zlib/gzio.c

   1 /* gzio.c -- IO on .gz files
   2  * Copyright (C) 1995-1998 Jean-loup Gailly.
   3  * For conditions of distribution and use, see copyright notice in zlib.h
   4  *
   5  * Compile this file with -DNO_DEFLATE to avoid the compression code.
   6  */
   7
   8 /* @(#) $Id$ */
   9
  10 #include <stdio.h>
  11
  12 #include "zutil.h"
  13
  14 struct internal_state {int dummy;}; /* for buggy compilers */
  15
  16 #ifndef Z_BUFSIZE
  17 #  ifdef MAXSEG_64K
  18 #    define Z_BUFSIZE 4096 /* minimize memory usage for 16-bit DOS */
  19 #  else
  20 #    define Z_BUFSIZE 16384
  21 #  endif
  22 #endif
  23 #ifndef Z_PRINTF_BUFSIZE
  24 #  define Z_PRINTF_BUFSIZE 4096
  25 #endif
  26
  27 #define ALLOC(size) malloc(size)
  28 #define TRYFREE(p) {if (p) free(p);}
  29
  30 static int gz_magic[2] = {0x1f, 0x8b}; /* gzip magic header */
  31
  32 /* gzip flag byte */
  33 #define ASCII_FLAG   0x01 /* bit 0 set: file probably ascii text */
  34 #define HEAD_CRC     0x02 /* bit 1 set: header CRC present */
  35 #define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
  36 #define ORIG_NAME    0x08 /* bit 3 set: original file name present */
  37 #define COMMENT      0x10 /* bit 4 set: file comment present */
  38 #define RESERVED     0xE0 /* bits 5..7: reserved */
  39
  40 typedef struct gz_stream {
  41     z_stream stream;
  42     int      z_err;   /* error code for last stream operation */
  43     int      z_eof;   /* set if end of input file */
  44     FILE     *file;   /* .gz file */
  45     Byte     *inbuf;  /* input buffer */
  46     Byte     *outbuf; /* output buffer */
  47     uLong    crc;     /* crc32 of uncompressed data */
  48     char     *msg;    /* error message */
  49     char     *path;   /* path name for debugging only */
  50     int      transparent; /* 1 if input file is not a .gz file */
  51     char     mode;    /* 'w' or 'r' */
  52     long     startpos; /* start of compressed data in file (header skipped) */
  53 } gz_stream;
  54
  55
  56 local gzFile gz_open      OF((const char *path, const char *mode, int  fd));
  57 local int do_flush        OF((gzFile file, int flush));
  58 local int    get_byte     OF((gz_stream *s));
  59 local void   check_header OF((gz_stream *s));
  60 local int    destroy      OF((gz_stream *s));
  61 local void   putLong      OF((FILE *file, uLong x));
  62 local uLong  getLong      OF((gz_stream *s));
  63
  64 /* ===========================================================================
  65      Opens a gzip (.gz) file for reading or writing. The mode parameter
  66    is as in fopen ("rb" or "wb"). The file is given either by file descriptor
  67    or path name (if fd == -1).
  68      gz_open return NULL if the file could not be opened or if there was
  69    insufficient memory to allocate the (de)compression state; errno
  70    can be checked to distinguish the two cases (if errno is zero, the
  71    zlib error is Z_MEM_ERROR).
