zlib/gzread.c

   1 /* gzread.c -- zlib functions for reading gzip files
   2  * Copyright (C) 2004-2017 Mark Adler
   3  * For conditions of distribution and use, see copyright notice in zlib.h
   4  */
   5
   6 #include "gzguts.h"
   7
   8 /* Local functions */
   9 local int gz_load OF((gz_statep, unsigned char *, unsigned, unsigned *));
  10 local int gz_avail OF((gz_statep));
  11 local int gz_look OF((gz_statep));
  12 local int gz_decomp OF((gz_statep));
  13 local int gz_fetch OF((gz_statep));
  14 local int gz_skip OF((gz_statep, z_off64_t));
  15 local z_size_t gz_read OF((gz_statep, voidp, z_size_t));
  16
  17 /* Use read() to load a buffer -- return -1 on error, otherwise 0.  Read from
  18    state->fd, and update state->eof, state->err, and state->msg as appropriate.
  19    This function needs to loop on read(), since read() is not guaranteed to
  20    read the number of bytes requested, depending on the type of descriptor. */
  21 local int gz_load(state, buf, len, have)
  22     gz_statep state;
  23     unsigned char *buf;
  24     unsigned len;
  25     unsigned *have;
  26 {
  27     int ret;
  28     unsigned get, max = ((unsigned)-1 >> 2) + 1;
  29
  30     *have = 0;
  31     do {
  32         get = len - *have;
  33         if (get > max)
  34             get = max;
  35         ret = read(state->fd, buf + *have, get);
  36         if (ret <= 0)
  37             break;
  38         *have += (unsigned)ret;
  39     } while (*have < len);
  40     if (ret < 0) {
  41         gz_error(state, Z_ERRNO, zstrerror());
  42         return -1;
  43     }
  44     if (ret == 0)
  45         state->eof = 1;
  46     return 0;
  47 }
  48
  49 /* Load up input buffer and set eof flag if last data loaded -- return -1 on
  50    error, 0 otherwise.  Note that the eof flag is set when the end of the input
  51    file is reached, even though there may be unused data in the buffer.  Once
  52    that data has been used, no more attempts will be made to read the file.
  53    If strm->avail_in != 0, then the current data is moved to the beginning of
  54    the input buffer, and then the remainder of the buffer is loaded with the
  55    available data from the input file. */
  56 local int gz_avail(state)
  57     gz_statep state;
  58 {
  59     unsigned got;
  60     z_streamp strm = &(state->strm);
  61
  62     if (state->err != Z_OK && state->err != Z_BUF_ERROR)
  63         return -1;
  64     if (state->eof == 0) {
  65         if (strm->avail_in) {       /* copy what's there to the start */
  66             unsigned char *p = state->in;
  67             unsigned const char *q = strm->next_in;
  68             unsigned n = strm->avail_in;
  69             do {
  70                 *p++ = *q++;
  71             } while (--n);
  72         }
  73         if (gz_load(state, state->in + strm->avail_in,
  74                     state->size - strm->avail_in, &got) == -1)
  75             return -1;
  76         strm->avail_in += got;
  77         strm->next_in = state->in;
  78     }
  79     return 0;
  80 }
  81
  82 /* Look for gzip header, set up for inflate or copy.  state->x.have must be 0.
  83    If this is the first time in, allocate required memory.  state->how will be
  84    left unchanged if there is no more input data available, will be set to COPY
  85    if there is no gzip header and direct copying will be performed, or it will
  86    be set to GZIP for decompression.  If direct copying, then leftover input
  87    data from the input buffer will be copied to the output buffer.  In that
  88    case, all further file reads will be directly to either the output buffer or
  89    a user buffer.  If decompressing, the inflate state will be initialized.
