zlib - Chicken - SWIG example

# zlib - Chicken - SWIG

## Table of Contents

Building the example
zlib.h
How the zlib wrapper was developed

## Building the example

zlib must be installed for this example to work.
Just type `make` to build this example.
If zlib is not installed in /usr/lib and /usr/include, then do something similar to the following:

>     make SWIGOPT="-I/usr/local/include" LIBS="-L/usr/local/lib -lz"

## zlib.h

>     001: /* zlib.h -- interface of the 'zlib' general purpose compression library
>     002:   version 1.1.4, March 11th, 2002
>     003:
>     004:   Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler
>     005:
>     006:   This software is provided 'as-is', without any express or implied
>     007:   warranty.  In no event will the authors be held liable for any damages
>     008:   arising from the use of this software.
>     009:
>     010:   Permission is granted to anyone to use this software for any purpose,
>     011:   including commercial applications, and to alter it and redistribute it
>     012:   freely, subject to the following restrictions:
>     013:
>     014:   1. The origin of this software must not be misrepresented; you must not
>     015:      claim that you wrote the original software. If you use this software
>     016:      in a product, an acknowledgment in the product documentation would be
>     017:      appreciated but is not required.
>     018:   2. Altered source versions must be plainly marked as such, and must not be
>     019:      misrepresented as being the original software.
>     020:   3. This notice may not be removed or altered from any source distribution.
>     021:
>     022:   Jean-loup Gailly        Mark Adler
>     023:   jloup@gzip.org          madler@alumni.caltech.edu
>     024:
>     025:
>     026:   The data format used by the zlib library is described by RFCs (Request for
>     027:   Comments) 1950 to 1952 in the files ftp://ds.internic.net/rfc/rfc1950.txt
>     028:   (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
>     029: */
>     030:
>     031: #ifndef _ZLIB_H
>     032: #define _ZLIB_H
>     033:
>     034: #include "zconf.h"
>     035:
>     036: #ifdef __cplusplus
>     037: extern "C" {
>     038: #endif
>     039:
>     040: #define ZLIB_VERSION "1.1.4"
>     041:
>     042: /*
>     043:      The 'zlib' compression library provides in-memory compression and
>     044:   decompression functions, including integrity checks of the uncompressed
>     045:   data.  This version of the library supports only one compression method
>     046:   (deflation) but other algorithms will be added later and will have the same
>     047:   stream interface.
>     048:
>     049:      Compression can be done in a single step if the buffers are large
>     050:   enough (for example if an input file is mmap'ed), or can be done by
>     051:   repeated calls of the compression function.  In the latter case, the
>     052:   application must provide more input and/or consume the output
>     053:   (providing more output space) before each call.
>     054:
>     055:      The library also supports reading and writing files in gzip (.gz) format
>     056:   with an interface similar to that of stdio.
>     057:
>     058:      The library does not install any signal handler. The decoder checks
>     059:   the consistency of the compressed data, so the library should never
>     060:   crash even in case of corrupted input.
>     061: */
>     062:
>     063: typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
>     064: typedef void   (*free_func)  OF((voidpf opaque, voidpf address));
>     065:
>     066: struct internal_state;
>     067:
>     068: typedef struct z_stream_s {
>     069:     Bytef    *next_in;  /* next input byte */
>     070:     uInt     avail_in;  /* number of bytes available at next_in */
>     071:     uLong    total_in;  /* total nb of input bytes read so far */
>     072:
>     073:     Bytef    *next_out; /* next output byte should be put there */
>     074:     uInt     avail_out; /* remaining free space at next_out */
>     075:     uLong    total_out; /* total nb of bytes output so far */
>     076:
>     077:     char     *msg;      /* last error message, NULL if no error */
>     078:     struct internal_state FAR *state; /* not visible by applications */
>     079:
>     080:     alloc_func zalloc;  /* used to allocate the internal state */
>     081:     free_func  zfree;   /* used to free the internal state */
>     082:     voidpf     opaque;  /* private data object passed to zalloc and zfree */
>     083:
>     084:     int     data_type;  /* best guess about the data type: ascii or binary */
>     085:     uLong   adler;      /* adler32 value of the uncompressed data */
>     086:     uLong   reserved;   /* reserved for future use */
>     087: } z_stream;
>     088:
>     089: typedef z_stream FAR *z_streamp;
>     090:
>     091: /*
>     092:    The application must update next_in and avail_in when avail_in has
>     093:    dropped to zero. It must update next_out and avail_out when avail_out
>     094:    has dropped to zero. The application must initialize zalloc, zfree and
>     095:    opaque before calling the init function. All other fields are set by the
>     096:    compression library and must not be updated by the application.
>     097:
>     098:    The opaque value provided by the application will be passed as the first
>     099:    parameter for calls of zalloc and zfree. This can be useful for custom
>     100:    memory management. The compression library attaches no meaning to the
>     101:    opaque value.
>     102:
>     103:    zalloc must return Z_NULL if there is not enough memory for the object.
>     104:    If zlib is used in a multi-threaded application, zalloc and zfree must be
>     105:    thread safe.
>     106:
>     107:    On 16-bit systems, the functions zalloc and zfree must be able to allocate
>     108:    exactly 65536 bytes, but will not be required to allocate more than this
>     109:    if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
>     110:    pointers returned by zalloc for objects of exactly 65536 bytes *must*
>     111:    have their offset normalized to zero. The default allocation function
>     112:    provided by this library ensures this (see zutil.c). To reduce memory
>     113:    requirements and avoid any allocation of 64K objects, at the expense of
>     114:    compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
>     115:
>     116:    The fields total_in and total_out can be used for statistics or
>     117:    progress reports. After compression, total_in holds the total size of
>     118:    the uncompressed data and may be saved for use in the decompressor
>     119:    (particularly if the decompressor wants to decompress everything in
>     120:    a single step).
>     121: */
>     122:
>     123:                         /* constants */
>     124:
>     125: #define Z_NO_FLUSH      0
>     126: #define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */
>     127: #define Z_SYNC_FLUSH    2
>     128: #define Z_FULL_FLUSH    3
>     129: #define Z_FINISH        4
>     130: /* Allowed flush values; see deflate() below for details */
>     131:
>     132: #define Z_OK            0
>     133: #define Z_STREAM_END    1
>     134: #define Z_NEED_DICT     2
>     135: #define Z_ERRNO        (-1)
>     136: #define Z_STREAM_ERROR (-2)
>     137: #define Z_DATA_ERROR   (-3)
>     138: #define Z_MEM_ERROR    (-4)
>     139: #define Z_BUF_ERROR    (-5)
>     140: #define Z_VERSION_ERROR (-6)
>     141: /* Return codes for the compression/decompression functions. Negative
>     142:  * values are errors, positive values are used for special but normal events.
>     143:  */
>     144:
>     145: #define Z_NO_COMPRESSION         0
>     146: #define Z_BEST_SPEED             1
>     147: #define Z_BEST_COMPRESSION       9
>     148: #define Z_DEFAULT_COMPRESSION  (-1)
>     149: /* compression levels */
>     150:
>     151: #define Z_FILTERED            1
>     152: #define Z_HUFFMAN_ONLY        2
>     153: #define Z_DEFAULT_STRATEGY    0
>     154: /* compression strategy; see deflateInit2() below for details */
>     155:
>     156: #define Z_BINARY   0
>     157: #define Z_ASCII    1
>     158: #define Z_UNKNOWN  2
>     159: /* Possible values of the data_type field */
>     160:
>     161: #define Z_DEFLATED   8
>     162: /* The deflate compression method (the only one supported in this version) */
>     163:
>     164: #define Z_NULL  0  /* for initializing zalloc, zfree, opaque */
>     165:
>     166: #define zlib_version zlibVersion()
>     167: /* for compatibility with versions < 1.0.2 */
>     168:
>     169:                         /* basic functions */
>     170:
>     171: ZEXTERN const char * ZEXPORT zlibVersion OF((void));
>     172: /* The application can compare zlibVersion and ZLIB_VERSION for consistency.
>     173:    If the first character differs, the library code actually used is
>     174:    not compatible with the zlib.h header file used by the application.
>     175:    This check is automatically made by deflateInit and inflateInit.
>     176:  */
>     177:
>     178: /*
>     179: ZEXTERN int ZEXPORT deflateInit OF((z_streamp strm, int level));
>     180:
>     181:      Initializes the internal stream state for compression. The fields
>     182:    zalloc, zfree and opaque must be initialized before by the caller.
>     183:    If zalloc and zfree are set to Z_NULL, deflateInit updates them to
>     184:    use default allocation functions.
>     185:
>     186:      The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
>     187:    1 gives best speed, 9 gives best compression, 0 gives no compression at
>     188:    all (the input data is simply copied a block at a time).
>     189:    Z_DEFAULT_COMPRESSION requests a default compromise between speed and
>     190:    compression (currently equivalent to level 6).
>     191:
>     192:      deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
>     193:    enough memory, Z_STREAM_ERROR if level is not a valid compression level,
>     194:    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
>     195:    with the version assumed by the caller (ZLIB_VERSION).
>     196:    msg is set to null if there is no error message.  deflateInit does not
>     197:    perform any compression: this will be done by deflate().
>     198: */
>     199:
>     200:
>     201: ZEXTERN int ZEXPORT deflate OF((z_streamp strm, int flush));
>     202: /*
>     203:     deflate compresses as much data as possible, and stops when the input
>     204:   buffer becomes empty or the output buffer becomes full. It may introduce some
>     205:   output latency (reading input without producing any output) except when
>     206:   forced to flush.
>     207:
>     208:     The detailed semantics are as follows. deflate performs one or both of the
>     209:   following actions:
>     210:
>     211:   - Compress more input starting at next_in and update next_in and avail_in
>     212:     accordingly. If not all input can be processed (because there is not
>     213:     enough room in the output buffer), next_in and avail_in are updated and
>     214:     processing will resume at this point for the next call of deflate().
>     215:
>     216:   - Provide more output starting at next_out and update next_out and avail_out
>     217:     accordingly. This action is forced if the parameter flush is non zero.
>     218:     Forcing flush frequently degrades the compression ratio, so this parameter
>     219:     should be set only when necessary (in interactive applications).
>     220:     Some output may be provided even if flush is not set.
>     221:
>     222:   Before the call of deflate(), the application should ensure that at least
>     223:   one of the actions is possible, by providing more input and/or consuming
>     224:   more output, and updating avail_in or avail_out accordingly; avail_out
>     225:   should never be zero before the call. The application can consume the
>     226:   compressed output when it wants, for example when the output buffer is full
>     227:   (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK
>     228:   and with zero avail_out, it must be called again after making room in the
>     229:   output buffer because there might be more output pending.
>     230:
