stdio.subproj/vfscanf.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Copyright (c) 1990, 1993
  24  *      The Regents of the University of California.  All rights reserved.
  25  *
  26  * This code is derived from software contributed to Berkeley by
  27  * Chris Torek.
  28  *
  29  * Redistribution and use in source and binary forms, with or without
  30  * modification, are permitted provided that the following conditions
  31  * are met:
  32  * 1. Redistributions of source code must retain the above copyright
  33  *    notice, this list of conditions and the following disclaimer.
  34  * 2. Redistributions in binary form must reproduce the above copyright
  35  *    notice, this list of conditions and the following disclaimer in the
  36  *    documentation and/or other materials provided with the distribution.
  37  * 3. All advertising materials mentioning features or use of this software
  38  *    must display the following acknowledgement:
  39  *      This product includes software developed by the University of
  40  *      California, Berkeley and its contributors.
  41  * 4. Neither the name of the University nor the names of its contributors
  42  *    may be used to endorse or promote products derived from this software
  43  *    without specific prior written permission.
  44  *
  45  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  46  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  47  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  48  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  49  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  50  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  51  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  52  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  53  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  54  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  55  * SUCH DAMAGE.
  56  */
  57
  58
  59 #include <stdio.h>
  60 #include <stdlib.h>
  61 #include <ctype.h>
  62 #if __STDC__
  63 #include <stdarg.h>
  64 #else
  65 #include <varargs.h>
  66 #endif
  67 #include "local.h"
  68
  69 #define FLOATING_POINT
  70
  71 #include "floatio.h"
  72 #define BUF             513     /* Maximum length of numeric string. */
  73
  74 /*
  75  * Flags used during conversion.
  76  */
  77 #define LONG            0x01    /* l: long or double */
  78 #define LONGDBL         0x02    /* L: long double; unimplemented */
  79 #define SHORT           0x04    /* h: short */
  80 #define SUPPRESS        0x08    /* suppress assignment */
  81 #define POINTER         0x10    /* weird %p pointer (`fake hex') */
  82 #define NOSKIP          0x20    /* do not skip blanks */
  83
  84 /*
  85  * The following are used in numeric conversions only:
  86  * SIGNOK, NDIGITS, DPTOK, and EXPOK are for floating point;
  87  * SIGNOK, NDIGITS, PFXOK, and NZDIGITS are for integral.
  88  */
  89 #define SIGNOK          0x40    /* +/- is (still) legal */
  90 #define NDIGITS         0x80    /* no digits detected */
  91
  92 #define DPTOK           0x100   /* (float) decimal point is still legal */
  93 #define EXPOK           0x200   /* (float) exponent (e+3, etc) still legal */
  94
  95 #define PFXOK           0x100   /* 0x prefix is (still) legal */
  96 #define NZDIGITS        0x200   /* no zero digits detected */
  97
  98 /*
  99  * Conversion types.
 100  */
 101 #define CT_CHAR         0       /* %c conversion */
 102 #define CT_CCL          1       /* %[...] conversion */
 103 #define CT_STRING       2       /* %s conversion */
 104 #define CT_INT          3       /* integer, i.e., strtol or strtoul */
 105 #define CT_FLOAT        4       /* floating, i.e., strtod */
 106
 107 #define u_char unsigned char
 108 #define u_long unsigned long
 109
 110 static u_char *__sccl();
 111
 112 /*
 113  * vfscanf
 114  */
 115 int
 116 __svfscanf(fp, fmt0, ap)
 117         register FILE *fp;
 118         char const *fmt0;
 119         va_list ap;
 120 {
 121         register u_char *fmt = (u_char *)fmt0;
 122         register int c;         /* character from format, or conversion */
 123         register size_t width;  /* field width, or 0 */
 124         register char *p;       /* points into all kinds of strings */
 125         register int n;         /* handy integer */
 126         register int flags;     /* flags as defined above */
 127         register char *p0;      /* saves original value of p when necessary */
 128         int nassigned;          /* number of fields assigned */
 129         int nread;              /* number of characters consumed from fp */
 130         int base;               /* base argument to strtol/strtoul */
 131         u_long (*ccfn)();       /* conversion function (strtol/strtoul) */
 132         char ccltab[256];       /* character class table for %[...] */
 133         char buf[BUF];          /* buffer for numeric conversions */
 134
 135         /* `basefix' is used to avoid `if' tests in the integer scanner */
 136         static short basefix[17] =
 137                 { 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
 138
 139         nassigned = 0;
 140         nread = 0;
 141         base = 0;               /* XXX just to keep gcc happy */
 142         ccfn = NULL;            /* XXX just to keep gcc happy */
 143         for (;;) {
 144                 c = *fmt++;
 145                 if (c == 0)
 146                         return (nassigned);
 147                 if (isspace(c)) {
 148                         for (;;) {
 149                                 if (fp->_r <= 0 && __srefill(fp))
 150                                         return (nassigned);
 151                                 if (!isspace(*fp->_p))
 152                                         break;
 153                                 nread++, fp->_r--, fp->_p++;
 154                         }
 155                         continue;
 156                 }
 157                 if (c != '%')
 158                         goto literal;
 159                 width = 0;
 160                 flags = 0;
 161                 /*
 162                  * switch on the format.  continue if done;
 163                  * break once format type is derived.