  90    gz_look() will return 0 on success or -1 on failure. */
  91 local int gz_look(state)
  92     gz_statep state;
  93 {
  94     z_streamp strm = &(state->strm);
  95
  96     /* allocate read buffers and inflate memory */
  97     if (state->size == 0) {
  98         /* allocate buffers */
  99         state->in = (unsigned char *)malloc(state->want);
 100         state->out = (unsigned char *)malloc(state->want << 1);
 101         if (state->in == NULL || state->out == NULL) {
 102             free(state->out);
 103             free(state->in);
 104             gz_error(state, Z_MEM_ERROR, "out of memory");
 105             return -1;
 106         }
 107         state->size = state->want;
 108
 109         /* allocate inflate memory */
 110         state->strm.zalloc = Z_NULL;
 111         state->strm.zfree = Z_NULL;
 112         state->strm.opaque = Z_NULL;
 113         state->strm.avail_in = 0;
 114         state->strm.next_in = Z_NULL;
 115         if (inflateInit2(&(state->strm), 15 + 16) != Z_OK) {    /* gunzip */
 116             free(state->out);
 117             free(state->in);
 118             state->size = 0;
 119             gz_error(state, Z_MEM_ERROR, "out of memory");
 120             return -1;
 121         }
 122     }
 123
 124     /* get at least the magic bytes in the input buffer */
 125     if (strm->avail_in < 2) {
 126         if (gz_avail(state) == -1)
 127             return -1;
 128         if (strm->avail_in == 0)
 129             return 0;
 130     }
 131
 132     /* look for gzip magic bytes -- if there, do gzip decoding (note: there is
 133        a logical dilemma here when considering the case of a partially written
 134        gzip file, to wit, if a single 31 byte is written, then we cannot tell
 135        whether this is a single-byte file, or just a partially written gzip
 136        file -- for here we assume that if a gzip file is being written, then
 137        the header will be written in a single operation, so that reading a
 138        single byte is sufficient indication that it is not a gzip file) */
 139     if (strm->avail_in > 1 &&
 140             strm->next_in[0] == 31 && strm->next_in[1] == 139) {
 141         inflateReset(strm);
 142         state->how = GZIP;
 143         state->direct = 0;
 144         return 0;
 145     }
 146
 147     /* no gzip header -- if we were decoding gzip before, then this is trailing
 148        garbage.  Ignore the trailing garbage and finish. */
 149     if (state->direct == 0) {
 150         strm->avail_in = 0;
 151         state->eof = 1;
 152         state->x.have = 0;
 153         return 0;
 154     }
 155
 156     /* doing raw i/o, copy any leftover input to output -- this assumes that
 157        the output buffer is larger than the input buffer, which also assures
 158        space for gzungetc() */
 159     state->x.next = state->out;
 160     if (strm->avail_in) {
 161         memcpy(state->x.next, strm->next_in, strm->avail_in);
 162         state->x.have = strm->avail_in;
 163         strm->avail_in = 0;
 164     }
 165     state->how = COPY;
 166     state->direct = 1;
 167     return 0;
 168 }
 169
 170 /* Decompress from input to the provided next_out and avail_out in the state.