>     231:     If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
>     232:   flushed to the output buffer and the output is aligned on a byte boundary, so
>     233:   that the decompressor can get all input data available so far. (In particular
>     234:   avail_in is zero after the call if enough output space has been provided
>     235:   before the call.)  Flushing may degrade compression for some compression
>     236:   algorithms and so it should be used only when necessary.
>     237:
>     238:     If flush is set to Z_FULL_FLUSH, all output is flushed as with
>     239:   Z_SYNC_FLUSH, and the compression state is reset so that decompression can
>     240:   restart from this point if previous compressed data has been damaged or if
>     241:   random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
>     242:   the compression.
>     243:
>     244:     If deflate returns with avail_out == 0, this function must be called again
>     245:   with the same value of the flush parameter and more output space (updated
>     246:   avail_out), until the flush is complete (deflate returns with non-zero
>     247:   avail_out).
>     248:
>     249:     If the parameter flush is set to Z_FINISH, pending input is processed,
>     250:   pending output is flushed and deflate returns with Z_STREAM_END if there
>     251:   was enough output space; if deflate returns with Z_OK, this function must be
>     252:   called again with Z_FINISH and more output space (updated avail_out) but no
>     253:   more input data, until it returns with Z_STREAM_END or an error. After
>     254:   deflate has returned Z_STREAM_END, the only possible operations on the
>     255:   stream are deflateReset or deflateEnd.
>     256:
>     257:     Z_FINISH can be used immediately after deflateInit if all the compression
>     258:   is to be done in a single step. In this case, avail_out must be at least
>     259:   0.1% larger than avail_in plus 12 bytes.  If deflate does not return
>     260:   Z_STREAM_END, then it must be called again as described above.
>     261:
>     262:     deflate() sets strm->adler to the adler32 checksum of all input read
>     263:   so far (that is, total_in bytes).
>     264:
>     265:     deflate() may update data_type if it can make a good guess about
>     266:   the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
>     267:   binary. This field is only for information purposes and does not affect
>     268:   the compression algorithm in any manner.
>     269:
>     270:     deflate() returns Z_OK if some progress has been made (more input
>     271:   processed or more output produced), Z_STREAM_END if all input has been
>     272:   consumed and all output has been produced (only when flush is set to
>     273:   Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
>     274:   if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible
>     275:   (for example avail_in or avail_out was zero).
>     276: */
>     277:
>     278:
>     279: ZEXTERN int ZEXPORT deflateEnd OF((z_streamp strm));
>     280: /*
>     281:      All dynamically allocated data structures for this stream are freed.
>     282:    This function discards any unprocessed input and does not flush any
>     283:    pending output.
>     284:
>     285:      deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
>     286:    stream state was inconsistent, Z_DATA_ERROR if the stream was freed
>     287:    prematurely (some input or output was discarded). In the error case,
>     288:    msg may be set but then points to a static string (which must not be
>     289:    deallocated).
>     290: */
>     291:
>     292:
>     293: /*
>     294: ZEXTERN int ZEXPORT inflateInit OF((z_streamp strm));
>     295:
>     296:      Initializes the internal stream state for decompression. The fields
>     297:    next_in, avail_in, zalloc, zfree and opaque must be initialized before by
>     298:    the caller. If next_in is not Z_NULL and avail_in is large enough (the exact
>     299:    value depends on the compression method), inflateInit determines the
>     300:    compression method from the zlib header and allocates all data structures
>     301:    accordingly; otherwise the allocation will be deferred to the first call of
>     302:    inflate.  If zalloc and zfree are set to Z_NULL, inflateInit updates them to
>     303:    use default allocation functions.
>     304:
>     305:      inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
>     306:    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
>     307:    version assumed by the caller.  msg is set to null if there is no error
>     308:    message. inflateInit does not perform any decompression apart from reading
>     309:    the zlib header if present: this will be done by inflate().  (So next_in and
>     310:    avail_in may be modified, but next_out and avail_out are unchanged.)
>     311: */
>     312:
>     313:
>     314: ZEXTERN int ZEXPORT inflate OF((z_streamp strm, int flush));
>     315: /*
>     316:     inflate decompresses as much data as possible, and stops when the input
>     317:   buffer becomes empty or the output buffer becomes full. It may some
>     318:   introduce some output latency (reading input without producing any output)
>     319:   except when forced to flush.
>     320:
>     321:   The detailed semantics are as follows. inflate performs one or both of the
>     322:   following actions:
>     323:
>     324:   - Decompress more input starting at next_in and update next_in and avail_in
>     325:     accordingly. If not all input can be processed (because there is not
>     326:     enough room in the output buffer), next_in is updated and processing
>     327:     will resume at this point for the next call of inflate().
>     328:
>     329:   - Provide more output starting at next_out and update next_out and avail_out
>     330:     accordingly.  inflate() provides as much output as possible, until there
>     331:     is no more input data or no more space in the output buffer (see below
>     332:     about the flush parameter).
>     333:
>     334:   Before the call of inflate(), the application should ensure that at least
>     335:   one of the actions is possible, by providing more input and/or consuming
>     336:   more output, and updating the next_* and avail_* values accordingly.
>     337:   The application can consume the uncompressed output when it wants, for
>     338:   example when the output buffer is full (avail_out == 0), or after each
>     339:   call of inflate(). If inflate returns Z_OK and with zero avail_out, it
>     340:   must be called again after making room in the output buffer because there
>     341:   might be more output pending.
>     342:
>     343:     If the parameter flush is set to Z_SYNC_FLUSH, inflate flushes as much
>     344:   output as possible to the output buffer. The flushing behavior of inflate is
>     345:   not specified for values of the flush parameter other than Z_SYNC_FLUSH
>     346:   and Z_FINISH, but the current implementation actually flushes as much output
>     347:   as possible anyway.
>     348:
>     349:     inflate() should normally be called until it returns Z_STREAM_END or an
>     350:   error. However if all decompression is to be performed in a single step
>     351:   (a single call of inflate), the parameter flush should be set to
>     352:   Z_FINISH. In this case all pending input is processed and all pending
>     353:   output is flushed; avail_out must be large enough to hold all the
>     354:   uncompressed data. (The size of the uncompressed data may have been saved
>     355:   by the compressor for this purpose.) The next operation on this stream must
>     356:   be inflateEnd to deallocate the decompression state. The use of Z_FINISH
>     357:   is never required, but can be used to inform inflate that a faster routine
>     358:   may be used for the single inflate() call.
>     359:
>     360:      If a preset dictionary is needed at this point (see inflateSetDictionary
>     361:   below), inflate sets strm-adler to the adler32 checksum of the
>     362:   dictionary chosen by the compressor and returns Z_NEED_DICT; otherwise
>     363:   it sets strm->adler to the adler32 checksum of all output produced
>     364:   so far (that is, total_out bytes) and returns Z_OK, Z_STREAM_END or
>     365:   an error code as described below. At the end of the stream, inflate()
>     366:   checks that its computed adler32 checksum is equal to that saved by the
>     367:   compressor and returns Z_STREAM_END only if the checksum is correct.
>     368:
>     369:     inflate() returns Z_OK if some progress has been made (more input processed
>     370:   or more output produced), Z_STREAM_END if the end of the compressed data has
>     371:   been reached and all uncompressed output has been produced, Z_NEED_DICT if a
>     372:   preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
>     373:   corrupted (input stream not conforming to the zlib format or incorrect
>     374:   adler32 checksum), Z_STREAM_ERROR if the stream structure was inconsistent
>     375:   (for example if next_in or next_out was NULL), Z_MEM_ERROR if there was not
>     376:   enough memory, Z_BUF_ERROR if no progress is possible or if there was not
>     377:   enough room in the output buffer when Z_FINISH is used. In the Z_DATA_ERROR
>     378:   case, the application may then call inflateSync to look for a good
>     379:   compression block.
>     380: */
>     381:
>     382:
>     383: ZEXTERN int ZEXPORT inflateEnd OF((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
>     387:    pending output.
>     388:
>     389:      inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
>     390:    was inconsistent. In the error case, msg may be set but then points to a
>     391:    static string (which must not be deallocated).
>     392: */
>     393:
>     394:                         /* Advanced functions */
>     395:
>     396: /*
>     397:     The following functions are needed only in some special applications.
>     398: */
>     399:
>     400: /*
>     401: ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,
>     402:                                      int  level,
>     403:                                      int  method,
>     404:                                      int  windowBits,
>     405:                                      int  memLevel,
>     406:                                      int  strategy));
>     407:
>     408:      This is another version of deflateInit with more compression options. The
>     409:    fields next_in, zalloc, zfree and opaque must be initialized before by
>     410:    the caller.
>     411:
>     412:      The method parameter is the compression method. It must be Z_DEFLATED in
>     413:    this version of the library.
>     414:
>     415:      The windowBits parameter is the base two logarithm of the window size
>     416:    (the size of the history buffer).  It should be in the range 8..15 for this
>     417:    version of the library. Larger values of this parameter result in better
>     418:    compression at the expense of memory usage. The default value is 15 if
>     419:    deflateInit is used instead.
>     420:
>     421:      The memLevel parameter specifies how much memory should be allocated
>     422:    for the internal compression state. memLevel=1 uses minimum memory but
>     423:    is slow and reduces compression ratio; memLevel=9 uses maximum memory
>     424:    for optimal speed. The default value is 8. See zconf.h for total memory
>     425:    usage as a function of windowBits and memLevel.
>     426:
>     427:      The strategy parameter is used to tune the compression algorithm. Use the
>     428:    value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
>     429:    filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman encoding only (no
>     430:    string match).  Filtered data consists mostly of small values with a
>     431:    somewhat random distribution. In this case, the compression algorithm is
>     432:    tuned to compress them better. The effect of Z_FILTERED is to force more
>     433:    Huffman coding and less string matching; it is somewhat intermediate
>     434:    between Z_DEFAULT and Z_HUFFMAN_ONLY. The strategy parameter only affects
>     435:    the compression ratio but not the correctness of the compressed output even