 164                  */
 165 again:          c = *fmt++;
 166                 switch (c) {
 167                 case '%':
 168 literal:
 169                         if (fp->_r <= 0 && __srefill(fp))
 170                                 goto input_failure;
 171                         if (*fp->_p != c)
 172                                 goto match_failure;
 173                         fp->_r--, fp->_p++;
 174                         nread++;
 175                         continue;
 176
 177                 case '*':
 178                         flags |= SUPPRESS;
 179                         goto again;
 180                 case 'l':
 181                         flags |= LONG;
 182                         goto again;
 183                 case 'L':
 184                         flags |= LONGDBL;
 185                         goto again;
 186                 case 'h':
 187                         flags |= SHORT;
 188                         goto again;
 189
 190                 case '0': case '1': case '2': case '3': case '4':
 191                 case '5': case '6': case '7': case '8': case '9':
 192                         width = width * 10 + c - '0';
 193                         goto again;
 194
 195                 /*
 196                  * Conversions.
 197                  * Those marked `compat' are for 4.[123]BSD compatibility.
 198                  *
 199                  * (According to ANSI, E and X formats are supposed
 200                  * to the same as e and x.  Sorry about that.)
 201                  */
 202                 case 'D':       /* compat */
 203                         flags |= LONG;
 204                         /* FALLTHROUGH */
 205                 case 'd':
 206                         c = CT_INT;
 207                         ccfn = (u_long (*)())strtol;
 208                         base = 10;
 209                         break;
 210
 211                 case 'i':
 212                         c = CT_INT;
 213                         ccfn = (u_long (*)())strtol;
 214                         base = 0;
 215                         break;
 216
 217                 case 'O':       /* compat */
 218                         flags |= LONG;
 219                         /* FALLTHROUGH */
 220                 case 'o':
 221                         c = CT_INT;
 222                         ccfn = strtoul;
 223                         base = 8;
 224                         break;
 225
 226                 case 'u':
 227                         c = CT_INT;
 228                         ccfn = strtoul;
 229                         base = 10;
 230                         break;
 231
 232                 case 'X':       /* compat   XXX */
 233                         flags |= LONG;
 234                         /* FALLTHROUGH */
 235                 case 'x':
 236                         flags |= PFXOK; /* enable 0x prefixing */
 237                         c = CT_INT;
 238                         ccfn = strtoul;
 239                         base = 16;
 240                         break;
 241
 242 #ifdef FLOATING_POINT
 243                 case 'E':       /* compat   XXX */
 244                 case 'F':       /* compat */
 245                         flags |= LONG;
 246                         /* FALLTHROUGH */
 247                 case 'e': case 'f': case 'g':
 248                         c = CT_FLOAT;
 249                         break;
 250 #endif
 251
 252                 case 's':
 253                         c = CT_STRING;
 254                         break;
 255
 256                 case '[':
 257                         fmt = __sccl(ccltab, fmt);
 258                         flags |= NOSKIP;
 259                         c = CT_CCL;
 260                         break;
 261
 262                 case 'c':
 263                         flags |= NOSKIP;
 264                         c = CT_CHAR;
 265                         break;
 266
 267                 case 'p':       /* pointer format is like hex */
 268                         flags |= POINTER | PFXOK;
 269                         c = CT_INT;
 270                         ccfn = strtoul;
 271                         base = 16;
 272                         break;
 273
 274                 case 'n':
 275                         if (flags & SUPPRESS)   /* ??? */
 276                                 continue;
 277                         if (flags & SHORT)
 278                                 *va_arg(ap, short *) = nread;
 279                         else if (flags & LONG)
 280                                 *va_arg(ap, long *) = nread;
 281                         else
 282                                 *va_arg(ap, int *) = nread;
 283                         continue;
 284
 285                 /*
 286                  * Disgusting backwards compatibility hacks.    XXX
 287                  */
 288                 case '\0':      /* compat */
 289                         return (EOF);
 290
 291                 default:        /* compat */
 292                         if (isupper(c))
 293                                 flags |= LONG;
 294                         c = CT_INT;
 295                         ccfn = (u_long (*)())strtol;
 296                         base = 10;
 297                         break;
 298                 }
 299
 300                 /*
 301                  * We have a conversion that requires input.