  72 */
  73 local gzFile gz_open (path, mode, fd)
  74     const char *path;
  75     const char *mode;
  76     int  fd;
  77 {
  78     int err;
  79     int level = Z_DEFAULT_COMPRESSION; /* compression level */
  80     int strategy = Z_DEFAULT_STRATEGY; /* compression strategy */
  81     char *p = (char*)mode;
  82     gz_stream *s;
  83     char fmode[80]; /* copy of mode, without the compression level */
  84     char *m = fmode;
  85
  86     if (!path || !mode) return Z_NULL;
  87
  88     s = (gz_stream *)ALLOC(sizeof(gz_stream));
  89     if (!s) return Z_NULL;
  90
  91     s->stream.zalloc = (alloc_func)0;
  92     s->stream.zfree = (free_func)0;
  93     s->stream.opaque = (voidpf)0;
  94     s->stream.next_in = s->inbuf = Z_NULL;
  95     s->stream.next_out = s->outbuf = Z_NULL;
  96     s->stream.avail_in = s->stream.avail_out = 0;
  97     s->file = NULL;
  98     s->z_err = Z_OK;
  99     s->z_eof = 0;
 100     s->crc = crc32(0L, Z_NULL, 0);
 101     s->msg = NULL;
 102     s->transparent = 0;
 103
 104     s->path = (char*)ALLOC(strlen(path)+1);
 105     if (s->path == NULL) {
 106         return destroy(s), (gzFile)Z_NULL;
 107     }
 108     strcpy(s->path, path); /* do this early for debugging */
 109
 110     s->mode = '\0';
 111     do {
 112         if (*p == 'r') s->mode = 'r';
 113         if (*p == 'w' || *p == 'a') s->mode = 'w';
 114         if (*p >= '0' && *p <= '9') {
 115             level = *p - '0';
 116         } else if (*p == 'f') {
 117           strategy = Z_FILTERED;
 118         } else if (*p == 'h') {
 119           strategy = Z_HUFFMAN_ONLY;
 120         } else {
 121             *m++ = *p; /* copy the mode */
 122         }
 123     } while (*p++ && m != fmode + sizeof(fmode));
 124     if (s->mode == '\0') return destroy(s), (gzFile)Z_NULL;
 125
 126     if (s->mode == 'w') {
 127 #ifdef NO_DEFLATE
 128         err = Z_STREAM_ERROR;
 129 #else
 130         err = deflateInit2(&(s->stream), level,
 131                            Z_DEFLATED, -MAX_WBITS, DEF_MEM_LEVEL, strategy);
 132         /* windowBits is passed < 0 to suppress zlib header */
 133
 134         s->stream.next_out = s->outbuf = (Byte*)ALLOC(Z_BUFSIZE);
 135 #endif
 136         if (err != Z_OK || s->outbuf == Z_NULL) {
 137             return destroy(s), (gzFile)Z_NULL;
 138         }
 139     } else {
 140         s->stream.next_in  = s->inbuf = (Byte*)ALLOC(Z_BUFSIZE);
 141
 142         err = inflateInit2(&(s->stream), -MAX_WBITS);
 143         /* windowBits is passed < 0 to tell that there is no zlib header.
 144          * Note that in this case inflate *requires* an extra "dummy" byte
 145          * after the compressed stream in order to complete decompression and
 146          * return Z_STREAM_END. Here the gzip CRC32 ensures that 4 bytes are
 147          * present after the compressed stream.
 148          */
 149         if (err != Z_OK || s->inbuf == Z_NULL) {
 150             return destroy(s), (gzFile)Z_NULL;
 151         }
 152     }
 153     s->stream.avail_out = Z_BUFSIZE;
 154
 155     errno = 0;
 156     s->file = fd < 0 ? F_OPEN(path, fmode) : (FILE*)fdopen(fd, fmode);
 157
 158     if (s->file == NULL) {
 159         return destroy(s), (gzFile)Z_NULL;
 160     }
 161     if (s->mode == 'w') {
 162         /* Write a very simple .gz header:
 163          */
 164         fprintf(s->file, "%c%c%c%c%c%c%c%c%c%c", gz_magic[0], gz_magic[1],
 165              Z_DEFLATED, 0 /*flags*/, 0,0,0,0 /*time*/, 0 /*xflags*/, OS_CODE);
 166         s->startpos = 10L;
 167         /* We use 10L instead of ftell(s->file) to because ftell causes an
 168          * fflush on some systems. This version of the library doesn't use
 169          * startpos anyway in write mode, so this initialization is not
 170          * necessary.
 171          */
 172     } else {
 173         check_header(s); /* skip the .gz header */
 174         s->startpos = (ftell(s->file) - s->stream.avail_in);
 175     }
 176
 177     return (gzFile)s;
 178 }
 179
 180 /* ===========================================================================
 181      Opens a gzip (.gz) file for reading or writing.
 182 */
 183 gzFile ZEXPORT gzopen (path, mode)
 184     const char *path;
 185     const char *mode;
 186 {
 187     return gz_open (path, mode, -1);
 188 }
 189
 190 /* ===========================================================================
 191      Associate a gzFile with the file descriptor fd. fd is not dup'ed here
 192    to mimic the behavio(u)r of fdopen.