>     436:    if it is not set appropriately.
>     437:
>     438:       deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
>     439:    memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
>     440:    method). msg is set to null if there is no error message.  deflateInit2 does
>     441:    not perform any compression: this will be done by deflate().
>     442: */
>     443:
>     444: ZEXTERN int ZEXPORT deflateSetDictionary OF((z_streamp strm,
>     445:                                              const Bytef *dictionary,
>     446:                                              uInt  dictLength));
>     447: /*
>     448:      Initializes the compression dictionary from the given byte sequence
>     449:    without producing any compressed output. This function must be called
>     450:    immediately after deflateInit, deflateInit2 or deflateReset, before any
>     451:    call of deflate. The compressor and decompressor must use exactly the same
>     452:    dictionary (see inflateSetDictionary).
>     453:
>     454:      The dictionary should consist of strings (byte sequences) that are likely
>     455:    to be encountered later in the data to be compressed, with the most commonly
>     456:    used strings preferably put towards the end of the dictionary. Using a
>     457:    dictionary is most useful when the data to be compressed is short and can be
>     458:    predicted with good accuracy; the data can then be compressed better than
>     459:    with the default empty dictionary.
>     460:
>     461:      Depending on the size of the compression data structures selected by
>     462:    deflateInit or deflateInit2, a part of the dictionary may in effect be
>     463:    discarded, for example if the dictionary is larger than the window size in
>     464:    deflate or deflate2. Thus the strings most likely to be useful should be
>     465:    put at the end of the dictionary, not at the front.
>     466:
>     467:      Upon return of this function, strm->adler is set to the Adler32 value
>     468:    of the dictionary; the decompressor may later use this value to determine
>     469:    which dictionary has been used by the compressor. (The Adler32 value
>     470:    applies to the whole dictionary even if only a subset of the dictionary is
>     471:    actually used by the compressor.)
>     472:
>     473:      deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
>     474:    parameter is invalid (such as NULL dictionary) or the stream state is
>     475:    inconsistent (for example if deflate has already been called for this stream
>     476:    or if the compression method is bsort). deflateSetDictionary does not
>     477:    perform any compression: this will be done by deflate().
>     478: */
>     479:
>     480: ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest,
>     481:                                     z_streamp source));
>     482: /*
>     483:      Sets the destination stream as a complete copy of the source stream.
>     484:
>     485:      This function can be useful when several compression strategies will be
>     486:    tried, for example when there are several ways of pre-processing the input
>     487:    data with a filter. The streams that will be discarded should then be freed
>     488:    by calling deflateEnd.  Note that deflateCopy duplicates the internal
>     489:    compression state which can be quite large, so this strategy is slow and
>     490:    can consume lots of memory.
>     491:
>     492:      deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
>     493:    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
>     494:    (such as zalloc being NULL). msg is left unchanged in both source and
>     495:    destination.
>     496: */
>     497:
>     498: ZEXTERN int ZEXPORT deflateReset OF((z_streamp strm));
>     499: /*
>     500:      This function is equivalent to deflateEnd followed by deflateInit,
>     501:    but does not free and reallocate all the internal compression state.
>     502:    The stream will keep the same compression level and any other attributes
>     503:    that may have been set by deflateInit2.
>     504:
>     505:       deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
>     506:    stream state was inconsistent (such as zalloc or state being NULL).
>     507: */
>     508:
>     509: ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm,
>     510: 				      int level,
>     511: 				      int strategy));
>     512: /*
>     513:      Dynamically update the compression level and compression strategy.  The
>     514:    interpretation of level and strategy is as in deflateInit2.  This can be
>     515:    used to switch between compression and straight copy of the input data, or
>     516:    to switch to a different kind of input data requiring a different
>     517:    strategy. If the compression level is changed, the input available so far
>     518:    is compressed with the old level (and may be flushed); the new level will
>     519:    take effect only at the next call of deflate().
>     520:
>     521:      Before the call of deflateParams, the stream state must be set as for
>     522:    a call of deflate(), since the currently available input may have to
>     523:    be compressed and flushed. In particular, strm->avail_out must be non-zero.
>     524:
>     525:      deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
>     526:    stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR
>     527:    if strm->avail_out was zero.
>     528: */
>     529:
>     530: /*
>     531: ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm,
>     532:                                      int  windowBits));
>     533:
>     534:      This is another version of inflateInit with an extra parameter. The
>     535:    fields next_in, avail_in, zalloc, zfree and opaque must be initialized
>     536:    before by the caller.
>     537:
>     538:      The windowBits parameter is the base two logarithm of the maximum window
>     539:    size (the size of the history buffer).  It should be in the range 8..15 for
>     540:    this version of the library. The default value is 15 if inflateInit is used
>     541:    instead. If a compressed stream with a larger window size is given as
>     542:    input, inflate() will return with the error code Z_DATA_ERROR instead of
>     543:    trying to allocate a larger window.
>     544:
>     545:       inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
>     546:    memory, Z_STREAM_ERROR if a parameter is invalid (such as a negative
>     547:    memLevel). msg is set to null if there is no error message.  inflateInit2
>     548:    does not perform any decompression apart from reading the zlib header if
>     549:    present: this will be done by inflate(). (So next_in and avail_in may be
>     550:    modified, but next_out and avail_out are unchanged.)
>     551: */
>     552:
>     553: ZEXTERN int ZEXPORT inflateSetDictionary OF((z_streamp strm,
>     554:                                              const Bytef *dictionary,
>     555:                                              uInt  dictLength));
>     556: /*
>     557:      Initializes the decompression dictionary from the given uncompressed byte
>     558:    sequence. This function must be called immediately after a call of inflate
>     559:    if this call returned Z_NEED_DICT. The dictionary chosen by the compressor
>     560:    can be determined from the Adler32 value returned by this call of
>     561:    inflate. The compressor and decompressor must use exactly the same
>     562:    dictionary (see deflateSetDictionary).
>     563:
>     564:      inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
>     565:    parameter is invalid (such as NULL dictionary) or the stream state is
>     566:    inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
>     567:    expected one (incorrect Adler32 value). inflateSetDictionary does not
>     568:    perform any decompression: this will be done by subsequent calls of
>     569:    inflate().
>     570: */
>     571:
>     572: ZEXTERN int ZEXPORT inflateSync OF((z_streamp strm));
>     573: /*
>     574:     Skips invalid compressed data until a full flush point (see above the
>     575:   description of deflate with Z_FULL_FLUSH) can be found, or until all
>     576:   available input is skipped. No output is provided.
>     577:
>     578:     inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERROR
>     579:   if no more input was provided, Z_DATA_ERROR if no flush point has been found,
>     580:   or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
>     581:   case, the application may save the current current value of total_in which
>     582:   indicates where valid compressed data was found. In the error case, the
>     583:   application may repeatedly call inflateSync, providing more input each time,
>     584:   until success or end of the input data.
>     585: */
>     586:
>     587: ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm));
>     588: /*
>     589:      This function is equivalent to inflateEnd followed by inflateInit,
>     590:    but does not free and reallocate all the internal decompression state.
>     591:    The stream will keep attributes that may have been set by inflateInit2.
>     592:
>     593:       inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
>     594:    stream state was inconsistent (such as zalloc or state being NULL).
>     595: */
>     596:
>     597:
>     598:                         /* utility functions */
>     599:
>     600: /*
>     601:      The following utility functions are implemented on top of the
>     602:    basic stream-oriented functions. To simplify the interface, some
>     603:    default options are assumed (compression level and memory usage,
>     604:    standard memory allocation functions). The source code of these
>     605:    utility functions can easily be modified if you need special options.
>     606: */
>     607:
>     608: ZEXTERN int ZEXPORT compress OF((Bytef *dest,   uLongf *destLen,
>     609:                                  const Bytef *source, uLong sourceLen));
>     610: /*
>     611:      Compresses the source buffer into the destination buffer.  sourceLen is
>     612:    the byte length of the source buffer. Upon entry, destLen is the total
>     613:    size of the destination buffer, which must be at least 0.1% larger than
>     614:    sourceLen plus 12 bytes. Upon exit, destLen is the actual size of the
>     615:    compressed buffer.
>     616:      This function can be used to compress a whole file at once if the
>     617:    input file is mmap'ed.
>     618:      compress returns Z_OK if success, Z_MEM_ERROR if there was not
>     619:    enough memory, Z_BUF_ERROR if there was not enough room in the output
>     620:    buffer.
>     621: */
>     622:
>     623: ZEXTERN int ZEXPORT compress2 OF((Bytef *dest,   uLongf *destLen,
>     624:                                   const Bytef *source, uLong sourceLen,
>     625:                                   int level));
>     626: /*
>     627:      Compresses the source buffer into the destination buffer. The level
>     628:    parameter has the same meaning as in deflateInit.  sourceLen is the byte
>     629:    length of the source buffer. Upon entry, destLen is the total size of the
>     630:    destination buffer, which must be at least 0.1% larger than sourceLen plus
>     631:    12 bytes. Upon exit, destLen is the actual size of the compressed buffer.
>     632:
>     633:      compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
>     634:    memory, Z_BUF_ERROR if there was not enough room in the output buffer,
>     635:    Z_STREAM_ERROR if the level parameter is invalid.
>     636: */
>     637:
>     638: ZEXTERN int ZEXPORT uncompress OF((Bytef *dest,   uLongf *destLen,
>     639:                                    const Bytef *source, uLong sourceLen));
>     640: /*
>     641:      Decompresses the source buffer into the destination buffer.  sourceLen is
>     642:    the byte length of the source buffer. Upon entry, destLen is the total
>     643:    size of the destination buffer, which must be large enough to hold the
>     644:    entire uncompressed data. (The size of the uncompressed data must have
>     645:    been saved previously by the compressor and transmitted to the decompressor
