileresult(L, fflush(tofile(L)) == 0, NULL);
694 }
695 
696 
697 /*
698 ** functions for 'io' library
699 */
700 static const luaL_Reg iolib[] = {
701   {"close", io_close},
702   {"flush", io_flush},
703   {"input", io_input},
704   {"lines", io_lines},
705   {"open", io_open},
706   {"output", io_output},
707   {"popen", io_popen},
708   {"read", io_read},
709   {"tmpfile", io_tmpfile},
710   {"type", io_type},
711   {"write", io_write},
712   {NULL, NULL}
713 };
714 
715 
716 /*
717 ** methods for file handles
718 */
719 static const luaL_Reg flib[] = {
720   {"close", f_close},
721   {"flush", f_flush},
722   {"lines", f_lines},
723   {"read", f_read},
724   {"seek", f_seek},
725   {"setvbuf", f_setvbuf},
726   {"write", f_write},
727   {"__gc", f_gc},
728   {"__tostring", f_tostring},
729   {NULL, NULL}
730 };
731 
732 
733 static void createmeta (lua_State *L) {
734   luaL_newmetatable(L, LUA_FILEHANDLE);  /* create metatable for file handles */
735   lua_pushvalue(L, -1);  /* push metatable */
736   lua_setfield(L, -2, "__index");  /* metatable.__index = metatable */
737   luaL_setfuncs(L, flib, 0);  /* add file methods to new metatable */
738   lua_pop(L, 1);  /* pop new metatable */
739 }
740 
741 
742 /*
743 ** function to (not) close the standard files stdin, stdout, and stderr
744 */
745 static int io_noclose (lua_State *L) {
746   LStream *p = tolstream(L);
747   p->closef = &io_noclose;  /* keep file opened */
748   lua_pushnil(L);
749   lua_pushliteral(L, "cannot close standard file");
750   return 2;
751 }
752 
753 
754 static void createstdfile (lua_State *L, FILE *f, const char *k,
755                            const char *fname) {
756   LStream *p = newprefile(L);
757   p->f = f;
758   p->closef = &io_noclose;
759   if (k != NULL) {
760     lua_pushvalue(L, -1);
761     lua_setfield(L, LUA_REGISTRYINDEX, k);  /* add file to registry */
762   }
763   lua_setfield(L, -2, fname);  /* add file to module */
764 }
765 
766 
767 LUAMOD_API int luaopen_io (lua_State *L) {
768   luaL_newlib(L, iolib);  /* new module */
769   createmeta(L);
770   /* create (and set) default files */
771   createstdfile(L, stdin, IO_INPUT, "stdin");
772   createstdfile(L, stdout, IO_OUTPUT, "stdout");
773   createstdfile(L, stderr, NULL, "stderr");
774   return 1;
775 }
776 
777