 302                  */
 303                 if (fp->_r <= 0 && __srefill(fp))
 304                         goto input_failure;
 305
 306                 /*
 307                  * Consume leading white space, except for formats
 308                  * that suppress this.
 309                  */
 310                 if ((flags & NOSKIP) == 0) {
 311                         while (isspace(*fp->_p)) {
 312                                 nread++;
 313                                 if (--fp->_r > 0)
 314                                         fp->_p++;
 315                                 else if (__srefill(fp))
 316                                         goto input_failure;
 317                         }
 318                         /*
 319                          * Note that there is at least one character in
 320                          * the buffer, so conversions that do not set NOSKIP
 321                          * ca no longer result in an input failure.
 322                          */
 323                 }
 324
 325                 /*
 326                  * Do the conversion.
 327                  */
 328                 switch (c) {
 329
 330                 case CT_CHAR:
 331                         /* scan arbitrary characters (sets NOSKIP) */
 332                         if (width == 0)
 333                                 width = 1;
 334                         if (flags & SUPPRESS) {
 335                                 size_t sum = 0;
 336                                 for (;;) {
 337                                         if ((n = fp->_r) < width) {
 338                                                 sum += n;
 339                                                 width -= n;
 340                                                 fp->_p += n;
 341                                                 if (__srefill(fp)) {
 342                                                         if (sum == 0)
 343                                                             goto input_failure;
 344                                                         break;
 345                                                 }
 346                                         } else {
 347                                                 sum += width;
 348                                                 fp->_r -= width;
 349                                                 fp->_p += width;
 350                                                 break;
 351                                         }
 352                                 }
 353                                 nread += sum;
 354                         } else {
 355                                 size_t r = fread((void *)va_arg(ap, char *), 1,
 356                                     width, fp);
 357
 358                                 if (r == 0)
 359                                         goto input_failure;
 360                                 nread += r;
 361                                 nassigned++;
 362                         }
 363                         break;
 364
 365                 case CT_CCL:
 366                         /* scan a (nonempty) character class (sets NOSKIP) */
 367                         if (width == 0)
 368                                 width = ~0;     /* `infinity' */
 369                         /* take only those things in the class */
 370                         if (flags & SUPPRESS) {
 371                                 n = 0;
 372                                 while (ccltab[*fp->_p]) {
 373                                         n++, fp->_r--, fp->_p++;
 374                                         if (--width == 0)
 375                                                 break;
 376                                         if (fp->_r <= 0 && __srefill(fp)) {
 377                                                 if (n == 0)
 378                                                         goto input_failure;
 379                                                 break;
 380                                         }
 381                                 }
 382                                 if (n == 0)
 383                                         goto match_failure;
 384                         } else {
 385                                 p0 = p = va_arg(ap, char *);
 386                                 while (ccltab[*fp->_p]) {
 387                                         fp->_r--;
 388                                         *p++ = *fp->_p++;
 389                                         if (--width == 0)
 390                                                 break;
 391                                         if (fp->_r <= 0 && __srefill(fp)) {
 392                                                 if (p == p0)
 393                                                         goto input_failure;
 394                                                 break;
 395                                         }
 396                                 }
 397                                 n = p - p0;
 398                                 if (n == 0)
 399                                         goto match_failure;
 400                                 *p = 0;
 401                                 nassigned++;
 402                         }
 403                         nread += n;
 404                         break;
 405
 406                 case CT_STRING:
 407                         /* like CCL, but zero-length string OK, & no NOSKIP */
 408                         if (width == 0)
 409                                 width = ~0;
 410                         if (flags & SUPPRESS) {
 411                                 n = 0;
 412                                 while (!isspace(*fp->_p)) {
 413                                         n++, fp->_r--, fp->_p++;
 414                                         if (--width == 0)
 415                                                 break;
 416                                         if (fp->_r <= 0 && __srefill(fp))
 417                                                 break;
 418                                 }