 171    On return, state->x.have and state->x.next point to the just decompressed
 172    data.  If the gzip stream completes, state->how is reset to LOOK to look for
 173    the next gzip stream or raw data, once state->x.have is depleted.  Returns 0
 174    on success, -1 on failure. */
 175 local int gz_decomp(state)
 176     gz_statep state;
 177 {
 178     int ret = Z_OK;
 179     unsigned had;
 180     z_streamp strm = &(state->strm);
 181
 182     /* fill output buffer up to end of deflate stream */
 183     had = strm->avail_out;
 184     do {
 185         /* get more input for inflate() */
 186         if (strm->avail_in == 0 && gz_avail(state) == -1)
 187             return -1;
 188         if (strm->avail_in == 0) {
 189             gz_error(state, Z_BUF_ERROR, "unexpected end of file");
 190             break;
 191         }
 192
 193         /* decompress and handle errors */
 194         ret = inflate(strm, Z_NO_FLUSH);
 195         if (ret == Z_STREAM_ERROR || ret == Z_NEED_DICT) {
 196             gz_error(state, Z_STREAM_ERROR,
 197                      "internal error: inflate stream corrupt");
 198             return -1;
 199         }
 200         if (ret == Z_MEM_ERROR) {
 201             gz_error(state, Z_MEM_ERROR, "out of memory");
 202             return -1;
 203         }
 204         if (ret == Z_DATA_ERROR) {              /* deflate stream invalid */
 205             gz_error(state, Z_DATA_ERROR,
 206                      strm->msg == NULL ? "compressed data error" : strm->msg);
 207             return -1;
 208         }
 209     } while (strm->avail_out && ret != Z_STREAM_END);
 210
 211     /* update available output */
 212     state->x.have = had - strm->avail_out;
 213     state->x.next = strm->next_out - state->x.have;
 214
 215     /* if the gzip stream completed successfully, look for another */
 216     if (ret == Z_STREAM_END)
 217         state->how = LOOK;
 218
 219     /* good decompression */
 220     return 0;
 221 }
 222
 223 /* Fetch data and put it in the output buffer.  Assumes state->x.have is 0.
 224    Data is either copied from the input file or decompressed from the input
 225    file depending on state->how.  If state->how is LOOK, then a gzip header is
 226    looked for to determine whether to copy or decompress.  Returns -1 on error,
 227    otherwise 0.  gz_fetch() will leave state->how as COPY or GZIP unless the
 228    end of the input file has been reached and all data has been processed.  */
 229 local int gz_fetch(state)
 230     gz_statep state;
 231 {
 232     z_streamp strm = &(state->strm);
 233
 234     do {
 235         switch(state->how) {
 236         case LOOK:      /* -> LOOK, COPY (only if never GZIP), or GZIP */
 237             if (gz_look(state) == -1)
 238                 return -1;
 239             if (state->how == LOOK)
 240                 return 0;
 241             break;
 242         case COPY:      /* -> COPY */
 243             if (gz_load(state, state->out, state->size << 1, &(state->x.have))
 244                     == -1)
 245                 return -1;
 246             state->x.next = state->out;
 247             return 0;
 248         case GZIP:      /* -> GZIP or LOOK (if end of gzip stream) */
 249             strm->avail_out = state->size << 1;
 250             strm->next_out = state->out;
 251             if (gz_decomp(state) == -1)
 252                 return -1;
 253         }
 254     } while (state->x.have == 0 && (!state->eof || strm->avail_in));
 255     return 0;
 256 }
 257
 258 /* Skip len uncompressed bytes of output.  Return -1 on error, 0 on success. */
 259 local int gz_skip(state, len)
 260     gz_statep state;
 261     z_off64_t len;
 262 {
 263     unsigned n;
 264
 265     /* skip over len bytes or reach end-of-file, whichever comes first */
 266     while (len)
 267         /* skip over whatever is in output buffer */
 268         if (state->x.have) {
 269             n = GT_OFF(state->x.have) || (z_off64_t)state->x.have > len ?