>     646:    by some mechanism outside the scope of this compression library.)
>     647:    Upon exit, destLen is the actual size of the compressed buffer.
>     648:      This function can be used to decompress a whole file at once if the
>     649:    input file is mmap'ed.
>     650:
>     651:      uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
>     652:    enough memory, Z_BUF_ERROR if there was not enough room in the output
>     653:    buffer, or Z_DATA_ERROR if the input data was corrupted.
>     654: */
>     655:
>     656:
>     657: typedef voidp gzFile;
>     658:
>     659: ZEXTERN gzFile ZEXPORT gzopen  OF((const char *path, const char *mode));
>     660: /*
>     661:      Opens a gzip (.gz) file for reading or writing. The mode parameter
>     662:    is as in fopen ("rb" or "wb") but can also include a compression level
>     663:    ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for
>     664:    Huffman only compression as in "wb1h". (See the description
>     665:    of deflateInit2 for more information about the strategy parameter.)
>     666:
>     667:      gzopen can be used to read a file which is not in gzip format; in this
>     668:    case gzread will directly read from the file without decompression.
>     669:
>     670:      gzopen returns NULL if the file could not be opened or if there was
>     671:    insufficient memory to allocate the (de)compression state; errno
>     672:    can be checked to distinguish the two cases (if errno is zero, the
>     673:    zlib error is Z_MEM_ERROR).  */
>     674:
>     675: ZEXTERN gzFile ZEXPORT gzdopen  OF((int fd, const char *mode));
>     676: /*
>     677:      gzdopen() associates a gzFile with the file descriptor fd.  File
>     678:    descriptors are obtained from calls like open, dup, creat, pipe or
>     679:    fileno (in the file has been previously opened with fopen).
>     680:    The mode parameter is as in gzopen.
>     681:      The next call of gzclose on the returned gzFile will also close the
>     682:    file descriptor fd, just like fclose(fdopen(fd), mode) closes the file
>     683:    descriptor fd. If you want to keep fd open, use gzdopen(dup(fd), mode).
>     684:      gzdopen returns NULL if there was insufficient memory to allocate
>     685:    the (de)compression state.
>     686: */
>     687:
>     688: ZEXTERN int ZEXPORT gzsetparams OF((gzFile file, int level, int strategy));
>     689: /*
>     690:      Dynamically update the compression level or strategy. See the description
>     691:    of deflateInit2 for the meaning of these parameters.
>     692:      gzsetparams returns Z_OK if success, or Z_STREAM_ERROR if the file was not
>     693:    opened for writing.
>     694: */
>     695:
>     696: ZEXTERN int ZEXPORT    gzread  OF((gzFile file, voidp buf, unsigned len));
>     697: /*
>     698:      Reads the given number of uncompressed bytes from the compressed file.
>     699:    If the input file was not in gzip format, gzread copies the given number
>     700:    of bytes into the buffer.
>     701:      gzread returns the number of uncompressed bytes actually read (0 for
>     702:    end of file, -1 for error). */
>     703:
>     704: ZEXTERN int ZEXPORT    gzwrite OF((gzFile file,
>     705: 				   const voidp buf, unsigned len));
>     706: /*
>     707:      Writes the given number of uncompressed bytes into the compressed file.
>     708:    gzwrite returns the number of uncompressed bytes actually written
>     709:    (0 in case of error).
>     710: */
>     711:
>     712: ZEXTERN int ZEXPORTVA   gzprintf OF((gzFile file, const char *format, ...));
>     713: /*
>     714:      Converts, formats, and writes the args to the compressed file under
>     715:    control of the format string, as in fprintf. gzprintf returns the number of
>     716:    uncompressed bytes actually written (0 in case of error).
>     717: */
>     718:
>     719: ZEXTERN int ZEXPORT gzputs OF((gzFile file, const char *s));
>     720: /*
>     721:       Writes the given null-terminated string to the compressed file, excluding
>     722:    the terminating null character.
>     723:       gzputs returns the number of characters written, or -1 in case of error.
>     724: */
>     725:
>     726: ZEXTERN char * ZEXPORT gzgets OF((gzFile file, char *buf, int len));
>     727: /*
>     728:       Reads bytes from the compressed file until len-1 characters are read, or
>     729:    a newline character is read and transferred to buf, or an end-of-file
>     730:    condition is encountered.  The string is then terminated with a null
>     731:    character.
>     732:       gzgets returns buf, or Z_NULL in case of error.
>     733: */
>     734:
>     735: ZEXTERN int ZEXPORT    gzputc OF((gzFile file, int c));
>     736: /*
>     737:       Writes c, converted to an unsigned char, into the compressed file.
>     738:    gzputc returns the value that was written, or -1 in case of error.
>     739: */
>     740:
>     741: ZEXTERN int ZEXPORT    gzgetc OF((gzFile file));
>     742: /*
>     743:       Reads one byte from the compressed file. gzgetc returns this byte
>     744:    or -1 in case of end of file or error.
>     745: */
>     746:
>     747: ZEXTERN int ZEXPORT    gzflush OF((gzFile file, int flush));
>     748: /*
>     749:      Flushes all pending output into the compressed file. The parameter
>     750:    flush is as in the deflate() function. The return value is the zlib
>     751:    error number (see function gzerror below). gzflush returns Z_OK if
>     752:    the flush parameter is Z_FINISH and all output could be flushed.
>     753:      gzflush should be called only when strictly necessary because it can
>     754:    degrade compression.
>     755: */
>     756:
>     757: ZEXTERN z_off_t ZEXPORT    gzseek OF((gzFile file,
>     758: 				      z_off_t offset, int whence));
>     759: /*
>     760:       Sets the starting position for the next gzread or gzwrite on the
>     761:    given compressed file. The offset represents a number of bytes in the
>     762:    uncompressed data stream. The whence parameter is defined as in lseek(2);
>     763:    the value SEEK_END is not supported.
>     764:      If the file is opened for reading, this function is emulated but can be
>     765:    extremely slow. If the file is opened for writing, only forward seeks are
>     766:    supported; gzseek then compresses a sequence of zeroes up to the new
>     767:    starting position.
>     768:
>     769:       gzseek returns the resulting offset location as measured in bytes from
>     770:    the beginning of the uncompressed stream, or -1 in case of error, in
>     771:    particular if the file is opened for writing and the new starting position
>     772:    would be before the current position.
>     773: */
>     774:
>     775: ZEXTERN int ZEXPORT    gzrewind OF((gzFile file));
>     776: /*
>     777:      Rewinds the given file. This function is supported only for reading.
>     778:
>     779:    gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
>     780: */
>     781:
>     782: ZEXTERN z_off_t ZEXPORT    gztell OF((gzFile file));
>     783: /*
>     784:      Returns the starting position for the next gzread or gzwrite on the
>     785:    given compressed file. This position represents a number of bytes in the
>     786:    uncompressed data stream.
>     787:
>     788:    gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
>     789: */
>     790:
>     791: ZEXTERN int ZEXPORT gzeof OF((gzFile file));
>     792: /*
>     793:      Returns 1 when EOF has previously been detected reading the given
>     794:    input stream, otherwise zero.
>     795: */
>     796:
>     797: ZEXTERN int ZEXPORT    gzclose OF((gzFile file));
>     798: /*
>     799:      Flushes all pending output if necessary, closes the compressed file
>     800:    and deallocates all the (de)compression state. The return value is the zlib
>     801:    error number (see function gzerror below).
>     802: */
>     803:
>     804: ZEXTERN const char * ZEXPORT gzerror OF((gzFile file, int *errnum));
>     805: /*
>     806:      Returns the error message for the last error which occurred on the
>     807:    given compressed file. errnum is set to zlib error number. If an
>     808:    error occurred in the file system and not in the compression library,
>     809:    errnum is set to Z_ERRNO and the application may consult errno
>     810:    to get the exact error code.
>     811: */
>     812:
>     813:                         /* checksum functions */
>     814:
>     815: /*
>     816:      These functions are not related to compression but are exported
>     817:    anyway because they might be useful in applications using the
>     818:    compression library.
>     819: */
>     820:
>     821: ZEXTERN uLong ZEXPORT adler32 OF((uLong adler, const Bytef *buf, uInt len));
>     822:
>     823: /*
>     824:      Update a running Adler-32 checksum with the bytes buf[0..len-1] and
>     825:    return the updated checksum. If buf is NULL, this function returns
>     826:    the required initial value for the checksum.
>     827:    An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
>     828:    much faster. Usage example:
>     829:
>     830:      uLong adler = adler32(0L, Z_NULL, 0);
>     831:
>     832:      while (read_buffer(buffer, length) != EOF) {
>     833:        adler = adler32(adler, buffer, length);
>     834:      }
>     835:      if (adler != original_adler) error();
>     836: */
>     837:
>     838: ZEXTERN uLong ZEXPORT crc32   OF((uLong crc, const Bytef *buf, uInt len));
>     839: /*
>     840:      Update a running crc with the bytes buf[0..len-1] and return the updated
>     841:    crc. If buf is NULL, this function returns the required initial value
>     842:    for the crc. Pre- and post-conditioning (one's complement) is performed
>     843:    within this function so it shouldn't be done by the application.
>     844:    Usage example:
>     845:
>     846:      uLong crc = crc32(0L, Z_NULL, 0);
>     847:
>     848:      while (read_buffer(buffer, length) != EOF) {
>     849:        crc = crc32(crc, buffer, length);
>     850:      }
>     851:      if (crc != original_crc) error();
>     852: */
>     853:
>     854:
>     855:                         /* various hacks, don't look :) */
>     856:
>     857: /* deflateInit and inflateInit are macros to allow checking the zlib version
>     858:  * and the compiler's view of z_stream:
>     859:  */
>     860: ZEXTERN int ZEXPORT deflateInit_ OF((z_streamp strm, int level,
>     861:                                      const char *version, int stream_size));
>     862: ZEXTERN int ZEXPORT inflateInit_ OF((z_streamp strm,
>     863:                                      const char *version, int stream_size));
>     864: ZEXTERN int ZEXPORT deflateInit2_ OF((z_streamp strm, int  level, int  method,
>     865:                                       int windowBits, int memLevel,
>     866:                                       int strategy, const char *version,
>     867:                                       int stream_size));
>     868: ZEXTERN int ZEXPORT inflateInit2_ OF((z_streamp strm, int  windowBits,
>     869:                                       const char *version, int stream_size));
>     870: #define deflateInit(strm, level) \
>     871:         deflateInit_((strm), (level),       ZLIB_VERSION, sizeof(z_stream))
>     872: #define inflateInit(strm) \
>     873:         inflateInit_((strm),                ZLIB_VERSION, sizeof(z_stream))
>     874: #define deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
>     875:         deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
>     876:                       (strategy),           ZLIB_VERSION, sizeof(z_stream))
>     877: #define inflateInit2(strm, windowBits) \
>     878:         inflateInit2_((strm), (windowBits), ZLIB_VERSION, sizeof(z_stream))
>     879:
>     880:
>     881: #if !defined(_Z_UTIL_H) && !defined(NO_DUMMY_DECL)
>     882:     struct internal_state {int dummy;}; /* hack for buggy compilers */
>     883: #endif
>     884:
>     885: ZEXTERN const char   * ZEXPORT zError           OF((int err));
>     886: ZEXTERN int            ZEXPORT inflateSyncPoint OF((z_streamp z));
>     887: ZEXTERN const uLongf * ZEXPORT get_crc_table    OF((void));
>     888:
>     889: #ifdef __cplusplus
>     890: }
>     891: #endif
>     892:
>     893: #endif /* _ZLIB_H */

