add man page for zlib(3). This is basically an mdoc version of <zlib.h>.

ok henning@ deraadt@

2 files changed, 1778 insertions, 2 deletions

diff --git a/lib/libz/Makefile b/lib/libz/Makefile
index 86e140cfd7c..ce3c8adb78c 100644
--- a/lib/libz/Makefile
+++ b/lib/libz/Makefile
@@ -1,11 +1,11 @@
-#	$OpenBSD: Makefile,v 1.7 2003/02/26 18:13:22 millert Exp $
+#	$OpenBSD: Makefile,v 1.8 2003/09/25 09:12:09 jmc Exp $
 
 LIB=	z
 HDRS=	zconf.h zlib.h
 SRCS=	adler32.c compress.c crc32.c deflate.c gzio.c infblock.c \
 	infcodes.c inffast.c inflate.c inftrees.c infutil.c trees.c \
 	uncompr.c zutil.c
-NOMAN=	noman
+MAN=	zlib.3
 CFLAGS+=-DHAVE_UNISTD_H -DHAVE_STRERROR -DHAVE_MEMCPY -DHAS_vsnprintf \
 	-DHAS_snprintf
 
diff --git a/lib/libz/zlib.3 b/lib/libz/zlib.3
new file mode 100644
index 00000000000..5978c834382
--- /dev/null
+++ b/lib/libz/zlib.3
@@ -0,0 +1,1776 @@
+.\"	$OpenBSD: zlib.3,v 1.1 2003/09/25 09:12:09 jmc Exp $
+.\"
+.\"  Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler
+.\"
+.\"  This software is provided 'as-is', without any express or implied
+.\"  warranty.  In no event will the authors be held liable for any damages
+.\"  arising from the use of this software.
+.\"
+.\"  Permission is granted to anyone to use this software for any purpose,
+.\"  including commercial applications, and to alter it and redistribute it
+.\"  freely, subject to the following restrictions:
+.\"
+.\"  The origin of this software must not be misrepresented; you must not
+.\"  claim that you wrote the original software. If you use this software
+.\"  in a product, an acknowledgment in the product documentation would be
+.\"  appreciated but is not required.
+.\"  Altered source versions must be plainly marked as such, and must not be
+.\"  misrepresented as being the original software.
+.\"  This notice may not be removed or altered from any source distribution.
+.\"
+.\" Converted to mdoc format for the OpenBSD project
+.\" by Jason McIntyre <jmc@openbsd.org>
+.\"
+.Dd September 17, 2003
+.Dt ZLIB 3
+.Os
+.Sh NAME
+.Nm zlib
+.Nd general purpose compression library
+.Sh SYNOPSIS
+.Fd "#include <zlib.h>"
+.Pp
+Basic functions
+.Pp
+.Ft const char *
+.Fn zlibVersion "void"
+.Ft int
+.Fn deflateInit "z_streamp strm" "int level"
+.Ft int
+.Fn deflate "z_streamp strm" "int flush"
+.Ft int
+.Fn deflateEnd "z_streamp strm"
+.Ft int
+.Fn inflateInit "z_streamp strm"
+.Ft int
+.Fn inflate "z_streamp strm" "int flush"
+.Ft int
+.Fn inflateEnd "z_streamp strm"
+.Pp
+Advanced functions
+.Pp
+.Ft int
+.Fn deflateInit2 "z_streamp strm" "int level" "int method" "int windowBits" "int memLevel" "int strategy"
+.Ft int
+.Fn deflateSetDictionary "z_streamp strm" "const Bytef *dictionary" "uInt dictLength"
+.Ft int
+.Fn deflateCopy "z_streamp dest" "z_streamp source"
+.Ft int
+.Fn deflateReset "z_streamp strm"
+.Ft int
+.Fn deflateParams "z_streamp strm" "int level" "int strategy"
+.Ft int
+.Fn inflateInit2 "z_streamp strm" "int windowBits"
+.Ft int
+.Fn inflateSetDictionary "z_streamp strm" "const Bytef *dictionary" "uInt dictLength"
+.Ft int
+.Fn inflateSync "z_streamp strm"
+.Ft int
+.Fn inflateReset "z_streamp strm"
+.Pp
+Utility functions
+.Pp
+.Fd typedef voidp gzFile;
+.Pp
+.Ft int
+.Fn compress "Bytef *dest" "uLongf *destLen" "const Bytef *source" "uLong sourceLen"
+.Ft int
+.Fn compress2 "Bytef *dest" "uLongf *destLen" "const Bytef *source" "uLong sourceLen" "int level"
+.Ft int
+.Fn uncompress "Bytef *dest" "uLongf *destLen" "const Bytef *source" "uLong sourceLen"
+.Ft gzFile
+.Fn gzopen "const char *path" "const char *mode"
+.Ft gzFile
+.Fn gzdopen "int fd" "const char *mode"
+.Ft int
+.Fn gzsetparams "gzFile file" "int level" "int strategy"
+.Ft int
+.Fn gzread "gzFile file" "voidp buf" "unsigned len"
+.Ft int
+.Fn gzwrite "gzFile file" "const voidp buf" "unsigned len"
+.Ft int
+.Fn gzprintf "gzFile file" "const char *format" "..."
+.Ft int
+.Fn gzputs "gzFile file" "const char *s"
+.Ft char *
+.Fn gzgets "gzFile file" "char *buf" "int len"
+.Ft int
+.Fn gzputc "gzFile file" "int c"
+.Ft int
+.Fn gzgetc "gzFile file"
+.Ft int
+.Fn gzflush "gzFile file" "int flush"
+.Ft z_off_t
+.Fn gzseek "gzFile file" "z_off_t offset" "int whence"
+.Ft int
+.Fn gzrewind "gzFile file"
+.Ft z_off_t
+.Fn gztell "gzFile file"
+.Ft int
+.Fn gzeof "gzFile file"
+.Ft int
+.Fn gzclose "gzFile file"
+.Ft const char *
+.Fn gzerror "gzFile file" "int *errnum"
+.Pp
+Checksum functions
+.Pp
+.Ft uLong
+.Fn adler32 "uLong adler" "const Bytef *buf" "uInt len"
+.Ft uLong
+.Fn crc32 "uLong crc" "const Bytef *buf" "uInt len"
+.Sh DESCRIPTION
+This manual page describes the
+.Nm
+general purpose compression library, version 1.1.4.
+.Pp
+The
+.Nm
+compression library provides in-memory compression and decompression functions,
+including integrity checks of the uncompressed data.
+This version of the library supports only one compression method
+.Pq deflation
+but other algorithms will be added later and will have the same
+stream interface.