 193 */
 194 gzFile ZEXPORT gzdopen (fd, mode)
 195     int fd;
 196     const char *mode;
 197 {
 198     char name[20];
 199
 200     if (fd < 0) return (gzFile)Z_NULL;
 201     sprintf(name, "<fd:%d>", fd); /* for debugging */
 202
 203     return gz_open (name, mode, fd);
 204 }
 205
 206 /* ===========================================================================
 207  * Update the compression level and strategy
 208  */
 209 int ZEXPORT gzsetparams (file, level, strategy)
 210     gzFile file;
 211     int level;
 212     int strategy;
 213 {
 214     gz_stream *s = (gz_stream*)file;
 215
 216     if (s == NULL || s->mode != 'w') return Z_STREAM_ERROR;
 217
 218     /* Make room to allow flushing */
 219     if (s->stream.avail_out == 0) {
 220
 221         s->stream.next_out = s->outbuf;
 222         if (fwrite(s->outbuf, 1, Z_BUFSIZE, s->file) != Z_BUFSIZE) {
 223             s->z_err = Z_ERRNO;
 224         }
 225         s->stream.avail_out = Z_BUFSIZE;
 226     }
 227
 228     return deflateParams (&(s->stream), level, strategy);
 229 }
 230
 231 /* ===========================================================================
 232      Read a byte from a gz_stream; update next_in and avail_in. Return EOF
 233    for end of file.
 234    IN assertion: the stream s has been sucessfully opened for reading.
 235 */
 236 local int get_byte(s)
 237     gz_stream *s;
 238 {
 239     if (s->z_eof) return EOF;
 240     if (s->stream.avail_in == 0) {
 241         errno = 0;
 242         s->stream.avail_in = fread(s->inbuf, 1, Z_BUFSIZE, s->file);
 243         if (s->stream.avail_in == 0) {
 244             s->z_eof = 1;
 245             if (ferror(s->file)) s->z_err = Z_ERRNO;
 246             return EOF;
 247         }
 248         s->stream.next_in = s->inbuf;
 249     }
 250     s->stream.avail_in--;
 251     return *(s->stream.next_in)++;
 252 }
 253
 254 /* ===========================================================================
 255       Check the gzip header of a gz_stream opened for reading. Set the stream
 256     mode to transparent if the gzip magic header is not present; set s->err
 257     to Z_DATA_ERROR if the magic header is present but the rest of the header
 258     is incorrect.
 259     IN assertion: the stream s has already been created sucessfully;
 260        s->stream.avail_in is zero for the first time, but may be non-zero
 261        for concatenated .gz files.
 262 */
 263 local void check_header(s)
 264     gz_stream *s;
 265 {
 266     int method; /* method byte */
 267     int flags;  /* flags byte */
 268     uInt len;
 269     int c;
 270
 271     /* Check the gzip magic header */
 272     for (len = 0; len < 2; len++) {
 273         c = get_byte(s);
 274         if (c != gz_magic[len]) {
 275             if (len != 0) s->stream.avail_in++, s->stream.next_in--;
 276             if (c != EOF) {
 277                 s->stream.avail_in++, s->stream.next_in--;
 278                 s->transparent = 1;
 279             }
 280             s->z_err = s->stream.avail_in != 0 ? Z_OK : Z_STREAM_END;
 281             return;
 282         }
 283     }
 284     method = get_byte(s);
 285     flags = get_byte(s);
 286     if (method != Z_DEFLATED || (flags & RESERVED) != 0) {
 287         s->z_err = Z_DATA_ERROR;
 288         return;
 289     }
 290
 291     /* Discard time, xflags and OS code: */
 292     for (len = 0; len < 6; len++) (void)get_byte(s);
 293
 294     if ((flags & EXTRA_FIELD) != 0) { /* skip the extra field */
 295         len  =  (uInt)get_byte(s);
 296         len += ((uInt)get_byte(s))<<8;
 297         /* len is garbage if EOF but the loop below will quit anyway */
 298         while (len-- != 0 && get_byte(s) != EOF) ;
 299     }
 300     if ((flags & ORIG_NAME) != 0) { /* skip the original file name */
 301         while ((c = get_byte(s)) != 0 && c != EOF) ;
 302     }
 303     if ((flags & COMMENT) != 0) {   /* skip the .gz file comment */
 304         while ((c = get_byte(s)) != 0 && c != EOF) ;
 305     }
 306     if ((flags & HEAD_CRC) != 0) {  /* skip the header crc */
 307         for (len = 0; len < 2; len++) (void)get_byte(s);
 308     }
 309     s->z_err = s->z_eof ? Z_DATA_ERROR : Z_OK;
 310 }
 311
 312  /* ===========================================================================
 313  * Cleanup then free the given gz_stream. Return a zlib error code.