 419                                 nread += n;
 420                         } else {
 421                                 p0 = p = va_arg(ap, char *);
 422                                 while (!isspace(*fp->_p)) {
 423                                         fp->_r--;
 424                                         *p++ = *fp->_p++;
 425                                         if (--width == 0)
 426                                                 break;
 427                                         if (fp->_r <= 0 && __srefill(fp))
 428                                                 break;
 429                                 }
 430                                 *p = 0;
 431                                 nread += p - p0;
 432                                 nassigned++;
 433                         }
 434                         continue;
 435
 436                 case CT_INT:
 437                         /* scan an integer as if by strtol/strtoul */
 438 #ifdef hardway
 439                         if (width == 0 || width > sizeof(buf) - 1)
 440                                 width = sizeof(buf) - 1;
 441 #else
 442                         /* size_t is unsigned, hence this optimisation */
 443                         if (--width > sizeof(buf) - 2)
 444                                 width = sizeof(buf) - 2;
 445                         width++;
 446 #endif
 447                         flags |= SIGNOK | NDIGITS | NZDIGITS;
 448                         for (p = buf; width; width--) {
 449                                 c = *fp->_p;
 450                                 /*
 451                                  * Switch on the character; `goto ok'
 452                                  * if we accept it as a part of number.
 453                                  */
 454                                 switch (c) {
 455
 456                                 /*
 457                                  * The digit 0 is always legal, but is
 458                                  * special.  For %i conversions, if no
 459                                  * digits (zero or nonzero) have been
 460                                  * scanned (only signs), we will have
 461                                  * base==0.  In that case, we should set
 462                                  * it to 8 and enable 0x prefixing.
 463                                  * Also, if we have not scanned zero digits
 464                                  * before this, do not turn off prefixing
 465                                  * (someone else will turn it off if we
 466                                  * have scanned any nonzero digits).
 467                                  */
 468                                 case '0':
 469                                         if (base == 0) {
 470                                                 base = 8;
 471                                                 flags |= PFXOK;
 472                                         }
 473                                         if (flags & NZDIGITS)
 474                                             flags &= ~(SIGNOK|NZDIGITS|NDIGITS);
 475                                         else
 476                                             flags &= ~(SIGNOK|PFXOK|NDIGITS);
 477                                         goto ok;
 478
 479                                 /* 1 through 7 always legal */
 480                                 case '1': case '2': case '3':
 481                                 case '4': case '5': case '6': case '7':
 482                                         base = basefix[base];
 483                                         flags &= ~(SIGNOK | PFXOK | NDIGITS);
 484                                         goto ok;
 485
 486                                 /* digits 8 and 9 ok iff decimal or hex */
 487                                 case '8': case '9':
 488                                         base = basefix[base];
 489                                         if (base <= 8)
 490                                                 break;  /* not legal here */
 491                                         flags &= ~(SIGNOK | PFXOK | NDIGITS);
 492                                         goto ok;
 493
 494                                 /* letters ok iff hex */
 495                                 case 'A': case 'B': case 'C':
 496                                 case 'D': case 'E': case 'F':
 497                                 case 'a': case 'b': case 'c':
 498                                 case 'd': case 'e': case 'f':
 499                                         /* no need to fix base here */
 500                                         if (base <= 10)
 501                                                 break;  /* not legal here */
 502                                         flags &= ~(SIGNOK | PFXOK | NDIGITS);
 503                                         goto ok;
 504
 505                                 /* sign ok only as first character */
 506                                 case '+': case '-':
 507                                         if (flags & SIGNOK) {
 508                                                 flags &= ~SIGNOK;
 509                                                 goto ok;
 510                                         }
 511                                         break;
 512
 513                                 /* x ok iff flag still set & 2nd char */
 514                                 case 'x': case 'X':
 515                                         if (flags & PFXOK && p == buf + 1) {
 516                                                 base = 16;      /* if %i */
 517                                                 flags &= ~PFXOK;
 518                                                 goto ok;
 519                                         }
 520                                         break;
 521                                 }
 522
 523                                 /*
 524                                  * If we got here, c is not a legal character
 525                                  * for a number.  Stop accumulating digits.