## How the zlib wrapper was developed

### Attempt #1

>     /* File : example.i */
>     %module example
>     %{
>     /* Put headers and other declarations here */
>     #include "zlib.h"
>     %}

>     %include typemaps.i

>     %include "zlib.h"

The result is:

>     % swig -chicken -I/usr/include example.i
>     /usr/include/zlib.h:63: Syntax error in input.
>     /usr/include/zlib.h:78: Syntax error in input.
>     /usr/include/zlib.h:80: Syntax error in input.

The first problem we see is that the macro `OF(...)` is not defined.

### Attempt #2

We make sure to include `zconf.h` so that SWIG can see the definition of `OF(...)`. We try again.

>     /* File : example.i */
>     %module example
>     %{
>     /* Put headers and other declarations here */
>     #include "zlib.h"
>     %}

>     %include typemaps.i

>     %include "zconf.h"
>     %include "zlib.h"

The result is:

>     % swig -chicken -I/usr/include example.i

This seems to work! But we should take a peek inside the generated `example_wrap.c` to see what the names of the Scheme procedures will be.

>     % grep C_intern example_wrap.c
>       C_word err = C_intern2 (&a, errorhook);
>         sym = C_intern (&a, 21, "example:max-mem-level");
>         sym = C_intern (&a, 17, "example:max-wbits");
>         sym = C_intern (&a, 16, "example:seek-set");
>         sym = C_intern (&a, 16, "example:seek-cur");
>         sym = C_intern (&a, 16, "example:seek-end");
>         sym = C_intern (&a, 20, "example:zlib-version");
>         sym = C_intern (&a, 28, "example:z-stream-next-in-set");
>         sym = C_intern (&a, 28, "example:z-stream-next-in-get");
>         sym = C_intern (&a, 29, "example:z-stream-avail-in-set");
>         sym = C_intern (&a, 29, "example:z-stream-avail-in-get");
>         sym = C_intern (&a, 29, "example:z-stream-total-in-set");
>         sym = C_intern (&a, 29, "example:z-stream-total-in-get");
>         sym = C_intern (&a, 29, "example:z-stream-next-out-set");
>         sym = C_intern (&a, 29, "example:z-stream-next-out-get");
>         sym = C_intern (&a, 30, "example:z-stream-avail-out-set");
>         sym = C_intern (&a, 30, "example:z-stream-avail-out-get");
>         sym = C_intern (&a, 30, "example:z-stream-total-out-set");
>         sym = C_intern (&a, 30, "example:z-stream-total-out-get");
>         sym = C_intern (&a, 24, "example:z-stream-msg-set");
>         sym = C_intern (&a, 24, "example:z-stream-msg-get");
>         sym = C_intern (&a, 26, "example:z-stream-state-set");
>         sym = C_intern (&a, 26, "example:z-stream-state-get");
>         sym = C_intern (&a, 27, "example:z-stream-zalloc-set");
>         sym = C_intern (&a, 27, "example:z-stream-zalloc-get");
>         sym = C_intern (&a, 26, "example:z-stream-zfree-set");
>         sym = C_intern (&a, 26, "example:z-stream-zfree-get");
>         sym = C_intern (&a, 27, "example:z-stream-opaque-set");
>         sym = C_intern (&a, 27, "example:z-stream-opaque-get");
>         sym = C_intern (&a, 30, "example:z-stream-data-type-set");
>         sym = C_intern (&a, 30, "example:z-stream-data-type-get");
>         sym = C_intern (&a, 26, "example:z-stream-adler-set");
>         sym = C_intern (&a, 26, "example:z-stream-adler-get");
>         sym = C_intern (&a, 29, "example:z-stream-reserved-set");
>         sym = C_intern (&a, 29, "example:z-stream-reserved-get");
>         sym = C_intern (&a, 20, "example:new-z-stream");
>         sym = C_intern (&a, 23, "example:delete-z-stream");
>         sym = C_intern (&a, 18, "example:z-no-flush");
>         sym = C_intern (&a, 23, "example:z-partial-flush");
>         sym = C_intern (&a, 20, "example:z-sync-flush");
>         sym = C_intern (&a, 20, "example:z-full-flush");
>         sym = C_intern (&a, 16, "example:z-finish");
>         sym = C_intern (&a, 12, "example:z-ok");
>         sym = C_intern (&a, 20, "example:z-stream-end");
>         sym = C_intern (&a, 19, "example:z-need-dict");
>         sym = C_intern (&a, 15, "example:z-errno");
>         sym = C_intern (&a, 22, "example:z-stream-error");
>         sym = C_intern (&a, 20, "example:z-data-error");
>         sym = C_intern (&a, 19, "example:z-mem-error");
>         sym = C_intern (&a, 19, "example:z-buf-error");
>         sym = C_intern (&a, 23, "example:z-version-error");
>         sym = C_intern (&a, 24, "example:z-no-compression");
>         sym = C_intern (&a, 20, "example:z-best-speed");
>         sym = C_intern (&a, 26, "example:z-best-compression");
>         sym = C_intern (&a, 29, "example:z-default-compression");
>         sym = C_intern (&a, 18, "example:z-filtered");
>         sym = C_intern (&a, 22, "example:z-huffman-only");
>         sym = C_intern (&a, 26, "example:z-default-strategy");
>         sym = C_intern (&a, 16, "example:z-binary");
>         sym = C_intern (&a, 15, "example:z-ascii");
>         sym = C_intern (&a, 17, "example:z-unknown");
>         sym = C_intern (&a, 18, "example:z-deflated");
>         sym = C_intern (&a, 14, "example:z-null");
>         sym = C_intern (&a, 19, "example:zlibversion");
>         sym = C_intern (&a, 15, "example:deflate");
>         sym = C_intern (&a, 18, "example:deflateend");
>         sym = C_intern (&a, 15, "example:inflate");
>         sym = C_intern (&a, 18, "example:inflateend");
>         sym = C_intern (&a, 28, "example:deflatesetdictionary");
>         sym = C_intern (&a, 19, "example:deflatecopy");
>         sym = C_intern (&a, 20, "example:deflatereset");
>         sym = C_intern (&a, 21, "example:deflateparams");
>         sym = C_intern (&a, 28, "example:inflatesetdictionary");
>         sym = C_intern (&a, 19, "example:inflatesync");
>         sym = C_intern (&a, 20, "example:inflatereset");
>         sym = C_intern (&a, 16, "example:compress");
>         sym = C_intern (&a, 17, "example:compress2");
>         sym = C_intern (&a, 18, "example:uncompress");
>         sym = C_intern (&a, 14, "example:gzopen");
>         sym = C_intern (&a, 15, "example:gzdopen");
>         sym = C_intern (&a, 19, "example:gzsetparams");
>         sym = C_intern (&a, 14, "example:gzread");
>         sym = C_intern (&a, 15, "example:gzwrite");
>         sym = C_intern (&a, 16, "example:gzprintf");
>         sym = C_intern (&a, 14, "example:gzputs");
>         sym = C_intern (&a, 14, "example:gzgets");
>         sym = C_intern (&a, 14, "example:gzputc");
>         sym = C_intern (&a, 14, "example:gzgetc");
>         sym = C_intern (&a, 15, "example:gzflush");
>         sym = C_intern (&a, 14, "example:gzseek");
>         sym = C_intern (&a, 16, "example:gzrewind");
>         sym = C_intern (&a, 14, "example:gztell");
>         sym = C_intern (&a, 13, "example:gzeof");
>         sym = C_intern (&a, 15, "example:gzclose");
>         sym = C_intern (&a, 15, "example:gzerror");
>         sym = C_intern (&a, 15, "example:adler32");
>         sym = C_intern (&a, 13, "example:crc32");
>         sym = C_intern (&a, 20, "example:deflateinit-");
>         sym = C_intern (&a, 20, "example:inflateinit-");
>         sym = C_intern (&a, 21, "example:deflateinit2-");
>         sym = C_intern (&a, 21, "example:inflateinit2-");
>         sym = C_intern (&a, 32, "example:internal-state-dummy-set");
>         sym = C_intern (&a, 32, "example:internal-state-dummy-get");
>         sym = C_intern (&a, 26, "example:new-internal-state");
>         sym = C_intern (&a, 29, "example:delete-internal-state");
>         sym = C_intern (&a, 14, "example:zerror");
>         sym = C_intern (&a, 24, "example:inflatesyncpoint");
>         sym = C_intern (&a, 21, "example:get-crc-table");