 314    Try freeing in the reverse order of allocations.
 315  */
 316 local int destroy (s)
 317     gz_stream *s;
 318 {
 319     int err = Z_OK;
 320
 321     if (!s) return Z_STREAM_ERROR;
 322
 323     TRYFREE(s->msg);
 324
 325     if (s->stream.state != NULL) {
 326         if (s->mode == 'w') {
 327 #ifdef NO_DEFLATE
 328             err = Z_STREAM_ERROR;
 329 #else
 330             err = deflateEnd(&(s->stream));
 331 #endif
 332         } else if (s->mode == 'r') {
 333             err = inflateEnd(&(s->stream));
 334         }
 335     }
 336     if (s->file != NULL && fclose(s->file)) {
 337 #ifdef ESPIPE
 338         if (errno != ESPIPE) /* fclose is broken for pipes in HP/UX */
 339 #endif
 340             err = Z_ERRNO;
 341     }
 342     if (s->z_err < 0) err = s->z_err;
 343
 344     TRYFREE(s->inbuf);
 345     TRYFREE(s->outbuf);
 346     TRYFREE(s->path);
 347     TRYFREE(s);
 348     return err;
 349 }
 350
 351 /* ===========================================================================
 352      Reads the given number of uncompressed bytes from the compressed file.
 353    gzread returns the number of bytes actually read (0 for end of file).
 354 */
 355 int ZEXPORT gzread (file, buf, len)
 356     gzFile file;
 357     voidp buf;
 358     unsigned len;
 359 {
 360     gz_stream *s = (gz_stream*)file;
 361     Bytef *start = (Bytef*)buf; /* starting point for crc computation */
 362     Byte  *next_out; /* == stream.next_out but not forced far (for MSDOS) */
 363
 364     if (s == NULL || s->mode != 'r') return Z_STREAM_ERROR;
 365
 366     if (s->z_err == Z_DATA_ERROR || s->z_err == Z_ERRNO) return -1;
 367     if (s->z_err == Z_STREAM_END) return 0;  /* EOF */
 368
 369     next_out = (Byte*)buf;
 370     s->stream.next_out = (Bytef*)buf;
 371     s->stream.avail_out = len;
 372
 373     while (s->stream.avail_out != 0) {
 374
 375         if (s->transparent) {
 376             /* Copy first the lookahead bytes: */
 377             uInt n = s->stream.avail_in;
 378             if (n > s->stream.avail_out) n = s->stream.avail_out;
 379             if (n > 0) {
 380                 zmemcpy(s->stream.next_out, s->stream.next_in, n);
 381                 next_out += n;
 382                 s->stream.next_out = next_out;
 383                 s->stream.next_in   += n;
 384                 s->stream.avail_out -= n;
 385                 s->stream.avail_in  -= n;
 386             }
 387             if (s->stream.avail_out > 0) {
 388                 s->stream.avail_out -= fread(next_out, 1, s->stream.avail_out,
 389                                              s->file);
 390             }
 391             len -= s->stream.avail_out;
 392             s->stream.total_in  += (uLong)len;
 393             s->stream.total_out += (uLong)len;
 394             if (len == 0) s->z_eof = 1;
 395             return (int)len;
 396         }
 397         if (s->stream.avail_in == 0 && !s->z_eof) {
 398
 399             errno = 0;
 400             s->stream.avail_in = fread(s->inbuf, 1, Z_BUFSIZE, s->file);
 401             if (s->stream.avail_in == 0) {
 402                 s->z_eof = 1;
 403                 if (ferror(s->file)) {
 404                     s->z_err = Z_ERRNO;
 405                     break;
 406                 }
 407             }
 408             s->stream.next_in = s->inbuf;
 409         }
 410         s->z_err = inflate(&(s->stream), Z_NO_FLUSH);
 411
 412         if (s->z_err == Z_STREAM_END) {
 413             /* Check CRC and original size */
 414             s->crc = crc32(s->crc, start, (uInt)(s->stream.next_out - start));
 415             start = s->stream.next_out;
 416
 417             if (getLong(s) != s->crc) {
 418                 s->z_err = Z_DATA_ERROR;
