The OpenD Programming Language

1 /* zlib.d: modified from zlib.h by Walter Bright */
2 /* updated from 1.2.1 to 1.2.3 by Thomas Kuehne */
3 /* updated from 1.2.3 to 1.2.8 by Dmitry Atamanov */
4 /* updated from 1.2.8 to 1.2.11 by Iain Buclaw */
5 /* updated from 1.2.11 to 1.2.12 by Brian Callahan */
6 
7 module etc.c.zlib;
8 
9 import core.stdc.config;
10 
11 /* zlib.h -- interface of the 'zlib' general purpose compression library
12   version 1.2.12, March 11th, 2022
13 
14   Copyright (C) 1995-2022 Jean-loup Gailly and Mark Adler
15 
16   This software is provided 'as-is', without any express or implied
17   warranty.  In no event will the authors be held liable for any damages
18   arising from the use of this software.
19 
20   Permission is granted to anyone to use this software for any purpose,
21   including commercial applications, and to alter it and redistribute it
22   freely, subject to the following restrictions:
23 
24   1. The origin of this software must not be misrepresented; you must not
25      claim that you wrote the original software. If you use this software
26      in a product, an acknowledgment in the product documentation would be
27      appreciated but is not required.
28   2. Altered source versions must be plainly marked as such, and must not be
29      misrepresented as being the original software.
30   3. This notice may not be removed or altered from any source distribution.
31 
32   Jean-loup Gailly        Mark Adler
33   jloup@gzip.org          madler@alumni.caltech.edu
34 
35 
36   The data format used by the zlib library is described by RFCs (Request for
37   Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950
38   (zlib format), rfc1951 (deflate format) and rfc1952 (gzip format).
39 */
40 
41 nothrow:
42 @nogc:
43 extern (C):
44 
45 // Those are extern(D) as they should be mangled
46 extern(D) immutable string ZLIB_VERSION = "1.2.12";
47 extern(D) immutable ZLIB_VERNUM = 0x12c0;
48 
49 /*
50     The 'zlib' compression library provides in-memory compression and
51   decompression functions, including integrity checks of the uncompressed data.
52   This version of the library supports only one compression method (deflation)
53   but other algorithms will be added later and will have the same stream
54   interface.
55 
56     Compression can be done in a single step if the buffers are large enough,
57   or can be done by repeated calls of the compression function.  In the latter
58   case, the application must provide more input and/or consume the output
59   (providing more output space) before each call.
60 
61     The compressed data format used by default by the in-memory functions is
62   the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
63   around a deflate stream, which is itself documented in RFC 1951.
64 
65     The library also supports reading and writing files in gzip (.gz) format
66   with an interface similar to that of stdio using the functions that start
67   with "gz".  The gzip format is different from the zlib format.  gzip is a
68   gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.
69 
70     This library can optionally read and write gzip and raw deflate streams in
71   memory as well.
72 
73     The zlib format was designed to be compact and fast for use in memory
74   and on communications channels.  The gzip format was designed for single-
75   file compression on file systems, has a larger header than zlib to maintain
76   directory information, and uses a different, slower check method than zlib.
77 
78     The library does not install any signal handler.  The decoder checks
79   the consistency of the compressed data, so the library should never crash
80   even in the case of corrupted input.
81 */
82 
83 alias alloc_func = void* function (void* opaque, uint items, uint size);
84 alias free_func = void  function (void* opaque, void* address);
85 
86 struct z_stream
87 {
88     const(ubyte)*   next_in;  /* next input byte */
89     uint     avail_in;  /* number of bytes available at next_in */
90     c_ulong  total_in;  /* total nb of input bytes read so far */
91 
92     ubyte*   next_out;  /* next output byte will go here */
93     uint     avail_out; /* remaining free space at next_out */
94     c_ulong  total_out; /* total nb of bytes output so far */
95 
96     const(char)*    msg;      /* last error message, NULL if no error */
97     void*    state;     /* not visible by applications */
98 
99     alloc_func zalloc;  /* used to allocate the internal state */
100     free_func  zfree;   /* used to free the internal state */
101     void*      opaque;  /* private data object passed to zalloc and zfree */
102 
103     int     data_type;  /* best guess about the data type: binary or text
104                            for deflate, or the decoding state for inflate */
105     c_ulong adler;      /* Adler-32 or CRC-32 value of the uncompressed data */
106     c_ulong reserved;   /* reserved for future use */
107 }
108 
109 alias z_streamp = z_stream*;
110 
111 /*
112      gzip header information passed to and from zlib routines.  See RFC 1952
113   for more details on the meanings of these fields.
114 */
115 struct gz_header
116 {
117     int     text;       /* true if compressed data believed to be text */
118     c_ulong time;       /* modification time */
119     int     xflags;     /* extra flags (not used when writing a gzip file) */
120     int     os;         /* operating system */
121     byte    *extra;     /* pointer to extra field or Z_NULL if none */
122     uint    extra_len;  /* extra field length (valid if extra != Z_NULL) */
123     uint    extra_max;  /* space at extra (only when reading header) */
124     byte*   name;      /* pointer to zero-terminated file name or Z_NULL */
125     uint    name_max;   /* space at name (only when reading header) */
126     byte*   comment;   /* pointer to zero-terminated comment or Z_NULL */
127     uint    comm_max;   /* space at comment (only when reading header) */
128     int     hcrc;       /* true if there was or will be a header crc */
129     int     done;       /* true when done reading gzip header (not used
130                            when writing a gzip file) */
131 }
132 
133 alias gz_headerp = gz_header*;
134 
135 /*
136      The application must update next_in and avail_in when avail_in has dropped
137    to zero.  It must update next_out and avail_out when avail_out has dropped
138    to zero.  The application must initialize zalloc, zfree and opaque before
139    calling the init function.  All other fields are set by the compression
140    library and must not be updated by the application.
141 
142      The opaque value provided by the application will be passed as the first
143    parameter for calls of zalloc and zfree.  This can be useful for custom
144    memory management.  The compression library attaches no meaning to the
145    opaque value.
146 
147      zalloc must return Z_NULL if there is not enough memory for the object.
148    If zlib is used in a multi-threaded application, zalloc and zfree must be
149    thread safe.  In that case, zlib is thread-safe.  When zalloc and zfree are
150    Z_NULL on entry to the initialization function, they are set to internal
151    routines that use the standard library functions malloc() and free().
152 
153      On 16-bit systems, the functions zalloc and zfree must be able to allocate
154    exactly 65536 bytes, but will not be required to allocate more than this if
155    the symbol MAXSEG_64K is defined (see zconf.h).  WARNING: On MSDOS, pointers
156    returned by zalloc for objects of exactly 65536 bytes *must* have their
157    offset normalized to zero.  The default allocation function provided by this
158    library ensures this (see zutil.c).  To reduce memory requirements and avoid
159    any allocation of 64K objects, at the expense of compression ratio, compile
160    the library with -DMAX_WBITS=14 (see zconf.h).
161 
162      The fields total_in and total_out can be used for statistics or progress
163    reports.  After compression, total_in holds the total size of the
164    uncompressed data and may be saved for use by the decompressor (particularly
165    if the decompressor wants to decompress everything in a single step).
166 */
167 
168                         /* constants */
169 
170 enum
171 {
172         Z_NO_FLUSH      = 0,
173         Z_PARTIAL_FLUSH = 1, /* will be removed, use Z_SYNC_FLUSH instead */
174         Z_SYNC_FLUSH    = 2,
175         Z_FULL_FLUSH    = 3,
176         Z_FINISH        = 4,
177         Z_BLOCK         = 5,
178         Z_TREES         = 6,
179 }
180 /* Allowed flush values; see deflate() and inflate() below for details */
181 
182 enum
183 {
184         Z_OK            = 0,
185         Z_STREAM_END    = 1,
186         Z_NEED_DICT     = 2,
187         Z_ERRNO         = -1,
188         Z_STREAM_ERROR  = -2,
189         Z_DATA_ERROR    = -3,
190         Z_MEM_ERROR     = -4,
191         Z_BUF_ERROR     = -5,
192         Z_VERSION_ERROR = -6,
193 }
194 /* Return codes for the compression/decompression functions. Negative
195  * values are errors, positive values are used for special but normal events.
196  */
197 
198 enum
199 {
200         Z_NO_COMPRESSION         = 0,
201         Z_BEST_SPEED             = 1,
202         Z_BEST_COMPRESSION       = 9,
203         Z_DEFAULT_COMPRESSION    = -1,
204 }
205 /* compression levels */
206 
207 enum
208 {
209         Z_FILTERED            = 1,
210         Z_HUFFMAN_ONLY        = 2,
211         Z_RLE                 = 3,
212         Z_FIXED               = 4,
213         Z_DEFAULT_STRATEGY    = 0,
214 }
215 /* compression strategy; see deflateInit2() below for details */
216 
217 enum
218 {
219         Z_BINARY   = 0,
220         Z_TEXT     = 1,
221         Z_UNKNOWN  = 2,
222 
223         Z_ASCII    = Z_TEXT
224 }
225 /* Possible values of the data_type field for deflate() */
226 
227 enum
228 {
229         Z_DEFLATED   = 8,
230 }
231 /* The deflate compression method (the only one supported in this version) */
232 
233 /// for initializing zalloc, zfree, opaque (extern(D) for mangling)
234 extern(D) immutable void* Z_NULL = null;
235 
236                         /* basic functions */
237 
238 const(char)* zlibVersion();
239 /* The application can compare zlibVersion and ZLIB_VERSION for consistency.
240    If the first character differs, the library code actually used is not
241    compatible with the zlib.h header file used by the application.  This check
242    is automatically made by deflateInit and inflateInit.
243  */
244 
245 int deflateInit(z_streamp strm, int level)
246 {
247     return deflateInit_(strm, level, ZLIB_VERSION.ptr, z_stream.sizeof);
248 }
249 /*
250      Initializes the internal stream state for compression.  The fields
251    zalloc, zfree and opaque must be initialized before by the caller.  If
252    zalloc and zfree are set to Z_NULL, deflateInit updates them to use default
253    allocation functions.
254 
255      The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
256    1 gives best speed, 9 gives best compression, 0 gives no compression at all
257    (the input data is simply copied a block at a time).  Z_DEFAULT_COMPRESSION
258    requests a default compromise between speed and compression (currently
259    equivalent to level 6).