+.Pp
+Compression can be done in a single step if the buffers are large enough
+.Pq for example if an input file is mmap'ed ,
+or can be done by repeated calls of the compression function.
+In the latter case, the application must provide more input
+and/or consume the output
+.Pq providing more output space
+before each call.
+.Pp
+The library also supports reading and writing files in
+.Xr gzip 1
+.Pq .gz
+format with an interface similar to that of
+.Xr stdio 3 .
+.Pp
+The library does not install any signal handler.
+The decoder checks the consistency of the compressed data,
+so the library should never crash even in case of corrupted input.
+.Pp
+The functions within the library are divided into the following sections:
+.Pp
+.Bl -dash -offset indent -compact
+.It
+Basic functions
+.It
+Advanced functions
+.It
+Utility functions
+.It
+Checksum functions
+.El
+.Sh BASIC FUNCTIONS
+.Bl -tag -width Ds
+.It Xo
+.Fa const char *
+.Fn zlibVersion "void" ;
+.Xc
+.Pp
+The application can compare
+.Fn zlibVersion
+and
+.Dv ZLIB_VERSION
+for consistency.
+If the first character differs, the library code actually used is
+not compatible with the
+.Aq Pa zlib.h
+header file used by the application.
+This check is automatically made by
+.Fn deflateInit
+and
+.Fn inflateInit .
+.It Xo
+.Fa int
+.Fn deflateInit "z_streamp strm" "int level" ;
+.Xc
+.Pp
+The
+.Fn deflateInit
+function initializes the internal stream state for compression.
+The fields
+.Fa zalloc ,
+.Fa zfree ,
+and
+.Fa opaque
+must be initialized before by the caller.
+If
+.Fa zalloc
+and
+.Fa zfree
+are set to
+.Dv Z_NULL ,
+.Fn deflateInit
+updates them to use default allocation functions.
+.Pp
+The compression level must be
+.Dv Z_DEFAULT_COMPRESSION ,
+or between 0 and 9:
+1 gives best speed, 9 gives best compression, 0 gives no compression at all
+(the input data is simply copied a block at a time).
+.Pp
+.Dv Z_DEFAULT_COMPRESSION
+requests a default compromise between speed and compression
+.Pq currently equivalent to level 6 .
+.Pp
+.Fn deflateInit
+returns
+.Dv Z_OK
+if successful,
+.Dv Z_MEM_ERROR
+if there was not enough memory,
+.Dv Z_STREAM_ERROR
+if level is not a valid compression level,
+.Dv Z_VERSION_ERROR
+if the
+.Nm
+library version
+.Pq zlib_version
+is incompatible with the version assumed by the caller
+.Pq ZLIB_VERSION .
+.Fa msg
+is set to null if there is no error message.
+.Fn deflateInit
+does not perform any compression: this will be done by
+.Fn deflate .
+.It Xo
+.Fa int
+.Fn deflate "z_streamp strm" "int flush" ;
+.Xc
+.Pp
+.Fn deflate
+compresses as much data as possible, and stops when the input
+buffer becomes empty or the output buffer becomes full.
+It may introduce some output latency
+.Pq reading input without producing any output
+except when forced to flush.
+.Pp
+The detailed semantics are as follows.
+.Fn deflate
+performs one or both of the following actions:
+.Pp
+Compress more input starting at
+.Fa next_in
+and update
+.Fa next_in
+and
+.Fa avail_in
+accordingly.
+If not all input can be processed
+(because there is not enough room in the output buffer),
+.Fa next_in
+and
+.Fa avail_in
+are updated and processing will resume at this point for the next call to
+.Fn deflate .
+.Pp
+Provide more output starting at
+.Fa next_out
+and update
+.Fa next_out
+and
+.Fa avail_out
+accordingly.
+This action is forced if the parameter
+.Fa flush
+is non-zero.
+Forcing
+.Fa flush
+frequently degrades the compression ratio,
+so this parameter should be set only when necessary
+.Pq in interactive applications .
+Some output may be provided even if
+.Fa flush
+is not set.
+.Pp
+Before the call to
+.Fn deflate ,
+the application should ensure that at least
+one of the actions is possible, by providing more input and/or consuming
+more output, and updating
+.Fa avail_in
+or
+.Fa avail_out
+accordingly;
+.Fa avail_out
+should never be zero before the call.
+The application can consume the compressed output when it wants,
+for example when the output buffer is full
+.Pq avail_out == 0 ,
+or after each call to
+.Fn deflate .
+If
+.Fn deflate
+returns
+.Dv Z_OK
+and with zero
+.Fa avail_out ,
+it must be called again after making room in the
+output buffer because there might be more output pending.
+.Pp
+If the parameter
+.Fa flush
+is set to
+.Dv Z_SYNC_FLUSH ,
+all pending output is flushed to the output buffer and the output
+is aligned on a byte boundary, so that the decompressor can get all
+input data available so far.
+(In particular,
+.Fa avail_in
+is zero after the call if enough output space
+has been provided before the call.)
+Flushing may degrade compression for some compression algorithms
+and so it should be used only when necessary.
+.Pp
+If
+.Fa flush
+is set to
+.Dv Z_FULL_FLUSH ,
+all output is flushed as with
+.Dv Z_SYNC_FLUSH ,
+and the compression state is reset so that decompression can restart from this
+point if previous compressed data has been damaged or if random access
+is desired.
+Using
+.Dv Z_FULL_FLUSH
+too often can seriously degrade the compression.
+.Pp
+If
+.Fn deflate
+returns with avail_out == 0, this function must be called again
+with the same value of the flush parameter and more output space
+(updated
+.Fa avail_out ) ,
+until the flush is complete
+.Pf ( Fn deflate
+returns with non-zero
+.Fa avail_out ) .
+.Pp
+If the parameter
+.Fa flush
+is set to
+.Dv Z_FINISH ,
+pending input is processed, pending output is flushed and
+.Fn deflate
+returns with
+.Dv Z_STREAM_END
+if there was enough output space; if
+.Fn deflate
+returns with
+.Dv Z_OK ,
+this function must be called again with
+.Dv Z_FINISH
+and more output space
+(updated
+.Fa avail_out
+but no more input data, until it returns with
+.Dv Z_STREAM_END
+or an error.
+After
+.Fn deflate
+has returned
+.Dv Z_STREAM_END ,
+the only possible operations on the stream are
+.Fn deflateReset
+or
+.Fn deflateEnd .
+.Pp
+.Dv Z_FINISH
+can be used immediately after
+.Fn deflateInit
+if all the compression is to be done in a single step.
+In this case,
+.Fa avail_out
+must be at least 0.1% larger than
+.Fa avail_in
+plus 12 bytes.
