src/system/libroot/posix/stdio/vfscanf.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Chris Torek.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #include <stdio.h>
  38 #include <stdlib.h>
  39 #include <ctype.h>
  40 #include <stdarg.h>
  41 #include "local.h"
  42
  43 #ifdef FLOATING_POINT
  44 #       include "floatio.h"
  45 #endif
  46
  47 #define BUF             513     /* Maximum length of numeric string. */
  48
  49 /*
  50  * Flags used during conversion.
  51  */
  52 #define LONG            0x01    /* l: long or double */
  53 #define LONGDBL         0x02    /* L: long double; unimplemented */
  54 #define SHORT           0x04    /* h: short */
  55 #define QUAD            0x08    /* q: quad */
  56 #define SUPPRESS        0x10    /* suppress assignment */
  57 #define POINTER         0x20    /* weird %p pointer (`fake hex') */
  58 #define NOSKIP          0x40    /* do not skip blanks */
  59
  60 /*
  61  * The following are used in numeric conversions only:
  62  * SIGNOK, NDIGITS, DPTOK, and EXPOK are for floating point;
  63  * SIGNOK, NDIGITS, PFXOK, and NZDIGITS are for integral.
  64  */
  65 #define SIGNOK          0x080   /* +/- is (still) legal */
  66 #define NDIGITS         0x100   /* no digits detected */
  67
  68 #define DPTOK           0x200   /* (float) decimal point is still legal */
  69 #define EXPOK           0x400   /* (float) exponent (e+3, etc) still legal */
  70
  71 #define PFXOK           0x200   /* 0x prefix is (still) legal */
  72 #define NZDIGITS        0x400   /* no zero digits detected */
  73
  74 /*
  75  * Conversion types.
  76  */
  77 #define CT_CHAR         0       /* %c conversion */
  78 #define CT_CCL          1       /* %[...] conversion */
  79 #define CT_STRING       2       /* %s conversion */
  80 #define CT_INT          3       /* integer, i.e., strtoll or strtoull */
  81 #define CT_FLOAT        4       /* floating, i.e., strtod */
  82
  83 #define u_char unsigned char
  84 #define u_long unsigned long
  85
  86 static u_char *__sccl(char *tab, u_char *fmt);
  87
  88 /*
  89  * vfscanf
  90  */
  91 int
  92 __svfscanf(fp, fmt0, ap)
  93         register FILE *fp;
  94         char const *fmt0;
  95         va_list ap;
  96 {
  97         register u_char *fmt = (u_char *)fmt0;
  98         register int c;         /* character from format, or conversion */
  99         register size_t width;  /* field width, or 0 */
 100         register char *p;       /* points into all kinds of strings */
 101         register int n;         /* handy integer */
 102         register int flags;     /* flags as defined above */
 103         register char *p0;      /* saves original value of p when necessary */
 104         int nassigned;          /* number of fields assigned */
 105         int nread;              /* number of characters consumed from fp */
 106         int base;               /* base argument to strtoll/strtoull */
 107         uint64 (*ccfn)();       /* conversion function (strtoll/strtoull) */
 108         char ccltab[256];       /* character class table for %[...] */
 109         char buf[BUF];          /* buffer for numeric conversions */
 110
 111         /* `basefix' is used to avoid `if' tests in the integer scanner */
 112         static short basefix[17] =
 113                 { 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
 114
 115         nassigned = 0;
 116         nread = 0;
 117         base = 0;               /* XXX just to keep gcc happy */
 118         ccfn = NULL;            /* XXX just to keep gcc happy */
 119         for (;;) {
 120                 c = *fmt++;
 121                 if (c == 0)
 122                         return (nassigned);
 123                 if (isspace(c)) {
 124                         while ((fp->_r > 0 || __srefill(fp) == 0) &&
 125                             isspace(*fp->_p))
 126                                 nread++, fp->_r--, fp->_p++;
 127                         continue;
 128                 }
 129                 if (c != '%')
 130                         goto literal;
 131                 width = 0;
 132                 flags = 0;
 133                 /*
 134                  * switch on the format.  continue if done;
 135                  * break once format type is derived.