260 
261      deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
262    memory, Z_STREAM_ERROR if level is not a valid compression level, or
263    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
264    with the version assumed by the caller (ZLIB_VERSION).  msg is set to null
265    if there is no error message.  deflateInit does not perform any compression:
266    this will be done by deflate().
267 */
268 
269 
270 int deflate(z_streamp strm, int flush);
271 /*
272     deflate compresses as much data as possible, and stops when the input
273   buffer becomes empty or the output buffer becomes full.  It may introduce
274   some output latency (reading input without producing any output) except when
275   forced to flush.
276 
277     The detailed semantics are as follows.  deflate performs one or both of the
278   following actions:
279 
280   - Compress more input starting at next_in and update next_in and avail_in
281     accordingly.  If not all input can be processed (because there is not
282     enough room in the output buffer), next_in and avail_in are updated and
283     processing will resume at this point for the next call of deflate().
284 
285   - Generate more output starting at next_out and update next_out and avail_out
286     accordingly.  This action is forced if the parameter flush is non zero.
287     Forcing flush frequently degrades the compression ratio, so this parameter
288     should be set only when necessary.  Some output may be provided even if
289     flush is zero.
290 
291     Before the call of deflate(), the application should ensure that at least
292   one of the actions is possible, by providing more input and/or consuming more
293   output, and updating avail_in or avail_out accordingly; avail_out should
294   never be zero before the call.  The application can consume the compressed
295   output when it wants, for example when the output buffer is full (avail_out
296   == 0), or after each call of deflate().  If deflate returns Z_OK and with
297   zero avail_out, it must be called again after making room in the output
298   buffer because there might be more output pending. See deflatePending(),
299   which can be used if desired to determine whether or not there is more ouput
300   in that case.
301 
302     Normally the parameter flush is set to Z_NO_FLUSH, which allows deflate to
303   decide how much data to accumulate before producing output, in order to
304   maximize compression.
305 
306     If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
307   flushed to the output buffer and the output is aligned on a byte boundary, so
308   that the decompressor can get all input data available so far.  (In
309   particular avail_in is zero after the call if enough output space has been
310   provided before the call.) Flushing may degrade compression for some
311   compression algorithms and so it should be used only when necessary.  This
312   completes the current deflate block and follows it with an empty stored block
313   that is three bits plus filler bits to the next byte, followed by four bytes
314   (00 00 ff ff).
315 
316     If flush is set to Z_PARTIAL_FLUSH, all pending output is flushed to the
317   output buffer, but the output is not aligned to a byte boundary.  All of the
318   input data so far will be available to the decompressor, as for Z_SYNC_FLUSH.
319   This completes the current deflate block and follows it with an empty fixed
320   codes block that is 10 bits long.  This assures that enough bytes are output
321   in order for the decompressor to finish the block before the empty fixed
322   codes block.
323 
324     If flush is set to Z_BLOCK, a deflate block is completed and emitted, as
325   for Z_SYNC_FLUSH, but the output is not aligned on a byte boundary, and up to
326   seven bits of the current block are held to be written as the next byte after
327   the next deflate block is completed.  In this case, the decompressor may not
328   be provided enough bits at this point in order to complete decompression of
329   the data provided so far to the compressor.  It may need to wait for the next
330   block to be emitted.  This is for advanced applications that need to control
331   the emission of deflate blocks.
332 
333     If flush is set to Z_FULL_FLUSH, all output is flushed as with
334   Z_SYNC_FLUSH, and the compression state is reset so that decompression can
335   restart from this point if previous compressed data has been damaged or if
336   random access is desired.  Using Z_FULL_FLUSH too often can seriously degrade
337   compression.
338 
339     If deflate returns with avail_out == 0, this function must be called again
340   with the same value of the flush parameter and more output space (updated
341   avail_out), until the flush is complete (deflate returns with non-zero
342   avail_out).  In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that
343   avail_out is greater than six to avoid repeated flush markers due to
344   avail_out == 0 on return.
345 
346     If the parameter flush is set to Z_FINISH, pending input is processed,
347   pending output is flushed and deflate returns with Z_STREAM_END if there was
348   enough output space.  If deflate returns with Z_OK or Z_BUF_ERROR, this
349   function must be called again with Z_FINISH and more output space (updated
350   avail_out) but no more input data, until it returns with Z_STREAM_END or an
351   error.  After deflate has returned Z_STREAM_END, the only possible operations
352   on the stream are deflateReset or deflateEnd.
353 
354     Z_FINISH can be used in the first deflate call after deflateInit if all the
355   compression is to be done in a single step.  In order to complete in one
356   call, avail_out must be at least the value returned by deflateBound (see
357   below).  Then deflate is guaranteed to return Z_STREAM_END.  If not enough
358   output space is provided, deflate will not return Z_STREAM_END, and it must
359   be called again as described above.
360 
361     deflate() sets strm->adler to the Adler-32 checksum of all input read
362   so far (that is, total_in bytes).  If a gzip stream is being generated, then
363   strm->adler will be the CRC-32 checksum of the input read so far.  (See
364   deflateInit2 below.)
365 
366     deflate() may update strm->data_type if it can make a good guess about
367   the input data type (Z_BINARY or Z_TEXT).  If in doubt, the data is
368   considered binary.  This field is only for information purposes and does not
369   affect the compression algorithm in any manner.
370 
371     deflate() returns Z_OK if some progress has been made (more input
372   processed or more output produced), Z_STREAM_END if all input has been
373   consumed and all output has been produced (only when flush is set to
374   Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
375   if next_in or next_out was Z_NULL or the state was inadvertently written over
376   by the application), or Z_BUF_ERROR if no progress is possible (for example
377   avail_in or avail_out was zero).  Note that Z_BUF_ERROR is not fatal, and
378   deflate() can be called again with more input and more output space to
379   continue compressing.
380 */
381 
382 
383 int deflateEnd(z_streamp strm);
384 /*
385      All dynamically allocated data structures for this stream are freed.
386    This function discards any unprocessed input and does not flush any pending
387    output.
388 
389      deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
390    stream state was inconsistent, Z_DATA_ERROR if the stream was freed
391    prematurely (some input or output was discarded).  In the error case, msg
392    may be set but then points to a static string (which must not be
393    deallocated).
394 */
395 
396 
397 int inflateInit(z_streamp strm)
398 {
399     return inflateInit_(strm, ZLIB_VERSION.ptr, z_stream.sizeof);
400 }
401 /*
402      Initializes the internal stream state for decompression.  The fields
403    next_in, avail_in, zalloc, zfree and opaque must be initialized before by
404    the caller.  In the current version of inflate, the provided input is not
405    read or consumed.  The allocation of a sliding window will be deferred to
406    the first call of inflate (if the decompression does not complete on the
407    first call).  If zalloc and zfree are set to Z_NULL, inflateInit updates
408    them to use default allocation functions.
409 
410      inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
411    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
412    version assumed by the caller, or Z_STREAM_ERROR if the parameters are
413    invalid, such as a null pointer to the structure.  msg is set to null if
414    there is no error message.  inflateInit does not perform any decompression.
415    Actual decompression will be done by inflate().  So next_in, and avail_in,
416    next_out, and avail_out are unused and unchanged.  The current
417    implementation of inflateInit() does not process any header information --
418    that is deferred until inflate() is called.
419 */
420 
421 
422 int inflate(z_streamp strm, int flush);
423 /*
424     inflate decompresses as much data as possible, and stops when the input
425   buffer becomes empty or the output buffer becomes full.  It may introduce
426   some output latency (reading input without producing any output) except when
427   forced to flush.
428 
429   The detailed semantics are as follows.  inflate performs one or both of the
430   following actions:
431 
432   - Decompress more input starting at next_in and update next_in and avail_in
433     accordingly.  If not all input can be processed (because there is not
434     enough room in the output buffer), then next_in and avail_in are updated
435     accordingly, and processing will resume at this point for the next call of
436     inflate().
437 
438   - Generate more output starting at next_out and update next_out and avail_out
439     accordingly.  inflate() provides as much output as possible, until there is
440     no more input data or no more space in the output buffer (see below about
441     the flush parameter).
442 
443     Before the call of inflate(), the application should ensure that at least
444   one of the actions is possible, by providing more input and/or consuming more
445   output, and updating the next_* and avail_* values accordingly.  If the
446   caller of inflate() does not provide both available input and available
447   output space, it is possible that there will be no progress made.  The
448   application can consume the uncompressed output when it wants, for example
449   when the output buffer is full (avail_out == 0), or after each call of
450   inflate().  If inflate returns Z_OK and with zero avail_out, it must be
451   called again after making room in the output buffer because there might be
452   more output pending.
453 
454     The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH, Z_FINISH,
455   Z_BLOCK, or Z_TREES.  Z_SYNC_FLUSH requests that inflate() flush as much
456   output as possible to the output buffer.  Z_BLOCK requests that inflate()
457   stop if and when it gets to the next deflate block boundary.  When decoding
458   the zlib or gzip format, this will cause inflate() to return immediately
459   after the header and before the first block.  When doing a raw inflate,
460   inflate() will go ahead and process the first block, and will return when it
461   gets to the end of that block, or when it runs out of data.
462 
463     The Z_BLOCK option assists in appending to or combining deflate streams.
464   To assist in this, on return inflate() always sets strm->data_type to the
465   number of unused bits in the last byte taken from strm->next_in, plus 64 if
466   inflate() is currently decoding the last block in the deflate stream, plus
467   128 if inflate() returned immediately after decoding an end-of-block code or
468   decoding the complete header up to just before the first byte of the deflate
469   stream.  The end-of-block will not be indicated until all of the uncompressed
470   data from that block has been written to strm->next_out.  The number of
471   unused bits may in general be greater than seven, except when bit 7 of
472   data_type is set, in which case the number of unused bits will be less than
473   eight.  data_type is set as noted here every time inflate() returns for all
474   flush options, and so can be used to determine the amount of currently
475   consumed input in bits.
476 
477     The Z_TREES option behaves as Z_BLOCK does, but it also returns when the
478   end of each deflate block header is reached, before any actual data in that
479   block is decoded.  This allows the caller to determine the length of the
480   deflate block header for later use in random access within a deflate block.
481   256 is added to the value of strm->data_type when inflate() returns
482   immediately after reaching the end of the deflate block header.