+If
+.Fn deflate
+does not return
+.Dv Z_STREAM_END ,
+then it must be called again as described above.
+.Pp
+.Fn deflate
+sets strm->adler to the adler32 checksum of all input read so far
+(that is,
+.Fa total_in
+bytes).
+.Pp
+.Fn deflate
+may update
+.Fa data_type
+if it can make a good guess about the input data type
+.Pq Z_ASCII or Z_BINARY .
+If in doubt, the data is considered binary.
+This field is only for information purposes and does not affect
+the compression algorithm in any manner.
+.Pp
+.Fn deflate
+returns
+.Dv Z_OK
+if some progress has been made
+.Pq more input processed or more output produced ,
+.Dv Z_STREAM_END
+if all input has been consumed and all output has been produced
+(only when
+.Fa flush
+is set to
+.Dv Z_FINISH ) ,
+.Dv Z_STREAM_ERROR
+if the stream state was inconsistent
+(for example, if
+.Fa next_in
+or
+.Fa next_out
+was
+.Dv NULL ) ,
+.Dv Z_BUF_ERROR
+if no progress is possible
+(for example,
+.Fa avail_in
+or
+.Fa avail_out
+was zero).
+.It Xo
+.Fa int
+.Fn deflateEnd "z_streamp strm" ;
+.Xc
+.Pp
+All dynamically allocated data structures for this stream are freed.
+This function discards any unprocessed input and does not flush any
+pending output.
+.Pp
+.Fn deflateEnd
+returns
+.Dv Z_OK
+if successful,
+.Dv Z_STREAM_ERROR
+if the stream state was inconsistent,
+.Dv Z_DATA_ERROR
+if the stream was freed prematurely
+.Pq some input or output was discarded .
+In the error case,
+.Fa msg
+may be set but then points to a static string
+.Pq which must not be deallocated .
+.It Xo
+.Fa int
+.Fn inflateInit "z_streamp strm" ;
+.Xc
+The
+.Fn inflateInit
+function initializes the internal stream state for decompression.
+The fields
+.Fa next_in ,
+.Fa avail_in ,
+.Fa zalloc ,
+.Fa zfree ,
+and
+.Fa opaque
+must be initialized before by the caller.
+If
+.Fa next_in
+is not
+.Dv Z_NULL
+and
+.Fa avail_in
+is large enough
+.Pq the exact value depends on the compression method ,
+.Fn inflateInit
+determines the compression method from the
+.Nm
+header and allocates all data structures accordingly;
+otherwise the allocation will be deferred to the first call to
+.Fn inflate .
+If
+.Fa zalloc
+and
+.Fa zfree
+are set to
+.Dv Z_NULL ,
+.Fn inflateInit
+updates them to use default allocation functions.
+.Pp
+.Fn inflateInit
+returns
+.Dv Z_OK
+if successful,
+.Dv Z_MEM_ERROR
+if there was not enough memory,
+.Dv Z_VERSION_ERROR
+if the
+.Nm
+library version is incompatible with the version assumed by the caller.
+.Fa msg
+is set to null if there is no error message.
+.Fn inflateInit
+does not perform any decompression apart from reading the
+.Nm
+header if present: this will be done by
+.Fn inflate .
+(So
+.Fa next_in
+and
+.Fa avail_in
+may be modified,
+but
+.Fa next_out
+and
+.Fa avail_out
+are unchanged.)
+.It Xo
+.Fa int
+.Fn inflate "z_streamp strm" "int flush" ;
+.Xc
+.Fn inflate
+decompresses as much data as possible, and stops when the input
+buffer becomes empty or the output buffer becomes full.
+It may introduce some output latency
+.Pq reading input without producing any output
+except when forced to flush.
+.Pp
+The detailed semantics are as follows.
+.Fn inflate
+performs one or both of the following actions:
+.Pp
+Decompress more input starting at
+.Fa next_in
+and update
+.Fa next_in
+and
+.Fa avail_in
+accordingly.
+If not all input can be processed
+(because there is not enough room in the output buffer),
+.Fa next_in
+is updated and processing will resume at this point for the next call to
+.Fn inflate .
+.Pp
+Provide more output starting at
+.Fa next_out
+and update
+.Fa next_out
+and
+.Fa avail_out
+accordingly.
+.Fn inflate
+provides as much output as possible,
+until there is no more input data or no more space in the output buffer
+.Pq see below about the flush parameter .
+.Pp
+Before the call to
+.Fn inflate ,
+the application should ensure that at least one of the actions is possible,
+by providing more input and/or consuming more output,
+and updating the next_* and avail_* values accordingly.
+The application can consume the uncompressed output when it wants,
+for example when the output buffer is full (avail_out == 0),
+or after each call to
+.Fn inflate .
+If
+.Fn inflate
+returns
+.Dv Z_OK
+and with zero
+.Fa avail_out ,
+it must be called again after making room
+in the output buffer because there might be more output pending.
+.Pp
+If the parameter
+.Fa flush
+is set to
+.Dv Z_SYNC_FLUSH ,
+.Fn inflate
+flushes as much output as possible to the output buffer.
+The flushing behavior of
+.Fn inflate
+is not specified for values of the flush parameter other than
+.Dv Z_SYNC_FLUSH
+and
+.Dv Z_FINISH ,
+but the current implementation actually flushes as much output
+as possible anyway.
+.Pp
+.Fn inflate
+should normally be called until it returns
+.Dv Z_STREAM_END
+or an error.
+However if all decompression is to be performed in a single step
+.Pq a single call to inflate ,
+the parameter
+.Fa flush
+should be set to
+.Dv Z_FINISH .
+In this case all pending input is processed and all pending output is flushed;
+.Fa avail_out
+must be large enough to hold all the uncompressed data.
+(The size of the uncompressed data may have been saved
+by the compressor for this purpose.)
+The next operation on this stream must be
+.Fn inflateEnd
+to deallocate the decompression state.
+The use of
+.Dv Z_FINISH
+is never required, but can be used to inform
+.Fn inflate
+that a faster routine may be used for the single
+.Fn inflate
+call.
+.Pp
+If a preset dictionary is needed at this point (see
+.Fn inflateSetDictionary
+below),
+.Fn inflate
+sets strm->adler to the adler32 checksum of the dictionary
+chosen by the compressor and returns
+.Dv Z_NEED_DICT ;
+otherwise it sets strm->adler to the adler32 checksum of all output produced
+so far
+(that is,
+.Fa total_out
+bytes)
+and returns
+.Dv Z_OK ,
+.Dv Z_STREAM_END ,
+or an error code as described below.