 270                 (unsigned)len : state->x.have;
 271             state->x.have -= n;
 272             state->x.next += n;
 273             state->x.pos += n;
 274             len -= n;
 275         }
 276
 277         /* output buffer empty -- return if we're at the end of the input */
 278         else if (state->eof && state->strm.avail_in == 0)
 279             break;
 280
 281         /* need more data to skip -- load up output buffer */
 282         else {
 283             /* get more output, looking for header if required */
 284             if (gz_fetch(state) == -1)
 285                 return -1;
 286         }
 287     return 0;
 288 }
 289
 290 /* Read len bytes into buf from file, or less than len up to the end of the
 291    input.  Return the number of bytes read.  If zero is returned, either the
 292    end of file was reached, or there was an error.  state->err must be
 293    consulted in that case to determine which. */
 294 local z_size_t gz_read(state, buf, len)
 295     gz_statep state;
 296     voidp buf;
 297     z_size_t len;
 298 {
 299     z_size_t got;
 300     unsigned n;
 301
 302     /* if len is zero, avoid unnecessary operations */
 303     if (len == 0)
 304         return 0;
 305
 306     /* process a skip request */
 307     if (state->seek) {
 308         state->seek = 0;
 309         if (gz_skip(state, state->skip) == -1)
 310             return 0;
 311     }
 312
 313     /* get len bytes to buf, or less than len if at the end */
 314     got = 0;
 315     do {
 316         /* set n to the maximum amount of len that fits in an unsigned int */
 317         n = (unsigned)-1;
 318         if (n > len)
 319             n = (unsigned)len;
 320
 321         /* first just try copying data from the output buffer */
 322         if (state->x.have) {
 323             if (state->x.have < n)
 324                 n = state->x.have;
 325             memcpy(buf, state->x.next, n);
 326             state->x.next += n;
 327             state->x.have -= n;
 328         }
 329
 330         /* output buffer empty -- return if we're at the end of the input */
 331         else if (state->eof && state->strm.avail_in == 0) {
 332             state->past = 1;        /* tried to read past end */
 333             break;
 334         }
 335
 336         /* need output data -- for small len or new stream load up our output
 337            buffer */
 338         else if (state->how == LOOK || n < (state->size << 1)) {
 339             /* get more output, looking for header if required */
 340             if (gz_fetch(state) == -1)
 341                 return 0;
 342             continue;       /* no progress yet -- go back to copy above */
 343             /* the copy above assures that we will leave with space in the
 344                output buffer, allowing at least one gzungetc() to succeed */
 345         }
 346
 347         /* large len -- read directly into user buffer */
 348         else if (state->how == COPY) {      /* read directly */
 349             if (gz_load(state, (unsigned char *)buf, n, &n) == -1)
 350                 return 0;
 351         }
 352
 353         /* large len -- decompress directly into user buffer */
 354         else {  /* state->how == GZIP */
 355             state->strm.avail_out = n;
 356             state->strm.next_out = (unsigned char *)buf;
 357             if (gz_decomp(state) == -1)
 358                 return 0;
 359             n = state->x.have;
 360             state->x.have = 0;
 361         }
 362
 363         /* update progress */
 364         len -= n;
 365         buf = (char *)buf + n;
 366         got += n;
 367         state->x.pos += n;
 368     } while (len);
 369
 370     /* return number of bytes read into user buffer */
 371     return got;
 372 }
 373
 374 /* -- see zlib.h -- */
 375 int ZEXPORT gzread(file, buf, len)
 376     gzFile file;
 377     voidp buf;
 378     unsigned len;
 379 {
 380     gz_statep state;
 381
 382     /* get internal structure */
 383     if (file == NULL)
 384         return -1;
 385     state = (gz_statep)file;
 386
 387     /* check that we're reading and that there's no (serious) error */
 388     if (state->mode != GZ_READ ||