 526                                  */
 527                                 break;
 528                 ok:
 529                                 /*
 530                                  * c is legal: store it and look at the next.
 531                                  */
 532                                 *p++ = c;
 533                                 if (--fp->_r > 0)
 534                                         fp->_p++;
 535                                 else if (__srefill(fp))
 536                                         break;          /* EOF */
 537                         }
 538                         /*
 539                          * If we had only a sign, it is no good; push
 540                          * back the sign.  If the number ends in `x',
 541                          * it was [sign] '0' 'x', so push back the x
 542                          * and treat it as [sign] '0'.
 543                          */
 544                         if (flags & NDIGITS) {
 545                                 if (p > buf)
 546                                         (void) ungetc(*(u_char *)--p, fp);
 547                                 goto match_failure;
 548                         }
 549                         c = ((u_char *)p)[-1];
 550                         if (c == 'x' || c == 'X') {
 551                                 --p;
 552                                 (void) ungetc(c, fp);
 553                         }
 554                         if ((flags & SUPPRESS) == 0) {
 555                                 u_long res;
 556
 557                                 *p = 0;
 558                                 res = (*ccfn)(buf, (char **)NULL, base);
 559                                 if (flags & POINTER)
 560                                         *va_arg(ap, void **) = (void *)res;
 561                                 else if (flags & SHORT)
 562                                         *va_arg(ap, short *) = res;
 563                                 else if (flags & LONG)
 564                                         *va_arg(ap, long *) = res;
 565                                 else
 566                                         *va_arg(ap, int *) = res;
 567                                 nassigned++;
 568                         }
 569                         nread += p - buf;
 570                         break;
 571
 572 #ifdef FLOATING_POINT
 573                 case CT_FLOAT:
 574                         /* scan a floating point number as if by strtod */
 575 #ifdef hardway
 576                         if (width == 0 || width > sizeof(buf) - 1)
 577                                 width = sizeof(buf) - 1;
 578 #else
 579                         /* size_t is unsigned, hence this optimisation */
 580                         if (--width > sizeof(buf) - 2)
 581                                 width = sizeof(buf) - 2;
 582                         width++;
 583 #endif
 584                         flags |= SIGNOK | NDIGITS | DPTOK | EXPOK;
 585                         for (p = buf; width; width--) {
 586                                 c = *fp->_p;
 587                                 /*
 588                                  * This code mimicks the integer conversion
 589                                  * code, but is much simpler.
 590                                  */
 591                                 switch (c) {
 592
 593                                 case '0': case '1': case '2': case '3':
 594                                 case '4': case '5': case '6': case '7':
 595                                 case '8': case '9':
 596                                         flags &= ~(SIGNOK | NDIGITS);
 597                                         goto fok;
 598
 599                                 case '+': case '-':
 600                                         if (flags & SIGNOK) {
 601                                                 flags &= ~SIGNOK;
 602                                                 goto fok;
 603                                         }
 604                                         break;
 605                                 case '.':
 606                                         if (flags & DPTOK) {
 607                                                 flags &= ~(SIGNOK | DPTOK);
 608                                                 goto fok;
 609                                         }
 610                                         break;
 611                                 case 'e': case 'E':
 612                                         /* no exponent without some digits */
 613                                         if ((flags&(NDIGITS|EXPOK)) == EXPOK) {
 614                                                 flags =
 615                                                     (flags & ~(EXPOK|DPTOK)) |
 616                                                     SIGNOK | NDIGITS;
 617                                                 goto fok;
 618                                         }
 619                                         break;
 620                                 }
 621                                 break;
 622                 fok:
 623                                 *p++ = c;
 624                                 if (--fp->_r > 0)
 625                                         fp->_p++;
 626                                 else if (__srefill(fp))
 627                                         break;  /* EOF */
 628                         }
 629                         /*
 630                          * If no digits, might be missing exponent digits
 631                          * (just give back the exponent) or might be missing
 632                          * regular digits, but had sign and/or decimal point.