+At the end of the stream,
+.Fn inflate
+checks that its computed adler32 checksum is equal to that saved by the
+compressor and returns
+.Dv Z_STREAM_END
+only if the checksum is correct.
+.Pp
+.Fn inflate
+returns
+.Dv Z_OK
+if some progress has been made
+.Pq more input processed or more output produced ,
+.Dv Z_STREAM_END
+if the end of the compressed data has been reached and all uncompressed output
+has been produced,
+.Dv Z_NEED_DICT
+if a preset dictionary is needed at this point,
+.Dv Z_DATA_ERROR
+if the input data was corrupted (input stream not conforming to the
+.Nm
+format or incorrect adler32 checksum),
+.Dv Z_STREAM_ERROR
+if the stream structure was inconsistent
+(for example, if
+.Fa next_in
+or
+.Fa next_out
+was
+.Dv NULL ) ,
+.Dv Z_MEM_ERROR
+if there was not enough memory,
+.Dv Z_BUF_ERROR
+if no progress is possible or if there was not enough room in the output buffer
+when
+.Dv Z_FINISH
+is used.
+In the
+.Dv Z_DATA_ERROR
+case, the application may then call
+.Fn inflateSync
+to look for a good compression block.
+.It Xo
+.Fa int
+.Fn inflateEnd "z_streamp strm" ;
+.Xc
+All dynamically allocated data structures for this stream are freed.
+This function discards any unprocessed input and does not flush any
+pending output.
+.Pp
+.Fn inflateEnd
+returns
+.Dv Z_OK
+if successful, or
+.Dv Z_STREAM_ERROR
+if the stream state was inconsistent.
+In the error case,
+.Fa msg
+may be set but then points to a static string
+.Pq which must not be deallocated .
+.El
+.Sh ADVANCED FUNCTIONS
+The following functions are needed only in some special applications.
+.Bl -tag -width Ds
+.It Xo
+.Fa int
+.Fn deflateInit2 "z_streamp strm" "int level" "int method" "int windowBits" "int memLevel" "int strategy" ;
+.Xc
+.Pp
+This is another version of
+.Fn deflateInit
+with more compression options.
+The fields
+.Fa next_in ,
+.Fa zalloc ,
+.Fa zfree ,
+and
+.Fa opaque
+must be initialized before by the caller.
+.Pp
+The
+.Fa method
+parameter is the compression method.
+It must be
+.Dv Z_DEFLATED
+in this version of the library.
+.Pp
+The
+.Fa windowBits
+parameter is the base two logarithm of the window size
+.Pq the size of the history buffer .
+It should be in the range 8..15 for this version of the library.
+Larger values of this parameter result in better compression
+at the expense of memory usage.
+The default value is 15 if
+.Fn deflateInit
+is used instead.
+.Pp
+The
+.Fa memLevel
+parameter specifies how much memory should be allocated
+for the internal compression state.
+memLevel=1 uses minimum memory but is slow and reduces compression ratio;
+memLevel=9 uses maximum memory for optimal speed.
+The default value is 8.
+See
+.Aq Pa zconf.h
+for total memory usage as a function of
+.Fa windowBits
+and
+.Fa memLevel .
+.Pp
+The
+.Fa strategy
+parameter is used to tune the compression algorithm.
+Use the value
+.Dv Z_DEFAULT_STRATEGY
+for normal data;
+.Dv Z_FILTERED
+for data produced by a filter
+.Pq or predictor ;
+or
+.Dv Z_HUFFMAN_ONLY
+to force Huffman encoding only
+.Pq no string match .
+Filtered data consists mostly of small values with a
+somewhat random distribution.
+In this case, the compression algorithm is tuned to compress them better.
+The effect of
+.Dv Z_FILTERED
+is to force more Huffman coding and less string matching;
+it is somewhat intermediate between
+.Dv Z_DEFAULT
+and
+.Dv Z_HUFFMAN_ONLY .
+The
+.Fa strategy
+parameter only affects the compression ratio but not the correctness of the
+compressed output, even if it is not set appropriately.
+.Pp
+.Fn deflateInit2
+returns
+.Dv Z_OK
+if successful,
+.Dv Z_MEM_ERROR
+if there was not enough memory,
+.Dv Z_STREAM_ERROR
+if a parameter is invalid
+.Pq such as an invalid method .
+.Fa msg
+is set to null if there is no error message.
+.Fn deflateInit2
+does not perform any compression: this will be done by
+.Fn deflate .
+.It Xo
+.Fa int
+.Fn deflateSetDictionary "z_streamp strm" "const Bytef *dictionary" "uInt dictLength" ;
+.Xc
+.Pp
+Initializes the compression dictionary from the given byte sequence
+without producing any compressed output.
+This function must be called immediately after
+.Fn deflateInit ,
+.Fn deflateInit2 ,
+or
+.Fn deflateReset ,
+before any call to
+.Fn deflate .
+The compressor and decompressor must use exactly the same dictionary
+(see
+.Fn inflateSetDictionary ) .
+.Pp
+The dictionary should consist of strings
+.Pq byte sequences
+that are likely to be encountered later in the data to be compressed,
+with the most commonly used strings preferably put towards
+the end of the dictionary.
+Using a dictionary is most useful when the data to be compressed is short
+and can be predicted with good accuracy;
+the data can then be compressed better than with the default empty dictionary.
+.Pp
+Depending on the size of the compression data structures selected by
+.Fn deflateInit
+or
+.Fn deflateInit2 ,
+a part of the dictionary may in effect be discarded,
+for example if the dictionary is larger than the window size in
+.Fn deflate
+or
+.Fn deflate2 .
+Thus the strings most likely to be useful should be
+put at the end of the dictionary, not at the front.
+.Pp
+Upon return of this function, strm->adler is set to the Adler32 value
+of the dictionary; the decompressor may later use this value to determine
+which dictionary has been used by the compressor.
+(The Adler32 value applies to the whole dictionary even if only a subset
+of the dictionary is actually used by the compressor.)
+.Pp
+.Fn deflateSetDictionary
+returns
+.Dv Z_OK
+if successful,
+or
+.Dv Z_STREAM_ERROR
+if a parameter is invalid
+.Pq such as NULL dictionary
+or the stream state is inconsistent
+(for example if
+.Fn deflate
+has already been called for this stream or if the compression method is bsort).
+.Fn deflateSetDictionary
+does not perform any compression: this will be done by
+.Fn deflate .
+.It Xo
+.Fa int
+.Fn deflateCopy "z_streamp dest" "z_streamp source" ;
+.Xc
+.Pp
+The
+.Fn deflateCopy
+function sets the destination stream as a complete copy of the source stream.