 136                  */
 137 again:          c = *fmt++;
 138                 switch (c) {
 139                 case '%':
 140 literal:
 141                         if (fp->_r <= 0 && __srefill(fp))
 142                                 goto input_failure;
 143                         if (*fp->_p != c)
 144                                 goto match_failure;
 145                         fp->_r--, fp->_p++;
 146                         nread++;
 147                         continue;
 148
 149                 case '*':
 150                         flags |= SUPPRESS;
 151                         goto again;
 152                 case 'L':
 153                         flags |= LONGDBL | QUAD;
 154                         goto again;
 155                 case 'h':
 156                         flags |= SHORT;
 157                         goto again;
 158                 case 'l':
 159                         if (*fmt == 'l') {
 160                                 fmt++;
 161                                 flags |= QUAD;
 162                         } else {
 163                                 flags |= LONG;
 164                         }
 165                         goto again;
 166                 case 'q':
 167                         flags |= QUAD;
 168                         goto again;
 169
 170                 case '0': case '1': case '2': case '3': case '4':
 171                 case '5': case '6': case '7': case '8': case '9':
 172                         width = width * 10 + c - '0';
 173                         goto again;
 174
 175                 /*
 176                  * Conversions.
 177                  * Those marked `compat' are for 4.[123]BSD compatibility.
 178                  *
 179                  * (According to ANSI, E and X formats are supposed
 180                  * to the same as e and x.  Sorry about that.)
 181                  */
 182                 case 'D':       /* compat */
 183                         flags |= LONG;
 184                         /* FALLTHROUGH */
 185                 case 'd':
 186                         c = CT_INT;
 187                         ccfn = (uint64 (*)())strtoll;
 188                         base = 10;
 189                         break;
 190
 191                 case 'i':
 192                         c = CT_INT;
 193                         ccfn = (uint64 (*)())strtoll;
 194                         base = 0;
 195                         break;
 196
 197                 case 'O':       /* compat */
 198                         flags |= LONG;
 199                         /* FALLTHROUGH */
 200                 case 'o':
 201                         c = CT_INT;
 202                         ccfn = strtoull;
 203                         base = 8;
 204                         break;
 205
 206                 case 'u':
 207                         c = CT_INT;
 208                         ccfn = strtoull;
 209                         base = 10;
 210                         break;
 211
 212                 case 'X':
 213                 case 'x':
 214                         flags |= PFXOK; /* enable 0x prefixing */
 215                         c = CT_INT;
 216                         ccfn = strtoull;
 217                         base = 16;
 218                         break;
 219
 220 #ifdef FLOATING_POINT
 221                 case 'E':
 222                 case 'G':
 223                 case 'e':
 224                 case 'f':
 225                 case 'g':
 226                         c = CT_FLOAT;
 227                         break;
 228 #endif
 229
 230                 case 's':
 231                         c = CT_STRING;
 232                         break;
 233
 234                 case '[':
 235                         fmt = __sccl(ccltab, fmt);
 236                         flags |= NOSKIP;
 237                         c = CT_CCL;
 238                         break;
 239
 240                 case 'c':
 241                         flags |= NOSKIP;
 242                         c = CT_CHAR;
 243                         break;
 244
 245                 case 'p':       /* pointer format is like hex */
 246                         flags |= POINTER | PFXOK;
 247                         c = CT_INT;
 248                         ccfn = strtoull;
 249                         base = 16;
 250                         break;
 251
 252                 case 'n':
 253                         if (flags & SUPPRESS)   /* ??? */
 254                                 continue;
 255                         if (flags & SHORT)
 256                                 *va_arg(ap, short *) = nread;
 257                         else if (flags & LONG)
 258                                 *va_arg(ap, long *) = nread;
 259                         else
 260                                 *va_arg(ap, int *) = nread;
 261                         continue;
 262
 263                 /*
 264                  * Disgusting backwards compatibility hacks.    XXX
 265                  */
 266                 case '\0':      /* compat */
 267                         return (EOF);
 268
 269                 default:        /* compat */
 270                         if (isupper(c))
 271                                 flags |= LONG;
 272                         c = CT_INT;
 273                         ccfn = (uint64 (*)())strtoll;
 274                         base = 10;
 275                         break;
 276                 }
 277
 278                 /*
 279                  * We have a conversion that requires input.