 389             (state->err != Z_OK && state->err != Z_BUF_ERROR))
 390         return -1;
 391
 392     /* since an int is returned, make sure len fits in one, otherwise return
 393        with an error (this avoids a flaw in the interface) */
 394     if ((int)len < 0) {
 395         gz_error(state, Z_STREAM_ERROR, "request does not fit in an int");
 396         return -1;
 397     }
 398
 399     /* read len or fewer bytes to buf */
 400     len = (unsigned)gz_read(state, buf, len);
 401
 402     /* check for an error */
 403     if (len == 0 && state->err != Z_OK && state->err != Z_BUF_ERROR)
 404         return -1;
 405
 406     /* return the number of bytes read (this is assured to fit in an int) */
 407     return (int)len;
 408 }
 409
 410 /* -- see zlib.h -- */
 411 z_size_t ZEXPORT gzfread(buf, size, nitems, file)
 412     voidp buf;
 413     z_size_t size;
 414     z_size_t nitems;
 415     gzFile file;
 416 {
 417     z_size_t len;
 418     gz_statep state;
 419
 420     /* get internal structure */
 421     if (file == NULL)
 422         return 0;
 423     state = (gz_statep)file;
 424
 425     /* check that we're reading and that there's no (serious) error */
 426     if (state->mode != GZ_READ ||
 427             (state->err != Z_OK && state->err != Z_BUF_ERROR))
 428         return 0;
 429
 430     /* compute bytes to read -- error on overflow */
 431     len = nitems * size;
 432     if (size && len / size != nitems) {
 433         gz_error(state, Z_STREAM_ERROR, "request does not fit in a size_t");
 434         return 0;
 435     }
 436
 437     /* read len or fewer bytes to buf, return the number of full items read */
 438     return len ? gz_read(state, buf, len) / size : 0;
 439 }
 440
 441 /* -- see zlib.h -- */
 442 #ifdef Z_PREFIX_SET
 443 #  undef z_gzgetc
 444 #else
 445 #  undef gzgetc
 446 #endif
 447 int ZEXPORT gzgetc(file)
 448     gzFile file;
 449 {
 450     unsigned char buf[1];
 451     gz_statep state;
 452
 453     /* get internal structure */
 454     if (file == NULL)
 455         return -1;
 456     state = (gz_statep)file;
 457
 458     /* check that we're reading and that there's no (serious) error */
 459     if (state->mode != GZ_READ ||
 460         (state->err != Z_OK && state->err != Z_BUF_ERROR))
 461         return -1;
 462
 463     /* try output buffer (no need to check for skip request) */
 464     if (state->x.have) {
 465         state->x.have--;
 466         state->x.pos++;
 467         return *(state->x.next)++;
 468     }
 469
 470     /* nothing there -- try gz_read() */
 471     return gz_read(state, buf, 1) < 1 ? -1 : buf[0];
 472 }
 473
 474 int ZEXPORT gzgetc_(file)
 475 gzFile file;
 476 {
 477     return gzgetc(file);
 478 }
 479
 480 /* -- see zlib.h -- */
 481 int ZEXPORT gzungetc(c, file)
 482     int c;
 483     gzFile file;
 484 {
 485     gz_statep state;
 486
 487     /* get internal structure */
 488     if (file == NULL)
 489         return -1;
 490     state = (gz_statep)file;
 491
 492     /* check that we're reading and that there's no (serious) error */
 493     if (state->mode != GZ_READ ||
 494         (state->err != Z_OK && state->err != Z_BUF_ERROR))
 495         return -1;
 496
 497     /* process a skip request */
 498     if (state->seek) {
 499         state->seek = 0;
 500         if (gz_skip(state, state->skip) == -1)
 501             return -1;
 502     }
 503
 504     /* can't push EOF */
 505     if (c < 0)
 506         return -1;
 507
 508     /* if output buffer empty, put byte at end (allows more pushing) */
 509     if (state->x.have == 0) {
 510         state->x.have = 1;
 511         state->x.next = state->out + (state->size << 1) - 1;
 512         state->x.next[0] = (unsigned char)c;
 513         state->x.pos--;
 514         state->past = 0;
 515         return c;
 516     }
 517
 518     /* if no room, give up (must have already done a gzungetc()) */
 519     if (state->x.have == (state->size << 1)) {
 520         gz_error(state, Z_DATA_ERROR, "out of room to push characters");
 521         return -1;
 522     }
 523
 524     /* slide output data if needed and insert byte before existing data */