+.Pp
+This function can be useful when several compression strategies will be
+tried, for example when there are several ways of pre-processing the input
+data with a filter.
+The streams that will be discarded should then be freed by calling
+.Fn deflateEnd .
+Note that
+.Fn deflateCopy
+duplicates the internal compression state which can be quite large,
+so this strategy is slow and can consume lots of memory.
+.Pp
+.Fn deflateCopy
+returns
+.Dv Z_OK
+if successful,
+.Dv Z_MEM_ERROR
+if there was not enough memory,
+.Dv Z_STREAM_ERROR
+if the source stream state was inconsistent
+(such as
+.Fa zalloc
+being NULL).
+.Fa msg
+is left unchanged in both source and destination.
+.It Xo
+.Fa int
+.Fn deflateReset "z_streamp strm" ;
+.Xc
+.Pp
+This function is equivalent to
+.Fn deflateEnd
+followed by
+.Fn deflateInit ,
+but does not free and reallocate all the internal compression state.
+The stream will keep the same compression level and any other attributes
+that may have been set by
+.Fn deflateInit2 .
+.Pp
+.Fn deflateReset
+returns
+.Dv Z_OK
+if successful, or
+.Dv Z_STREAM_ERROR
+if the source stream state was inconsistent
+(such as
+.Fa zalloc
+or
+.Fa state
+being NULL).
+.It Xo
+.Fa int
+.Fn deflateParams "z_streamp strm" "int level" "int strategy" ;
+.Xc
+.Pp
+The
+.Fn deflateParams
+function dynamically updates the compression level and compression strategy.
+The interpretation of level and strategy is as in
+.Fn deflateInit2 .
+This can be used to switch between compression and straight copy
+of the input data, or to switch to a different kind of input data
+requiring a different strategy.
+If the compression level is changed, the input available so far
+is compressed with the old level
+.Pq and may be flushed ;
+the new level will take effect only at the next call to
+.Fn deflate .
+.Pp
+Before the call to
+.Fn deflateParams ,
+the stream state must be set as for a call to
+.Fn deflate ,
+since the currently available input may have to be compressed and flushed.
+In particular, strm->avail_out must be non-zero.
+.Pp
+.Fn deflateParams
+returns
+.Dv Z_OK
+if successful,
+.Dv Z_STREAM_ERROR
+if the source stream state was inconsistent or if a parameter was invalid, or
+.Dv Z_BUF_ERROR
+if strm->avail_out was zero.
+.It Xo
+.Fa int
+.Fn inflateInit2 "z_streamp strm" "int windowBits" ;
+.Xc
+.Pp
+This is another version of
+.Fn inflateInit
+with an extra parameter.
+The fields
+.Fa next_in ,
+.Fa avail_in ,
+.Fa zalloc ,
+.Fa zfree ,
+and
+.Fa opaque
+must be initialized before by the caller.
+.Pp
+The
+.Fa windowBits
+parameter is the base two logarithm of the maximum window size
+.Pq the size of the history buffer .
+It should be in the range 8..15 for this version of the library.
+The default value is 15 if
+.Fn inflateInit
+is used instead.
+If a compressed stream with a larger window size is given as input,
+.Fn inflate
+will return with the error code
+.Dv Z_DATA_ERROR
+instead of trying to allocate a larger window.
+.Pp
+.Fn inflateInit2
+returns
+.Dv Z_OK
+if successful,
+.Dv Z_MEM_ERROR
+if there was not enough memory,
+.Dv Z_STREAM_ERROR
+if a parameter is invalid
+(such as a negative
+.Fa memLevel ) .
+.Fa msg
+is set to null if there is no error message.
+.Fn inflateInit2
+does not perform any decompression apart from reading the
+.Nm
+header if present: this will be done by
+.Fn inflate .
+(So
+.Fa next_in
+and
+.Fa avail_in
+may be modified, but
+.Fa next_out
+and
+.Fa avail_out
+are unchanged.)
+.It Xo
+.Fa int
+.Fn inflateSetDictionary "z_streamp strm" "const Bytef *dictionary" "uInt dictLength" ;
+.Xc
+.Pp
+Initializes the decompression dictionary from the given uncompressed byte
+sequence.
+This function must be called immediately after a call to
+.Fn inflate
+if this call returned
+.Dv Z_NEED_DICT .
+The dictionary chosen by the compressor can be determined from the
+Adler32 value returned by this call to
+.Fn inflate .
+The compressor and decompressor must use exactly the same dictionary
+(see
+.Fn deflateSetDictionary ) .
+.Pp
+.Fn inflateSetDictionary
+returns
+.Dv Z_OK
+if successful,
+.Dv Z_STREAM_ERROR
+if a parameter is invalid
+.Pq such as NULL dictionary
+or the stream state is inconsistent,
+.Dv Z_DATA_ERROR
+if the given dictionary doesn't match the expected one
+.Pq incorrect Adler32 value .
+.Fn inflateSetDictionary
+does not perform any decompression: this will be done by subsequent calls of
+.Fn inflate .
+.It Xo
+.Fa int
+.Fn inflateSync "z_streamp strm" ;
+.Xc
+.Pp
+Skips invalid compressed data until a full flush point
+(see above the description of
+.Fn deflate
+with
+.Dv Z_FULL_FLUSH )
+can be found, or until all available input is skipped.
+No output is provided.
+.Pp
+.Fn inflateSync
+returns
+.Dv Z_OK
+if a full flush point has been found,
+.Dv Z_BUF_ERROR
+if no more input was provided,
+.Dv Z_DATA_ERROR
+if no flush point has been found, or
+.Dv Z_STREAM_ERROR
+if the stream structure was inconsistent.
+In the success case, the application may save the current value of
+.Fa total_in
+which indicates where valid compressed data was found.
+In the error case, the application may repeatedly call
+.Fn inflateSync ,
+providing more input each time, until success or end of the input data.
+.It Xo
+.Fa int
+.Fn inflateReset "z_streamp strm" ;
+.Xc
+.Pp
+This function is equivalent to
+.Fn inflateEnd
+followed by
+.Fn inflateInit ,
+but does not free and reallocate all the internal decompression state.
+The stream will keep attributes that may have been set by
+.Fn inflateInit2 .
+.Pp
+.Fn inflateReset
+returns
+.Dv Z_OK
+if successful, or
+.Dv Z_STREAM_ERROR
+if the source stream state was inconsistent
+(such as
+.Fa zalloc
+or
+.Fa state
+being NULL).
+.El
+.Sh UTILITY FUNCTIONS
+The following utility functions are implemented on top of the
+basic stream-oriented functions.
+To simplify the interface,
+some default options are assumed (compression level and memory usage,
+standard memory allocation functions).