 280                  */
 281                 if (fp->_r <= 0 && __srefill(fp))
 282                         goto input_failure;
 283
 284                 /*
 285                  * Consume leading white space, except for formats
 286                  * that suppress this.
 287                  */
 288                 if ((flags & NOSKIP) == 0) {
 289                         while (isspace(*fp->_p)) {
 290                                 nread++;
 291                                 if (--fp->_r > 0)
 292                                         fp->_p++;
 293                                 else if (__srefill(fp))
 294                                         goto input_failure;
 295                         }
 296                         /*
 297                          * Note that there is at least one character in
 298                          * the buffer, so conversions that do not set NOSKIP
 299                          * ca no longer result in an input failure.
 300                          */
 301                 }
 302
 303                 /*
 304                  * Do the conversion.
 305                  */
 306                 switch (c) {
 307
 308                 case CT_CHAR:
 309                         /* scan arbitrary characters (sets NOSKIP) */
 310                         if (width == 0)
 311                                 width = 1;
 312                         if (flags & SUPPRESS) {
 313                                 size_t sum = 0;
 314                                 for (;;) {
 315                                         if ((n = fp->_r) < width) {
 316                                                 sum += n;
 317                                                 width -= n;
 318                                                 fp->_p += n;
 319                                                 if (__srefill(fp)) {
 320                                                         if (sum == 0)
 321                                                             goto input_failure;
 322                                                         break;
 323                                                 }
 324                                         } else {
 325                                                 sum += width;
 326                                                 fp->_r -= width;
 327                                                 fp->_p += width;
 328                                                 break;
 329                                         }
 330                                 }
 331                                 nread += sum;
 332                         } else {
 333                                 size_t r = fread((void *)va_arg(ap, char *), 1,
 334                                     width, fp);
 335
 336                                 if (r == 0)
 337                                         goto input_failure;
 338                                 nread += r;
 339                                 nassigned++;
 340                         }
 341                         break;
 342
 343                 case CT_CCL:
 344                         /* scan a (nonempty) character class (sets NOSKIP) */
 345                         if (width == 0)
 346                                 width = (size_t)~0;     /* `infinity' */
 347                         /* take only those things in the class */
 348                         if (flags & SUPPRESS) {
 349                                 n = 0;
 350                                 while (ccltab[*fp->_p]) {
 351                                         n++, fp->_r--, fp->_p++;
 352                                         if (--width == 0)
 353                                                 break;
 354                                         if (fp->_r <= 0 && __srefill(fp)) {
 355                                                 if (n == 0)
 356                                                         goto input_failure;
 357                                                 break;
 358                                         }
 359                                 }
 360                                 if (n == 0)
 361                                         goto match_failure;
 362                         } else {
 363                                 p0 = p = va_arg(ap, char *);
 364                                 while (ccltab[*fp->_p]) {
 365                                         fp->_r--;
 366                                         *p++ = *fp->_p++;
 367                                         if (--width == 0)
 368                                                 break;
 369                                         if (fp->_r <= 0 && __srefill(fp)) {
 370                                                 if (p == p0)
 371                                                         goto input_failure;
 372                                                 break;
 373                                         }
 374                                 }
 375                                 n = p - p0;
 376                                 if (n == 0)
 377                                         goto match_failure;
 378                                 *p = 0;
 379                                 nassigned++;
 380                         }
 381                         nread += n;
 382                         break;
 383
 384                 case CT_STRING:
 385                         /* like CCL, but zero-length string OK, & no NOSKIP */
 386                         if (width == 0)
 387                                 width = (size_t)~0;
 388                         if (flags & SUPPRESS) {
 389                                 n = 0;
 390                                 while (!isspace(*fp->_p)) {
 391                                         n++, fp->_r--, fp->_p++;
 392                                         if (--width == 0)
 393                                                 break;
 394                                         if (fp->_r <= 0 && __srefill(fp))
 395                                                 break;
 396                                 }
 397                                 nread += n;
 398                         } else {
 399                                 p0 = p = va_arg(ap, char *);
 400                                 while (!isspace(*fp->_p)) {
 401                                         fp->_r--;
 402                                         *p++ = *fp->_p++;
 403                                         if (--width == 0)
 404                                                 break;
 405                                         if (fp->_r <= 0 && __srefill(fp))
 406                                                 break;
 407                                 }
 408                                 *p = 0;
 409                                 nread += p - p0;
 410                                 nassigned++;
 411                         }
 412                         continue;
 413
 414                 case CT_INT:
 415                         /* scan an integer as if by strtoll/strtoull */
 416 #ifdef hardway
 417                         if (width == 0 || width > sizeof(buf) - 1)
 418                                 width = sizeof(buf) - 1;
 419 #else
 420                         /* size_t is unsigned, hence this optimisation */
 421                         if (--width > sizeof(buf) - 2)
 422                                 width = sizeof(buf) - 2;
 423                         width++;
 424 #endif
 425                         flags |= SIGNOK | NDIGITS | NZDIGITS;
 426                         for (p = buf; width; width--) {
 427                                 c = *fp->_p;
 428                                 /*
 429                                  * Switch on the character; `goto ok'
 430                                  * if we accept it as a part of number.