 525     if (state->x.next == state->out) {
 526         unsigned char *src = state->out + state->x.have;
 527         unsigned char *dest = state->out + (state->size << 1);
 528         while (src > state->out)
 529             *--dest = *--src;
 530         state->x.next = dest;
 531     }
 532     state->x.have++;
 533     state->x.next--;
 534     state->x.next[0] = (unsigned char)c;
 535     state->x.pos--;
 536     state->past = 0;
 537     return c;
 538 }
 539
 540 /* -- see zlib.h -- */
 541 char * ZEXPORT gzgets(file, buf, len)
 542     gzFile file;
 543     char *buf;
 544     int len;
 545 {
 546     unsigned left, n;
 547     char *str;
 548     unsigned char *eol;
 549     gz_statep state;
 550
 551     /* check parameters and get internal structure */
 552     if (file == NULL || buf == NULL || len < 1)
 553         return NULL;
 554     state = (gz_statep)file;
 555
 556     /* check that we're reading and that there's no (serious) error */
 557     if (state->mode != GZ_READ ||
 558         (state->err != Z_OK && state->err != Z_BUF_ERROR))
 559         return NULL;
 560
 561     /* process a skip request */
 562     if (state->seek) {
 563         state->seek = 0;
 564         if (gz_skip(state, state->skip) == -1)
 565             return NULL;
 566     }
 567
 568     /* copy output bytes up to new line or len - 1, whichever comes first --
 569        append a terminating zero to the string (we don't check for a zero in
 570        the contents, let the user worry about that) */
 571     str = buf;
 572     left = (unsigned)len - 1;
 573     if (left) do {
 574         /* assure that something is in the output buffer */
 575         if (state->x.have == 0 && gz_fetch(state) == -1)
 576             return NULL;                /* error */
 577         if (state->x.have == 0) {       /* end of file */
 578             state->past = 1;            /* read past end */
 579             break;                      /* return what we have */
 580         }
 581
 582         /* look for end-of-line in current output buffer */
 583         n = state->x.have > left ? left : state->x.have;
 584         eol = (unsigned char *)memchr(state->x.next, '\n', n);
 585         if (eol != NULL)
 586             n = (unsigned)(eol - state->x.next) + 1;
 587
 588         /* copy through end-of-line, or remainder if not found */
 589         memcpy(buf, state->x.next, n);
 590         state->x.have -= n;
 591         state->x.next += n;
 592         state->x.pos += n;
 593         left -= n;
 594         buf += n;
 595     } while (left && eol == NULL);
 596
 597     /* return terminated string, or if nothing, end of file */
 598     if (buf == str)
 599         return NULL;
 600     buf[0] = 0;
 601     return str;
 602 }
 603
 604 /* -- see zlib.h -- */
 605 int ZEXPORT gzdirect(file)
 606     gzFile file;
 607 {
 608     gz_statep state;
 609
 610     /* get internal structure */
 611     if (file == NULL)
 612         return 0;
 613     state = (gz_statep)file;
 614
 615     /* if the state is not known, but we can find out, then do so (this is
 616        mainly for right after a gzopen() or gzdopen()) */
 617     if (state->mode == GZ_READ && state->how == LOOK && state->x.have == 0)
 618         (void)gz_look(state);
 619
 620     /* return 1 if transparent, 0 if processing a gzip stream */
 621     return state->direct;
 622 }
 623
 624 /* -- see zlib.h -- */
 625 int ZEXPORT gzclose_r(file)
 626     gzFile file;
 627 {
 628     int ret, err;
 629     gz_statep state;
 630
 631     /* get internal structure */
 632     if (file == NULL)
 633         return Z_STREAM_ERROR;
 634     state = (gz_statep)file;
 635
 636     /* check that we're reading */
 637     if (state->mode != GZ_READ)
 638         return Z_STREAM_ERROR;
 639
 640     /* free memory and close file */
 641     if (state->size) {
 642         inflateEnd(&(state->strm));
 643         free(state->out);
 644         free(state->in);
 645     }
 646     err = state->err == Z_BUF_ERROR ? Z_BUF_ERROR : Z_OK;
 647     gz_error(state, Z_OK, NULL);
 648     free(state->path);
 649     ret = close(state->fd);
 650     free(state);
 651     return ret ? Z_ERRNO : err;
 652 }