+The source code of these utility functions can easily be modified
+if you need special options.
+.Bl -tag -width Ds
+.It Xo
+.Fa int
+.Fn compress "Bytef *dest" "uLongf *destLen" "const Bytef *source" "uLong sourceLen" ;
+.Xc
+.Pp
+The
+.Fn compress
+function compresses the source buffer into the destination buffer.
+.Fa sourceLen
+is the byte length of the source buffer.
+Upon entry,
+.Fa destLen
+is the total size of the destination buffer,
+which must be at least 0.1% larger than
+.Fa sourceLen
+plus 12 bytes.
+Upon exit,
+.Fa destLen
+is the actual size of the compressed buffer.
+This function can be used to compress a whole file at once if the
+input file is mmap'ed.
+.Pp
+.Fn compress
+returns
+.Dv Z_OK
+if successful,
+.Dv Z_MEM_ERROR
+if there was not enough memory, or
+.Dv Z_BUF_ERROR
+if there was not enough room in the output buffer.
+.It Xo
+.Fa int
+.Fn compress2 "Bytef *dest" "uLongf *destLen" "const Bytef *source" "uLong sourceLen" "int level" ;
+.Xc
+.Pp
+The
+.Fn compress2
+function compresses the source buffer into the destination buffer.
+The
+.Fa level
+parameter has the same meaning as in
+.Fn deflateInit .
+.Fa sourceLen
+is the byte length of the source buffer.
+Upon entry,
+.Fa destLen
+is the total size of the destination buffer,
+which must be at least 0.1% larger than
+.Fa sourceLen
+plus 12 bytes.
+Upon exit,
+.Fa destLen
+is the actual size of the compressed buffer.
+.Pp
+.Fn compress2
+returns
+.Dv Z_OK
+if successful,
+.Dv Z_MEM_ERROR
+if there was not enough memory,
+.Dv Z_BUF_ERROR
+if there was not enough room in the output buffer, or
+.Dv Z_STREAM_ERROR
+if the level parameter is invalid.
+.It Xo
+.Fa int
+.Fn uncompress "Bytef *dest" "uLongf *destLen" "const Bytef *source" "uLong sourceLen" ;
+.Xc
+.Pp
+The
+.Fn uncompress
+function decompresses the source buffer into the destination buffer.
+.Fa sourceLen
+is the byte length of the source buffer.
+Upon entry,
+.Fa destLen
+is the total size of the destination buffer,
+which must be large enough to hold the entire uncompressed data.
+(The size of the uncompressed data must have been saved previously
+by the compressor and transmitted to the decompressor
+by some mechanism outside the scope of this compression library.)
+Upon exit,
+.Fa destLen
+is the actual size of the compressed buffer.
+This function can be used to decompress a whole file at once if the
+input file is mmap'ed.
+.Pp
+.Fn uncompress
+returns
+.Dv Z_OK
+if successful,
+.Dv Z_MEM_ERROR
+if there was not enough memory,
+.Dv Z_BUF_ERROR
+if there was not enough room in the output buffer, or
+.Dv Z_DATA_ERROR
+if the input data was corrupted.
+.It Xo
+.Fa gzFile
+.Fn gzopen "const char *path" "const char *mode" ;
+.Xc
+.Pp
+The
+.Fn gzopen
+function opens a gzip
+.Pq .gz
+file for reading or writing.
+The mode parameter is as in
+.Xr fopen 3
+.Pq \&"rb\&" or \&"wb\&"
+but can also include a compression level
+.Pq "wb9"
+or a strategy:
+.Sq f
+for filtered data, as in
+.Qq wb6f ;
+.Sq h
+for Huffman only compression, as in
+.Qq wb1h .
+(See the description of
+.Fn deflateInit2
+for more information about the strategy parameter.)
+.Pp
+.Fn gzopen
+can be used to read a file which is not in gzip format;
+in this case
+.Fn gzread
+will directly read from the file without decompression.
+.Pp
+.Fn gzopen
+returns
+.Dv NULL
+if the file could not be opened or if there was
+insufficient memory to allocate the (de)compression state;
+errno can be checked to distinguish the two cases (if errno is zero, the
+.Nm
+error is
+.Dv Z_MEM_ERROR ) .
+.It Xo
+.Fa gzFile
+.Fn gzdopen "int fd" "const char *mode" ;
+.Xc
+.Pp
+The
+.Fn gzdopen
+function associates a gzFile with the file descriptor
+.Fa fd .
+File descriptors are obtained from calls like
+.Xr open 2 ,
+.Xr dup 2 ,
+.Xr creat 3 ,
+.Xr pipe 2 ,
+or
+.Xr fileno 3
+(if the file has been previously opened with
+.Xr fopen 3 ) .
+The
+.Fa mode
+parameter is as in
+.Fn gzopen .
+.Pp
+The next call to
+.Fn gzclose
+on the returned gzFile will also close the file descriptor fd,
+just like fclose(fdopen(fd), mode) closes the file descriptor fd.
+If you want to keep fd open, use gzdopen(dup(fd), mode).
+.Pp
+.Fn gzdopen
+returns
+.Dv NULL
+if there was insufficient memory to allocate the (de)compression state.
+.It Xo
+.Fa int
+.Fn gzsetparams "gzFile file" "int level" "int strategy" ;
+.Xc
+.Pp
+The
+.Fn gzsetparams
+function dynamically updates the compression level or strategy.
+See the description of
+.Fn deflateInit2
+for the meaning of these parameters.
+.Pp
+.Fn gzsetparams
+returns
+.Dv Z_OK
+if successful, or
+.Dv Z_STREAM_ERROR
+if the file was not opened for writing.
+.It Xo
+.Fa int
+.Fn gzread "gzFile file" "voidp buf" "unsigned len" ;
+.Xc
+.Pp
+The
+.Fn gzread
+function reads the given number of uncompressed bytes from the compressed file.
+If the input file was not in gzip format,
+.Fn gzread
+copies the given number of bytes into the buffer.
+.Pp
+.Fn gzread
+returns the number of uncompressed bytes actually read
+(0 for end of file, \-1 for error).
+.It Xo
+.Fa int
+.Fn gzwrite "gzFile file" "const voidp buf" "unsigned len" ;
+.Xc
+.Pp
+The
+.Fn gzwrite
+function writes the given number of uncompressed bytes into the compressed file.
+.Fn gzwrite
+returns the number of uncompressed bytes actually written
+.Pq 0 in case of error .
+.It Xo
+.Fa int
+.Fn gzprintf "gzFile file" "const char *format" "..." ;
+.Xc
+.Pp
+The
+.Fn gzprintf
+function converts, formats, and writes the args to the compressed file
+under control of the format string, as in
+.Xr fprintf 3 .