 431                                  */
 432                                 switch (c) {
 433
 434                                 /*
 435                                  * The digit 0 is always legal, but is
 436                                  * special.  For %i conversions, if no
 437                                  * digits (zero or nonzero) have been
 438                                  * scanned (only signs), we will have
 439                                  * base==0.  In that case, we should set
 440                                  * it to 8 and enable 0x prefixing.
 441                                  * Also, if we have not scanned zero digits
 442                                  * before this, do not turn off prefixing
 443                                  * (someone else will turn it off if we
 444                                  * have scanned any nonzero digits).
 445                                  */
 446                                 case '0':
 447                                         if (base == 0) {
 448                                                 base = 8;
 449                                                 flags |= PFXOK;
 450                                         }
 451                                         if (flags & NZDIGITS)
 452                                             flags &= ~(SIGNOK|NZDIGITS|NDIGITS);
 453                                         else
 454                                             flags &= ~(SIGNOK|PFXOK|NDIGITS);
 455                                         goto ok;
 456
 457                                 /* 1 through 7 always legal */
 458                                 case '1': case '2': case '3':
 459                                 case '4': case '5': case '6': case '7':
 460                                         base = basefix[base];
 461                                         flags &= ~(SIGNOK | PFXOK | NDIGITS);
 462                                         goto ok;
 463
 464                                 /* digits 8 and 9 ok iff decimal or hex */
 465                                 case '8': case '9':
 466                                         base = basefix[base];
 467                                         if (base <= 8)
 468                                                 break;  /* not legal here */
 469                                         flags &= ~(SIGNOK | PFXOK | NDIGITS);
 470                                         goto ok;
 471
 472                                 /* letters ok iff hex */
 473                                 case 'A': case 'B': case 'C':
 474                                 case 'D': case 'E': case 'F':
 475                                 case 'a': case 'b': case 'c':
 476                                 case 'd': case 'e': case 'f':
 477                                         /* no need to fix base here */
 478                                         if (base <= 10)
 479                                                 break;  /* not legal here */
 480                                         flags &= ~(SIGNOK | PFXOK | NDIGITS);
 481                                         goto ok;
 482
 483                                 /* sign ok only as first character */
 484                                 case '+': case '-':
 485                                         if (flags & SIGNOK) {
 486                                                 flags &= ~SIGNOK;
 487                                                 goto ok;
 488                                         }
 489                                         break;
 490
 491                                 /* x ok iff flag still set & 2nd char */
 492                                 case 'x': case 'X':
 493                                         if (flags & PFXOK && p == buf + 1) {
 494                                                 base = 16;      /* if %i */
 495                                                 flags &= ~PFXOK;
 496                                                 goto ok;
 497                                         }
 498                                         break;
 499                                 }
 500
 501                                 /*
 502                                  * If we got here, c is not a legal character
 503                                  * for a number.  Stop accumulating digits.
 504                                  */
 505                                 break;
 506                 ok:
 507                                 /*
 508                                  * c is legal: store it and look at the next.