483 
484     inflate() should normally be called until it returns Z_STREAM_END or an
485   error.  However if all decompression is to be performed in a single step (a
486   single call of inflate), the parameter flush should be set to Z_FINISH.  In
487   this case all pending input is processed and all pending output is flushed;
488   avail_out must be large enough to hold all of the uncompressed data for the
489   operation to complete.  (The size of the uncompressed data may have been
490   saved by the compressor for this purpose.)  The use of Z_FINISH is not
491   required to perform an inflation in one step.  However it may be used to
492   inform inflate that a faster approach can be used for the single inflate()
493   call.  Z_FINISH also informs inflate to not maintain a sliding window if the
494   stream completes, which reduces inflate's memory footprint.  If the stream
495   does not complete, either because not all of the stream is provided or not
496   enough output space is provided, then a sliding window will be allocated and
497   inflate() can be called again to continue the operation as if Z_NO_FLUSH had
498   been used.
499 
500      In this implementation, inflate() always flushes as much output as
501   possible to the output buffer, and always uses the faster approach on the
502   first call.  So the effects of the flush parameter in this implementation are
503   on the return value of inflate() as noted below, when inflate() returns early
504   when Z_BLOCK or Z_TREES is used, and when inflate() avoids the allocation of
505   memory for a sliding window when Z_FINISH is used.
506 
507      If a preset dictionary is needed after this call (see inflateSetDictionary
508   below), inflate sets strm->adler to the Adler-32 checksum of the dictionary
509   chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
510   strm->adler to the Adler-32 checksum of all output produced so far (that is,
511   total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
512   below.  At the end of the stream, inflate() checks that its computed Adler-32
513   checksum is equal to that saved by the compressor and returns Z_STREAM_END
514   only if the checksum is correct.
515 
516     inflate() can decompress and check either zlib-wrapped or gzip-wrapped
517   deflate data.  The header type is detected automatically, if requested when
518   initializing with inflateInit2().  Any information contained in the gzip
519   header is not retained unless inflateGetHeader() is used.  When processing
520   gzip-wrapped deflate data, strm->adler32 is set to the CRC-32 of the output
521   produced so far.  The CRC-32 is checked against the gzip trailer, as is the
522   uncompressed length, modulo 2^32.
523 
524     inflate() returns Z_OK if some progress has been made (more input processed
525   or more output produced), Z_STREAM_END if the end of the compressed data has
526   been reached and all uncompressed output has been produced, Z_NEED_DICT if a
527   preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
528   corrupted (input stream not conforming to the zlib format or incorrect check
529   value, in which case strm->msg points to a string with a more specific
530   error), Z_STREAM_ERROR if the stream structure was inconsistent (for example
531   next_in or next_out was Z_NULL, or the state was inadvertently written over
532   by the application), Z_MEM_ERROR if there was not enough memory, Z_BUF_ERROR
533   if no progress was possible or if there was not enough room in the output
534   buffer when Z_FINISH is used.  Note that Z_BUF_ERROR is not fatal, and
535   inflate() can be called again with more input and more output space to
536   continue decompressing.  If Z_DATA_ERROR is returned, the application may
537   then call inflateSync() to look for a good compression block if a partial
538   recovery of the data is to be attempted.
539 */
540 
541 
542 int inflateEnd(z_streamp strm);
543 /*
544      All dynamically allocated data structures for this stream are freed.
545    This function discards any unprocessed input and does not flush any pending
546    output.
547 
548      inflateEnd returns Z_OK if success, or Z_STREAM_ERROR if the stream state
549    was inconsistent.
550 */
551 
552                         /* Advanced functions */
553 
554 /*
555     The following functions are needed only in some special applications.
556 */
557 
558 int deflateInit2(z_streamp strm,
559                  int  level,
560                  int  method,
561                  int  windowBits,
562                  int  memLevel,
563                  int  strategy)
564 {
565     return deflateInit2_(strm, level, method, windowBits, memLevel,
566                          strategy, ZLIB_VERSION.ptr, z_stream.sizeof);
567 }
568 /*
569      This is another version of deflateInit with more compression options.  The
570    fields zalloc, zfree and opaque must be initialized before by the caller.
571 
572      The method parameter is the compression method.  It must be Z_DEFLATED in
573    this version of the library.
574 
575      The windowBits parameter is the base two logarithm of the window size
576    (the size of the history buffer).  It should be in the range 8 .. 15 for this
577    version of the library.  Larger values of this parameter result in better
578    compression at the expense of memory usage.  The default value is 15 if
579    deflateInit is used instead.
580 
581      For the current implementation of deflate(), a windowBits value of 8 (a
582    window size of 256 bytes) is not supported.  As a result, a request for 8
583    will result in 9 (a 512-byte window).  In that case, providing 8 to
584    inflateInit2() will result in an error when the zlib header with 9 is
585    checked against the initialization of inflate().  The remedy is to not use 8
586    with deflateInit2() with this initialization, or at least in that case use 9
587    with inflateInit2().
588 
589      windowBits can also be -8 .. -15 for raw deflate.  In this case, -windowBits
590    determines the window size.  deflate() will then generate raw deflate data
591    with no zlib header or trailer, and will not compute a check value.
592 
593      windowBits can also be greater than 15 for optional gzip encoding.  Add
594    16 to windowBits to write a simple gzip header and trailer around the
595    compressed data instead of a zlib wrapper.  The gzip header will have no
596    file name, no extra data, no comment, no modification time (set to zero), no
597    header crc, and the operating system will be set to the appropriate value,
598    if the operating system was determined at compile time.  If a gzip stream is
599    being written, strm->adler is a CRC-32 instead of an Adler-32.
600 
601      For raw deflate or gzip encoding, a request for a 256-byte window is
602    rejected as invalid, since only the zlib header provides a means of
603    transmitting the window size to the decompressor.
604 
605      The memLevel parameter specifies how much memory should be allocated
606    for the internal compression state.  memLevel=1 uses minimum memory but is
607    slow and reduces compression ratio; memLevel=9 uses maximum memory for
608    optimal speed.  The default value is 8.  See zconf.h for total memory usage
609    as a function of windowBits and memLevel.
610 
611      The strategy parameter is used to tune the compression algorithm.  Use the
612    value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
613    filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no
614    string match), or Z_RLE to limit match distances to one (run-length
615    encoding).  Filtered data consists mostly of small values with a somewhat
616    random distribution.  In this case, the compression algorithm is tuned to
617    compress them better.  The effect of Z_FILTERED is to force more Huffman
618    coding and less string matching; it is somewhat intermediate between
619    Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY.  Z_RLE is designed to be almost as
620    fast as Z_HUFFMAN_ONLY, but give better compression for PNG image data.  The
621    strategy parameter only affects the compression ratio but not the
622    correctness of the compressed output even if it is not set appropriately.
623    Z_FIXED prevents the use of dynamic Huffman codes, allowing for a simpler
624    decoder for special applications.
625 
626      deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
627    memory, Z_STREAM_ERROR if any parameter is invalid (such as an invalid
628    method), or Z_VERSION_ERROR if the zlib library version (zlib_version) is
629    incompatible with the version assumed by the caller (ZLIB_VERSION).  msg is
630    set to null if there is no error message.  deflateInit2 does not perform any
631    compression: this will be done by deflate().
632 */
633 
634 int deflateSetDictionary(z_streamp strm, const(ubyte)* dictionary, uint  dictLength);
635 /*
636      Initializes the compression dictionary from the given byte sequence
637    without producing any compressed output.  When using the zlib format, this
638    function must be called immediately after deflateInit, deflateInit2 or
639    deflateReset, and before any call of deflate.  When doing raw deflate, this
640    function must be called either before any call of deflate, or immediately
641    after the completion of a deflate block, i.e. after all input has been
642    consumed and all output has been delivered when using any of the flush
643    options Z_BLOCK, Z_PARTIAL_FLUSH, Z_SYNC_FLUSH, or Z_FULL_FLUSH.  The
644    compressor and decompressor must use exactly the same dictionary (see
645    inflateSetDictionary).
646 
647      The dictionary should consist of strings (byte sequences) that are likely
648    to be encountered later in the data to be compressed, with the most commonly
649    used strings preferably put towards the end of the dictionary.  Using a
650    dictionary is most useful when the data to be compressed is short and can be
651    predicted with good accuracy; the data can then be compressed better than
652    with the default empty dictionary.
653 
654      Depending on the size of the compression data structures selected by
655    deflateInit or deflateInit2, a part of the dictionary may in effect be
656    discarded, for example if the dictionary is larger than the window size
657    provided in deflateInit or deflateInit2.  Thus the strings most likely to be
658    useful should be put at the end of the dictionary, not at the front.  In
659    addition, the current implementation of deflate will use at most the window
660    size minus 262 bytes of the provided dictionary.
661 
662      Upon return of this function, strm->adler is set to the Adler-32 value
663    of the dictionary; the decompressor may later use this value to determine
664    which dictionary has been used by the compressor.  (The Adler-32 value
665    applies to the whole dictionary even if only a subset of the dictionary is
666    actually used by the compressor.) If a raw deflate was requested, then the
667    Adler-32 value is not computed and strm->adler is not set.
668 
669      deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
670    parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is
671    inconsistent (for example if deflate has already been called for this stream
672    or if not at a block boundary for raw deflate).  deflateSetDictionary does
673    not perform any compression: this will be done by deflate().
674 */
675 
676 int deflateGetDictionary(z_streamp strm, ubyte *dictionary, uint  dictLength);
677 /*
678      Returns the sliding dictionary being maintained by deflate.  dictLength is
679    set to the number of bytes in the dictionary, and that many bytes are copied
680    to dictionary.  dictionary must have enough space, where 32768 bytes is
681    always enough.  If deflateGetDictionary() is called with dictionary equal to
682    Z_NULL, then only the dictionary length is returned, and nothing is copied.
683    Similary, if dictLength is Z_NULL, then it is not set.
684 
685      deflateGetDictionary() may return a length less than the window size, even
686    when more than the window size in input has been provided. It may return up
687    to 258 bytes less in that case, due to how zlib's implementation of deflate
688    manages the sliding window and lookahead for matches, where matches can be
689    up to 258 bytes long. If the application needs the last window-size bytes of
690    input, then that would need to be saved by the application outside of zlib.