 419             } else {
 420                 (void)getLong(s);
 421                 /* The uncompressed length returned by above getlong() may
 422                  * be different from s->stream.total_out) in case of
 423                  * concatenated .gz files. Check for such files:
 424                  */
 425                 check_header(s);
 426                 if (s->z_err == Z_OK) {
 427                     uLong total_in = s->stream.total_in;
 428                     uLong total_out = s->stream.total_out;
 429
 430                     inflateReset(&(s->stream));
 431                     s->stream.total_in = total_in;
 432                     s->stream.total_out = total_out;
 433                     s->crc = crc32(0L, Z_NULL, 0);
 434                 }
 435             }
 436         }
 437         if (s->z_err != Z_OK || s->z_eof) break;
 438     }
 439     s->crc = crc32(s->crc, start, (uInt)(s->stream.next_out - start));
 440
 441     return (int)(len - s->stream.avail_out);
 442 }
 443
 444
 445 /* ===========================================================================
 446       Reads one byte from the compressed file. gzgetc returns this byte
 447    or -1 in case of end of file or error.
 448 */
 449 int ZEXPORT gzgetc(file)
 450     gzFile file;
 451 {
 452     unsigned char c;
 453
 454     return gzread(file, &c, 1) == 1 ? c : -1;
 455 }
 456
 457
 458 /* ===========================================================================
 459       Reads bytes from the compressed file until len-1 characters are
 460    read, or a newline character is read and transferred to buf, or an
 461    end-of-file condition is encountered.  The string is then terminated
 462    with a null character.
 463       gzgets returns buf, or Z_NULL in case of error.
 464
 465       The current implementation is not optimized at all.
 466 */
 467 char * ZEXPORT gzgets(file, buf, len)
 468     gzFile file;
 469     char *buf;
 470     int len;
 471 {
 472     char *b = buf;
 473     if (buf == Z_NULL || len <= 0) return Z_NULL;
 474
 475     while (--len > 0 && gzread(file, buf, 1) == 1 && *buf++ != '\n') ;
 476     *buf = '\0';
 477     return b == buf && len > 0 ? Z_NULL : b;
 478 }
 479
 480
 481 #ifndef NO_DEFLATE
 482 /* ===========================================================================
 483      Writes the given number of uncompressed bytes into the compressed file.
 484    gzwrite returns the number of bytes actually written (0 in case of error).
 485 */
 486 int ZEXPORT gzwrite (file, buf, len)
 487     gzFile file;
 488     const voidp buf;
 489     unsigned len;
 490 {
 491     gz_stream *s = (gz_stream*)file;
 492
 493     if (s == NULL || s->mode != 'w') return Z_STREAM_ERROR;
 494
 495     s->stream.next_in = (Bytef*)buf;
 496     s->stream.avail_in = len;
 497
 498     while (s->stream.avail_in != 0) {
 499
 500         if (s->stream.avail_out == 0) {
 501
 502             s->stream.next_out = s->outbuf;
 503             if (fwrite(s->outbuf, 1, Z_BUFSIZE, s->file) != Z_BUFSIZE) {
 504                 s->z_err = Z_ERRNO;
 505                 break;
 506             }
 507             s->stream.avail_out = Z_BUFSIZE;
 508         }
 509         s->z_err = deflate(&(s->stream), Z_NO_FLUSH);
 510         if (s->z_err != Z_OK) break;
 511     }
 512     s->crc = crc32(s->crc, (const Bytef *)buf, len);
 513
 514     return (int)(len - s->stream.avail_in);
 515 }
 516
 517 /* ===========================================================================
 518      Converts, formats, and writes the args to the compressed file under
 519    control of the format string, as in fprintf. gzprintf returns the number of
 520    uncompressed bytes actually written (0 in case of error).