 509                                  */
 510                                 *p++ = c;
 511                                 if (--fp->_r > 0)
 512                                         fp->_p++;
 513                                 else if (__srefill(fp))
 514                                         break;          /* EOF */
 515                         }
 516                         /*
 517                          * If we had only a sign, it is no good; push
 518                          * back the sign.  If the number ends in `x',
 519                          * it was [sign] '0' 'x', so push back the x
 520                          * and treat it as [sign] '0'.
 521                          */
 522                         if (flags & NDIGITS) {
 523                                 if (p > buf)
 524                                         (void) ungetc(*(u_char *)--p, fp);
 525                                 goto match_failure;
 526                         }
 527                         c = ((u_char *)p)[-1];
 528                         if (c == 'x' || c == 'X') {
 529                                 --p;
 530                                 (void) ungetc(c, fp);
 531                         }
 532                         if ((flags & SUPPRESS) == 0) {
 533                                 uint64 res;
 534
 535                                 *p = 0;
 536                                 res = (*ccfn)(buf, (char **)NULL, base);
 537                                 if (flags & POINTER)
 538                                         *va_arg(ap, void **) =
 539                                             (void *)(long)res;
 540                                 else if (flags & QUAD)
 541                                         *va_arg(ap, int64 *) = res;
 542                                 else if (flags & LONG)
 543                                         *va_arg(ap, long *) = res;
 544                                 else if (flags & SHORT)
 545                                         *va_arg(ap, short *) = res;
 546                                 else
 547                                         *va_arg(ap, int *) = res;
 548                                 nassigned++;
 549                         }
 550                         nread += p - buf;
 551                         break;
 552
 553 #ifdef FLOATING_POINT
 554                 case CT_FLOAT:
 555                         /* scan a floating point number as if by strtod */
 556 #ifdef hardway
 557                         if (width == 0 || width > sizeof(buf) - 1)
 558                                 width = sizeof(buf) - 1;
 559 #else
 560                         /* size_t is unsigned, hence this optimisation */
 561                         if (--width > sizeof(buf) - 2)
 562                                 width = sizeof(buf) - 2;
 563                         width++;
 564 #endif
 565                         flags |= SIGNOK | NDIGITS | DPTOK | EXPOK;
 566                         for (p = buf; width; width--) {
 567                                 c = *fp->_p;
 568                                 /*
 569                                  * This code mimicks the integer conversion
 570                                  * code, but is much simpler.
 571                                  */
 572                                 switch (c) {
 573
 574                                 case '0': case '1': case '2': case '3':
 575                                 case '4': case '5': case '6': case '7':
 576                                 case '8': case '9':
 577                                         flags &= ~(SIGNOK | NDIGITS);
 578                                         goto fok;
 579
 580                                 case '+': case '-':
 581                                         if (flags & SIGNOK) {
 582                                                 flags &= ~SIGNOK;
 583                                                 goto fok;
 584                                         }
 585                                         break;
 586                                 case '.':
 587                                         if (flags & DPTOK) {
 588                                                 flags &= ~(SIGNOK | DPTOK);
 589                                                 goto fok;
 590                                         }
 591                                         break;
 592                                 case 'e': case 'E':
 593                                         /* no exponent without some digits */
 594                                         if ((flags&(NDIGITS|EXPOK)) == EXPOK) {
 595                                                 flags =
 596                                                     (flags & ~(EXPOK|DPTOK)) |
 597                                                     SIGNOK | NDIGITS;
 598                                                 goto fok;
 599                                         }
 600                                         break;
 601                                 }
 602                                 break;
 603                 fok:
 604                                 *p++ = c;
 605                                 if (--fp->_r > 0)
 606                                         fp->_p++;
 607                                 else if (__srefill(fp))
 608                                         break;  /* EOF */
 609                         }
 610                         /*
 611                          * If no digits, might be missing exponent digits
 612                          * (just give back the exponent) or might be missing
 613                          * regular digits, but had sign and/or decimal point.