691 
692      deflateGetDictionary returns Z_OK on success, or Z_STREAM_ERROR if the
693    stream state is inconsistent.
694 */
695 
696 int deflateCopy(z_streamp dest, z_streamp source);
697 /*
698      Sets the destination stream as a complete copy of the source stream.
699 
700      This function can be useful when several compression strategies will be
701    tried, for example when there are several ways of pre-processing the input
702    data with a filter.  The streams that will be discarded should then be freed
703    by calling deflateEnd.  Note that deflateCopy duplicates the internal
704    compression state which can be quite large, so this strategy is slow and can
705    consume lots of memory.
706 
707      deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
708    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
709    (such as zalloc being Z_NULL).  msg is left unchanged in both source and
710    destination.
711 */
712 
713 int deflateReset(z_streamp strm);
714 /*
715      This function is equivalent to deflateEnd followed by deflateInit, but
716    does not free and reallocate the internal compression state.  The stream
717    will leave the compression level and any other attributes that may have been
718    set unchanged.
719 
720      deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
721    stream state was inconsistent (such as zalloc or state being Z_NULL).
722 */
723 
724 int deflateParams(z_streamp strm, int level, int strategy);
725 /*
726      Dynamically update the compression level and compression strategy.  The
727    interpretation of level and strategy is as in deflateInit2().  This can be
728    used to switch between compression and straight copy of the input data, or
729    to switch to a different kind of input data requiring a different strategy.
730    If the compression approach (which is a function of the level) or the
731    strategy is changed, and if there have been any deflate() calls since the
732    state was initialized or reset, then the input available so far is
733    compressed with the old level and strategy using deflate(strm, Z_BLOCK).
734    There are three approaches for the compression levels 0, 1 .. 3, and 4 .. 9
735    respectively.  The new level and strategy will take effect at the next call
736    of deflate().
737 
738      If a deflate(strm, Z_BLOCK) is performed by deflateParams(), and it does
739    not have enough output space to complete, then the parameter change will not
740    take effect.  In this case, deflateParams() can be called again with the
741    same parameters and more output space to try again.
742 
743      In order to assure a change in the parameters on the first try, the
744    deflate stream should be flushed using deflate() with Z_BLOCK or other flush
745    request until strm.avail_out is not zero, before calling deflateParams().
746    Then no more input data should be provided before the deflateParams() call.
747    If this is done, the old level and strategy will be applied to the data
748    compressed before deflateParams(), and the new level and strategy will be
749    applied to the the data compressed after deflateParams().
750 
751      deflateParams returns Z_OK on success, Z_STREAM_ERROR if the source stream
752    state was inconsistent or if a parameter was invalid, or Z_BUF_ERROR if
753    there was not enough output space to complete the compression of the
754    available input data before a change in the strategy or approach.  Note that
755    in the case of a Z_BUF_ERROR, the parameters are not changed.  A return
756    value of Z_BUF_ERROR is not fatal, in which case deflateParams() can be
757    retried with more output space.
758 */
759 
760 int deflateTune(z_streamp strm, int good_length, int max_lazy, int nice_length,
761         int max_chain);
762 /*
763      Fine tune deflate's internal compression parameters.  This should only be
764    used by someone who understands the algorithm used by zlib's deflate for
765    searching for the best matching string, and even then only by the most
766    fanatic optimizer trying to squeeze out the last compressed bit for their
767    specific input data.  Read the deflate.c source code for the meaning of the
768    max_lazy, good_length, nice_length, and max_chain parameters.
769 
770      deflateTune() can be called after deflateInit() or deflateInit2(), and
771    returns Z_OK on success, or Z_STREAM_ERROR for an invalid deflate stream.
772  */
773 
774 size_t deflateBound(z_streamp strm, size_t sourceLen);
775 /*
776      deflateBound() returns an upper bound on the compressed size after
777    deflation of sourceLen bytes.  It must be called after deflateInit() or
778    deflateInit2(), and after deflateSetHeader(), if used.  This would be used
779    to allocate an output buffer for deflation in a single pass, and so would be
780    called before deflate().  If that first deflate() call is provided the
781    sourceLen input bytes, an output buffer allocated to the size returned by
782    deflateBound(), and the flush value Z_FINISH, then deflate() is guaranteed
783    to return Z_STREAM_END.  Note that it is possible for the compressed size to
784    be larger than the value returned by deflateBound() if flush options other
785    than Z_FINISH or Z_NO_FLUSH are used.
786 */
787 
788 int deflatePending(z_streamp strm, uint* pending, int* bits);
789 /*
790      deflatePending() returns the number of bytes and bits of output that have
791    been generated, but not yet provided in the available output.  The bytes not
792    provided would be due to the available output space having being consumed.
793    The number of bits of output not provided are between 0 and 7, where they
794    await more bits to join them in order to fill out a full byte.  If pending
795    or bits are Z_NULL, then those values are not set.
796 
797      deflatePending returns Z_OK if success, or Z_STREAM_ERROR if the source
798    stream state was inconsistent.
799  */
800 
801 int deflatePrime(z_streamp strm, int bits, int value);
802 /*
803      deflatePrime() inserts bits in the deflate output stream.  The intent
804    is that this function is used to start off the deflate output with the bits
805    leftover from a previous deflate stream when appending to it.  As such, this
806    function can only be used for raw deflate, and must be used before the first
807    deflate() call after a deflateInit2() or deflateReset().  bits must be less
808    than or equal to 16, and that many of the least significant bits of value
809    will be inserted in the output.
810 
811      deflatePrime returns Z_OK if success, Z_BUF_ERROR if there was not enough
812    room in the internal buffer to insert the bits, or Z_STREAM_ERROR if the
813    source stream state was inconsistent.
814 */
815 
816 int deflateSetHeader(z_streamp strm, gz_headerp head);
817 /*
818      deflateSetHeader() provides gzip header information for when a gzip
819    stream is requested by deflateInit2().  deflateSetHeader() may be called
820    after deflateInit2() or deflateReset() and before the first call of
821    deflate().  The text, time, os, extra field, name, and comment information
822    in the provided gz_header structure are written to the gzip header (xflag is
823    ignored -- the extra flags are set according to the compression level).  The
824    caller must assure that, if not Z_NULL, name and comment are terminated with
825    a zero byte, and that if extra is not Z_NULL, that extra_len bytes are
826    available there.  If hcrc is true, a gzip header crc is included.  Note that
827    the current versions of the command-line version of gzip (up through version
828    1.3.x) do not support header crc's, and will report that it is a "multi-part
829    gzip file" and give up.
830 
831      If deflateSetHeader is not used, the default gzip header has text false,
832    the time set to zero, and os set to 255, with no extra, name, or comment
833    fields.  The gzip header is returned to the default state by deflateReset().
834 
835      deflateSetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
836    stream state was inconsistent.
837 */
838 
839 int inflateInit2(z_streamp strm, int windowBits)
840 {
841     return inflateInit2_(strm, windowBits, ZLIB_VERSION.ptr, z_stream.sizeof);
842 }
843 /*
844      This is another version of inflateInit with an extra parameter.  The
845    fields next_in, avail_in, zalloc, zfree and opaque must be initialized
846    before by the caller.
847 
848      The windowBits parameter is the base two logarithm of the maximum window
849    size (the size of the history buffer).  It should be in the range 8 .. 15 for
850    this version of the library.  The default value is 15 if inflateInit is used
851    instead.  windowBits must be greater than or equal to the windowBits value
852    provided to deflateInit2() while compressing, or it must be equal to 15 if
853    deflateInit2() was not used.  If a compressed stream with a larger window
854    size is given as input, inflate() will return with the error code
855    Z_DATA_ERROR instead of trying to allocate a larger window.
856 
857      windowBits can also be zero to request that inflate use the window size in
858    the zlib header of the compressed stream.
859 
860      windowBits can also be -8 .. -15 for raw inflate.  In this case, -windowBits
861    determines the window size.  inflate() will then process raw deflate data,
862    not looking for a zlib or gzip header, not generating a check value, and not
863    looking for any check values for comparison at the end of the stream.  This
864    is for use with other formats that use the deflate compressed data format
865    such as zip.  Those formats provide their own check values.  If a custom
866    format is developed using the raw deflate format for compressed data, it is
867    recommended that a check value such as an Adler-32 or a CRC-32 be applied to
868    the uncompressed data as is done in the zlib, gzip, and zip formats.  For
869    most applications, the zlib format should be used as is.  Note that comments
870    above on the use in deflateInit2() applies to the magnitude of windowBits.
871 
872      windowBits can also be greater than 15 for optional gzip decoding.  Add
873    32 to windowBits to enable zlib and gzip decoding with automatic header
874    detection, or add 16 to decode only the gzip format (the zlib format will
875    return a Z_DATA_ERROR).  If a gzip stream is being decoded, strm->adler is a
876    CRC-32 instead of an Adler-32.  Unlike the gunzip utility and gzread() (see
877    below), inflate() will *not* automatically decode concatenated gzip members.
878    inflate() will return Z_STREAM_END at the end of the gzip member.  The state
879    would need to be reset to continue decoding a subsequent gzip member.  This
880    *must* be done if there is more data after a gzip member, in order for the
881    decompression to be compliant with the gzip standard (RFC 1952).
882 
883      inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
884    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
885    version assumed by the caller, or Z_STREAM_ERROR if the parameters are
886    invalid, such as a null pointer to the structure.  msg is set to null if
887    there is no error message.  inflateInit2 does not perform any decompression
888    apart from possibly reading the zlib header if present: actual decompression
889    will be done by inflate().  (So next_in and avail_in may be modified, but
890    next_out and avail_out are unused and unchanged.) The current implementation
891    of inflateInit2() does not process any header information -- that is
892    deferred until inflate() is called.
893 */
894 
895 int inflateSetDictionary(z_streamp strm, const(ubyte)* dictionary, uint  dictLength);
896 /*
897      Initializes the decompression dictionary from the given uncompressed byte
898    sequence.  This function must be called immediately after a call of inflate,
899    if that call returned Z_NEED_DICT.  The dictionary chosen by the compressor
900    can be determined from the Adler-32 value returned by that call of inflate.
901    The compressor and decompressor must use exactly the same dictionary (see
902    deflateSetDictionary).  For raw inflate, this function can be called at any
903    time to set the dictionary.  If the provided dictionary is smaller than the
904    window and there is already data in the window, then the provided dictionary
905    will amend what's there.  The application must insure that the dictionary
906    that was used for compression is provided.