+.Fn gzprintf
+returns the number of uncompressed bytes actually written
+.Pq 0 in case of error .
+.It Xo
+.Fa int
+.Fn gzputs "gzFile file" "const char *s" ;
+.Xc
+.Pp
+The
+.Fn gzputs
+function writes the given null-terminated string to the compressed file,
+excluding the terminating null character.
+.Pp
+.Fn gzputs
+returns the number of characters written, or \-1 in case of error.
+.It Xo
+.Fa char *
+.Fn gzgets "gzFile file" "char *buf" "int len" ;
+.Xc
+.Pp
+The
+.Fn gzgets
+function reads bytes from the compressed file until len\-1 characters are read,
+or a newline character is read and transferred to
+.Fa buf ,
+or an end-of-file condition is encountered.
+The string is then terminated with a null character.
+.Pp
+.Fn gzgets
+returns
+.Fa buf ,
+or
+.Dv Z_NULL
+in case of error.
+.It Xo
+.Fa int
+.Fn gzputc "gzFile file" "int c" ;
+.Xc
+.Pp
+The
+.Fn gzputc
+function writes
+.Fa c ,
+converted to an unsigned char, into the compressed file.
+.Fn gzputc
+returns the value that was written, or \-1 in case of error.
+.It Xo
+.Fa int
+.Fn gzgetc "gzFile file" ;
+.Xc
+.Pp
+The
+.Fn gzgetc
+function reads one byte from the compressed file.
+.Fn gzgetc
+returns this byte or \-1 in case of end of file or error.
+.It Xo
+.Fa int
+.Fn gzflush "gzFile file" "int flush" ;
+.Xc
+.Pp
+The
+.Fn gzflush
+function flushes all pending output into the compressed file.
+The parameter
+.Fa flush
+is as in the
+.Fn deflate
+function.
+The return value is the
+.Nm
+error number (see function
+.Fn gzerror
+below).
+.Fn gzflush
+returns
+.Dv Z_OK
+if the flush parameter is
+.Dv Z_FINISH
+and all output could be flushed.
+.Pp
+.Fn gzflush
+should be called only when strictly necessary because it can
+degrade compression.
+.It Xo
+.Fa z_off_t
+.Fn gzseek "gzFile file" "z_off_t offset" "int whence" ;
+.Xc
+.Pp
+Sets the starting position for the next
+.Fn gzread
+or
+.Fn gzwrite
+on the given compressed file.
+The offset represents a number of bytes in the uncompressed data stream.
+The whence parameter is defined as in
+.Xr lseek 2 ;
+the value
+.Dv SEEK_END
+is not supported.
+.Pp
+If the file is opened for reading, this function is emulated but can be
+extremely slow.
+If the file is opened for writing, only forward seeks are supported;
+.Fn gzseek
+then compresses a sequence of zeroes up to the new starting position.
+.Pp
+.Fn gzseek
+returns the resulting offset location as measured in bytes from
+the beginning of the uncompressed stream, or \-1 in case of error,
+in particular if the file is opened for writing and the new starting position
+would be before the current position.
+.It Xo
+.Fa int
+.Fn gzrewind "gzFile file" ;
+.Xc
+.Pp
+The
+.Fn gzrewind
+function rewinds the given
+.Fa file .
+This function is supported only for reading.
+.Pp
+gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET).
+.It Xo
+.Fa z_off_t
+.Fn gztell "gzFile file" ;
+.Xc
+.Pp
+The
+.Fn gztell
+function returns the starting position for the next
+.Fn gzread
+or
+.Fn gzwrite
+on the given compressed file.
+This position represents a number of bytes in the uncompressed data stream.
+.Pp
+gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR).
+.It Xo
+.Fa int
+.Fn gzeof "gzFile file" ;
+.Xc
+.Pp
+The
+.Fn gzeof
+function returns 1 when
+.Dv EOF
+has previously been detected reading the given input stream, otherwise zero.
+.It Xo
+.Fa int
+.Fn gzclose "gzFile file" ;
+.Xc
+.Pp
+The
+.Fn gzclose
+function flushes all pending output if necessary, closes the compressed file
+and deallocates all the (de)compression state.
+The return value is the
+.Nm
+error number (see function
+.Fn gzerror
+below).
+.It Xo
+.Fa const char *
+.Fn gzerror "gzFile file" "int *errnum" ;
+.Xc
+.Pp
+The
+.Fn gzerror
+function returns the error message for the last error which occurred on the
+given compressed
+.Fa file .
+.Fa errnum
+is set to the
+.Nm
+error number.
+If an error occurred in the file system and not in the compression library,
+.Fa errnum
+is set to
+.Dv Z_ERRNO
+and the application may consult errno to get the exact error code.
+.El
+.Sh CHECKSUM FUNCTIONS
+These functions are not related to compression but are exported
+anyway because they might be useful in applications using the
+compression library.
+.Bl -tag -width Ds
+.It Xo
+.Fa uLong
+.Fn adler32 "uLong adler" "const Bytef *buf" "uInt len" ;
+.Xc
+The
+.Fn adler32
+function updates a running Adler-32 checksum with the bytes buf[0..len-1]
+and returns the updated checksum.
+If
+.Fa buf
+is
+.Dv NULL ,
+this function returns the required initial value for the checksum.
+.Pp
+An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
+much faster.
+Usage example:
+.Bd -unfilled -offset indent
+uLong adler = adler32(0L, Z_NULL, 0);
+
+while (read_buffer(buffer, length) != EOF) {
+adler = adler32(adler, buffer, length);
+}
+if (adler != original_adler) error();
+.Ed
+.It Xo
+.Fa uLong
+.Fn crc32 "uLong crc" "const Bytef *buf" "uInt len" ;
+.Xc
+The
+.Fn crc32
+function updates a running CRC with the bytes buf[0..len-1]
+and returns the updated CRC.
+If
+.Fa buf
+is
+.Dv NULL ,
+this function returns the required initial value for the CRC.
+Pre- and post-conditioning
+.Pq one's complement
+is performed within this function so it shouldn't be done by the application.