In fact, we want the Scheme procedure names to begin with `zlib` instead of `example`. For `example:zlib-version`, we want `zlib-version`. And we want dashes when the case switches to/from upper/lowercase; ex. the function `deflateEnd()` should be the Scheme procedure `zlib-deflate-end`.

### Attempt #3

We make sure to add `-prefix zlib -mixed` to the `swig` command line, and we rename `ZLIB_VERSION` to `VERSION`. We try again.

>     /* File : example.i */
>     %module example
>     %{
>     /* Put headers and other declarations here */
>     #include "zlib.h"
>     %}

>     %include typemaps.i

>     %rename(VERSION) ZLIB_VERSION;

>     %include "zconf.h"
>     %include "zlib.h"

The result is:

>     % swig -chicken -prefix zlib -mixed -I/usr/include example.i
>     % grep C_intern example_wrap.c
>       C_word err = C_intern2 (&a, errorhook);
>         sym = C_intern (&a, 18, "zlib:max-mem-level");
>         sym = C_intern (&a, 14, "zlib:max-wbits");
>         sym = C_intern (&a, 13, "zlib:seek-set");
>         sym = C_intern (&a, 13, "zlib:seek-cur");
>         sym = C_intern (&a, 13, "zlib:seek-end");
>         sym = C_intern (&a, 12, "zlib:version");
>         sym = C_intern (&a, 25, "zlib:z-stream-next-in-set");
>         sym = C_intern (&a, 25, "zlib:z-stream-next-in-get");
>         sym = C_intern (&a, 26, "zlib:z-stream-avail-in-set");
>         sym = C_intern (&a, 26, "zlib:z-stream-avail-in-get");
>         sym = C_intern (&a, 26, "zlib:z-stream-total-in-set");
>         sym = C_intern (&a, 26, "zlib:z-stream-total-in-get");
>         sym = C_intern (&a, 26, "zlib:z-stream-next-out-set");
>         sym = C_intern (&a, 26, "zlib:z-stream-next-out-get");
>         sym = C_intern (&a, 27, "zlib:z-stream-avail-out-set");
>         sym = C_intern (&a, 27, "zlib:z-stream-avail-out-get");
>         sym = C_intern (&a, 27, "zlib:z-stream-total-out-set");
>         sym = C_intern (&a, 27, "zlib:z-stream-total-out-get");
>         sym = C_intern (&a, 21, "zlib:z-stream-msg-set");
>         sym = C_intern (&a, 21, "zlib:z-stream-msg-get");
>         sym = C_intern (&a, 23, "zlib:z-stream-state-set");
>         sym = C_intern (&a, 23, "zlib:z-stream-state-get");
>         sym = C_intern (&a, 24, "zlib:z-stream-zalloc-set");
>         sym = C_intern (&a, 24, "zlib:z-stream-zalloc-get");
>         sym = C_intern (&a, 23, "zlib:z-stream-zfree-set");
>         sym = C_intern (&a, 23, "zlib:z-stream-zfree-get");
>         sym = C_intern (&a, 24, "zlib:z-stream-opaque-set");
>         sym = C_intern (&a, 24, "zlib:z-stream-opaque-get");
>         sym = C_intern (&a, 27, "zlib:z-stream-data-type-set");
>         sym = C_intern (&a, 27, "zlib:z-stream-data-type-get");
>         sym = C_intern (&a, 23, "zlib:z-stream-adler-set");
>         sym = C_intern (&a, 23, "zlib:z-stream-adler-get");
>         sym = C_intern (&a, 26, "zlib:z-stream-reserved-set");
>         sym = C_intern (&a, 26, "zlib:z-stream-reserved-get");
>         sym = C_intern (&a, 17, "zlib:new-z-stream");
>         sym = C_intern (&a, 20, "zlib:delete-z-stream");
>         sym = C_intern (&a, 15, "zlib:z-no-flush");
>         sym = C_intern (&a, 20, "zlib:z-partial-flush");
>         sym = C_intern (&a, 17, "zlib:z-sync-flush");
>         sym = C_intern (&a, 17, "zlib:z-full-flush");
>         sym = C_intern (&a, 13, "zlib:z-finish");
>         sym = C_intern (&a, 9, "zlib:z-ok");
>         sym = C_intern (&a, 17, "zlib:z-stream-end");
>         sym = C_intern (&a, 16, "zlib:z-need-dict");
>         sym = C_intern (&a, 12, "zlib:z-errno");
>         sym = C_intern (&a, 19, "zlib:z-stream-error");
>         sym = C_intern (&a, 17, "zlib:z-data-error");
>         sym = C_intern (&a, 16, "zlib:z-mem-error");
>         sym = C_intern (&a, 16, "zlib:z-buf-error");
>         sym = C_intern (&a, 20, "zlib:z-version-error");
>         sym = C_intern (&a, 21, "zlib:z-no-compression");
>         sym = C_intern (&a, 17, "zlib:z-best-speed");
>         sym = C_intern (&a, 23, "zlib:z-best-compression");
>         sym = C_intern (&a, 26, "zlib:z-default-compression");
>         sym = C_intern (&a, 15, "zlib:z-filtered");
>         sym = C_intern (&a, 19, "zlib:z-huffman-only");
>         sym = C_intern (&a, 23, "zlib:z-default-strategy");
>         sym = C_intern (&a, 13, "zlib:z-binary");
>         sym = C_intern (&a, 12, "zlib:z-ascii");
>         sym = C_intern (&a, 14, "zlib:z-unknown");
>         sym = C_intern (&a, 15, "zlib:z-deflated");
>         sym = C_intern (&a, 11, "zlib:z-null");
>         sym = C_intern (&a, 17, "zlib:zlib-version");
>         sym = C_intern (&a, 12, "zlib:deflate");
>         sym = C_intern (&a, 16, "zlib:deflate-end");
>         sym = C_intern (&a, 12, "zlib:inflate");
>         sym = C_intern (&a, 16, "zlib:inflate-end");
>         sym = C_intern (&a, 27, "zlib:deflate-set-dictionary");
>         sym = C_intern (&a, 17, "zlib:deflate-copy");
>         sym = C_intern (&a, 18, "zlib:deflate-reset");
>         sym = C_intern (&a, 19, "zlib:deflate-params");
>         sym = C_intern (&a, 27, "zlib:inflate-set-dictionary");
>         sym = C_intern (&a, 17, "zlib:inflate-sync");
>         sym = C_intern (&a, 18, "zlib:inflate-reset");
>         sym = C_intern (&a, 13, "zlib:compress");
>         sym = C_intern (&a, 14, "zlib:compress2");
>         sym = C_intern (&a, 15, "zlib:uncompress");
>         sym = C_intern (&a, 11, "zlib:gzopen");
>         sym = C_intern (&a, 12, "zlib:gzdopen");
>         sym = C_intern (&a, 16, "zlib:gzsetparams");
>         sym = C_intern (&a, 11, "zlib:gzread");
>         sym = C_intern (&a, 12, "zlib:gzwrite");
>         sym = C_intern (&a, 13, "zlib:gzprintf");
>         sym = C_intern (&a, 11, "zlib:gzputs");
>         sym = C_intern (&a, 11, "zlib:gzgets");
>         sym = C_intern (&a, 11, "zlib:gzputc");
>         sym = C_intern (&a, 11, "zlib:gzgetc");
>         sym = C_intern (&a, 12, "zlib:gzflush");
>         sym = C_intern (&a, 11, "zlib:gzseek");
>         sym = C_intern (&a, 13, "zlib:gzrewind");
>         sym = C_intern (&a, 11, "zlib:gztell");
>         sym = C_intern (&a, 10, "zlib:gzeof");
>         sym = C_intern (&a, 12, "zlib:gzclose");
>         sym = C_intern (&a, 12, "zlib:gzerror");
>         sym = C_intern (&a, 12, "zlib:adler32");
>         sym = C_intern (&a, 10, "zlib:crc32");
>         sym = C_intern (&a, 18, "zlib:deflate-init-");
>         sym = C_intern (&a, 18, "zlib:inflate-init-");
>         sym = C_intern (&a, 19, "zlib:deflate-init2-");
>         sym = C_intern (&a, 19, "zlib:inflate-init2-");
>         sym = C_intern (&a, 29, "zlib:internal-state-dummy-set");
>         sym = C_intern (&a, 29, "zlib:internal-state-dummy-get");
>         sym = C_intern (&a, 23, "zlib:new-internal-state");
>         sym = C_intern (&a, 26, "zlib:delete-internal-state");
>         sym = C_intern (&a, 12, "zlib:ze-rror");
>         sym = C_intern (&a, 23, "zlib:inflate-sync-point");
>         sym = C_intern (&a, 18, "zlib:get-crc-table");