907 
908      inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
909    parameter is invalid (e.g.  dictionary being Z_NULL) or the stream state is
910    inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
911    expected one (incorrect Adler-32 value).  inflateSetDictionary does not
912    perform any decompression: this will be done by subsequent calls of
913    inflate().
914 */
915 
916 int inflateGetDictionary(z_streamp strm, ubyte* dictionary, uint* dictLength);
917 /*
918      Returns the sliding dictionary being maintained by inflate.  dictLength is
919    set to the number of bytes in the dictionary, and that many bytes are copied
920    to dictionary.  dictionary must have enough space, where 32768 bytes is
921    always enough.  If inflateGetDictionary() is called with dictionary equal to
922    Z_NULL, then only the dictionary length is returned, and nothing is copied.
923    Similary, if dictLength is Z_NULL, then it is not set.
924 
925      inflateGetDictionary returns Z_OK on success, or Z_STREAM_ERROR if the
926    stream state is inconsistent.
927 */
928 
929 int inflateSync(z_streamp strm);
930 /*
931      Skips invalid compressed data until a possible full flush point (see above
932    for the description of deflate with Z_FULL_FLUSH) can be found, or until all
933    available input is skipped.  No output is provided.
934 
935      inflateSync searches for a 00 00 FF FF pattern in the compressed data.
936    All full flush points have this pattern, but not all occurrences of this
937    pattern are full flush points.
938 
939      inflateSync returns Z_OK if a possible full flush point has been found,
940    Z_BUF_ERROR if no more input was provided, Z_DATA_ERROR if no flush point
941    has been found, or Z_STREAM_ERROR if the stream structure was inconsistent.
942    In the success case, the application may save the current current value of
943    total_in which indicates where valid compressed data was found.  In the
944    error case, the application may repeatedly call inflateSync, providing more
945    input each time, until success or end of the input data.
946 */
947 
948 int inflateCopy(z_streamp dest, z_streamp source);
949 /*
950      Sets the destination stream as a complete copy of the source stream.
951 
952      This function can be useful when randomly accessing a large stream.  The
953    first pass through the stream can periodically record the inflate state,
954    allowing restarting inflate at those points when randomly accessing the
955    stream.
956 
957      inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
958    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
959    (such as zalloc being Z_NULL).  msg is left unchanged in both source and
960    destination.
961 */
962 
963 int inflateReset(z_streamp strm);
964 /*
965      This function is equivalent to inflateEnd followed by inflateInit,
966    but does not free and reallocate the internal decompression state.  The
967    stream will keep attributes that may have been set by inflateInit2.
968 
969      inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
970    stream state was inconsistent (such as zalloc or state being Z_NULL).
971 */
972 
973 int inflateReset2(z_streamp strm, int windowBits);
974 /*
975      This function is the same as inflateReset, but it also permits changing
976    the wrap and window size requests.  The windowBits parameter is interpreted
977    the same as it is for inflateInit2.  If the window size is changed, then the
978    memory allocated for the window is freed, and the window will be reallocated
979    by inflate() if needed.
980 
981      inflateReset2 returns Z_OK if success, or Z_STREAM_ERROR if the source
982    stream state was inconsistent (such as zalloc or state being Z_NULL), or if
983    the windowBits parameter is invalid.
984 */
985 
986 int inflatePrime(z_streamp strm, int bits, int value);
987 /*
988      This function inserts bits in the inflate input stream.  The intent is
989    that this function is used to start inflating at a bit position in the
990    middle of a byte.  The provided bits will be used before any bytes are used
991    from next_in.  This function should only be used with raw inflate, and
992    should be used before the first inflate() call after inflateInit2() or
993    inflateReset().  bits must be less than or equal to 16, and that many of the
994    least significant bits of value will be inserted in the input.
995 
996      If bits is negative, then the input stream bit buffer is emptied.  Then
997    inflatePrime() can be called again to put bits in the buffer.  This is used
998    to clear out bits leftover after feeding inflate a block description prior
999    to feeding inflate codes.
1000 
1001      inflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
1002    stream state was inconsistent.
1003 */
1004 
1005 c_long inflateMark(z_streamp strm);
1006 /*
1007      This function returns two values, one in the lower 16 bits of the return
1008    value, and the other in the remaining upper bits, obtained by shifting the
1009    return value down 16 bits.  If the upper value is -1 and the lower value is
1010    zero, then inflate() is currently decoding information outside of a block.
1011    If the upper value is -1 and the lower value is non-zero, then inflate is in
1012    the middle of a stored block, with the lower value equaling the number of
1013    bytes from the input remaining to copy.  If the upper value is not -1, then
1014    it is the number of bits back from the current bit position in the input of
1015    the code (literal or length/distance pair) currently being processed.  In
1016    that case the lower value is the number of bytes already emitted for that
1017    code.
1018 
1019      A code is being processed if inflate is waiting for more input to complete
1020    decoding of the code, or if it has completed decoding but is waiting for
1021    more output space to write the literal or match data.
1022 
1023      inflateMark() is used to mark locations in the input data for random
1024    access, which may be at bit positions, and to note those cases where the
1025    output of a code may span boundaries of random access blocks.  The current
1026    location in the input stream can be determined from avail_in and data_type
1027    as noted in the description for the Z_BLOCK flush parameter for inflate.
1028 
1029      inflateMark returns the value noted above, or -65536 if the provided
1030    source stream state was inconsistent.
1031 */
1032 
1033 int inflateGetHeader(z_streamp strm, gz_headerp head);
1034 /*
1035      inflateGetHeader() requests that gzip header information be stored in the
1036    provided gz_header structure.  inflateGetHeader() may be called after
1037    inflateInit2() or inflateReset(), and before the first call of inflate().
1038    As inflate() processes the gzip stream, head->done is zero until the header
1039    is completed, at which time head->done is set to one.  If a zlib stream is
1040    being decoded, then head->done is set to -1 to indicate that there will be
1041    no gzip header information forthcoming.  Note that Z_BLOCK or Z_TREES can be
1042    used to force inflate() to return immediately after header processing is
1043    complete and before any actual data is decompressed.
1044 
1045      The text, time, xflags, and os fields are filled in with the gzip header
1046    contents.  hcrc is set to true if there is a header CRC.  (The header CRC
1047    was valid if done is set to one.) If extra is not Z_NULL, then extra_max
1048    contains the maximum number of bytes to write to extra.  Once done is true,
1049    extra_len contains the actual extra field length, and extra contains the
1050    extra field, or that field truncated if extra_max is less than extra_len.
1051    If name is not Z_NULL, then up to name_max characters are written there,
1052    terminated with a zero unless the length is greater than name_max.  If
1053    comment is not Z_NULL, then up to comm_max characters are written there,
1054    terminated with a zero unless the length is greater than comm_max.  When any
1055    of extra, name, or comment are not Z_NULL and the respective field is not
1056    present in the header, then that field is set to Z_NULL to signal its
1057    absence.  This allows the use of deflateSetHeader() with the returned
1058    structure to duplicate the header.  However if those fields are set to
1059    allocated memory, then the application will need to save those pointers
1060    elsewhere so that they can be eventually freed.
1061 
1062      If inflateGetHeader is not used, then the header information is simply
1063    discarded.  The header is always checked for validity, including the header
1064    CRC if present.  inflateReset() will reset the process to discard the header
1065    information.  The application would need to call inflateGetHeader() again to
1066    retrieve the header from the next gzip stream.
1067 
1068      inflateGetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
1069    stream state was inconsistent.
1070 */
1071 
1072 
1073 int inflateBackInit(z_stream* strm, int windowBits, ubyte* window)
1074 {
1075     return inflateBackInit_(strm, windowBits, window, ZLIB_VERSION.ptr, z_stream.sizeof);
1076 }
1077 /*
1078      Initialize the internal stream state for decompression using inflateBack()
1079    calls.  The fields zalloc, zfree and opaque in strm must be initialized
1080    before the call.  If zalloc and zfree are Z_NULL, then the default library-
1081    derived memory allocation routines are used.  windowBits is the base two
1082    logarithm of the window size, in the range 8 .. 15.  window is a caller
1083    supplied buffer of that size.  Except for special applications where it is
1084    assured that deflate was used with small window sizes, windowBits must be 15
1085    and a 32K byte window must be supplied to be able to decompress general
1086    deflate streams.
1087 
1088      See inflateBack() for the usage of these routines.
1089 
1090      inflateBackInit will return Z_OK on success, Z_STREAM_ERROR if any of
1091    the parameters are invalid, Z_MEM_ERROR if the internal state could not be
1092    allocated, or Z_VERSION_ERROR if the version of the library does not match
1093    the version of the header file.
1094 */
1095 
1096 alias in_func = uint function(void*, ubyte**);
1097 alias out_func = int function(void*, ubyte*, uint);
1098 
1099 int inflateBack(z_stream* strm,
1100                 in_func f_in,
1101                 void* in_desc,
1102                 out_func f_out,
1103                 void* out_desc);
1104 /*
1105      inflateBack() does a raw inflate with a single call using a call-back
1106    interface for input and output.  This is potentially more efficient than
1107    inflate() for file i/o applications, in that it avoids copying between the
1108    output and the sliding window by simply making the window itself the output
1109    buffer.  inflate() can be faster on modern CPUs when used with large
1110    buffers.  inflateBack() trusts the application to not change the output
1111    buffer passed by the output function, at least until inflateBack() returns.
1112 
1113      inflateBackInit() must be called first to allocate the internal state
1114    and to initialize the state with the user-provided window buffer.
1115    inflateBack() may then be used multiple times to inflate a complete, raw
1116    deflate stream with each call.  inflateBackEnd() is then called to free the
1117    allocated state.
1118 
1119      A raw deflate stream is one with no zlib or gzip header or trailer.
1120    This routine would normally be used in a utility that reads zip or gzip
1121    files and writes out uncompressed files.  The utility would decode the
1122    header and process the trailer on its own, hence this routine expects only
1123    the raw deflate stream to decompress.  This is different from the default
1124    behavior of inflate(), which expects a zlib header and trailer around the
1125    deflate stream.