+Usage example:
+.Bd -unfilled -offset indent
+uLong crc = crc32(0L, Z_NULL, 0);
+
+while (read_buffer(buffer, length) != EOF) {
+crc = crc32(crc, buffer, length);
+}
+if (crc != original_crc) error();
+.Ed
+.El
+.Sh STRUCTURES
+.Bd -unfilled
+struct internal_state;
+
+typedef struct z_stream_s {
+    Bytef    *next_in;  /* next input byte */
+    uInt     avail_in;  /* number of bytes available at next_in */
+    uLong    total_in;  /* total nb of input bytes read so far */
+
+    Bytef    *next_out; /* next output byte should be put there */
+    uInt     avail_out; /* remaining free space at next_out */
+    uLong    total_out; /* total nb of bytes output so far */
+
+    char     *msg;      /* last error message, NULL if no error */
+    struct internal_state FAR *state; /* not visible by applications */
+
+    alloc_func zalloc;  /* used to allocate the internal state */
+    free_func  zfree;   /* used to free the internal state */
+    voidpf     opaque;  /* private data object passed to zalloc and zfree*/
+
+    int     data_type;  /*best guess about the data type: ascii or binary*/
+    uLong   adler;      /* adler32 value of the uncompressed data */
+    uLong   reserved;   /* reserved for future use */
+} z_stream;
+
+typedef z_stream FAR * z_streamp;
+.Ed
+.Pp
+The application must update
+.Fa next_in
+and
+.Fa avail_in
+when
+.Fa avail_in
+has dropped to zero.
+It must update
+.Fa next_out
+and
+.Fa avail_out
+when
+.Fa avail_out
+has dropped to zero.
+The application must initialize
+.Fa zalloc ,
+.Fa zfree ,
+and
+.Fa opaque
+before calling the init function.
+All other fields are set by the compression library
+and must not be updated by the application.
+.Pp
+The
+.Fa opaque
+value provided by the application will be passed as the first
+parameter for calls to
+.Fn zalloc
+and
+.Fn zfree .
+This can be useful for custom memory management.
+The compression library attaches no meaning to the
+.Fa opaque
+value.
+.Pp
+.Fa zalloc
+must return
+.Dv Z_NULL
+if there is not enough memory for the object.
+If
+.Nm
+is used in a multi-threaded application,
+.Fa zalloc
+and
+.Fa zfree
+must be thread safe.
+.Pp
+On 16-bit systems, the functions
+.Fa zalloc
+and
+.Fa zfree
+must be able to allocate exactly 65536 bytes,
+but will not be required to allocate more than this if the symbol MAXSEG_64K
+is defined (see
+.Aq Pa zconf.h ) .
+.Pp
+WARNING: On MSDOS, pointers returned by
+.Fa zalloc
+for objects of exactly 65536 bytes *must* have their offset normalized to zero.
+The default allocation function provided by this library ensures this (see
+.Pa zutil.c ) .
+To reduce memory requirements and avoid any allocation of 64K objects,
+at the expense of compression ratio,
+compile the library with -DMAX_WBITS=14 (see
+.Aq Pa zconf.h ) .
+.Pp
+The fields
+.Fa total_in
+and
+.Fa total_out
+can be used for statistics or progress reports.
+After compression,
+.Fa total_in
+holds the total size of the uncompressed data and may be saved for use
+in the decompressor
+(particularly if the decompressor wants to decompress everything
+in a single step).
+.Sh CONSTANTS
+.Bd -unfilled
+#define Z_NO_FLUSH      0
+#define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */
+#define Z_SYNC_FLUSH    2
+#define Z_FULL_FLUSH    3
+#define Z_FINISH        4
+/* Allowed flush values; see deflate() below for details */
+
+#define Z_OK            0
+#define Z_STREAM_END    1
+#define Z_NEED_DICT     2
+#define Z_ERRNO        (-1)
+#define Z_STREAM_ERROR (-2)
+#define Z_DATA_ERROR   (-3)
+#define Z_MEM_ERROR    (-4)
+#define Z_BUF_ERROR    (-5)
+#define Z_VERSION_ERROR (-6)
+/* Return codes for the compression/decompression functions.
+ * Negative values are errors,
+ * positive values are used for special but normal events.
+ */
+
+#define Z_NO_COMPRESSION         0
+#define Z_BEST_SPEED             1
+#define Z_BEST_COMPRESSION       9
+#define Z_DEFAULT_COMPRESSION  (-1)
+/* compression levels */
+
+#define Z_FILTERED            1
+#define Z_HUFFMAN_ONLY        2
+#define Z_DEFAULT_STRATEGY    0
+/* compression strategy; see deflateInit2() below for details */
+
+#define Z_BINARY   0
+#define Z_ASCII    1
+#define Z_UNKNOWN  2
+/* Possible values of the data_type field */
+
+#define Z_DEFLATED   8
+/* The deflate compression method
+ * (the only one supported in this version)
+*/
+
+#define Z_NULL  0  /* for initializing zalloc, zfree, opaque */
+
+#define zlib_version zlibVersion()
+/* for compatibility with versions < 1.0.2 */
+.Ed
+.Sh VARIOUS HACKS
+deflateInit and inflateInit are macros to allow checking the
+.Nm
+version and the compiler's view of
+.Fa z_stream .
+.Bl -tag -width Ds
+.It Xo
+.Fa int
+.Fn deflateInit_ "z_stream strm" "int level" "const char *version" "int stream_size" ;
+.Xc
+.It Xo
+.Fa int
+.Fn inflateInit_ "z_stream strm" "const char *version" "int stream_size" ;
+.Xc
+.It Xo
+.Fa int
+.Fo deflateInit2_
+.Fa "z_stream strm"
+.Fa "int level"
+.Fa "int method"
+.Fa "int windowBits"
+.Fa "int memLevel"
+.Fa "int strategy"
+.Fa "const char *version"
+.Fa "int stream_size"
+.Fc
+.Xc
+.It Xo
+.Fa int
+.Fn inflateInit2_ "z_stream strm" "int windowBits" "const char *version" "int stream_size" ;
+.Xc
+.It Xo
+.Fa const char *
+.Fn zError "int err" ;
+.Xc
+.It Xo
+.Fa int
+.Fn inflateSyncPoint "z_streamp z" ;
+.Xc
+.It Xo
+.Fa const uLongf *
+.Fn "get_crc_table" "void" ;
+.Xc
+.El
+.Sh SEE ALSO
+.Bl -tag -width 12n -compact
+.It RFC 1950
+ZLIB Compressed Data Format Specification.
+.It RFC 1951
+DEFLATE Compressed Data Format Specification.
+.It RFC 1952
+GZIP File Format Specification.
+.El
+.Pp
+.Pa http://ftp.cdrom.com/pub/infozip/zlib/
+.Sh HISTORY
+This manual page is based on an HTML version of
+.Aq Pa zlib.h
+converted by
+.An piaip Aq piaip@csie.ntu.edu.tw
+and was converted to mdoc format by the OpenBSD project.
+.Sh AUTHORS
+.An Jean-loup Gailly Aq jloup@gzip.org
+.An Mark Adler Aq madler@alumni.caltech.edu