 633                          */
 634                         if (flags & NDIGITS) {
 635                                 if (flags & EXPOK) {
 636                                         /* no digits at all */
 637                                         while (p > buf)
 638                                                 ungetc(*(u_char *)--p, fp);
 639                                         goto match_failure;
 640                                 }
 641                                 /* just a bad exponent (e and maybe sign) */
 642                                 c = *(u_char *)--p;
 643                                 if (c != 'e' && c != 'E') {
 644                                         (void) ungetc(c, fp);/* sign */
 645                                         c = *(u_char *)--p;
 646                                 }
 647                                 (void) ungetc(c, fp);
 648                         }
 649                         if ((flags & SUPPRESS) == 0) {
 650                                 double res;
 651
 652                                 *p = 0;
 653                                 res = strtod(buf,(char **) NULL);
 654                                 if (flags & LONG)
 655                                         *va_arg(ap, double *) = res;
 656                                 else
 657                                         *va_arg(ap, float *) = res;
 658                                 nassigned++;
 659                         }
 660                         nread += p - buf;
 661                         break;
 662 #endif /* FLOATING_POINT */
 663                 }
 664         }
 665 input_failure:
 666         return (nassigned ? nassigned : -1);
 667 match_failure:
 668         return (nassigned);
 669 }
 670
 671 /*
 672  * Fill in the given table from the scanset at the given format
 673  * (just after `[').  Return a pointer to the character past the
 674  * closing `]'.  The table has a 1 wherever characters should be
 675  * considered part of the scanset.
 676  */
 677 static u_char *
 678 __sccl(tab, fmt)
 679         register char *tab;
 680         register u_char *fmt;
 681 {
 682         register int c, n, v;
 683
 684         /* first `clear' the whole table */
 685         c = *fmt++;             /* first char hat => negated scanset */
 686         if (c == '^') {
 687                 v = 1;          /* default => accept */
 688                 c = *fmt++;     /* get new first char */
 689         } else
 690                 v = 0;          /* default => reject */
 691         /* should probably use memset here */
 692         for (n = 0; n < 256; n++)
 693                 tab[n] = v;
 694         if (c == 0)
 695                 return (fmt - 1);/* format ended before closing ] */
 696
 697         /*
 698          * Now set the entries corresponding to the actual scanset
 699          * to the opposite of the above.
 700          *
 701          * The first character may be ']' (or '-') without being special;
 702          * the last character may be '-'.
 703          */
 704         v = 1 - v;
 705         for (;;) {
 706                 tab[c] = v;             /* take character c */
 707 doswitch:
 708                 n = *fmt++;             /* and examine the next */
 709                 switch (n) {
 710
 711                 case 0:                 /* format ended too soon */
 712                         return (fmt - 1);
 713
 714                 case '-':
 715                         /*
 716                          * A scanset of the form
 717                          *      [01+-]
 718                          * is defined as `the digit 0, the digit 1,
 719                          * the character +, the character -', but
 720                          * the effect of a scanset such as
 721                          *      [a-zA-Z0-9]
 722                          * is implementation defined.  The V7 Unix
 723                          * scanf treats `a-z' as `the letters a through
 724                          * z', but treats `a-a' as `the letter a, the
 725                          * character -, and the letter a'.
 726                          *
 727                          * For compatibility, the `-' is not considerd
 728                          * to define a range if the character following
 729                          * it is either a close bracket (required by ANSI)
 730                          * or is not numerically greater than the character
 731                          * we just stored in the table (c).
 732                          */
 733                         n = *fmt;
 734                         if (n == ']' || n < c) {
 735                                 c = '-';
 736                                 break;  /* resume the for(;;) */
 737                         }
 738                         fmt++;
 739                         do {            /* fill in the range */
 740                                 tab[++c] = v;
 741                         } while (c < n);
 742 #if 1   /* XXX another disgusting compatibility hack */
 743                         /*
 744                          * Alas, the V7 Unix scanf also treats formats
 745                          * such as [a-c-e] as `the letters a through e'.
 746                          * This too is permitted by the standard....
 747                          */
 748                         goto doswitch;
 749 #else
 750                         c = *fmt++;
 751                         if (c == 0)
 752                                 return (fmt - 1);
 753                         if (c == ']')
 754                                 return (fmt);
 755 #endif
 756                         break;
 757
 758                 case ']':               /* end of scanset */
 759                         return (fmt);
 760
 761                 default:                /* just another character */
 762                         c = n;
 763                         break;
 764                 }
 765         }
 766         /* NOTREACHED */
 767 }