1126 
1127      inflateBack() uses two subroutines supplied by the caller that are then
1128    called by inflateBack() for input and output.  inflateBack() calls those
1129    routines until it reads a complete deflate stream and writes out all of the
1130    uncompressed data, or until it encounters an error.  The function's
1131    parameters and return types are defined above in the in_func and out_func
1132    typedefs.  inflateBack() will call in(in_desc, &buf) which should return the
1133    number of bytes of provided input, and a pointer to that input in buf.  If
1134    there is no input available, in() must return zero -- buf is ignored in that
1135    case -- and inflateBack() will return a buffer error.  inflateBack() will
1136    call out(out_desc, buf, len) to write the uncompressed data buf[0 .. len-1].
1137    out() should return zero on success, or non-zero on failure.  If out()
1138    returns non-zero, inflateBack() will return with an error.  Neither in() nor
1139    out() are permitted to change the contents of the window provided to
1140    inflateBackInit(), which is also the buffer that out() uses to write from.
1141    The length written by out() will be at most the window size.  Any non-zero
1142    amount of input may be provided by in().
1143 
1144      For convenience, inflateBack() can be provided input on the first call by
1145    setting strm->next_in and strm->avail_in.  If that input is exhausted, then
1146    in() will be called.  Therefore strm->next_in must be initialized before
1147    calling inflateBack().  If strm->next_in is Z_NULL, then in() will be called
1148    immediately for input.  If strm->next_in is not Z_NULL, then strm->avail_in
1149    must also be initialized, and then if strm->avail_in is not zero, input will
1150    initially be taken from strm->next_in[0 ..  strm->avail_in - 1].
1151 
1152      The in_desc and out_desc parameters of inflateBack() is passed as the
1153    first parameter of in() and out() respectively when they are called.  These
1154    descriptors can be optionally used to pass any information that the caller-
1155    supplied in() and out() functions need to do their job.
1156 
1157      On return, inflateBack() will set strm->next_in and strm->avail_in to
1158    pass back any unused input that was provided by the last in() call.  The
1159    return values of inflateBack() can be Z_STREAM_END on success, Z_BUF_ERROR
1160    if in() or out() returned an error, Z_DATA_ERROR if there was a format error
1161    in the deflate stream (in which case strm->msg is set to indicate the nature
1162    of the error), or Z_STREAM_ERROR if the stream was not properly initialized.
1163    In the case of Z_BUF_ERROR, an input or output error can be distinguished
1164    using strm->next_in which will be Z_NULL only if in() returned an error.  If
1165    strm->next_in is not Z_NULL, then the Z_BUF_ERROR was due to out() returning
1166    non-zero.  (in() will always be called before out(), so strm->next_in is
1167    assured to be defined if out() returns non-zero.)  Note that inflateBack()
1168    cannot return Z_OK.
1169 */
1170 
1171 int inflateBackEnd(z_stream* strm);
1172 /*
1173      All memory allocated by inflateBackInit() is freed.
1174 
1175      inflateBackEnd() returns Z_OK on success, or Z_STREAM_ERROR if the stream
1176    state was inconsistent.
1177 */
1178 
1179 uint zlibCompileFlags();
1180 /* Return flags indicating compile-time options.
1181 
1182     Type sizes, two bits each, 00 = 16 bits, 01 = 32, 10 = 64, 11 = other:
1183      1.0: size of uInt
1184      3.2: size of uLong
1185      5.4: size of voidpf (pointer)
1186      7.6: size of z_off_t
1187 
1188     Compiler, assembler, and debug options:
1189      8: ZLIB_DEBUG
1190      9: ASMV or ASMINF -- use ASM code
1191      10: ZLIB_WINAPI -- exported functions use the WINAPI calling convention
1192      11: 0 (reserved)
1193 
1194     One-time table building (smaller code, but not thread-safe if true):
1195      12: BUILDFIXED -- build static block decoding tables when needed
1196      13: DYNAMIC_CRC_TABLE -- build CRC calculation tables when needed
1197      14,15: 0 (reserved)
1198 
1199     Library content (indicates missing functionality):
1200      16: NO_GZCOMPRESS -- gz* functions cannot compress (to avoid linking
1201                           deflate code when not needed)
1202      17: NO_GZIP -- deflate can't write gzip streams, and inflate can't detect
1203                     and decode gzip streams (to avoid linking crc code)
1204      18-19: 0 (reserved)
1205 
1206     Operation variations (changes in library functionality):
1207      20: PKZIP_BUG_WORKAROUND -- slightly more permissive inflate
1208      21: FASTEST -- deflate algorithm with only one, lowest compression level
1209      22,23: 0 (reserved)
1210 
1211     The sprintf variant used by gzprintf (zero is best):
1212      24: 0 = vs*, 1 = s* -- 1 means limited to 20 arguments after the format
1213      25: 0 = *nprintf, 1 = *printf -- 1 means gzprintf() not secure!
1214      26: 0 = returns value, 1 = void -- 1 means inferred string length returned
1215 
1216     Remainder:
1217      27-31: 0 (reserved)
1218  */
1219 
1220                         /* utility functions */
1221 
1222 /*
1223      The following utility functions are implemented on top of the basic
1224    stream-oriented functions.  To simplify the interface, some default options
1225    are assumed (compression level and memory usage, standard memory allocation
1226    functions).  The source code of these utility functions can be modified if
1227    you need special options.
1228 */
1229 
1230 int compress(ubyte* dest,
1231              size_t* destLen,
1232              const(ubyte)* source,
1233              size_t sourceLen);
1234 /*
1235      Compresses the source buffer into the destination buffer.  sourceLen is
1236    the byte length of the source buffer.  Upon entry, destLen is the total size
1237    of the destination buffer, which must be at least the value returned by
1238    compressBound(sourceLen).  Upon exit, destLen is the actual size of the
1239    compressed data.  compress() is equivalent to compress2() with a level
1240    parameter of Z_DEFAULT_COMPRESSION.
1241 
1242      compress returns Z_OK if success, Z_MEM_ERROR if there was not
1243    enough memory, Z_BUF_ERROR if there was not enough room in the output
1244    buffer.
1245 */
1246 
1247 int compress2(ubyte* dest,
1248               size_t* destLen,
1249               const(ubyte)* source,
1250               size_t sourceLen,
1251               int level);
1252 /*
1253      Compresses the source buffer into the destination buffer.  The level
1254    parameter has the same meaning as in deflateInit.  sourceLen is the byte
1255    length of the source buffer.  Upon entry, destLen is the total size of the
1256    destination buffer, which must be at least the value returned by
1257    compressBound(sourceLen).  Upon exit, destLen is the actual size of the
1258    compressed data.
1259 
1260      compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
1261    memory, Z_BUF_ERROR if there was not enough room in the output buffer,
1262    Z_STREAM_ERROR if the level parameter is invalid.
1263 */
1264 
1265 size_t compressBound(size_t sourceLen);
1266 /*
1267      compressBound() returns an upper bound on the compressed size after
1268    compress() or compress2() on sourceLen bytes.  It would be used before a
1269    compress() or compress2() call to allocate the destination buffer.
1270 */
1271 
1272 int uncompress(ubyte* dest,
1273                size_t* destLen,
1274                const(ubyte)* source,
1275                size_t sourceLen);
1276 /*
1277      Decompresses the source buffer into the destination buffer.  sourceLen is
1278    the byte length of the source buffer.  Upon entry, destLen is the total size
1279    of the destination buffer, which must be large enough to hold the entire
1280    uncompressed data.  (The size of the uncompressed data must have been saved
1281    previously by the compressor and transmitted to the decompressor by some
1282    mechanism outside the scope of this compression library.) Upon exit, destLen
1283    is the actual size of the uncompressed data.
1284 
1285      uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
1286    enough memory, Z_BUF_ERROR if there was not enough room in the output
1287    buffer, or Z_DATA_ERROR if the input data was corrupted or incomplete.  In
1288    the case where there is not enough room, uncompress() will fill the output
1289    buffer with the uncompressed data up to that point.
1290 */
1291 
1292 int uncompress2(ubyte* dest,
1293                 size_t* destLen,
1294                 const(ubyte)* source,
1295                 size_t* sourceLen);
1296 /*
1297      Same as uncompress, except that sourceLen is a pointer, where the
1298    length of the source is *sourceLen.  On return, *sourceLen is the number of
1299    source bytes consumed.
1300 */
1301 
1302                         /* gzip file access functions */
1303 
1304 /*
1305      This library supports reading and writing files in gzip (.gz) format with
1306    an interface similar to that of stdio, using the functions that start with
1307    "gz".  The gzip format is different from the zlib format.  gzip is a gzip
1308    wrapper, documented in RFC 1952, wrapped around a deflate stream.
1309 */
1310 
1311 alias gzFile = void*;
1312 alias z_off_t = int;              // file offset
1313 alias z_size_t = size_t;
1314 
1315 gzFile gzopen(const(char)* path, const(char)* mode);
1316 /*
1317      Open the gzip (.gz) file at path for reading and decompressing, or
1318    compressing and writing.  The mode parameter is as in fopen ("rb" or "wb")
1319    but can also include a compression level ("wb9") or a strategy: 'f' for
1320    filtered data as in "wb6f", 'h' for Huffman-only compression as in "wb1h",
1321    'R' for run-length encoding as in "wb1R", or 'F' for fixed code compression
1322    as in "wb9F".  (See the description of deflateInit2 for more information
1323    about the strategy parameter.)  'T' will request transparent writing or
1324    appending with no compression and not using the gzip format.
1325 
1326      "a" can be used instead of "w" to request that the gzip stream that will
1327    be written be appended to the file.  "+" will result in an error, since
1328    reading and writing to the same gzip file is not supported.  The addition of
1329    "x" when writing will create the file exclusively, which fails if the file
1330    already exists.  On systems that support it, the addition of "e" when
1331    reading or writing will set the flag to close the file on an execve() call.
1332 
1333      These functions, as well as gzip, will read and decode a sequence of gzip
1334    streams in a file.  The append function of gzopen() can be used to create
1335    such a file.  (Also see gzflush() for another way to do this.)  When
1336    appending, gzopen does not test whether the file begins with a gzip stream,
1337    nor does it look for the end of the gzip streams to begin appending.  gzopen
1338    will simply append a gzip stream to the existing file.
1339 
1340      gzopen can be used to read a file which is not in gzip format; in this
1341    case gzread will directly read from the file without decompression.  When
1342    reading, this will be detected automatically by looking for the magic two-
1343    byte gzip header.
