zlib/gzread.c

   1 /* gzread.c -- zlib functions for reading gzip files
   2  * Copyright (C) 2004, 2005, 2010, 2011, 2012, 2013, 2016 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 = -1;
 318         if (n > len)
 319             n = 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 = 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     int ret;
 451     unsigned char buf[1];
 452     gz_statep state;
 453
 454     /* get internal structure */
 455     if (file == NULL)
 456         return -1;
 457     state = (gz_statep)file;
 458
 459     /* check that we're reading and that there's no (serious) error */
 460     if (state->mode != GZ_READ ||
 461         (state->err != Z_OK && state->err != Z_BUF_ERROR))
 462         return -1;
 463
 464     /* try output buffer (no need to check for skip request) */
 465     if (state->x.have) {
 466         state->x.have--;
 467         state->x.pos++;
 468         return *(state->x.next)++;
 469     }
 470
 471     /* nothing there -- try gz_read() */
 472     ret = gz_read(state, buf, 1);
 473     return ret < 1 ? -1 : buf[0];
 474 }
 475
 476 int ZEXPORT gzgetc_(file)
 477 gzFile file;
 478 {
 479     return gzgetc(file);
 480 }
 481
 482 /* -- see zlib.h -- */
 483 int ZEXPORT gzungetc(c, file)
 484     int c;
 485     gzFile file;
 486 {
 487     gz_statep state;
 488
 489     /* get internal structure */
 490     if (file == NULL)
 491         return -1;
 492     state = (gz_statep)file;
 493
 494     /* check that we're reading and that there's no (serious) error */
 495     if (state->mode != GZ_READ ||
 496         (state->err != Z_OK && state->err != Z_BUF_ERROR))
 497         return -1;
 498
 499     /* process a skip request */
 500     if (state->seek) {
 501         state->seek = 0;
 502         if (gz_skip(state, state->skip) == -1)
 503             return -1;
 504     }
 505
 506     /* can't push EOF */
 507     if (c < 0)
 508         return -1;
 509
 510     /* if output buffer empty, put byte at end (allows more pushing) */
 511     if (state->x.have == 0) {
 512         state->x.have = 1;
 513         state->x.next = state->out + (state->size << 1) - 1;
 514         state->x.next[0] = (unsigned char)c;
 515         state->x.pos--;
 516         state->past = 0;
 517         return c;
 518     }
 519
 520     /* if no room, give up (must have already done a gzungetc()) */
 521     if (state->x.have == (state->size << 1)) {
 522         gz_error(state, Z_DATA_ERROR, "out of room to push characters");
 523         return -1;
 524     }
 525
 526     /* slide output data if needed and insert byte before existing data */
 527     if (state->x.next == state->out) {
 528         unsigned char *src = state->out + state->x.have;
 529         unsigned char *dest = state->out + (state->size << 1);
 530         while (src > state->out)
 531             *--dest = *--src;
 532         state->x.next = dest;
 533     }
 534     state->x.have++;
 535     state->x.next--;
 536     state->x.next[0] = (unsigned char)c;
 537     state->x.pos--;
 538     state->past = 0;
 539     return c;
 540 }
 541
 542 /* -- see zlib.h -- */
 543 char * ZEXPORT gzgets(file, buf, len)
 544     gzFile file;
 545     char *buf;
 546     int len;
 547 {
 548     unsigned left, n;
 549     char *str;
 550     unsigned char *eol;
 551     gz_statep state;
 552
 553     /* check parameters and get internal structure */
 554     if (file == NULL || buf == NULL || len < 1)
 555         return NULL;
 556     state = (gz_statep)file;
 557
 558     /* check that we're reading and that there's no (serious) error */
 559     if (state->mode != GZ_READ ||
 560         (state->err != Z_OK && state->err != Z_BUF_ERROR))
 561         return NULL;
 562
 563     /* process a skip request */
 564     if (state->seek) {
 565         state->seek = 0;
 566         if (gz_skip(state, state->skip) == -1)
 567             return NULL;
 568     }
 569
 570     /* copy output bytes up to new line or len - 1, whichever comes first --
 571        append a terminating zero to the string (we don't check for a zero in
 572        the contents, let the user worry about that) */
 573     str = buf;
 574     left = (unsigned)len - 1;
 575     if (left) do {
 576         /* assure that something is in the output buffer */
 577         if (state->x.have == 0 && gz_fetch(state) == -1)
 578             return NULL;                /* error */
 579         if (state->x.have == 0) {       /* end of file */
 580             state->past = 1;            /* read past end */
 581             break;                      /* return what we have */
 582         }
 583
 584         /* look for end-of-line in current output buffer */
 585         n = state->x.have > left ? left : state->x.have;
 586         eol = (unsigned char *)memchr(state->x.next, '\n', n);
 587         if (eol != NULL)
 588             n = (unsigned)(eol - state->x.next) + 1;
 589
 590         /* copy through end-of-line, or remainder if not found */
 591         memcpy(buf, state->x.next, n);
 592         state->x.have -= n;
 593         state->x.next += n;
 594         state->x.pos += n;
 595         left -= n;
 596         buf += n;
 597     } while (left && eol == NULL);
 598
 599     /* return terminated string, or if nothing, end of file */
 600     if (buf == str)
 601         return NULL;
 602     buf[0] = 0;
 603     return str;
 604 }
 605
 606 /* -- see zlib.h -- */
 607 int ZEXPORT gzdirect(file)
 608     gzFile file;
 609 {
 610     gz_statep state;
 611
 612     /* get internal structure */
 613     if (file == NULL)
 614         return 0;
 615     state = (gz_statep)file;
 616
 617     /* if the state is not known, but we can find out, then do so (this is
 618        mainly for right after a gzopen() or gzdopen()) */
 619     if (state->mode == GZ_READ && state->how == LOOK && state->x.have == 0)
 620         (void)gz_look(state);
 621
 622     /* return 1 if transparent, 0 if processing a gzip stream */
 623     return state->direct;
 624 }
 625
 626 /* -- see zlib.h -- */
 627 int ZEXPORT gzclose_r(file)
 628     gzFile file;
 629 {
 630     int ret, err;
 631     gz_statep state;
 632
 633     /* get internal structure */
 634     if (file == NULL)
 635         return Z_STREAM_ERROR;
 636     state = (gz_statep)file;
 637
 638     /* check that we're reading */
 639     if (state->mode != GZ_READ)
 640         return Z_STREAM_ERROR;
 641
 642     /* free memory and close file */
 643     if (state->size) {
 644         inflateEnd(&(state->strm));
 645         free(state->out);
 646         free(state->in);
 647     }
 648     err = state->err == Z_BUF_ERROR ? Z_BUF_ERROR : Z_OK;
 649     gz_error(state, Z_OK, NULL);
 650     free(state->path);
 651     ret = close(state->fd);
 652     free(state);
 653     return ret ? Z_ERRNO : err;
 654 }