 614                          */
 615                         if (flags & NDIGITS) {
 616                                 if (flags & EXPOK) {
 617                                         /* no digits at all */
 618                                         while (p > buf)
 619                                                 ungetc(*(u_char *)--p, fp);
 620                                         goto match_failure;
 621                                 }
 622                                 /* just a bad exponent (e and maybe sign) */
 623                                 c = *(u_char *)--p;
 624                                 if (c != 'e' && c != 'E') {
 625                                         (void) ungetc(c, fp);/* sign */
 626                                         c = *(u_char *)--p;
 627                                 }
 628                                 (void) ungetc(c, fp);
 629                         }
 630                         if ((flags & SUPPRESS) == 0) {
 631                                 double res;
 632
 633                                 *p = 0;
 634                                 res = strtod(buf, (char **) NULL);
 635                                 if (flags & LONGDBL)
 636                                         *va_arg(ap, long double *) = res;
 637                                 else if (flags & LONG)
 638                                         *va_arg(ap, double *) = res;
 639                                 else
 640                                         *va_arg(ap, float *) = res;
 641                                 nassigned++;
 642                         }
 643                         nread += p - buf;
 644                         break;
 645 #endif /* FLOATING_POINT */
 646                 }
 647         }
 648 input_failure:
 649         return (nassigned ? nassigned : -1);
 650 match_failure:
 651         return (nassigned);
 652 }
 653
 654 /*
 655  * Fill in the given table from the scanset at the given format
 656  * (just after `[').  Return a pointer to the character past the
 657  * closing `]'.  The table has a 1 wherever characters should be
 658  * considered part of the scanset.
 659  */
 660 static u_char *
 661 __sccl(tab, fmt)
 662         register char *tab;
 663         register u_char *fmt;
 664 {
 665         register int c, n, v;
 666
 667         /* first `clear' the whole table */
 668         c = *fmt++;             /* first char hat => negated scanset */
 669         if (c == '^') {
 670                 v = 1;          /* default => accept */
 671                 c = *fmt++;     /* get new first char */
 672         } else
 673                 v = 0;          /* default => reject */
 674         /* should probably use memset here */
 675         for (n = 0; n < 256; n++)
 676                 tab[n] = v;
 677         if (c == 0)
 678                 return (fmt - 1);/* format ended before closing ] */
 679
 680         /*
 681          * Now set the entries corresponding to the actual scanset
 682          * to the opposite of the above.
 683          *
 684          * The first character may be ']' (or '-') without being special;
 685          * the last character may be '-'.
 686          */
 687         v = 1 - v;
 688         for (;;) {
 689                 tab[c] = v;             /* take character c */
 690 doswitch:
 691                 n = *fmt++;             /* and examine the next */
 692                 switch (n) {
 693
 694                 case 0:                 /* format ended too soon */
 695                         return (fmt - 1);
 696
 697                 case '-':
 698                         /*
 699                          * A scanset of the form
 700                          *      [01+-]
 701                          * is defined as `the digit 0, the digit 1,
 702                          * the character +, the character -', but
 703                          * the effect of a scanset such as
 704                          *      [a-zA-Z0-9]
 705                          * is implementation defined.  The V7 Unix
 706                          * scanf treats `a-z' as `the letters a through
 707                          * z', but treats `a-a' as `the letter a, the
 708                          * character -, and the letter a'.
 709                          *
 710                          * For compatibility, the `-' is not considerd
 711                          * to define a range if the character following
 712                          * it is either a close bracket (required by ANSI)
 713                          * or is not numerically greater than the character
 714                          * we just stored in the table (c).
 715                          */
 716                         n = *fmt;
 717                         if (n == ']' || n < c) {
 718                                 c = '-';
 719                                 break;  /* resume the for(;;) */
 720                         }
 721                         fmt++;
 722                         do {            /* fill in the range */
 723                                 tab[++c] = v;
 724                         } while (c < n);
 725 #if 1   /* XXX another disgusting compatibility hack */
 726                         /*
 727                          * Alas, the V7 Unix scanf also treats formats
 728                          * such as [a-c-e] as `the letters a through e'.
 729                          * This too is permitted by the standard....
 730                          */
 731                         goto doswitch;
 732 #else
 733                         c = *fmt++;
 734                         if (c == 0)
 735                                 return (fmt - 1);
 736                         if (c == ']')
 737                                 return (fmt);
 738 #endif
 739                         break;
 740
 741                 case ']':               /* end of scanset */
 742                         return (fmt);
 743
 744                 default:                /* just another character */
 745                         c = n;
 746                         break;
 747                 }
 748         }
 749         /* NOTREACHED */
 750 }