1344 
1345      gzopen returns NULL if the file could not be opened, if there was
1346    insufficient memory to allocate the gzFile state, or if an invalid mode was
1347    specified (an 'r', 'w', or 'a' was not provided, or '+' was provided).
1348    errno can be checked to determine if the reason gzopen failed was that the
1349    file could not be opened.
1350 */
1351 
1352 gzFile gzdopen(int fd, const(char)* mode);
1353 /*
1354      Associate a gzFile with the file descriptor fd.  File descriptors are
1355    obtained from calls like open, dup, creat, pipe or fileno (if the file has
1356    been previously opened with fopen).  The mode parameter is as in gzopen.
1357 
1358      The next call of gzclose on the returned gzFile will also close the file
1359    descriptor fd, just like fclose(fdopen(fd, mode)) closes the file descriptor
1360    fd.  If you want to keep fd open, use fd = dup(fd_keep); gz = gzdopen(fd,
1361    mode);.  The duplicated descriptor should be saved to avoid a leak, since
1362    gzdopen does not close fd if it fails.  If you are using fileno() to get the
1363    file descriptor from a FILE *, then you will have to use dup() to avoid
1364    double-close()ing the file descriptor.  Both gzclose() and fclose() will
1365    close the associated file descriptor, so they need to have different file
1366    descriptors.
1367 
1368      gzdopen returns NULL if there was insufficient memory to allocate the
1369    gzFile state, if an invalid mode was specified (an 'r', 'w', or 'a' was not
1370    provided, or '+' was provided), or if fd is -1.  The file descriptor is not
1371    used until the next gz* read, write, seek, or close operation, so gzdopen
1372    will not detect if fd is invalid (unless fd is -1).
1373 */
1374 
1375 int gzbuffer(gzFile file, uint size);
1376 /*
1377      Set the internal buffer size used by this library's functions for file to
1378    size.  The default buffer size is 8192 bytes.  This function must be called
1379    after gzopen() or gzdopen(), and before any other calls that read or write
1380    the file.  The buffer memory allocation is always deferred to the first read
1381    or write.  Three times that size in buffer space is allocated.  A larger
1382    buffer size of, for example, 64K or 128K bytes will noticeably increase the
1383    speed of decompression (reading).
1384 
1385      The new buffer size also affects the maximum length for gzprintf().
1386 
1387      gzbuffer() returns 0 on success, or -1 on failure, such as being called
1388    too late.
1389 */
1390 
1391 int gzsetparams(gzFile file, int level, int strategy);
1392 /*
1393      Dynamically update the compression level and strategy for file.  See the
1394    description of deflateInit2 for the meaning of these parameters. Previously
1395    provided data is flushed before applying the parameter changes.
1396 
1397      gzsetparams returns Z_OK if success, Z_STREAM_ERROR if the file was not
1398    opened for writing, Z_ERRNO if there is an error writing the flushed data,
1399    or Z_MEM_ERROR if there is a memory allocation error.
1400 */
1401 
1402 int gzread(gzFile file, void* buf, uint len);
1403 /*
1404      Read and decompress up to len uncompressed bytes from file into buf.  If
1405    the input file is not in gzip format, gzread copies the given number of
1406    bytes into the buffer directly from the file.
1407 
1408      After reaching the end of a gzip stream in the input, gzread will continue
1409    to read, looking for another gzip stream.  Any number of gzip streams may be
1410    concatenated in the input file, and will all be decompressed by gzread().
1411    If something other than a gzip stream is encountered after a gzip stream,
1412    that remaining trailing garbage is ignored (and no error is returned).
1413 
1414      gzread can be used to read a gzip file that is being concurrently written.
1415    Upon reaching the end of the input, gzread will return with the available
1416    data.  If the error code returned by gzerror is Z_OK or Z_BUF_ERROR, then
1417    gzclearerr can be used to clear the end of file indicator in order to permit
1418    gzread to be tried again.  Z_OK indicates that a gzip stream was completed
1419    on the last gzread.  Z_BUF_ERROR indicates that the input file ended in the
1420    middle of a gzip stream.  Note that gzread does not return -1 in the event
1421    of an incomplete gzip stream.  This error is deferred until gzclose(), which
1422    will return Z_BUF_ERROR if the last gzread ended in the middle of a gzip
1423    stream.  Alternatively, gzerror can be used before gzclose to detect this
1424    case.
1425 
1426      gzread returns the number of uncompressed bytes actually read, less than
1427    len for end of file, or -1 for error.  If len is too large to fit in an int,
1428    then nothing is read, -1 is returned, and the error state is set to
1429    Z_STREAM_ERROR.
1430 */
1431 
1432 z_size_t gzfread(void* buf, z_size_t size, z_size_t nitems, gzFile file);
1433 /*
1434      Read and decompress up to nitems items of size size from file into buf,
1435    otherwise operating as gzread() does.  This duplicates the interface of
1436    stdio's fread(), with size_t request and return types.  If the library
1437    defines size_t, then z_size_t is identical to size_t.  If not, then z_size_t
1438    is an unsigned integer type that can contain a pointer.
1439 
1440      gzfread() returns the number of full items read of size size, or zero if
1441    the end of the file was reached and a full item could not be read, or if
1442    there was an error.  gzerror() must be consulted if zero is returned in
1443    order to determine if there was an error.  If the multiplication of size and
1444    nitems overflows, i.e. the product does not fit in a z_size_t, then nothing
1445    is read, zero is returned, and the error state is set to Z_STREAM_ERROR.
1446 
1447      In the event that the end of file is reached and only a partial item is
1448    available at the end, i.e. the remaining uncompressed data length is not a
1449    multiple of size, then the final partial item is nevetheless read into buf
1450    and the end-of-file flag is set.  The length of the partial item read is not
1451    provided, but could be inferred from the result of gztell().  This behavior
1452    is the same as the behavior of fread() implementations in common libraries,
1453    but it prevents the direct use of gzfread() to read a concurrently written
1454    file, reseting and retrying on end-of-file, when size is not 1.
1455 */
1456 
1457 int gzwrite(gzFile file, void* buf, uint len);
1458 /*
1459      Compress and write the len uncompressed bytes at buf to file. gzwrite
1460    returns the number of uncompressed bytes written or 0 in case of error.
1461 */
1462 
1463 z_size_t gzfwrite(void* buf, z_size_t size, z_size_t nitems, gzFile file);
1464 /*
1465      Compress and write nitems items of size size from buf to file, duplicating
1466    the interface of stdio's fwrite(), with size_t request and return types.  If
1467    the library defines size_t, then z_size_t is identical to size_t.  If not,
1468    then z_size_t is an unsigned integer type that can contain a pointer.
1469 
1470      gzfwrite() returns the number of full items written of size size, or zero
1471    if there was an error.  If the multiplication of size and nitems overflows,
1472    i.e. the product does not fit in a z_size_t, then nothing is written, zero
1473    is returned, and the error state is set to Z_STREAM_ERROR.
1474 */
1475 
1476 int gzprintf(gzFile file, const(char)* format, ...);
1477 /*
1478      Convert, format, compress, and write the arguments (...) to file under
1479    control of the string format, as in fprintf.  gzprintf returns the number of
1480    uncompressed bytes actually written, or a negative zlib error code in case
1481    of error.  The number of uncompressed bytes written is limited to 8191, or
1482    one less than the buffer size given to gzbuffer().  The caller should assure
1483    that this limit is not exceeded.  If it is exceeded, then gzprintf() will
1484    return an error (0) with nothing written.  In this case, there may also be a
1485    buffer overflow with unpredictable consequences, which is possible only if
1486    zlib was compiled with the insecure functions sprintf() or vsprintf(),
1487    because the secure snprintf() or vsnprintf() functions were not available.
1488    This can be determined using zlibCompileFlags().
1489 */
1490 
1491 int gzputs(gzFile file, const(char)* s);
1492 /*
1493      Compress and write the given null-terminated string s to file, excluding
1494    the terminating null character.
1495 
1496      gzputs returns the number of characters written, or -1 in case of error.
1497 */
1498 
1499 const(char)* gzgets(gzFile file, const(char)* buf, int len);
1500 /*
1501      Read and decompress bytes from file into buf, until len-1 characters are
1502    read, or until a newline character is read and transferred to buf, or an
1503    end-of-file condition is encountered.  If any characters are read or if len
1504    is one, the string is terminated with a null character.  If no characters
1505    are read due to an end-of-file or len is less than one, then the buffer is
1506    left untouched.
1507 
1508      gzgets returns buf which is a null-terminated string, or it returns NULL
1509    for end-of-file or in case of error.  If there was an error, the contents at
1510    buf are indeterminate.
1511 */
1512 
1513 int gzputc(gzFile file, int c);
1514 /*
1515      Compress and write c, converted to an unsigned char, into file.  gzputc
1516    returns the value that was written, or -1 in case of error.
1517 */
1518 
1519 int gzgetc(gzFile file);
1520 /*
1521      Read and decompress one byte from file.  gzgetc returns this byte or -1
1522    in case of end of file or error.  This is implemented as a macro for speed.
1523    As such, it does not do all of the checking the other functions do.  I.e.
1524    it does not check to see if file is NULL, nor whether the structure file
1525    points to has been clobbered or not.
1526 */
1527 
1528 int gzungetc(int c, gzFile file);
1529 /*
1530      Push c back onto the stream for file to be read as the first character on
1531    the next read.  At least one character of push-back is always allowed.
1532    gzungetc() returns the character pushed, or -1 on failure.  gzungetc() will
1533    fail if c is -1, and may fail if a character has been pushed but not read
1534    yet.  If gzungetc is used immediately after gzopen or gzdopen, at least the
1535    output buffer size of pushed characters is allowed.  (See gzbuffer above.)
1536    The pushed character will be discarded if the stream is repositioned with
1537    gzseek() or gzrewind().
1538 */
1539 
1540 int gzflush(gzFile file, int flush);
1541 /*
1542      Flush all pending output to file.  The parameter flush is as in the
1543    deflate() function.  The return value is the zlib error number (see function
1544    gzerror below).  gzflush is only permitted when writing.
1545 
1546      If the flush parameter is Z_FINISH, the remaining data is written and the
1547    gzip stream is completed in the output.  If gzwrite() is called again, a new
1548    gzip stream will be started in the output.  gzread() is able to read such
1549    concatenated gzip streams.