 521 */
 522 #ifdef STDC
 523 #include <stdarg.h>
 524
 525 int ZEXPORTVA gzprintf (gzFile file, const char *format, /* args */ ...)
 526 {
 527     char buf[Z_PRINTF_BUFSIZE];
 528     va_list va;
 529     int len;
 530
 531     va_start(va, format);
 532 #ifdef HAS_vsnprintf
 533     (void)vsnprintf(buf, sizeof(buf), format, va);
 534 #else
 535     (void)vsprintf(buf, format, va);
 536 #endif
 537     va_end(va);
 538     len = strlen(buf); /* some *sprintf don't return the nb of bytes written */
 539     if (len <= 0) return 0;
 540
 541     return gzwrite(file, buf, (unsigned)len);
 542 }
 543 #else /* not ANSI C */
 544
 545 int ZEXPORTVA gzprintf (file, format, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10,
 546                        a11, a12, a13, a14, a15, a16, a17, a18, a19, a20)
 547     gzFile file;
 548     const char *format;
 549     int a1, a2, a3, a4, a5, a6, a7, a8, a9, a10,
 550         a11, a12, a13, a14, a15, a16, a17, a18, a19, a20;
 551 {
 552     char buf[Z_PRINTF_BUFSIZE];
 553     int len;
 554
 555 #ifdef HAS_snprintf
 556     snprintf(buf, sizeof(buf), format, a1, a2, a3, a4, a5, a6, a7, a8,
 557              a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20);
 558 #else
 559     sprintf(buf, format, a1, a2, a3, a4, a5, a6, a7, a8,
 560             a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20);
 561 #endif
 562     len = strlen(buf); /* old sprintf doesn't return the nb of bytes written */
 563     if (len <= 0) return 0;
 564
 565     return gzwrite(file, buf, len);
 566 }
 567 #endif
 568
 569 /* ===========================================================================
 570       Writes c, converted to an unsigned char, into the compressed file.
 571    gzputc returns the value that was written, or -1 in case of error.
 572 */
 573 int ZEXPORT gzputc(file, c)
 574     gzFile file;
 575     int c;
 576 {
 577     unsigned char cc = (unsigned char) c; /* required for big endian systems */
 578
 579     return gzwrite(file, &cc, 1) == 1 ? (int)cc : -1;
 580 }
 581
 582
 583 /* ===========================================================================
 584       Writes the given null-terminated string to the compressed file, excluding
 585    the terminating null character.
 586       gzputs returns the number of characters written, or -1 in case of error.
 587 */
 588 int ZEXPORT gzputs(file, s)
 589     gzFile file;
 590     const char *s;
 591 {
 592     return gzwrite(file, (char*)s, (unsigned)strlen(s));
 593 }
 594
 595
 596 /* ===========================================================================
 597      Flushes all pending output into the compressed file. The parameter
 598    flush is as in the deflate() function.
 599 */
 600 local int do_flush (file, flush)
 601     gzFile file;
 602     int flush;
 603 {
 604     uInt len;
 605     int done = 0;
 606     gz_stream *s = (gz_stream*)file;
 607
 608     if (s == NULL || s->mode != 'w') return Z_STREAM_ERROR;
 609
 610     s->stream.avail_in = 0; /* should be zero already anyway */
 611
 612     for (;;) {
 613         len = Z_BUFSIZE - s->stream.avail_out;
 614
 615         if (len != 0) {
 616             if ((uInt)fwrite(s->outbuf, 1, len, s->file) != len) {
 617                 s->z_err = Z_ERRNO;
 618                 return Z_ERRNO;
 619             }
 620             s->stream.next_out = s->outbuf;
 621             s->stream.avail_out = Z_BUFSIZE;
 622         }
 623         if (done) break;
 624         s->z_err = deflate(&(s->stream), flush);
 625
 626         /* Ignore the second of two consecutive flushes: */
 627         if (len == 0 && s->z_err == Z_BUF_ERROR) s->z_err = Z_OK;
 628
 629         /* deflate has finished flushing only when it hasn't used up
 630          * all the available space in the output buffer:
 631          */
 632         done = (s->stream.avail_out != 0 || s->z_err == Z_STREAM_END);
 633
 634         if (s->z_err != Z_OK && s->z_err != Z_STREAM_END) break;
 635     }
 636     return  s->z_err == Z_STREAM_END ? Z_OK : s->z_err;
 637 }
 638
 639 int ZEXPORT gzflush (file, flush)
 640      gzFile file;
 641      int flush;
 642 {
 643     gz_stream *s = (gz_stream*)file;
 644     int err = do_flush (file, flush);
 645
 646     if (err) return err;
 647     fflush(s->file);
 648     return  s->z_err == Z_STREAM_END ? Z_OK : s->z_err;
 649 }
 650 #endif /* NO_DEFLATE */
 651
 652 /* ===========================================================================
 653       Sets the starting position for the next gzread or gzwrite on the given
 654    compressed file. The offset represents a number of bytes in the
 655       gzseek returns the resulting offset location as measured in bytes from
 656    the beginning of the uncompressed stream, or -1 in case of error.