Much better. The only problem is the identifier `zlib:ze-rror`, and we are missing `zlib:deflate-init` and `zlib:inflate-init` because they are defined as macros (see macro definitions).

### Attempt #4

We make sure to rename `zError` to `z_error`, and we inline some helper functions for the `zlib:...-init` macros. We try again.

>     /* File : example.i */
>     %module example
>     %{
>     /* Put headers and other declarations here */
>     #include "zlib.h"
>     %}

>     %include typemaps.i

>     %rename(VERSION) ZLIB_VERSION;
>     %rename(z_error) zError;

>     %include "zconf.h"
>     %include "zlib.h"

>     %inline %{
>     /* %inline blocks are seen by SWIG and are inserted into the header
>        portion of example_wrap.c, so that they are also seen by the C
>        compiler. */
>     int deflate_init(z_streamp strm, int level) {
>       return deflateInit(strm,level); /* call macro */
>     }
>     int inflate_init(z_streamp strm) {
>       return inflateInit(strm); /* call macro */
>     }
>     %}

The result is:

>     % swig -chicken -prefix zlib -mixed -I/usr/include example.i
>     % grep C_intern example_wrap.c
>       C_word err = C_intern2 (&a, errorhook);
>         sym = C_intern (&a, 18, "zlib:max-mem-level");
>         sym = C_intern (&a, 14, "zlib:max-wbits");
>         sym = C_intern (&a, 13, "zlib:seek-set");
>         sym = C_intern (&a, 13, "zlib:seek-cur");
>         sym = C_intern (&a, 13, "zlib:seek-end");
>         sym = C_intern (&a, 12, "zlib:version");
>         sym = C_intern (&a, 25, "zlib:z-stream-next-in-set");
>         sym = C_intern (&a, 25, "zlib:z-stream-next-in-get");
>         sym = C_intern (&a, 26, "zlib:z-stream-avail-in-set");
>         sym = C_intern (&a, 26, "zlib:z-stream-avail-in-get");
>         sym = C_intern (&a, 26, "zlib:z-stream-total-in-set");
>         sym = C_intern (&a, 26, "zlib:z-stream-total-in-get");
>         sym = C_intern (&a, 26, "zlib:z-stream-next-out-set");
>         sym = C_intern (&a, 26, "zlib:z-stream-next-out-get");
>         sym = C_intern (&a, 27, "zlib:z-stream-avail-out-set");
>         sym = C_intern (&a, 27, "zlib:z-stream-avail-out-get");
>         sym = C_intern (&a, 27, "zlib:z-stream-total-out-set");
>         sym = C_intern (&a, 27, "zlib:z-stream-total-out-get");
>         sym = C_intern (&a, 21, "zlib:z-stream-msg-set");
>         sym = C_intern (&a, 21, "zlib:z-stream-msg-get");
>         sym = C_intern (&a, 23, "zlib:z-stream-state-set");
>         sym = C_intern (&a, 23, "zlib:z-stream-state-get");
>         sym = C_intern (&a, 24, "zlib:z-stream-zalloc-set");
>         sym = C_intern (&a, 24, "zlib:z-stream-zalloc-get");
>         sym = C_intern (&a, 23, "zlib:z-stream-zfree-set");
>         sym = C_intern (&a, 23, "zlib:z-stream-zfree-get");
>         sym = C_intern (&a, 24, "zlib:z-stream-opaque-set");
>         sym = C_intern (&a, 24, "zlib:z-stream-opaque-get");
>         sym = C_intern (&a, 27, "zlib:z-stream-data-type-set");
>         sym = C_intern (&a, 27, "zlib:z-stream-data-type-get");
>         sym = C_intern (&a, 23, "zlib:z-stream-adler-set");
>         sym = C_intern (&a, 23, "zlib:z-stream-adler-get");
>         sym = C_intern (&a, 26, "zlib:z-stream-reserved-set");
>         sym = C_intern (&a, 26, "zlib:z-stream-reserved-get");
>         sym = C_intern (&a, 17, "zlib:new-z-stream");
>         sym = C_intern (&a, 20, "zlib:delete-z-stream");
>         sym = C_intern (&a, 15, "zlib:z-no-flush");
>         sym = C_intern (&a, 20, "zlib:z-partial-flush");
>         sym = C_intern (&a, 17, "zlib:z-sync-flush");
>         sym = C_intern (&a, 17, "zlib:z-full-flush");
>         sym = C_intern (&a, 13, "zlib:z-finish");
>         sym = C_intern (&a, 9, "zlib:z-ok");
>         sym = C_intern (&a, 17, "zlib:z-stream-end");
>         sym = C_intern (&a, 16, "zlib:z-need-dict");
>         sym = C_intern (&a, 12, "zlib:z-errno");
>         sym = C_intern (&a, 19, "zlib:z-stream-error");
>         sym = C_intern (&a, 17, "zlib:z-data-error");
>         sym = C_intern (&a, 16, "zlib:z-mem-error");
>         sym = C_intern (&a, 16, "zlib:z-buf-error");
>         sym = C_intern (&a, 20, "zlib:z-version-error");
>         sym = C_intern (&a, 21, "zlib:z-no-compression");
>         sym = C_intern (&a, 17, "zlib:z-best-speed");
>         sym = C_intern (&a, 23, "zlib:z-best-compression");
>         sym = C_intern (&a, 26, "zlib:z-default-compression");
>         sym = C_intern (&a, 15, "zlib:z-filtered");
>         sym = C_intern (&a, 19, "zlib:z-huffman-only");
>         sym = C_intern (&a, 23, "zlib:z-default-strategy");
>         sym = C_intern (&a, 13, "zlib:z-binary");
>         sym = C_intern (&a, 12, "zlib:z-ascii");
>         sym = C_intern (&a, 14, "zlib:z-unknown");
>         sym = C_intern (&a, 15, "zlib:z-deflated");
>         sym = C_intern (&a, 11, "zlib:z-null");
>         sym = C_intern (&a, 17, "zlib:zlib-version");
>         sym = C_intern (&a, 12, "zlib:deflate");
>         sym = C_intern (&a, 16, "zlib:deflate-end");
>         sym = C_intern (&a, 12, "zlib:inflate");
>         sym = C_intern (&a, 16, "zlib:inflate-end");
>         sym = C_intern (&a, 27, "zlib:deflate-set-dictionary");
>         sym = C_intern (&a, 17, "zlib:deflate-copy");
>         sym = C_intern (&a, 18, "zlib:deflate-reset");
>         sym = C_intern (&a, 19, "zlib:deflate-params");
>         sym = C_intern (&a, 27, "zlib:inflate-set-dictionary");
>         sym = C_intern (&a, 17, "zlib:inflate-sync");
>         sym = C_intern (&a, 18, "zlib:inflate-reset");
>         sym = C_intern (&a, 13, "zlib:compress");
>         sym = C_intern (&a, 14, "zlib:compress2");
>         sym = C_intern (&a, 15, "zlib:uncompress");
>         sym = C_intern (&a, 11, "zlib:gzopen");
>         sym = C_intern (&a, 12, "zlib:gzdopen");
>         sym = C_intern (&a, 16, "zlib:gzsetparams");
>         sym = C_intern (&a, 11, "zlib:gzread");
>         sym = C_intern (&a, 12, "zlib:gzwrite");
>         sym = C_intern (&a, 13, "zlib:gzprintf");
>         sym = C_intern (&a, 11, "zlib:gzputs");
>         sym = C_intern (&a, 11, "zlib:gzgets");
>         sym = C_intern (&a, 11, "zlib:gzputc");
>         sym = C_intern (&a, 11, "zlib:gzgetc");
>         sym = C_intern (&a, 12, "zlib:gzflush");
>         sym = C_intern (&a, 11, "zlib:gzseek");
>         sym = C_intern (&a, 13, "zlib:gzrewind");
>         sym = C_intern (&a, 11, "zlib:gztell");
>         sym = C_intern (&a, 10, "zlib:gzeof");
>         sym = C_intern (&a, 12, "zlib:gzclose");
>         sym = C_intern (&a, 12, "zlib:gzerror");
>         sym = C_intern (&a, 12, "zlib:adler32");
>         sym = C_intern (&a, 10, "zlib:crc32");
>         sym = C_intern (&a, 18, "zlib:deflate-init-");
>         sym = C_intern (&a, 18, "zlib:inflate-init-");
>         sym = C_intern (&a, 19, "zlib:deflate-init2-");
>         sym = C_intern (&a, 19, "zlib:inflate-init2-");
>         sym = C_intern (&a, 29, "zlib:internal-state-dummy-set");
>         sym = C_intern (&a, 29, "zlib:internal-state-dummy-get");
>         sym = C_intern (&a, 23, "zlib:new-internal-state");
>         sym = C_intern (&a, 26, "zlib:delete-internal-state");
>         sym = C_intern (&a, 12, "zlib:z-error");
>         sym = C_intern (&a, 23, "zlib:inflate-sync-point");
>         sym = C_intern (&a, 18, "zlib:get-crc-table");
>         sym = C_intern (&a, 17, "zlib:deflate-init");
>         sym = C_intern (&a, 17, "zlib:inflate-init");