1550 
1551      gzflush should be called only when strictly necessary because it will
1552    degrade compression if called too often.
1553 */
1554 
1555 z_off_t gzseek(gzFile file, z_off_t offset, int whence);
1556 /*
1557      Set the starting position to offset relative to whence for the next gzread
1558    or gzwrite on file.  The offset represents a number of bytes in the
1559    uncompressed data stream.  The whence parameter is defined as in lseek(2);
1560    the value SEEK_END is not supported.
1561 
1562      If the file is opened for reading, this function is emulated but can be
1563    extremely slow.  If the file is opened for writing, only forward seeks are
1564    supported; gzseek then compresses a sequence of zeroes up to the new
1565    starting position.
1566 
1567      gzseek returns the resulting offset location as measured in bytes from
1568    the beginning of the uncompressed stream, or -1 in case of error, in
1569    particular if the file is opened for writing and the new starting position
1570    would be before the current position.
1571 */
1572 
1573 int gzrewind(gzFile file);
1574 /*
1575      Rewind file. This function is supported only for reading.
1576 
1577      gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET).
1578 */
1579 
1580 z_off_t gztell(gzFile file);
1581 /*
1582      Return the starting position for the next gzread or gzwrite on file.
1583    This position represents a number of bytes in the uncompressed data stream,
1584    and is zero when starting, even if appending or reading a gzip stream from
1585    the middle of a file using gzdopen().
1586 
1587      gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
1588 */
1589 
1590 z_off_t gzoffset(gzFile file);
1591 /*
1592      Return the current compressed (actual) read or write offset of file.  This
1593    offset includes the count of bytes that precede the gzip stream, for example
1594    when appending or when using gzdopen() for reading.  When reading, the
1595    offset does not include as yet unused buffered input.  This information can
1596    be used for a progress indicator.  On error, gzoffset() returns -1.
1597 */
1598 
1599 int gzeof(gzFile file);
1600 /*
1601      Return true (1) if the end-of-file indicator for file has been set while
1602    reading, false (0) otherwise.  Note that the end-of-file indicator is set
1603    only if the read tried to go past the end of the input, but came up short.
1604    Therefore, just like feof(), gzeof() may return false even if there is no
1605    more data to read, in the event that the last read request was for the exact
1606    number of bytes remaining in the input file.  This will happen if the input
1607    file size is an exact multiple of the buffer size.
1608 
1609      If gzeof() returns true, then the read functions will return no more data,
1610    unless the end-of-file indicator is reset by gzclearerr() and the input file
1611    has grown since the previous end of file was detected.
1612 */
1613 
1614 int gzdirect(gzFile file);
1615 /*
1616      Return true (1) if file is being copied directly while reading, or false
1617    (0) if file is a gzip stream being decompressed.
1618 
1619      If the input file is empty, gzdirect() will return true, since the input
1620    does not contain a gzip stream.
1621 
1622      If gzdirect() is used immediately after gzopen() or gzdopen() it will
1623    cause buffers to be allocated to allow reading the file to determine if it
1624    is a gzip file.  Therefore if gzbuffer() is used, it should be called before
1625    gzdirect().
1626 
1627      When writing, gzdirect() returns true (1) if transparent writing was
1628    requested ("wT" for the gzopen() mode), or false (0) otherwise.  (Note:
1629    gzdirect() is not needed when writing.  Transparent writing must be
1630    explicitly requested, so the application already knows the answer.  When
1631    linking statically, using gzdirect() will include all of the zlib code for
1632    gzip file reading and decompression, which may not be desired.)
1633 */
1634 
1635 int gzclose(gzFile file);
1636 /*
1637      Flush all pending output for file, if necessary, close file and
1638    deallocate the (de)compression state.  Note that once file is closed, you
1639    cannot call gzerror with file, since its structures have been deallocated.
1640    gzclose must not be called more than once on the same file, just as free
1641    must not be called more than once on the same allocation.
1642 
1643      gzclose will return Z_STREAM_ERROR if file is not valid, Z_ERRNO on a
1644    file operation error, Z_MEM_ERROR if out of memory, Z_BUF_ERROR if the
1645    last read ended in the middle of a gzip stream, or Z_OK on success.
1646 */
1647 
1648 int gzclose_r(gzFile file);
1649 int gzclose_w(gzFile file);
1650 /*
1651      Same as gzclose(), but gzclose_r() is only for use when reading, and
1652    gzclose_w() is only for use when writing or appending.  The advantage to
1653    using these instead of gzclose() is that they avoid linking in zlib
1654    compression or decompression code that is not used when only reading or only
1655    writing respectively.  If gzclose() is used, then both compression and
1656    decompression code will be included the application when linking to a static
1657    zlib library.
1658 */
1659 
1660 const(char)* gzerror(gzFile file, int* errnum);
1661 /*
1662      Return the error message for the last error which occurred on file.
1663    errnum is set to zlib error number.  If an error occurred in the file system
1664    and not in the compression library, errnum is set to Z_ERRNO and the
1665    application may consult errno to get the exact error code.
1666 
1667      The application must not modify the returned string.  Future calls to
1668    this function may invalidate the previously returned string.  If file is
1669    closed, then the string previously returned by gzerror will no longer be
1670    available.
1671 
1672      gzerror() should be used to distinguish errors from end-of-file for those
1673    functions above that do not distinguish those cases in their return values.
1674 */
1675 
1676 void gzclearerr(gzFile file);
1677 /*
1678      Clear the error and end-of-file flags for file.  This is analogous to the
1679    clearerr() function in stdio.  This is useful for continuing to read a gzip
1680    file that is being written concurrently.
1681 */
1682 
1683                         /* checksum functions */
1684 
1685 /*
1686      These functions are not related to compression but are exported
1687    anyway because they might be useful in applications using the compression
1688    library.
1689 */
1690 
1691 uint adler32(uint adler, const(ubyte)* buf, uint len);
1692 /*
1693      Update a running Adler-32 checksum with the bytes buf[0 .. len-1] and
1694    return the updated checksum. An Adler-32 value is in the range of a 32-bit
1695    unsigned integer. If buf is Z_NULL, this function returns the required
1696    initial value for the checksum.
1697 
1698      An Adler-32 checksum is almost as reliable as a CRC-32 but can be computed
1699    much faster.
1700 
1701    Usage example:
1702 
1703      uLong adler = adler32(0L, Z_NULL, 0);
1704 
1705      while (read_buffer(buffer, length) != EOF)
1706        adler = adler32(adler, buffer, length);
1707 
1708      if (adler != original_adler) error();
1709 */
1710 
1711 uint adler32_z (uint adler, const(ubyte)* buf, z_size_t len);
1712 /*
1713      Same as adler32(), but with a size_t length.
1714 */
1715 
1716 uint adler32_combine(uint adler1, uint adler2, z_off_t len2);
1717 /*
1718      Combine two Adler-32 checksums into one.  For two sequences of bytes, seq1
1719    and seq2 with lengths len1 and len2, Adler-32 checksums were calculated for
1720    each, adler1 and adler2.  adler32_combine() returns the Adler-32 checksum of
1721    seq1 and seq2 concatenated, requiring only adler1, adler2, and len2.  Note
1722    that the z_off_t type (like off_t) is a signed integer.  If len2 is
1723    negative, the result has no meaning or utility.
1724 */
1725 
1726 uint crc32(uint crc, const(ubyte)* buf, uint len);
1727 /*
1728      Update a running CRC-32 with the bytes buf[0 .. len-1] and return the
1729    updated CRC-32. A CRC-32 value is in the range of a 32-bit unsigned integer.
1730    If buf is Z_NULL, this function returns the required initial value for the
1731    crc. Pre- and post-conditioning (one's complement) is performed within this
1732    function so it shouldn't be done by the application.
1733 
1734    Usage example:
1735 
1736      uLong crc = crc32(0L, Z_NULL, 0);
1737 
1738      while (read_buffer(buffer, length) != EOF)
1739        crc = crc32(crc, buffer, length);
1740 
1741      if (crc != original_crc) error();
1742 */
1743 
1744 uint crc32_z(uint crc, const(ubyte)* buf, z_size_t len);
1745 /*
1746      Same as crc32(), but with a size_t length.
1747 */
1748 
1749 uint crc32_combine(uint crc1, uint crc2, z_off_t len2);
1750 
1751 /*
1752      Combine two CRC-32 check values into one.  For two sequences of bytes,
1753    seq1 and seq2 with lengths len1 and len2, CRC-32 check values were
1754    calculated for each, crc1 and crc2.  crc32_combine() returns the CRC-32
1755    check value of seq1 and seq2 concatenated, requiring only crc1, crc2, and
1756    len2.
1757 */
1758 
1759 uint crc32_combine_gen(z_off_t len2);
1760 /*
1761      Return the operator corresponding to length len2, to be used with
1762    crc32_combine_op().
1763 */
1764 
1765 uint crc32_combine_op(uint crc1, uint crc2, uint op);
1766 /*
1767      Give the same result as crc32_combine(), using op in place of len2. op is
1768    is generated from len2 by crc32_combine_gen(). This will be faster than
1769    crc32_combine() if the generated op is used more than once.
1770 */
1771 
1772                         /* various hacks, don't look :) */
1773 
1774 /* deflateInit and inflateInit are macros to allow checking the zlib version
1775  * and the compiler's view of z_stream:
1776  */
1777 int deflateInit_(z_streamp strm,
1778                  int level,
1779                  const(char)* versionx,
1780                  int stream_size);
1781 
1782 int inflateInit_(z_streamp strm,
1783                  const(char)* versionx,
1784                  int stream_size);
1785 
1786 int deflateInit2_(z_streamp strm,
1787                   int level,
1788                   int method,
1789                   int windowBits,
1790                   int memLevel,
1791                   int strategy,
1792                   const(char)* versionx,
1793                   int stream_size);
1794 
1795 int inflateBackInit_(z_stream* strm,
1796                      int windowBits,
1797                      ubyte* window,
1798                      const(char)* z_version,
1799                      int stream_size);
1800 
1801 int inflateInit2_(z_streamp strm,
1802                   int windowBits,
1803                   const(char)* versionx,
1804                   int stream_size);
1805 
1806 const(char)* zError(int err);
1807 int inflateSyncPoint(z_streamp z);
1808 const(uint)* get_crc_table();