 657       SEEK_END is not implemented, returns error.
 658       In this version of the library, gzseek can be extremely slow.
 659 */
 660 z_off_t ZEXPORT gzseek (file, offset, whence)
 661     gzFile file;
 662     z_off_t offset;
 663     int whence;
 664 {
 665     gz_stream *s = (gz_stream*)file;
 666
 667     if (s == NULL || whence == SEEK_END ||
 668         s->z_err == Z_ERRNO || s->z_err == Z_DATA_ERROR) {
 669         return -1L;
 670     }
 671
 672     if (s->mode == 'w') {
 673 #ifdef NO_DEFLATE
 674         return -1L;
 675 #else
 676         if (whence == SEEK_SET) {
 677             offset -= s->stream.total_in;
 678         }
 679         if (offset < 0) return -1L;
 680
 681         /* At this point, offset is the number of zero bytes to write. */
 682         if (s->inbuf == Z_NULL) {
 683             s->inbuf = (Byte*)ALLOC(Z_BUFSIZE); /* for seeking */
 684             zmemzero(s->inbuf, Z_BUFSIZE);
 685         }
 686         while (offset > 0)  {
 687             uInt size = Z_BUFSIZE;
 688             if (offset < Z_BUFSIZE) size = (uInt)offset;
 689
 690             size = gzwrite(file, s->inbuf, size);
 691             if (size == 0) return -1L;
 692
 693             offset -= size;
 694         }
 695         return (z_off_t)s->stream.total_in;
 696 #endif
 697     }
 698     /* Rest of function is for reading only */
 699
 700     /* compute absolute position */
 701     if (whence == SEEK_CUR) {
 702         offset += s->stream.total_out;
 703     }
 704     if (offset < 0) return -1L;
 705
 706     if (s->transparent) {
 707         /* map to fseek */
 708         s->stream.avail_in = 0;
 709         s->stream.next_in = s->inbuf;
 710         if (fseek(s->file, offset, SEEK_SET) < 0) return -1L;
 711
 712         s->stream.total_in = s->stream.total_out = (uLong)offset;
 713         return offset;
 714     }
 715
 716     /* For a negative seek, rewind and use positive seek */
 717     if ((uLong)offset >= s->stream.total_out) {
 718         offset -= s->stream.total_out;
 719     } else if (gzrewind(file) < 0) {
 720         return -1L;
 721     }
 722     /* offset is now the number of bytes to skip. */
 723
 724     if (offset != 0 && s->outbuf == Z_NULL) {
 725         s->outbuf = (Byte*)ALLOC(Z_BUFSIZE);
 726     }
 727     while (offset > 0)  {
 728         int size = Z_BUFSIZE;
 729         if (offset < Z_BUFSIZE) size = (int)offset;
 730
 731         size = gzread(file, s->outbuf, (uInt)size);
 732         if (size <= 0) return -1L;
 733         offset -= size;
 734     }
 735     return (z_off_t)s->stream.total_out;
 736 }
 737
 738 /* ===========================================================================
 739      Rewinds input file.
 740 */
 741 int ZEXPORT gzrewind (file)
 742     gzFile file;
 743 {
 744     gz_stream *s = (gz_stream*)file;
 745
 746     if (s == NULL || s->mode != 'r') return -1;
 747
 748     s->z_err = Z_OK;
 749     s->z_eof = 0;
 750     s->stream.avail_in = 0;
 751     s->stream.next_in = s->inbuf;
 752     s->crc = crc32(0L, Z_NULL, 0);
 753
 754     if (s->startpos == 0) { /* not a compressed file */
 755         rewind(s->file);
 756         return 0;
 757     }
 758
 759     (void) inflateReset(&s->stream);
 760     return fseek(s->file, s->startpos, SEEK_SET);
 761 }
 762
 763 /* ===========================================================================
 764      Returns the starting position for the next gzread or gzwrite on the
 765    given compressed file. This position represents a number of bytes in the
 766    uncompressed data stream.