Perfect! Now let's integrate this zlib extension into a CHICKEN interpreter. To save some time, in this Examples/chicken/zlib directory:

1. Backup the original `example.i`.
2. Copy and paste the `example.i` text from above and put it into the file called `example.i`
3. Run 'make' as per Building the example.
4. Run the resultant executable `zlib`.

The interpreter interaction is as follows:

>     % ./zlib
>     zlib

>       A SWIG example for the CHICKEN compiler
>       Author: Jonah Beckford, February 2003

>     Scheme Procedures:

>     zlib:max-mem-level
>     zlib:max-wbits
>     zlib:seek-set
>     zlib:seek-cur
>     zlib:seek-end
>     zlib:version
>     zlib:z-stream-next-in-set
>     zlib:z-stream-next-in-get
>     zlib:z-stream-avail-in-set
>     ...
>     zlib:get-crc-table
>     zlib:deflate-init
>     zlib:inflate-init
>     ; This is the CHICKEN interpreter - Version 0, Build 1095 - windows-cygwin-x86
>     ; (c)2000-2003 Felix L. Winkelmann
>     >>> (define s (zlib:new-z-stream))
>     >>> s
>     #<tagged pointer #<c++ "z_stream *">(#<pointer 6d9290>)>
>     >>> (zlib:z-stream-next-in-get s)
>     #f
>     >>> (zlib:z-stream-next-in-set s "some dummy stream data")
>     Error: Type error. Expected _p_Bytef: "bad argument type"
>     >>> (exit)

Apparently we cannot use Scheme strings as `Bytef *`. The SWIG manual shows many ways how to handle strings and byte arrays, but to be simplistic, let's just make the `Bytef *` look like a `char *`, which is automatically handled as a string by SWIG CHICKEN.

### Attempt #5

We make sure to add an %apply construct so that `Bytef *` is handled the same as `char *` to SWIG. We try again.

>     /* File : example.i */
>     %module example
>     %{
>     /* Put headers and other declarations here */
>     #include "zlib.h"
>     %}

>     %include typemaps.i

>     %rename(VERSION) ZLIB_VERSION;
>     %rename(z_error) zError;
>     %apply char * { Bytef * };

>     %include "zconf.h"
>     %include "zlib.h"

>     %inline %{
>     /* %inline blocks are seen by SWIG and are inserted into the header
>        portion of example_wrap.c, so that they are also seen by the C
>        compiler. */
>     int deflate_init(z_streamp strm, int level) {
>       return deflateInit(strm,level); /* call macro */
>     }
>     int inflate_init(z_streamp strm) {
>       return inflateInit(strm); /* call macro */
>     }
>     %}

Build the example once more.
The interpreter interaction is as follows:

>     % ./zlib
>     zlib

>       A SWIG example for the CHICKEN compiler
>       Author: Jonah Beckford, February 2003

>     Scheme Procedures:

>     zlib:max-mem-level
>     zlib:max-wbits
>     zlib:seek-set
>     zlib:seek-cur
>     zlib:seek-end
>     zlib:version
>     zlib:z-stream-next-in-set
>     zlib:z-stream-next-in-get
>     zlib:z-stream-avail-in-set
>     ...
>     zlib:get-crc-table
>     zlib:deflate-init
>     zlib:inflate-init
>     ; This is the CHICKEN interpreter - Version 0, Build 1095 - windows-cygwin-x86
>     ; (c)2000-2003 Felix L. Winkelmann
>     >>> (define s (zlib:new-z-stream))
>     Init zstream
>     >>> (zlib:z-stream-zalloc-set s #f)
>     >>> (zlib:z-stream-zfree-set s #f)
>     >>> (zlib:z-stream-opaque-set s #f)
>     >>> (zlib:deflate-init s (zlib:z-default-compression))
>     0
>     Deflate something small so we don't need to loop/stream data
>     >>> (define in "some dummy data")
>     >>> (define out (make-string 1000))
>     >>> (zlib:z-stream-next-in-set s in)
>     >>> (zlib:z-stream-avail-in-set s (string-length in))
>     >>> (zlib:z-stream-next-out-set s out)
>     >>> (zlib:z-stream-avail-out-set s (string-length out))
>     >>> (zlib:deflate s (zlib:z-finish))
>     1 ;; (zlib:z-stream-end) == 1, which is good
>     >>> (zlib:z-stream-total-out-get s)
>     23.
>     >>> out
>     "                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        "

We see the problem ... the compression is occurring as it should, but we cannot see any of the compressed output. This is because when SWIG CHICKEN passes a Scheme string to a C function, it duplicates the string before calling the C function. We want to save the memory address that `zlib:z-stream-next-out-set` is using, so we can display this later. While we are at it, we can foresee that `compress`, `compress2` and `uncompress` will all need some finessing to work with mutating strings.

### Attempt #6

When we have to finesse strings, we must use typemaps. As well, we define some functions to save and restore the `next_out` element. We try again.

>     /* File : example.i */
>     %module example
>     %{
>     /* Put headers and other declarations here */
>     #include "zlib.h"
>     %}

>     %include typemaps.i

>     %rename(VERSION) ZLIB_VERSION;
>     %rename(z_error) zError;
>     %apply char * { Bytef * };

>     /* Allow the sourceLen to be automatically filled in from the length
>        of the 'source' string */
>     %typemap(in) (const Bytef *source, uLong sourceLen)
>     %{  if (!C_swig_is_string ($input)) {
>         swig_barf (SWIG_BARF1_BAD_ARGUMENT_TYPE, "Argument $input is not a string");
>       }
>       $2 = (uLong) C_header_size ($input);
>       $1 = C_c_string ($input);
>     %}

>     /* Allocate space the size of which is determined by the Scheme
>        integer argument, and make a temporary integer so we can set
>        destLen. */
>     %typemap(in) (Bytef *dest, uLongf *destLen) (uLong len)
>     %{  if (!C_swig_is_fixnum ($input)) {
>         swig_barf (SWIG_BARF1_BAD_ARGUMENT_TYPE, "Argument $input is not a integer");
>       }
>       len = (uLong) C_unfix ($input);
>       $2 = &len;
>       $1 = (char *) malloc (*$2);
>     %}

>     /* Return the mutated string as a new object. */
>     %typemap(argout) (Bytef *dest, uLongf *destLen)
>     (C_word *scmstr)
>     %{  scmstr = C_alloc (C_SIZEOF_STRING (*$2));
>       SWIG_APPEND_VALUE(C_string (&scmstr, *$2, $1));
>       free ($1);
>     %}

>     %include "zconf.h"
>     %include "zlib.h"

>     /* Ignore destLen as an input argument, and make a temporary integer so
>        we can set destLen. */
>     %typemap(in, numinputs=0) uLongf *destLen (uLong len)
>     "$1 = &len;";

>     /* Return a sized string as a new object. */
>     %typemap(argout)
>     (void *outstr, uLongf *destLen) (C_word *scmstr)
>     %{  scmstr = C_alloc (C_SIZEOF_STRING (*$2));
>       SWIG_APPEND_VALUE(C_string (&scmstr, *$2, $1));
>     %}

>     %inline %{
>     /* %inline blocks are seen by SWIG and are inserted into the header
>        portion of example_wrap.c, so that they are also seen by the C
>        compiler. */
>     int deflate_init(z_streamp strm, int level) {
>       return deflateInit(strm,level); /* call macro */
>     }
>     int inflate_init(z_streamp strm) {
>       return inflateInit(strm); /* call macro */
>     }
>     void* z_stream_save_next_out(z_streamp strm) {
>       return (void*) strm->next_out;
>     }
>     void z_stream_get_next_chunk(z_streamp strm, void *outstr, uLongf *destLen) {
>       *destLen = strm->next_out - (Bytef*)outstr;
>     }
>     %}

And that's it. Try building the entire example from the Makefile. Run `./zlib test-zlib.scm` to test it out.