 767 */
 768 z_off_t ZEXPORT gztell (file)
 769     gzFile file;
 770 {
 771     return gzseek(file, 0L, SEEK_CUR);
 772 }
 773
 774 /* ===========================================================================
 775      Returns 1 when EOF has previously been detected reading the given
 776    input stream, otherwise zero.
 777 */
 778 int ZEXPORT gzeof (file)
 779     gzFile file;
 780 {
 781     gz_stream *s = (gz_stream*)file;
 782
 783     return (s == NULL || s->mode != 'r') ? 0 : s->z_eof;
 784 }
 785
 786 /* ===========================================================================
 787    Outputs a long in LSB order to the given file
 788 */
 789 local void putLong (file, x)
 790     FILE *file;
 791     uLong x;
 792 {
 793     int n;
 794     for (n = 0; n < 4; n++) {
 795         fputc((int)(x & 0xff), file);
 796         x >>= 8;
 797     }
 798 }
 799
 800 /* ===========================================================================
 801    Reads a long in LSB order from the given gz_stream. Sets z_err in case
 802    of error.
 803 */
 804 local uLong getLong (s)
 805     gz_stream *s;
 806 {
 807     uLong x = (uLong)get_byte(s);
 808     int c;
 809
 810     x += ((uLong)get_byte(s))<<8;
 811     x += ((uLong)get_byte(s))<<16;
 812     c = get_byte(s);
 813     if (c == EOF) s->z_err = Z_DATA_ERROR;
 814     x += ((uLong)c)<<24;
 815     return x;
 816 }
 817
 818 /* ===========================================================================
 819      Flushes all pending output if necessary, closes the compressed file
 820    and deallocates all the (de)compression state.
 821 */
 822 int ZEXPORT gzclose (file)
 823     gzFile file;
 824 {
 825     int err;
 826     gz_stream *s = (gz_stream*)file;
 827
 828     if (s == NULL) return Z_STREAM_ERROR;
 829
 830     if (s->mode == 'w') {
 831 #ifdef NO_DEFLATE
 832         return Z_STREAM_ERROR;
 833 #else
 834         err = do_flush (file, Z_FINISH);
 835         if (err != Z_OK) return destroy((gz_stream*)file);
 836
 837         putLong (s->file, s->crc);
 838         putLong (s->file, s->stream.total_in);
 839 #endif
 840     }
 841     return destroy((gz_stream*)file);
 842 }
 843
 844 /* ===========================================================================
 845      Returns the error message for the last error which occured on the
 846    given compressed file. errnum is set to zlib error number. If an
 847    error occured in the file system and not in the compression library,
 848    errnum is set to Z_ERRNO and the application may consult errno
 849    to get the exact error code.
 850 */
 851 const char*  ZEXPORT gzerror (file, errnum)
 852     gzFile file;
 853     int *errnum;
 854 {
 855     char *m;
 856     gz_stream *s = (gz_stream*)file;
 857
 858     if (s == NULL) {
 859         *errnum = Z_STREAM_ERROR;
 860         return (const char*)ERR_MSG(Z_STREAM_ERROR);
 861     }
 862     *errnum = s->z_err;
 863     if (*errnum == Z_OK) return (const char*)"";
 864
 865     m =  (char*)(*errnum == Z_ERRNO ? zstrerror(errno) : s->stream.msg);
 866
 867     if (m == NULL || *m == '\0') m = (char*)ERR_MSG(s->z_err);
 868
 869     TRYFREE(s->msg);
 870     s->msg = (char*)ALLOC(strlen(s->path) + strlen(m) + 3);
 871     strcpy(s->msg, s->path);
 872     strcat(s->msg, ": ");
 873     strcat(s->msg, m);
 874     return (const char*)s->msg;
 875 }